Ulolwe Vol 2 Issue 9B

THE ULOLWE SOUTH AFRICA – SUID-AFRIKA A monthly railway research / historical publication ‘n Maandelikse spoorweg historiese en navorsing publikasie Vol 2 no 9B Un-official / Nie Amptelik Everything to do with the former South African Railways: i.e.

Stations, Harbours, Airways, RMT, SAR Police, Armoured Trains, Lighthouses, Pipelines, Catering, SAR Models, Diagrams of Locomotives etc and books on the Railways in Southern Africa Hennie Heymans, Pretoria, South Africa heymanshb@gmail.com September 2011

Patron - Les Pivnic - Beskermheer

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Contents Foreword by Les Pivnic, South African Railway Historian, on the Paper: OUR STEAM LOCOMOTIVES by Dr Raimund Loubser ................................... 4 Conclusion ...................................................................................................... 6 OUR STEAM LOCOMOTIVES .............................................................................. 7 1. Introduction ..................................................................................................... 8 1.1 The Motive for Writing this Story .............................................................. 8 1.2 General Comments ..................................................................................... 9 2. The Main ‘Building Blocks’ of the Steam Locomotive ................................... 10 3. Its Historical Development ............................................................................ 11 4. The Main Building Blocks of the Steam Locomotive - A First Approach ....... 13 4.1 The Boiler ................................................................................................ 13 4.2 The Engine of the Locomotive ................................................................. 15 4.3. Auxiliaries .............................................................................................. 16 5. The Boiler and its Accessories ...................................................................... 16 5.1 General .................................................................................................... 16 5.2 Boiler Efficiency .................................................................................. 16 5.3 Boiler Efficiency - Cls 26 ..................................................................... 19 5.4 Boiler Maintenance .............................................................................. 20 5.5 Smokebox ............................................................................................ 21 5.6 Safety and Other Ancillaries .................................................................... 22 5.7 Keeping the Boiler Clean Inside ........................................................... 26 6 The Engine of the Locomotive ...................................................................... 27 6.1 Reciprocating vs. Turbine Engines........................................................ 27 6.2 Pistons and Cylinders (Fig 30) .............................................................. 28 6.3 Rods ..................................................................................................... 29 6.4 Coupled Wheels ................................................................................... 31 6.5 The Control of the Steam ...................................................................... 33 6.6 Frame, Suspension and Curve Handling ................................................... 38 6.7 Lubrication ........................................................................................... 42 6.8 Tender .................................................................................................. 42 6.9 Vacuum Brakes .................................................................................... 44 7. Problem Solving for the Railways - Personal Experiences ........................... 45 7.1 The Case of the Fractures of the Unbreakable Connecting Rods ............ 46 7.2 Case II: The Fractured Blower Turbine Blades ..................................... 49 7.3 Rails ..................................................................................................... 52 7.4 Dynamometer Tests on the Narrow Gauge Railway ............................... 55 Appendix A ........................................................................................................ 56 Locomotive and Tender Numbering Systems .................................................. 56 Appendix B ......................................................................................................... 57 Eleven Representative SAR Locomotives ................................................. 57 19 and 19d ..................................................................................................... 57 S1 Shunter ..................................................................................................... 57 24 .................................................................................................................. 58 16E ................................................................................................................ 58 15F ................................................................................................................ 58 23 .................................................................................................................. 59 GMAM .......................................................................................................... 59

3 25 .................................................................................................................. 60 26 .................................................................................................................. 60 The Final Verdict ........................................................................................... 61 B7 ..................................................................................................................... 63 Table B1 - Locomotive Power Data ............................................................... 63 Table B2 - Locomotive Performance Comparisons ...................................... 64 Appendix 1 ......................................................................................................... 66 Summary of Robin Barker’s View of the Origin of the 4’-8½” Rail Gauge .... 66 Figures .............................................................................................................. 67 FIG 1 & 2 ...................................................................................................... 67 FIG 3 & 4 ...................................................................................................... 69 FIG 5 & 6 ...................................................................................................... 70 FIG 7 & 8 ...................................................................................................... 71 FIG 9 ............................................................................................................. 72 FIG 10 – Class 25 & 25NC (1953 – 1955) ...................................................... 73 Fig 11 ............................................................................................................ 73 Fig 12 Local & USA Mallets .......................................................................... 75 Fig 13 ............................................................................................................ 76 Fig 14 ............................................................................................................ 76 Fig 15 & 16 ................................................................................................... 77 Fig 17 ............................................................................................................ 78 Fig 18 ............................................................................................................ 78 Fig 19 ............................................................................................................ 79 Fig 20 ............................................................................................................ 79 Fig 21 ............................................................................................................ 80 Fig 22 ............................................................................................................ 80 Fig 23 ............................................................................................................ 81 Fig 24 Cab of GMAM 4051 ........................................................................... 81 Fig 25 ............................................................................................................ 83 Fig 26 ............................................................................................................ 84 Fig 27 ............................................................................................................ 84 Fig 28 ............................................................................................................ 85 Fig 29 ............................................................................................................ 85 Fig 30 ............................................................................................................ 86 Fig 31 ............................................................................................................ 87 Fig 32 ............................................................................................................ 88 Fig 33 Loss of White Metal after Overheating ............................................... 88 Fig 34 & 35 ................................................................................................... 89 Fig 36 & 37 ................................................................................................... 90 Fig 38 – Model of a Walschaert Valve Gear ................................................... 91 Fig 38 - Settings ............................................................................................ 91 Fig 39 ............................................................................................................ 92 Fig 40 & 41 ................................................................................................... 93 Fig 42 ............................................................................................................ 94 Fig 43 ............................................................................................................ 95 Fig 44 ............................................................................................................ 96 Fig 45: Class 25 Overlubricated ..................................................................... 97 Fig 46 ............................................................................................................ 97

4 Fig 47 ............................................................................................................ 98 Fig 48 ............................................................................................................ 98 Fig 49 ............................................................................................................ 99 Fig 50 ............................................................................................................ 99 Fig 51 .......................................................................................................... 100 Fig 52 .......................................................................................................... 101 Fig 53 .......................................................................................................... 101 Fig 54 .......................................................................................................... 102 Fig 55 ......................................................................................................... 103 Fig 56a ........................................................................................................ 103 Fig 56b ........................................................................................................ 103 Fig 57 .......................................................................................................... 104 Fig 58 .......................................................................................................... 104 Steamloco Images ........................................................................................... 105 Photographs .................................................................................................. 107

Foreword by Les Pivnic, South African Railway Historian, on the Paper: OUR STEAM LOCOMOTIVES by Dr Raimund Loubser I would like to compliment Dr. R. Loubser for producing a really excellent Paper most informative and written in a lovely informal style that should be enjoyed by the lay-reader and professional alike.

The incident about watching a family of cheetahs clear the line in front of a class 24 in the KNP with the Author observing this from the loco's front buffer beam, bears witness to this!

The Author's work in finding the Henschel fault - having to rectify faulty milling and the unacceptable work done to rectify the problem - was brilliant to say the least!

On page 27 1: First paragraph - last sentence: Dr Loubser says:....but the engines were converted back to the 1930/50 design after only a short period of service - and I don't know why.

In answer to that question, I am quoting an item here that appeared recently in the SAR-L chat line and it reads:-

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Now page 31 - HBH

5 "Both condensers and the others (25 and 25NC) were initially built with alligator crossheads except for 5 x 25's that experimentally had the multi ledge slidebar.

From conversations with people that were intimately involved with the maintenance of these locos I learnt that the motion girder of the alligator crosshead was very prone to cracking and this could not be solved. Having recently looked at the drawing of this motion girder I am not that surprised. Thus from 1959 onwards the multi ledge slidebar and its simpler and stronger motion girder became the preferred arrangement. In any case, as an example of American mechanical design it is not very difficult to see how it is superior and in fact most of the mechanical design of the 25/25NC is contemporary (1940's) American practice."

The item continues and I am sure that the Doctor would be interested in the balance, which is as follows:In response to the statement from Andre that tests with the Class 20 persuaded Grubb to proceed with the Class 25, this is certainly not true. Grubb and his department had severe reservations about the mass ordering of these locomotives.

From many conversations with the late Murray Franz, who was part of the Test and Design section at the time of the Laingsburg boiler tests, and who knew many of the people who were intimately involved in the gestation of the design of the 25/GMAM classes (which proceeded more or less in parallel) it is clear that the 25's (condensers) were a result of a clear directive from the GM's office. I have a copy of a letter from Grubb to the GM which clearly states that this was the reason for the designation of 25NC (or alternatively the suggestion of 25N) and is a result of Grubb's supposition that many variants of the 25's would be necessary in subsequent modifications to make a successful class. In fact Franz told me that Grubb had told the GM that, if it was their wish that the 25's were delivered en masse, that they (the CME's department) would do their best to make them work.

There is good evidence to suggest that the huge problems with these locomotives was instrumental in early opinion for turning the SAR away from steam, especially with the very successful dieselisation of SWA just a few years away, almost contemporary and almost certainly gestating during the period when the problems with the 25's were a running sore in the late 1950's. Notwithstanding the fact that the effort in solving these problems resulted in the 25's being a hugely successful class, the cost of maintaining the condensing tenders was large and with the electrification of the Karoo the need for them was lost, even though use for them was found for them elsewhere. In terms of overall cost, a condensing tender cost as much to overhaul as the locomotive itself However, as a tribute to American mechanical sophistication a 25NC cost just 50& of its cousins of more basic design (15F, 23, etc) in mechanical maintenance.

End quote.

Page 54:2

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Now page 59 - HBH

6 Class 16E: Dr Loubser refers to the 16Es being sadly relegated to minor duties after being withdrawn from "Blue Train" service.

If I may, I would like to offer a correction in this regard.

These locos were built to haul the Union Limited and Union Express (fore-runners of the Blue Train) and were placed in service in 1935, stationed at the old Kimberley Loco opposite the Station. They worked the Expresses north to Johannesburg and south to Beaufort West.

In 1939 when those trains were equipped with steel-bodied air-conditioned stock, it was considered that the 16E might not be able to re-start the train on a grade if brought to a stand at a signal. For this reason, class 23 locos were used in place of the 16Es and wide-firebox 16DAs that had been in use previously. All the 16DAs and 16Es were then transferred to Bloemfontein loco, from where they continued to work fast main line passenger trains including the Orange Express from 1947.

Even when the Orange Express was re-equipped with steel coaches (C-34 and E16), the 16DAs and 16Es continued to work that train between Bloemfontein and Kimberley.

It was only in the final years of service that the 16Es were relegated to minor duties before being withdrawn from service in 1972.

Conclusion Overall, the Paper is a wonderful document that goes a long way to explain the inner facets of locomotive design and operation.

The descriptions of the tests conducted on a 3B boiler on a class 23; the tests on class 25 connecting rods and the smokebox turbine blades, make for totally fascinating reading for anyone with an interest in the SAR steam locomotive.

Yours sincerely

HL Pivnic P.S. I would be in a position to provide photographs of all the locomotives under discussion should they be required.

This would be possible towards the end of this year due to the fact that unfortunately, with my emigration to Australia, my SAR material is presently not accessible.

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OUR STEAM LOCOMOTIVES

The simple but ingenious devices and design principles that made them work well - most of the time! by

Raimund Loubser

TEXT Ter herinnering aan my Pa Thys (“MM�) Loubser Die skepper en vriend van goeie lokomotiewe Jammer, Pa, dat die teks nie in Afrikaans is nie!

Dedicated to the many innovators who solved the problems of the emerging steam locomotive, the designers, workshop staff and those on the footplates who made them run well, and their poor wives who had to keep the loco home fires burning while their hubbies were playing with their trains.

August 2005 Improved June 2009

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1. Introduction 1.1 The Motive for Writing this Story The author offers the following information on his background which induced him to write up something about steam locomotives - after all, they are no longer relevant in today’s world. They remain, however, very much of interest to me as they are so intimately associated with our family history. My father Thys ( MM ) Loubser spent most of his career in the then SA Railways, my brother Kobus (JGH) his full business life, and myself the first five years as engineer, all of us involved with steam locomotives in one way or another. It also appeals to me that the steam locomotive, in spite of its noise, dirt and inefficiency compared to diesel locomotives and electric units, kept going for a half a century before they were supplanted by the latter. What helped them to survive are the simple but effective concepts and component design features that were adopted in the first century of their existence which made them good performers (well, most of the time!) I would like to share this with you.

To elaborate on the family background, my father Thys already wanted to become a railway engineer as a teenager. After gaining his B-degree at Victoria College (now Univ. Stellenbosch) in 1910, he went to the Technische Hochschule Charlottenburg, Berlin, where he got his Diplomingenieur in railway engineering in 1914, unfortunately after the War had already begun. (This Diplom has been evaluated as one year more advanced than the local B Sc Eng). He returned to South Africa in 1919 but had to wait until 1925 before he could get an appointment in the SAR, as the first Test Engineer in the Mechanical Dept. He commissioned the new Dynamometer Coach (Coach 60) 3 and in 1926 submitted his design for the Class 19 * Locomotive to the then Chief Mechanical Engineer (CME), Col Collins. “MM� was Chief Mechanical Engineer from 1939 to 1949, during which time he introduced several further innovations in the locomotives he designed. See Appendix B for some details of these and a few other locomotives introduced mainly in the period 1925 to 1955.

During this time my brother Kobus was mainly involved in establishing improved manufacturing processes in the SAR Workshops, which reduced maintenance costs and improved locomotive reliability. By the time he became CME, steam locomotives were on their way out.

Raimund learnt a lot from his Dad, such as his experiences with the correct design of blast caps on Garratt locomotives which were notoriously bad steamers (See Section 5 on Boilers). He attained his B Sc, B Sc Ing (Werkt) at Stellenbosch, and 3

Photo of coach no 60 supplied by Les Pivnic - HBH See Appendix A for Locomotive and Tender - Class and Numbering Systems. The other Appendices make good reading at this stage if you are not familiar with locomotives. *

9 joined the SAR as Pupil Engineer in Jan 1949. He resigned in 1954 to become Research Officer at the CSIR’s National Mechanical Engineering Research Institute (NMERI), Strength of Materials Section. He left the CSIR in 1964 for Pelindaba.

His experiences in the SAR included the Mechanical Workshops in Pretoria, boiler efficiency improvement tests on the Cls 23 (Cls = class) at Laingsburg which led to the improved boiler for the Cls 25/25NC*. He took part in traffic tests using the Dynamometer Coach and introduced the new Cls 24 to the (long defunct) Selati line for hauling Palaborwa ore exports. His last job was accepting the first GMAM (4051) on behalf of the Northern Transvaal System. This included a hair-raising run up the bank from Waterval Onder to Boven - see Appendix B. While at the CSIR, investigations were carried out at the request of the SAR. These included fatigue tests on rails, solving the early failures of Cls 25NC connecting rods, and fatigue failures of blower turbine blades on the new Cls 25. For the PPC Company, traffic tests were carried out on the narrow gauge line to Port Elizabeth. No narrow gauge dynamometer coach was available, improvised measuring practices were used.

1.2 General Comments • The old British units of measurement were retained. All SAR steam locomotives were designed and built before metrication in 1961, therefore all original drawings and instruction booklets use feet & inches; tons, cwt & lbs; miles per hour, etc. So these have been used here, with only a few comparisons with metric units to assist in understanding for the younger generation. ‘lb’ is used even for lbs force, not lbf.

10 • The use of tons, however, remains confusing, as a ton of 2000 lb was also commonly used in this country. It was used in the SAR for coal and train loads.

Axle loads were however given in British long tons of 2240 lb and in hundredweights (cwt) of 112 lb. (This ton is practically the same as the metric ton of 1000kg or 2204 lb.) This practice has been retained in these notes.

• The drawings of locomotives in Appendix B were copied from Holland’s book (Ref 3). They were, in turn, redrawn from the original SAR Locomotive Index.

The SAR peculiarities were retained, eg boiler pressure as abbreviated to “200 lbs” instead of “200 lb/sq in”.

• Locomotives of the SAR were designed locally in broad terms, but standard components were specified in full detail using the drawings issued to the SAR Workshops for the manufacture of spares. New locos were all imported in a semi-complete form and assembled in the SAR Workshops. Detail drawings had to be supplied by the manufacturer and the SAR retained the right to copy these drawings and to manufacture any component for their own use, or to specify that particular design in any further orders for locomotives. The main exception to loco supplies from overseas was the first batch of the Cls S1 shunter which was built in the Salt River Workshops towards the end of World War II. • “MM” was the driving force to ensure that all steam locomotive drawings were completely bilingual, in English and Afrikaans. Afrikaans terms were created as needed and issued in dictionaries, copies of which I have.

2. The Main ‘Building Blocks’ of the Steam Locomotive What is a Steam Locomotive?

The term Locomotion is derived from old French, meaning to move from place to place, based on the Latin loco + motivus.(Ref McGraw-Hill’s Heritage Dictionary) For practical purposes, a Steam Locomotive is a traction machine, moving (we would now use the term running) on a rail track, capable of hauling a load of coaches or trucks weighing several times as much as the locomotive. It carries its own supplies of coal and water which are used to generate steam, the latter being the source of power to drive the engine of the locomotive. This develops the Tractive Force to haul the load.

The locomotive functions are best dealt with in three parts, ie the Boiler, in which the coal is burnt to produce the steam at high pressure and temperature, the Engine, which converts the energy contained in the steam to traction power, and the Tender, the storage unit for the coal and water. There is considerable interaction between these three, which will be dealt with. In the case of Garratt locomotives, however, there is no tender, the coal and some of the water is carried on the engine as such. Extra water is usually drawn from an auxiliary tank car.

11 At this stage it would be convenient to start with a brief history of the steam locomotive.

3. Its Historical Development The start of the locomotive is really based on the availability of some form of railroad. This takes us back to the Roman roads of about 2000 years ago, solidly built using stone laid in mortar some 16’ broad. There were paved roads even earlier in the Middle East, but it was the Romans with their organising ability that went so far as to lay down standards for the breadth of the roads and the wheel spacing of about 5’ outside to outside, which comfortably made do for a one horse chariot or cart . A case has been made (Ref 10) that the ruts that have been found in some of these strips (we found none on the roads left in England), were cut to guide the wheels, but I have my doubts. There is a case that the ruts were caused by wear - those I have seen at Pompeii could have been. Intentionally cutting them in, meant that it would have been very difficult on the roads to pass each other. However, the important point is that a method was developed for the easier movement of loads, ie Locomotion!

The Roman principles used can be summarised as follows: a) use a solid smooth carriageway; b) lay them on a solid foundation; c) standardise the wheel spacing (the Gauge as we call it) and d) keep gradients to a reasonably low value so that your horse (or locomotive) can haul a fair load of one or more vehicles at a fair speed.

This discipline was lost for many centuries and the unmade Elizabethan roads were marshes at times. But the advent of coal mining in those times led to a start of wooden strip roads, at first in the mines, then to the nearest port. It helped if the wooden strips were laid to a standard gauge to suit a wheel spacing that could accommodate a horse- the restart of the 5’ outside gauge in about 1650! About 1740, cast iron wheels were introduced, and shortly afterwards it became practical to cast iron strips with ridges, to be used as rails fixed on top of the wooden strips.

(See Appendix 1 for more exact details) At first they broke under the iron wheels of the heavy trucks: the trucks were made smaller and a train of several trucks was used. Eventually the problem was solved when the art of casting malleable iron was developed (1805). The first railway was there and now a horse could haul a few trucks with many tons of coal out of the mine to the nearest port, canal or navigable river, on its way to towns and the nearest new industries.

When Watt’s stationary steam engines was built in the 1770’s, it showed the way to develop a successor to the horse. The Cornishman Trevithick took the lead: he first worked on steam road vehicles, but when one of them capsized on the muddy English roads and badly injured him, he turned to rail locomotives for collieries.

The first one opened a new age around 1804, just over two centuries ago. It is well known that Stephenson, also a Cornishman, built the first really effective rail locomotive, the Locomotion, for the Stockton and Darlington Railway in 1825. It hauled a load of 90 tons: 38 (!) wagons and coaches at a speed of average 10, max 15 mph. The Locomotion already had two coupled driving wheel pairs and his 1845

12 model the Derwent, three. His Rocket, which won the 1829 ‘Rainhills’ Competition by reaching 30 mph, had only one driven wheel pair (configuration therefore 0-22).

The important innovations that Stephenson introduced or developed, were • Most important, developing Trevithick’s idea of blowing the exhaust steam up the chimney, to the point where the draft it created in the fire produced just the right amount of steam in the boiler to maintain that power output. It worked adequately over a wide power range.

• The 4’-8½” rail gauge, on wheels with inner flanges. Proper ‘rails’ were used, not ruts in a strip.

• A long chimney, topping at about 12 ft above rail level. It helped to keep smoke out of the driver’s and passengers’ eyes, but more important for the future, it opened up the concept of a large loading gauge (Fig 13).

• A double eccentric driven valve gear (It controls the steam entrance to and exhaust from the cylinders) which easily allowed the driver to smoothly adjust the cut-off (power level) and to change into reverse with a single control lever.

When the railways came into being in this country, it remained the main choice for valve gear until about 1910.

• Addressing the complaints of the “Greens” of those days. Smoke! Coke making had just been invented, and he promptly used coke on the Rocket run. It may have helped to win the day, but it seems that its use was stopped when the bills for the coke started to mount up. What is new?

Other innovations that were introduced during the first century of locomotion were: • Superheating of the steam, which only slowly found its way into the local standards as from 1904. Superheating reduces the risk of water in the cylinders which can lead to severe failures; it also improves power and efficiency.

• Walschaert’s valve gear, which he invented in 1844 in Belgium. It was soon adopted in Europe, but was not favoured in the British tradition and only found its well-deserved way into our country when the Dutch of the ZASM introduced it on their ‘46-tonner’ in 1892. It gradually became our standard valve gear. It has big advantages over Stephenson’s gear in that the valve can be given a longer stroke and that the gear is accessible on the outside of the engine.

In South Africa, the building of railroads started around 1860 in the Durban and Cape areas, British engineers and developers being the main initiators. The initial choice of gauge for the Cape - Wellington line was therefore 4’-8½” as in England.

When the problems and costs of building lines through our passes became clear (even before the Hex River pass was planned), it was decided to fix the rail gauge for all new lines at 3’-6” (42” = 1067mm, as also used in Norway, Queensland, Tasmania and in pre-WWII Japan) and to convert already built lines to the same gauge. What proved a big advantage was that the big Loading Gauge was retained, as the platforms etc, were already built for the broader gauge. Fig 13 shows the comparison between the local, British and USA rail and loading gauges.

Obviously the USA can build far bigger and stronger engines such as ‘Big Boy’.

13 We and the UK have the same smaller potential. One difference is the rail gauge: we can build track with a 26% smaller minimum radius. It would not have been practical to use the pre-1980 route up the Hex River Pass with a broader gauge. On the other hand, our maximum allowable speeds must be less than in the UK, the bigger overhang leading to a lower stability.

The use of the narrower gauge also meant that there is more room on the outside of a locomotive frame which makes larger diameter outside cylinders possible 24” diameter in practice. Even then, we are at a practical limit. Steam pressures up to 225 lb/sq in. have to be used to obtain the reasonable maximum tractive effort we need on a 4-coupled engine like the Cls 25 with only 5’-0” d. wheels. There is not sufficient room for cylinders and their valve gear between the frames. The proof of the pudding lies in the Cls 16A and 18, which were retired early as they gave far too many problems with their inside cylinder(s) and valve gear.

A reasonable summary of the SAR steam locomotive history from about 1925 can be made by looking at what happened to eleven of the classes up to 1955, when the last of the new locos of the Cls 25 were delivered. One further class is dealt with, the conversion of one of the Cls 25NC to the ‘experimental’ Cls 26. These are summarised in Appendix B. Their data relevant to their power outputs have been tabled in Table B1 together with that of a comparable Electric Unit and two Diesel classes. From this data, the Load capacity and Horsepower of the Cls 25NC and 26 are compared with that of the Electric Cls 6E1 and the Diesel class 34, to give some insight as to why steam locomotives became museum pieces about 1990.

4. The Main Building Blocks of the Steam Locomotive - A First Approach Reverting to the Main Building Blocks of the steam locomotive, it was thought prudent to give a summary of what will be dealt with in more detail later. It will also help to get used to the language that is commonly used!

4.1 The Boiler With reference to Fig 14, which is a diagrammatic ‘cut-through’ sketch of a boiler of about a 19D vintage, the boiler has three basic sections: starting on the right, is the Firebox, which includes the Grate at its lowest level; the Boiler barrel is in the centre, and the Smokebox is attached to its left (front) end.

Firebox: The firebox top, the Crown Plate (B), is flattened to fit under the water level at the barrel top. Along its sides and end there is a water space of about 6”(R). The whole box is prevented from imploding from the high boiler pressure, by a forest of anchors called boiler stays (not shown on the drawing) fitted from the outer shell of the boiler to the firebox inner wall(C) and the crown plate. The entrances to the firebox are through the Firebox Door (stookgat) at the far right where the coal is shovelled in, and the grate at the bottom where the coal burns with the air drawn through the grate. The outlet of the firebox is through the

14 multitude of Boiler Tubes (G) welded into the firebox Tubeplate (A) at the left of the firebox drawing. The firebox houses a Firearch (Q) of bricks supported by Syphonor Archtubes running from the lower back wall up to the higher part of back wall (C). Water circulating through these tubes keeps them from overheating and adds to the steam production Boiler Barrel: The Boiler Tubes (G) are in the lower two-thirds of the barrel and the bigger Superheater tubes (F) in the higher part. The top, however, is kept clear to have room for water to cover the crown plate and tubes by at least 6” and to have still more room above the water level to contain the steam under pressure. On the top of the boiler is fixed the dome (H) from where the steam is collected. Close to the dome are the safety valves which release steam to the atmosphere if the pressure exceeds the prescribed boiler pressure.

Smokebox: As far as steam supply is concerned, the smokebox contains the Superheater header (K) which draws Saturated Steam from the dome through the Main Steam Feedpipe (J). The header supplies the steam to the Superheater Elements (L) and on the superheated steam’s return, feeds it down to the cylinder valves (not shown).

Exhaust steam from the cylinders is piped to the Blast Cap (M) where it blows with the smoke through the Chimney (N) to the atmosphere, creating a partial vacuum in the smokebox. This creates the fire grate draft which keeps the fire going. The harder the blast, the bigger the draft and the coal burning rate. The steam production rate can be made to match the steam demand rate by design of the correct blast cap and chimney size. The Spark Arrestor (not shown) fits around the blast pipe and chimney; it will be dealt with later in section 5.5.

Entrance to the smokebox is through the Smokebox Door (O) at far left. It is screwed closed and needs to be airtight to maintain the partial vacuum when steaming.

A general summary of how the boiler works is as follows: A ‘new’ boiler will first need to be filled with water by hose, up to the level shown in Fig 14. Hot water is used in the running shed to cut the time to reach full boiler pressure to about an hour; with cold water it needs three hours or more. About 4000 gallons of water are needed to fill a big boiler. To get the fire going, burning coal is brought in wheelbarrows to the cab and handed up shovel by shovel to the stoker who throws it in through the opened fire door onto the grate. Just imagine the heat, smoke and sweat involved for those men - one to two tons of burning coal is needed! To speed up the fire, air needs to be forced through the fire grate. Around the blast cap in the smokebox is an annular blower with holes pointing up into the chimney.

As it blows, it pulls enough air through the fire grate. Compressed air can be fed to it by a pipe entering from the outside of the smokebox. Loco sheds always have compressed air on tap and that is used until the steam pressure reaches about 30 lb/sq in, when the locomotive’s own boiler can supply the blower with steam.

Shortly after that, a mechanical stoker can also take over from the hand shovel and

15 then normal working carries on. This includes using the steam-fed Injector (Section 5.6.5) to pump water from the tender into the boiler as needed. Boiler pressures depend on the loco class, but they are all around 200 lb/sq in - enough to push a column of water (say, in a pipe) 450’ up to reach the top of a 45 storey building. The load pushing the crown plate of the firebox down in the case of the cls 23 boiler is almost 1000 tons at normal boiler pressure, so stand well clear the next time you come across a working steam loco!

When the locomotive has to start pulling a train, the driver opens the Regulator in the header (K), and the saturated (wet) steam, still at the boiling water temperature of about 200 0 C, rushes through the very hot superheater elements, emerging as superheated steam of at least 300 0 C (Ouch - it will melt tin!) on its way to the cylinders. It is still at full boiler pressure. This steam is transparent; if it leaks outside the boiler, you see nothing until it has blown a foot or so away only then does the white cloud start forming. Again, keep well away.

Heat from the fire is conducted to the water in the boiler through the steel walls of the firebox and the pipe walls of the arch tubes, then through the boiler and superheater tubes, the smoke emerging into the smokebox with most of its heat transferred to the water and superheated steam. Unfortunately it also carries with it unburnt coal and char, causing black smoke. The harder the boiler works, the faster the air is drawn through the grate and the bigger are the char and smoke losses. Steps to reduce these losses are dealt with in Section 5.

4.2 The Engine of the Locomotive In this part of the locomotive, the energy available in the hot, high pressure steam is converted into kinetic (in common terms, moving) energy by forcing the pistons backwards and forwards in the cylinders. In the process it losses most of its pressure and cools down considerably; there is a pressure of a few lbs/sq in. left to create the blast in the smokebox from the blast cap to the chimney, drawing the smoke with it. (As I am writing this rough draft, we are sitting on the beach at Victoria Bay, and the ‘Outeniqua Choo-Choo’ is passing us on its last lap to George. It is being drawn by a splendidly renovated 19D with a ‘Perdeby’ tender (Fig 2) and steaming well. (Baie dankie, Pa Thys!)

The backwards-and-forwards (The engineers would say reciprocating) motion of the pistons is converted into a powerful rotational force at the driving wheels through the connecting rods and then the coupling rods Thank you, Mr Stephenson, for your simple but effective idea. More about this and the not-so-simple valve gear which controls the inlet, expansion and exhaust of the steam in the cylinders, will follow in Section 6.

The Engine part of the locomotive is mainly made up of the loco Main Frame, the wheel system and the cylinders; it forms only a fraction of the locomotive and tender. In an Electric Unit nearly all of it is dedicated to power output, its

16 equivalent to the steam locomotive’s tender and boiler being little more than the pantographs on the roof and the limited control gear, provided of course that the overhead power line is doing its job. Steam cylinders are a bit more compact than electric motors for a given power output, but in the end Electric Units are only about half the size of their steam equivalents (Appendix B, Table B2).

4.3. Auxiliaries These include the tender with its Mechanical Stoker and Brake Systems, they will be dealt with in Section 6.8 & 6.9.

5. The Boiler and its Accessories 5.1 General An unusual approach will be followed in discussing the details of the boiler, ie to deal with them from a) the boiler efficiency and then b) the boiler maintenance point of view. This will automatically lead to the what and why’s in the design and constructional details. It should also be pointed out that in the period up to 1955, we engineers still did not have the capabilities to design a boiler in detail from first principles, either from the heat generation and transfer (thermodynamics), or from the strength point of view - computers were not yet there. So designs were based largely on experience gained from available locomotives and tests done on them. Intelligent intuition played its role: as my brother’s favourite and respected practical team member, Les Mitchell, used to say, “A good guess is better than a bad calculation”. I agree!

5.2

Boiler Efficiency

By 1949 it became clear that more main line steam locomotives would have to be ordered within the next three years or so. It was also felt that a more effective, lower maintenance and more powerful boiler than the existing Std. 3B boiler was desperately needed for the new loco. All locomotives with a Std 3 boiler had trouble with a fire that was more intense in some parts than the other, contributing to ‘drawn fires’ at high stoking rates. The burning coal layer is broken up by the draft and vibration, some being thrown into other parts of the grate, leaving open grate pockets. The cold incoming air concentrates in the open areas, the burning rate in the rest goes down and of course so does the steaming rate. The fire is not easily restarted in the open parts and the loco fails in section (ie between stations) for a quarter of an hour or more. Also char loss became high and therefore boiler efficiency fairly low. (Maintenance problems will be dealt with in Section 5.4).

The CME’s Test Section was therefore called on by “MM”, just before he retired, to get going with boiler efficiency tests on a 3B boiler and to try to improve the design. They needed more staff and Raimund, who was one of the fledgling Pupil Engineers (Don’t ask me what we were called behind our backs in Afrikaans!) was called up from the Workshops training session and transferred to the Test Section, in the middle of 1949, in anticipation of these and traffic tests. We were going to

17 use the old Dynamometer Coach (Coach No 60, Fig 15) which can measure and record on a large roll of paper, the drawbar pull where the coach is coupled to the tender, as well as the speed and boiler pressures, etc on the locomotive. In anticipation of the boiler tests, Raimund was also instructed to design and build measuring equipment to measure the steam consumption of the mechanical stoker (of course it was powered by a small two-cylinder steam engine!) that would be used on the Cls 23 loco, No 3211, allocated to the tests, as well as the pressure below atmosphere under the grate, in the firebox and the smokebox etc. ‘Keep it simple, and remember it will be bolted to the end of the tender in the open and subject to plenty of bumps and vibration!’ (Fig 16) ‘Also start thinking of how we can estimate the steam loss if the safety valve(s) blow - there is no way that it can be measured directly’.

Maybe we should stop a bit and explain what is meant by boiler efficiency. In simple terms it is the ratio of the extra energy in the superheated steam fed to the cylinders over and above that of the cold tender water fed to the boiler, compared to the heat value contained in the coal stoked (or burnt) during the same time. We accepted that the heat value is that determined by ideal combustion of the coal we left it to the coal suppliers to calculate that from the coal analysis. To make practical sense of these values, they have to be related to the efficiency with which the engine part works, which means that the tests must be carried out with the loco hauling a load, so that a power determination can be made from the drawbar pull, the speed and the known weights of the locomotive and the load.

The next factor to be taken into consideration is the known fact that both boiler efficiency as well as engine efficiency vary with power level, so that an assessment of how well the boiler (and engine, in a different way) performs, must be done over a wide power range. Moreover, it is difficult to keep the test conditions constant and to ensure that the inevitable variations between the beginning and end conditions of the test run do not significantly influence the test results. After all, if you start a test with, say one ton of coal on the grate, how much more or less coal do you estimate there is by the end? And how much more or less is it burnt?

It helps if you have a long run with a constant uphill gradient which will consume a few tons of coal, carefully measured, and then to use a practiced eye to estimate the start and finish condition of the fire. The best place available was the run from Laingsburg to Pietermeintjies, with an average gradient of 1 in 66 all the way except through the sidings and stations. It worked well to warm up the loco by running the load at the required rate to one of the first stations, stop and quickly measure the water level in the tender and estimate the fire condition, then rapidly get the train up to the test power rate and keep it constant right up to Pietermeintjies, then repeat the water level readings to give the total water consumption which is equal to the steam output. The latter needed corrections for the stoker and safety valve losses. Now how do you keep the power output constant? Simple, if you know how - attach a small pipe to the blast pipe, and run it to a pressure gauge placed in front of the driver. He is told to run the engine so that the blast pressure remains constant at, say, 6 lb/sq in. As the train picks up

18 speed through the level track of a station, he reduces the cut-off on the valve gear (See Section 6) correspondingly to keep the blast pipe pressure constant, opening up gradually as the train starts climbing again and loses speed. A constant blast cap pressure leads to a constant draft through the fire. If the stoker keeps the fire thickness constant, we have a constant coal consumption ie Firing Rate, which is what we need. But how do we measure the coal consumption? The Civil Engineering Section built a mini coal loading platform next to a siding at Laingsburg. A supervised gang of labourers filled sacks of coal, each with exactly 50 lbs of coal, and a few tons of these were loaded onto the tender each morning for the two trips planned for the day. There was severe competition not to get the job of sitting in the tender amongst the muck and dust to count the number of sacks dumped into the conveyer screw during the test proper and to estimate the fraction of a sack not used!.

Measuring the steam loss when the safety valve(s) blow was a problem. The best we could do was to place 3211 stationary on a flat track and close the injector. The fireman opened the (smokebox) blower while two of us kept check on the water level in the boiler. When a safety valve opened, the fireman closed the blower valve and a stopwatch was started to measure the duration of the blow. At the end of the blow, the stopwatch clicked and we watched the boiler water level until it stabilised. We then took the water level reading. From the drawing of the boiler we could calculate the amount of boiling water that had been used up, which was taken as the steam loss. A first snag was that as the safety valve opened, the sudden release of the steam led to increased ‘bubbling’ of the boiler water and an increase in the water level shown in the gauge. After the valve closed, the water level shown kept dropping for a while before settling down again. How long should one wait to reach the same condition as before the safety valve opened?

The next snag was that one could hear that the blow was harder if the steaming rate was higher. So we had to repeat the test over the whole range of firing rates.

Anyway, we could get a reasonable guestimate of the steam loss from a safety valve blow, but also got the fireman to understand that blowing safety valves were ‘not on’ during the test run.

After one half day had been spent on such a test trip and all had gone well, we would have only one point on the graph of boiler efficiency vs firing rate after an evening’s calculations - and we needed at least six such points spread over the whole practical firing range, to have data which could be used for comparisons between different designs of the boiler.

The boiler efficiency graphs for the 3B boiler before and after the ‘best’ alterations are given in Fig 17 (Ref 1). One rather disconcerting graph is included, ie the efficiency achieved by hand-firing 3211 with most of the improvements tested: It is far better than any of the others, in fact calculations show that the same steam production could be achieved by hand-firing at 145 lb/sq ft than by mechanically stoking at 180 lb/sq ft! The latter needs to crush the coal in the feed screws to enable the steam jets to blow the coal into the firebox. The fine bits of coal are easily lifted

19 from the grate by the air entering from the ash pan and are blown out of the chimney, largely unburnt, hence the lower efficiencies. In hindsight, it is strange that none of the engineers saw this as an opportunity to develop a mechanical stoker that could work well with lump coal, like Scheffel did for improved bogie design.

To cut a long story short, the tests gave a clear indication that the following changes should be worked into the new class 25 boiler design, as shown in Fig 18a & 18 b, to increase the efficiency by at least 5 percentage points over the medium to high firing rate range: • Increase the number of air holes in the fire grates as far as practical, but not their size.

• Reduce the downward slope of the firebox grate to about half that of the 3B boiler.

• Increase the angle between arch and grate from 25 o on the 3B, to 30 o • The brick arch top centre to be in line with the centre of the grate, and a bit shorter at the sides • Preferably use siphon tubes to support the brick arch rather than arch tubes • Reduce the breadth of the grate • Make the grate area as large as the weight limitations will allow The Standard Stoker design was retained in spite of it leading to low boiler efficiencies.

A ‘combustion chamber’ was introduced at the firebox front end. It is needed to reduce maintenance costs: it would not influence the efficiency.

These changes were incorporated into the Cls 25 boiler, which proved to be very successful. The grate size became 7’ x 10’ (3B was 8’ x 8’), giving a 12% greater area; siphon tubes were used and a combustion chamber fitted, which meant that the boiler tube length could be reduced from 22’ 6” to 19’. For a given steam production (Power output), the coal consumption was reduced by about 20% at fairly high power levels on the cls 25. It could, however, only be achieved by replacing the two-wheel trailing bogie under the ash pan with a four-wheel bogie.

5.3

Boiler Efficiency - Cls 26

In Appendix B1 a general summary is given of Wardale’s supervision on a class 25NC locomotive power. It became the (only) Cls 26 locomotive. The diagrammatically in Fig 19, in order that they can normal boiler shown in Fig 14.

the changes effected under to improve its efficiency and changes are shown somewhat be compared easily with the

The most important change is the diverting of some exhaust steam from the cylinders to the ash pan, from where it is sprayed under the grate to mix with the air as it reaches the burning coal. The steam reacts with the hot coal to form hydrogen (H 2 ) and carbon monoxide (CO) gases. The reaction partially cools down

20 the coal to a dull red heat. A portion of the carbon still burns to CO 2 which keeps the coal sufficiently hot. Presumably some care is needed to regulate the ratio of steam to air, so that the best working conditions are maintained. The flow rate of the steam-air mix is much lower through the grate than that of the air in the Cls 25 boiler, so that the loss of coal particles is greatly reduced. Extra air is now introduced from the sides, presumably just above the grate, to allow the H 2 & CO mix to burn as completely as possible. The process certainly lends itself to better boiler efficiency, but probably not much better than with hand-firing, if one takes into account that the steam which is injected before the grate, leaves the boiler still as steam, but its temperature is now probably around 250 o C compared to about 100 o C on the Cls 25 locomotive as exhaust steam up the chimney - a loss which will counteract some of the gain.

It would have been really interesting to have given the Porta/Wardale principle a go at the Laingsburg tests in spite of our time limits, had it already then been effectively used elsewhere. It was not yet so; we can only think of the Cls 26 as being a real Red Devil who had come with too much, 30 years too late.

5.4

Boiler Maintenance

The design of a boiler from the strength and low maintenance point of view was largely based on experience gained from older designs. Some of the factors which influence the design are the enormous loads due to the high boiler pressures (up to 225 lb/sq in), differential expansions due to varying temperatures as the steaming rate changes and particularly when the boiler is shut down and restarted for boiler shut downs, and the fact that the boiler takes some of the frame load.

Some idea of the pressure effect can be obtained by noting that on the Cls 25 the boiler cylindrical barrel has to resist an outward force of about 300 tons per foot length. The load forcing the firebox crown plate down, away from the boiler shell is about 1000 tons. This explains why there is a veritable forest of stays between the crown plate and the outer boiler roof as can be seen in the sectional drawing of a class 25 in Fig 20. The stay support continues on all sides of the firebox: here the stays are short (about 6� between plates) and they are stressed further by lateral movement between the plates. The firebox shell heats up quicker and reaches a far higher temperature than the outside plate: the differential expansion which leads to bending of the stays was so high that it led to failure of the stays and the plates to which they are fixed within two years on some 3B boilers. They were replaced by flexible stays. Between the stay head on the outside of the boiler and the shell is a washer with ridges, as shown in Fig 21. I do not have its formal name, but let us call it a rocking washer. It allows the stay to cant a few degrees in any direction, sufficient to eliminate the worst bending stresses. Simple, but it works well even under the dirty water conditions in the boiler. More judicious use of these and other types of flexible stays in the Cls 25 led to vastly reduced maintenance costs.

A further improvement was to get rid of the curved Wooten firebox: under the steam pressure it tends to straighten, leading to additional stresses in the firebox

21 inside plates and in the boiler shell. These improvements far outweigh the small loss in combustion volume above the arch.

Further strength improvements were made by more use of welded joints - the quality of welds had reached the stage that the welded joint was stronger and more reliable than the overlap riveted joint. It is also lighter. The best example is the replacing of the solid and very rigid foundation ring (it is really a rectangle!) of the firebox with a U-shaped ring made from steel plate of similar thickness and welded to the boiler and firebox plates (Figs 18b & 20). It keeps to the same temperatures as the plates and has the same stiffness. Weight is saved, even though a cross stay was fitted between the two sides of the firebox. I can vouch for it that rapid changes in the cross-sectional areas of stressed members are highly detrimental to the long-term strength of the member - it becomes prone to fatigue failure. These changes were all steps in the right direction.

Moving on to the boiler as such, a combustion chamber was fitted, mainly to reduce the length of the boiler tubes, as was mentioned in Section 5.2. The length was reduced from 22’ 6” to 19’. It led to some tenfold increase in the life of the tubes without any difference in the boiler efficiency, as proven on a Cls 23 test.

The main differences between the 3B and Cls 25 boilers around the firebox are shown diagrammatically in Fig 18.

Regarding Tubes, the old practice of placing as many as practical small (2½” diameter) tubes in the lower two-thirds of the boiler barrel and the 5½” superheater tubes just above them has proven effective and was retained for the Cls 25. The number of tubes in the Cls 25 was increased as the boiler diameter could be increased slightly over that of the 3B (see the notes in the diagrams of Figs 7 & 10 for details).

5.5

Smokebox

The combination of the Blast Cap with the Blower around it in the bottom of the smokebox and the Petticoat plus Chimney aligned above them is the key to the good functioning of the locomotive (Fig 22). On 3211 the angle of divergence of the exhaust steam jet was 17 o as measured from the top of the blast cap to the neck (smallest diameter) of the petticoat/chimney, and 7¼ o in the chimney from the neck upwards. This should be taken as a good guideline, but the best angle does vary a bit with size and the distance the jet travels. I must leave it to the likes of “MM” or THE Test Engineer during my time, Nick Bestbier, to do the full calculations for the new big loco you want designed! I do know that if the angle is correctly chosen and the loco lags a bit on steam output, the best cure is to fit four ‘tips’ onto the top of the cap (Fig22) to give the steam jet a bigger surface area to drag in the smoke without disturbing the jet angle and to slightly increase the ‘back pressure’ of the steam - increased jet energy and speed. Loco 3211 had four tips of 5/8” x 1-

22 3/8” which reduced the cap area by 8%. How do I know? Check Fig 23 taken at Laingsburg.

My dad told me about his experiences with blast caps and chimneys, way back around 1926. He was called out to check one of the early Garratt engines that were poor steamers. The locals had fitted a smaller blast cap to get a stronger blast, but to no avail. “MM” borrowed a fishing rod (was it in Natal near the coast?), tied a bit of old rag around the tip, and let the driver start her at full power. As he put the rod’s tip next to the chimney top, the rag was torn off - and sucked into the smokebox! The cap was so small that the exhaust jet never touched the side of the chimney. Fitting a bigger cap with tips solved the problem and raised “MM”s reputation a lot.

One is inclined to relate a sharp bark from a loco as a symptom of a good steamer.

Not always. The 15CA we tested at Laingsburg had the same size cylinder and wheels as the 15F but the grate size was only 48 sq ft. Consequently a much smaller chimney and cap was fitted to overcome the increased flow resistance through the grate and boiler. You could hear the bark from miles away, and she kept her boiler pressure, but the maximum power output was far smaller than that of the 15F or 23.

Char Steam locomotives can be nasty neighbours to forests and dry fields due to the burning coal particles or char blown out, leading to fires. In an attempt to reduce this risk, the so called American Front End is fitted to all smoke boxes (Fig 22). The back Diaphragm Plate and the lower Table and Breaker Plates help to break up the larger burning particles, and the deflector also directs a strong smoke flow to the bottom front of the smokebox where char otherwise tends to accumulate.

Lastly, the smoke plus remaining char has to pass through the front spark arrestor plate which is perforated with holes of about 1/8” x 3/8”. Their total area is about 20% more than the area of the boiler tubes so that the extra resistance to flow is relatively small.

The main problem that does sometime happen is that the plates deform when overheated, particularly if the smokebox door does not seal perfectly and air leaks in setting fire to unburnt gasses and char. Big gaps open in the spark arrestor and large burning particles escape up the chimney. The extra heat warps the smokebox door even more, so the problem keeps getting worse. (I was going to say that it snowballs, but somehow that does not sound suitable!)

5.6 Safety and Other Ancillaries 5.6.1 Boiler Steam Pressure Gauge The gauge is mounted in front of the driver and fireman (Fig 24), with a red line drawn on the dial at the prescribed maximum boiler pressure. The gauge is regularly checked and adjusted by the maintenance staff and then sealed.

23

5.6.2 Safety Valves At least two safety valves are fitted onto each boiler. A large boiler with little space left on the top such as the GMAM, has four. They are set and sealed by the maintenance staff; one blows at the set boiler pressure and the next at one or two lb/sq in higher. This makes it clear to the footplate staff that when the second safety valve also opens, they are steaming well above the mark, encouraging them to take other steps such as to cut in the second water injector.

Older locomotives were fitted with Ramsbottom valves (Fig 25a), but they were succeeded by Ross-pop valves (Fig 25b) which became the standard. They were already in use on the first cls19 in 1928. Ramsbottom valves have the disadvantage that they are slow to open and only close when the boiler pressure drops to about 5lb/sq in below the opening pressure. This may stall the locomotive when starting a heavy train, and leads to a considerable loss in energy.

The Ross-pop valve does not have these problems. It makes use of the principle that when the valve starts to open, when the pressure on that part of the valve which is exposed to the boiler just exceeds the valve spring load, it immediately exposes a further area on edge of the valve to the full steam pressure, and the valve opens rapidly with a ‘pop’ sound, hence the name. The steam then jets out through the many holes in the valve head reaching the top of the valve where it blasts out through the six or so holes in the top cover. It lifts the cover with the spindle, as well as the actual valve at the bottom, allowing a large flow of steam to occur rapidly. The rate can be adjusted by the maintenance staff (and sealed!) by closing one or more of the top holes. When the boiler pressure drops to a fraction below the set boiler pressure, the reverse takes place and the valve closes with another ‘pop’.

The Ross Pop valve has proven itself and remains the standard safety valve in spite of its higher manufacturing cost.

5.6.3 Water Gauge Column It is critically important that the footplate staff should at all times know where the water level is in the boiler. The water level has to be ‘managed’. There must always be at least a few inches of water above all parts of the firebox crown to prevent overheating of the crown plate and melting of the fusible plugs (See Section 5.6.4). However, it does not help to increase the water level to say a foot above the plate, for then the boiler is almost full and the surface area of the boiling water has reduced so far (due to the cylindrical top of the boiler) that the steam tends to prime, ie the intense flow of the steam drags water with it. The superheat temperature drops rapidly. Some of the water may be carried through to the cylinders. In the worst case this can lead to the rapidly moving piston (up to 5 strokes per second) to bang out the cylinder covers or fracture the cylinder casting.

24 Water, unlike steam, is incompressible and at the end of the piston’s stroke the steam port is closed.

A complication which the driver has to keep in mind is that the level of the water shown in the water gauge relative to the water coverage over the crown plate depends on the locomotive’s position and how the steaming rate changes. For a Cls 23 locomotive going up a 1/60 gradient the gauge will show about 3” higher and after going over the top and drifting down the 1/60 downhill, 3” lower than on the level - a change of about 6” for the same amount of water in the boiler!

Standing on a curve which is canted (Fig44), will show about 6” difference between the two gauges. Another factor is that when the boiler is steaming hard the large number of steam bubbles in the water makes the water level rise and vice versa; lastly, braking hard leads to a drop in water level at the back of the boiler, ie over the crown. It needs a lot of experience to make all the right decisions!

Coming back to the water gauge, from the above it becomes clear why there is no red line to show what the correct level is and why there are two columns: one near the driver, and one near the fireman, as both help to keep the water at the right level for the given condition.

The column is essentially a pyrex glass tube fitted in a vertical position. It is about a foot long, connected top and bottom via cut-off cocks to the inside of the boiler (Fig 26). Under normal stationary and level conditions with both cocks open, the correct water height would be near halfway up the tube.

In view of the high temperature and pressure conditions, many safety features are included. Even pyrex glass is slowly but surely dissolved by boiler water, it may fracture unexpectedly at any time before the normal replacement period. A thick three-sided armour-plated glass shield is fitted around the column which shields the footplate staff from flying glass shreds as well as the water/steam outburst. The reducing and ball valves in the cocks should stop the flow, but sometimes they do not work well. I have not personally experienced such a failure, but I accept that sometimes all Hell is let loose, as everything is obscured by the steam cloud. The footplate staff dive out of the cab hanging onto the outside, until one of them can wrap a thick wad of cotton waste around a hand and reach in to close both cocks.

Thereafter they can slowly recover their wits and replace the column tube - the driver always has a spare on hand - but first they must regain control of the locomotive!

5.6.4 Fusible Plugs The Fusible Plugs (Fig 27) are screwed into the crown plate from the bottom. On the larger locomotives there are three: one at the centre back, the other two in the front, one on each side. This protects the crown plate under low water conditions, also under high or low gradient as well as cant conditions. The plug is filled with lead which projects into the boiler water. As the melting point of lead is 327ºC and

25 the boiling water temperature is about 200ºC, the lead will not melt, but if the water level drops below the top of the plug (ie with about ½” water still covering the plate), the steam cannot cool the lead sufficiently and it will melt: the steam jet will blast down into the firebox, enough to quench the fire in a standing locomotive but not on a running engine. However it will alert the footplate staff who knows they must get both injectors going and start quenching the fire. Failed in section again! But rather that than a boiler explosion when the crown plate overheats and implodes.

It must have taken someone quite a time - probably by trial and error - to get the proportions of the plug just right so that it does the job when it must, without too many premature failures. Another simple but effective device. They are renewed at every boiler washout.

Have there ever been any boiler explosions on the SAR? I have heard of only one case which happened on a locomotive in the Free State heading south for Bloemfontein with a goods train. It was late on a dark, stormy night in the pelting rain when they took water at Glen from the Modder River, scrambling back into the cab as soon as possible. At Bloemfontein they were unexpectedly diverted onto a sideline in a deserted yard and received a warning to put on the injectors then get out and run as far and as quickly as possible. Looking up into the firebox they saw that the crown plate was red hot and bulging already - they got out just in time. Apparently the storm had muddied the water that had been used to fill their tender at Modder River (!) to such an extent that a layer of mud settled onto the crown plate and became baked in position. It also choked the fusible plugs .The steam did not penetrate the clay layer sufficiently to warn them. One of those one in a million accidents. (The train after them at the water station had sufficient light to notice the problem and the loco plus station staff did some quick thinking to get the warning through).

5.6.5 Injectors Injectors are there to pump the cold feed water from the tender into the boiler under operating conditions - maybe not primarily a safety device but more part of the operating components; however, if they don’t work ----.

In Europe the feed water is pumped into the boiler with a piston pump, driven by a steam engine, but we have standardised on the injector which has only one moving part and already preheats the water to quite an extent, all in one operation.

In Figure 3 of a class S1, the stoker is leaning out of the window looking at the injector from which some steam is blowing to the rear. Fig 28 is a cross-sectional view of an injector. The components are all made of bronze. Injectors are mounted vertically downwards under the footplate, as shown in the figure, in the lowest position practical - the water from the tender must be able to flow down

26 under gravity Steam from the boiler and the water from the tender are fed to the top of the injector. The stoker can regulate the flow rate of each individually by controls in the cab which operate valves on the inlets. The steam flows from the inlet at the top through the steam cone which first converges, then diverges. This shape causes the steam to become a very high speed jet at a low pressure, so that it will suck the water into the annular opening and into the mixing cone, where the steam condenses with the feed water to form a hot water jet. The partial vacuum in volume A now sucks up the movable suction cone until it seals at the top, cutting off contact with the overflow pipe at left. The flow of water out of the injector stops and the fireman now knows that he has set his control valves correctly (that is what is happening in Fig 3).

But how does the water manage to overcome the boiler pressure? When the hot water jet leaves the mixing cone at B it is travelling at a very high speed. As it flows down the diverging delivery cone, the drop in speed (by a factor of about 6) leads to an increase in pressure by a factor of about 6x6, which is sufficient to force the water up the delivery pipe to the top of the boiler, open the non-return valve and overcome the boiler pressure.

There are helical vanes around the movable cone, but they are not there to spin the cone: their sole purpose is to keep the cone accurately aligned with the mixing cone. Straight vanes would lead to groove wear of the injector body and decrease its life. They have a lot of work to do; a Cls 25 can consume about 5000 gallons of water per hour.

5.7

Keeping the Boiler Clean Inside

We all know how the tea kettle keeps liming up and forming a dirty white sludge over the months - particularly with Karoo or dolomitic waters. The loco boiler has the same problem, but it is roughly 100 000 times worse. The SAR had a Section working on cleaning up the water before it was made available for the tenders, but it proved impractical to do it to the ideal limit. They tended rather to concentrate on making additives available to reduce the tendency for the boiler to prime (See Sect 5.6.3, first paragraph). So the footplate and shed maintenance staff had to take care of the problem - it would literally be fatal to have lime build-up on the crown plate. The following facilities were made use of.

5.7.1 Blowdown Valve At the lowest point on each side of the boiler a large valve is fitted which can release water from the boiler. These can be operated from the cab. To be effective, a strong jet must be released to carry with it the sludge and the saltiest water that accumulates there. The outlet is formed to blast out sideways. The driver must ensure that it is only used where it will not cause problems. It is quite a sight, as seen in Fig 29. It is used a few times per day. Obviously the injector(s) will also be on while the blowdown is in operation.

27 5.7.2 Washout of the Boiler In addition to the above, boilers need a thorough washout at regular intervals, every one to three weeks depending on the conditions. This is one of the big factors leading to low availability of the steam locomotive. The fire has to be dropped, the grate cleaned and the boiler cooled down before it is safe to open the many plugs screwed into the boiler at strategic places and drain the water. The boiler can then be inspected internally through these openings before the washout crew bring their high pressure hosepipes to flush out the remaining muck. Minor repairs can also be carried out, eg to leaking valves. Then the fusible and washout plugs are replaced before the boiler is refilled and started up as was described in Sect 4.1. A day or more is lost with every washout.

The question which has to be answered is could these problems be overcome by feed water treatment? It could only be possible with distilled water, as is done at the large power stations, but there the steam is condensed as part of the power cycle and the quantity of make-up water is minimal. The nearest we came to it is in the condenser locomotive Cls 25, where the exhaust steam was condensed to be re-used, but the make-up water was still Karoo water. Washouts could be reduced, but other maintenance problems outweighed this advantage and the condensers were all converted back to the non-condenser Cls 25NC in later years.

They were then no longer operating in the drier Karoo areas.

6 The Engine of the Locomotive Summary: Why reciprocating instead of rotating turbine engines? - Cylinders and pistons - Rods - Driving wheels - Control of the steam - Regulator and Walschaerts valve gear - Bearings and axle boxes - Frame - Coupling to tender.

6.1

Reciprocating vs. Turbine Engines

Question: “Why were turbines not used as the driving engines on our locomotives? After all, ESCOM uses them on all their power stations, manages to keep practically smoke-free fires going and produces electricity with something like 30% efficiency, in spite of the poor quality coal they use. You can get rid of the complex set of rods and slides to turn the wheels! After all, it was used in the 50’s or so in the USA” Yes, on a few engines for the hard run over the Rockies but not for long before they disappeared.

The answer lies in several drawbacks that become dominant if the ESCOM system is forced into a relatively small space on a loco which has to perform over the whole range from fast reverse to very fast forward. Firstly, the turbine has a very good performance at one fixed speed only: its power output and efficiency drops rapidly if the speed exceeds or falls below the design speed; moreover, it usually has a ‘critical’ speed a bit below the design speed at which a strong resonant vibration occurs - it must be accelerated through that speed to prevent damage. It is a no-no part of the speed range. As far as its high efficiency is concerned, much of it is due to a system where the exhaust steam from the high pressure turbine, is

28 allowed to expand through a very large turbine, which is many times as large as the high pressure turbine. The size of these two combined will be larger than the locomotive engine. The steam must also expand to a pressure well below atmospheric into a LARGE condenser sealed from the atmosphere. The condenser again has to be kept as cold as possible (below 20º C) by cooling water from the cooling towers. Remember the concrete )(-shaped towers, maybe 300’ high, at Arnot and other Power Stations? That’s them! Cooling down by a fan system as on the Cls25 condenser tender, is enough to regain the water from the exhaust steam, but you need far more than that to get the sub-atmospheric pressure essential for a high efficiency. Lastly, as far as the mechanics are concerned, the turbine needs to run at a high speed which means building in a large gearbox, with the possibility of changing gears as in a car (Say three-speed) AND with a reverse gear, as the turbine works very poorly in reverse. No go! In contrast, the reciprocating engine with a Walschaerts valve gear can develop full power (within the limits of the boiler capacity) over the whole range of speeds from backwards to forwards.

What is more, the changes can be made effortlessly and smoothly without steps, with one control lever.

The last alternative would be to go for a turbine - electric generator system, exhausting to atmosphere, with electric motors on the driving wheels: rather like the Diesel-Electric locomotives. It would probably lead to a locomotive mass of about 1½ times that of the already overweight standard reciprocating locomotive (Check Tables B1 and B2 in App B), which is enough to discourage any engineer.

It was never tried as far as I know.

I am not surprised that the turbine locomotive did not make the grade and that that Old Man Piston was retained for two centuries.

6.2

Pistons and Cylinders (Fig 30)

The Piston (A), bolted to the Piston Rod (B), reciprocates (ie moves backwards and forwards) in the Cylinder(C). Our surviving locomotives were all built with one pair of outside cylinders per engine. The few that were tried with an additional cylinder or two between the frames were found to be impractical and soon disappeared (See Section 3 and Fig 13).

The cylinders are double acting, ie the piston is power driven at both the front and the back strokes, in contrast to your car’s pistons which are only powered on the down stroke, and that only at every second rotation of the crank.

With one pair of cylinders the locomotive can therefore be started from any position provided that the Driving Wheel Cranks are positioned at a quarter turn (90º) to each other - see also Section 6.4 and Fig 34.

The basic double acting steam cycle is briefly as follows: Let us start with the piston in its full front position (In Fig 30 it is shown in the midstroke position ; the

29 front position is shown in the diagrammatic sketch Fig 31a, with its corresponding Connecting Rod (Also Fig 30D) and Crank Pin (Fig 30 I)positions). The Front Port is admitting live steam into the front part of the cylinder which pushes the piston towards the back past the middle position (Fig 31b) with a force as high as 50 tons compression on the piston rod until it reaches the end position (Fig 31c). During this period the volume behind the piston, ie to its right, has had the steam port open to the exhaust and its pressure against the piston has been a small fraction of that on the front side. The Connecting Rod has also in the meantime forced the Crank Pin and the Driving Wheel round half a turn. The cycle now reverses: The front steam port is now open to the exhaust and the back port to the live steam.

The Piston Rod Gland (Fig 30E) now plays its part to prevent the live steam from blowing past the piston rod into the atmosphere. The piston is forced to the front ie to the left, the piston rod and the connecting rod are in tension to nearly the same force as in the first part. (There is a small loss in load due to the reduction in surface area of the piston by the piston rod). The wheel keeps rotating anticlockwise (Fig 31d). When the piston reaches the end of the back stroke the cycle is complete and the sequence starts again as in Fig 31a - except that the engine is now one wheel rotation further down the line.

Further refinements in the cycle such as live steam Cut-off before the stroke is complete to allow expansion of the steam (already shown in Fig 31) and Precompression will be dealt with later when the valve gear is described on p24.

The piston is usually made of steel with an almost bell shaped disc, the purpose being to reduce the thermal stresses when it is suddenly exposed to superheated steam. The outer sleeve is of cast iron for less wear on the cylinder liner. In addition its bottom is extended to form a slipper to reduce wear still more. In Europe, a more elegant solution was to extend the piston rod through the front cover where it could be supported - but another gland had to be fitted to prevent steam leakage.

Cast iron piston rings are fitted into grooves around the piston’s outside to limit the leakage of steam from one side to the other. They wore rapidly and were part of the replacement program when the locomotive came for its 15M running repair ie every 15 000 miles. An improved design was used for the cls 25, which lasted much longer, but I do not have the details.

6.3

Rods

We have already had an introductory glance at the most important rod, the Connecting Rod. We remain indebted to Trevithick and Stephenson who broke away from the cumbersome planetary gear system as used by Watt of converting reciprocating motion to rotation, by making the connecting rod do the work.

The connecting rod is coupled to the piston rod via the Crosshead (Fig 30F): the back end of the piston rod is tapered, fitting neatly into the crosshead front end

30 where it is locked in position by a flat tapered locking pin. To remove the piston for maintenance, the front cylinder cover is removed and the crosshead locking pin extracted, where after the piston with its rod can be pulled forward through the gland opening and out. Just behind the piston rod joint is the round Gudgeon pin (Fig 30H), inserted from the inside through the Small End of the connecting rod and locked on the outside. A smaller diameter part of the pin projects a few inches further to carry the Union Link (Fig 30G), which will be dealt with in the next section.

The crosshead’s function is to keep the piston rod dead in line with the centre of the piston plus cylinder. It has to resist the high vertical force acting on it of 15% of the force on the piston rod, ie up to 7 tons at midstroke. This vertical force is caused by the angle of the connecting rod’s force relative to the piston centreline.

At the same time the crosshead is rubbing backwards and forwards against the Top Slide Bar (Fig 30S) at a speed of up to 25 mph. (With the engine in reverse, it will be forced downwards onto the lower slidebar). So the crosshead is made of steel, with the steel shoe between the slide bars given a thin layer of white-metal both top and bottom for a better bearing surface. It is well lubricated but with all the dust swirling around, it often overheats, as we experienced at Laingsburg - see Figs 32 and 33 - and the white metal melts. The loco has to drop its load, and then run slowly to the nearest loco depot, with plenty of cylinder oil on the slidebar.

Whence the name Crosshead? On our older locomotives, eg the Mallet in Fig 12, the whole crosshead fitted between a top slide bar above the centreline and a bottom slide bar below the centreline. Viewed from the side the crosshead then had an Xshape, hence the name. This design was repeated for the Cls 25. The symmetric shape of this type of crosshead eliminates inertia bending stresses on the piston rod which are found during high speeds with the Fig 30 design. It is still shown in the drawings of Fig 10, but the engines were converted back to the 1930/50 design after only a short period of service, as can be seen in the photographs in Fig 10 and 11. I don’t know why.4 As mentioned before, the Connecting Rod transfers the piston force to the driving wheels of the engine. Its Big End fits around the Crank Pin (Fig 30 I) which is forcefitted into the Driving Wheel (Fig 30J). Connecting rods are big brutes - they have to be, taking into consideration the high forces they have to transmit (Up to 35 tons on the Cls 19 and 50 tons on the Cls 25, oscillating between tension and compression during each stroke, up to 5 times per second). More about these stresses are dealt with in section 7.1.

In Fig 34 the positions of the crank pins in a driving wheel can be seen. The crank pin on the right hand wheel is always leading when running forward, on all SAR engines. The bearing between the big end and the crank pin is subject to high but varying loads and high rubbing speeds, which makes for difficult bearing conditions. The normal design was to fit a floating bush (Fig 35a) between rod and 4

See Les Pivnic’s comment - HBH

31 pin. The series of chamfered holes in the bronze bush were filled with hard grease, regularly augmented by the driver. The grease came in sticks about ¾” diameter, forced into the bearing with a cantilever grease gun (Fig 36). In spite of these efforts, overheating of the big end bearing happened too often, as seen in Fig 36. The problem was only solved on the Cls 25 by fitting Timken Double Taper Roller Bearings (Fig 35B) instead of the floating bush.

The repetitive high stresses on the connecting rod under hard running conditions, occasionally led to their failure, usually close to the small end. One can imagine how the rod front point would fall down and jam into the track sleepers, with the possibility of throwing the locomotive onto its side. To prevent this, a form of Safety Strap was often fitted to engines (See eg Figs 1 & 6) to catch the broken rod before it stuck into the track.

6.4

Coupled Wheels

In Stephenson’s time, the engine could pull its load with only one driving wheel set, but it soon became clear that more would be needed as loads increased. It became common practice to fit more wheel pairs of the same size Coupled to the driving wheel. Figures 1 & 6 show three Coupling Rods connecting the driving wheel to the other Coupled Wheels on a so-called Eight Coupled engine. They share the traction force equally with the driving wheel - they all pull together, or slip together. The front and the back coupling rods are connected to the intermediate coupling rod with Knuckle Pin Joints to allow slight relative vertical movement within the limits of the spring suspension system dealt with in Section 7.

There are limits to the number of wheel pairs that can be used. If 5’-0”d (1524mm) wheels are used, four coupled wheel pairs are the maximum which can comfortably negotiate the sharpest SAR curve of 300’radius. At 5’-3” d, the class 23 could just squeeze round the curve, but the additional lateral loads on the frame contributed to its early failure. If a ten-coupled wheel arrangement is used, the wheel diameter would need to be around 3’-8”d, which means it, would not run well at speeds over about 40mph - too low for main line working. The experimental Cls 18 locomotive (ten-coupled) used 4’-9’’d wheels, of which two pairs were flangeless: she derailed regularly, was rarely used, and was soon scrapped. In any case, if a ten-coupled main line engine is to be used to the full, it would need to have bigger or more than one pair of 24”d cylinders. There is really not enough room on the outside of the frame for bigger cylinders, so that a third cylinder would have to be fitted between the frames, as was tried on the class 18 without success. The only alternative that was tried and worked well within limits was the GMAM Garratt which with its auxiliary water tank kept the load on the driving wheels a bit nearer constant. Its tractive effort is 134% of that of the Cls 25NC, but its limitations lay in the 4’-6” driving wheels which made it too slow for Karoo main line working. An engine should not work at speeds greater than a mile per hour for every inch of the wheel diameter ie 54 mph for the GMAM .

32 As mentioned above, the Crank Pin Spacing of 90º. (It needs a special boring machine with a hefty support for the heavy wheel to do the machining known as quartering, in the workshops) does enable the locomotive to start from any position. That, plus the connecting rod angularity (a maximum at midstroke), does however lead to several problems, ie • The tractive force on the track is not constant. At slow speeds it varies by about 30% between maximum and minimum at constant steam feed pressure in the cylinders. It calls for some expert juggling of the regulator by the driver on starting to reduce the effect to a minimum. The effect reduces as the speed increases.

• The weight of the crankpin plus the connecting rod big end plus the coupling rods and their pins, is out of centre on the wheel. It has to be balanced by a counterweight on the corresponding wheel and another small counterweight on the other wheel of the wheel pair, because the counterbalance weight has to be fitted on a slightly different plane than the connecting rod. (The mechanics of this exercise becomes quite complicated and will not be dealt with in detail.

Engineers can read all about it in Ref 5, Appendix 2. I will be happy to supply copies on request). The out of balance weight is about 1000 lb per side for the Cls 23 locomotive. With correct counterbalancing this potentially disturbing effect is eliminated at all speeds.

• The backwards and forwards reciprocation of the pistons, piston rods, crossheads and the front part of the connecting rods causes an oscillation of the engine. The mass is about 1300 lb per side on the Cls 23, stroking at 28”. The sum effect of both sides is about 1800 lb at 28” stroke for the two combined. If left unbalanced, it would lead to a backwards and forwards oscillation of the 115 ton (230 000lb) locomotive (less tender) of 28” x 1800 ÷ 230 000 = approx 0, 2” stroke, which is not acceptable. It is not practical to fit a horizontally stroking counterbalance to eliminate this oscillation, the best that can be done on a two-cylinder engine is to fit a further counterbalance weight opposite the crankpin which will reduce this oscillation, but it leads to a vertically oscillating force, called the hammerblow, onto the track. It is not really felt on the locomotive, but the additional force on the track can cause problems to civil engineering structures. The civil engineers limit this additional load to 1½ tons per axle at 45 mph, which means that the oscillation can be reduced only by a quarter, ie to 0,15” stroke.

• There is one further step that can be taken and which proved practical, that is to couple the tender and engine so tightly that as far as the backwards-forwards oscillation is concerned, they act as one body. The details will be dealt with later, but with this coupling of the Cls 23 to its 107 ton tender, the oscillation reduced by one half to about 0,08”, with which we can live. (Where an engine is fitted with three or four cylinders, the abovementioned horizontal oscillation can be greatly reduced and the hammerblow is small.)

• The next problem is caused by the sum of the two connecting rod forces being alternatively on the right and the left side of the engine. One has to keep in mind that the high pressure steam in the cylinder not only tries to push the piston, it is also pushing the corresponding cylinder cover with the same force

33 in the opposite direction. This tends to slew the front of the engine once to the left and once to the right per every one revolution of the driving wheels. On the cab of the locomotive one can feel and even see this movement if you look forward along the track. It is most noticeable at slow speeds when the locomotive is pulling hard, and it gradually reduces as the speed increases and the tractive force becomes smaller. (To the applied mechanics experts: yes, I know this is a bit of a simplification, but I can vouch that the slewing did take place on the Cls 23 - not normally on the Garratt.) • Lastly, there is the unbalanced vertical force of the crosshead onto the slidebars, a maximum at midstroke, reducing to nil at the ends of the stroke when the connecting rod is in line with the piston rod. When running forward, the force is upward both on the forward and on the backward stroke. Due to the quarter circle difference in the positions of the left and right crankpins, we now find a force of up to 7 tons trying to lift the front of the engine alternatively on the right and the left side near the front, not twice but four times per revolution of the driving wheels. As the force is only a fraction of the previously mentioned slewing force, the effect is much less but still noticeable at slow speeds. What one feels is a small tendency for the locomotive to cant (to roll from side to side), at twice the rate of the slewing action. I was not aware of any tendency for the locomotive to sway up and down, the loco wheel base length of 37’ is too long for those forces to have much effect, whereas transversely the alternate vertical forces are at twice the span of the restraining wheel support on the rails.

Well, let us try to simplify matters by saying that a locomotive like the Cls 23 has a most interesting, I would even like to say fascinating or creative quality to its movement, particularly when it is starting to pick up speed - it is not just a smooth pulling away which one finds with an electric locomotive. In a sense it has something challenging to it, like the movement when riding a horse up an incline in comparison to driving up in a modern smooth running car.

To be more mundane, the motion of the locomotive pulling at slow speeds has something in common with a goose waddle as viewed from behind, but not so extreme. The goose has the sideways slewing waddle and the forward and backward oscillation, but to this must still be added the double frequency roll which is unique to the steam locomotive.

6.5

The Control of the Steam

The locomotive, like the motorcar, has two regulating mechanisms to control the power output at a given speed. The motorcar’s accelerator (petrol pedal) controls the energy feed rate, ie the petrol; the corresponding function on the locomotive being done by the Regulator which controls the steam flow rate to the cylinders and, moreover, can stop it altogether. In addition, the locomotive also needs a control of the feed rate of the primary energy source, ie the coal, by the fireman directly by his shovelling rate, or by adjusting the mechanical stoker speed.

34 The function of the car’s gearbox is taken over on the locomotive engine by its Valve Gear. It is far more flexible than the gearbox, as it has a steplessly variable control from ‘hard forward’ through neutral to ‘hard reverse’, regardless of the speed at which the engine is running.

In both cases operating the brakes is a separate function which will be dealt with later.

6.5.1 Regulator The Regulator Valve on older locomotives is a large valve in the dome of the boiler.

In the locomotives being considered, several small valves working in parallel are fitted into the header in the top of the smokebox (Fig 14). In both cases, control is by a lever at the driver’s left hand, coupled by a long rod to the valve.

The valve shown in Fig 37 is the type used on the older locomotives, but the principle is the same on the modern locomotives with up to 8 smaller valves which open one after the other as the regulator lever is pulled open. The control is better and requires less brute force by the driver. The valves are of the Double Beat type, ie there is the same full boiler pressure on both ends of the valve when closed, making it possible for the driver to open the valve gently without extra power assistance. Quite simple but effective. It does mean that both valve faces have to be carefully lapped in so that both seal simultaneously, but that seems not to be a problem.

It has been found expedient to regulate the saturated steam before it passes to the superheater elements. It is safer if leaks develop in the elements as the regulator can shut them off and the valve life is also increased. The time delay for the first steam to reach the cylinders is negligible. Steam locomotives don’t run in 100m sprint competitions.

6.5.2 Valve Gear The function of the Valve Gear (Fig 30) which controls the Piston Valve (Fig 30 I), which in turn opens and closes the Steam Ports (Fig 30J) to and from the cylinders, is difficult to describe on paper; it is best dealt with by demonstrating the movements on a scale model. To this end, a model of the Walschaerts Valve Gear was built by the author (See Fig 38). The scale is approximately 1: 10, which is adequate to show the piston valve function and how it is influenced by the Cut-Off settings. What follows is more of an explanation of what is needed than the details of how it is achieved.

To expand on the summary given in Sect 6.2, p 19 - 20, on the action of the steam in the cylinder, the valve gear has to perform the following functions (For convenience, we will look only at the front part of the cylinder - Fig 39a - with the engine starting off with the piston in front dead centre (FDC) in forward ‘gear’;

35 rotation therefore anti-clock). The figure is not to scale so that the port opening can be clearly shown: 1. (Stroke 0%. Rotation 0º); the port is already fully open to steam inlet; it started to open up just before FDC. Port fully closed to exhaust.

2. The best use of the steam is to ‘cut-off’ the inlet along the stroke, somewhere between 20% and 75% of the stroke. Steam, in contrast to water, can expand after cut-off and still convert much of its energy into piston force. In doing so, it loses much of its heat which helps to limit the pressure drop. However, a cut-off at about 30% of stroke is the smallest practical setting, as below that the outlet pressure is too low for a good exhaust and also the engine starts ‘banging’. If even less power is needed, the steam inlet rate is best reduced with use of the regulator. The valve gear is so designed that it only starts opening at about 20% cut-off. A cut-off of 75% would only be used to start the train, together with careful control of the steam with the regulator. For this description, a cut-off of 50% (Midstroke, Fig 39b & 31b) was chosen - it is well within the normal working range. At this point the piston valve must quickly close the cylinder port to the inlet steam but not yet open it to the exhaust. This is why a valve head must be at least twice as long as the cylinder port opening. It should be noted that when the piston is in the midstroke position, the crank pin is still a little distance from the bottom dead centre due to the angularity of the connecting rod. In the Cls 23 it is only about 2º - nothing to worry about.

The stroke is therefore 50% and rotation 88º in this case; the steam starts to expand - there is no opening to inlet or exhaust.

3. (Fig 39c, apr. 95% stroke, 160º rot.) The steam expansion comes to an end the outlet to the exhaust is starting to open. The pressure, already low, drops further to the blast cap pressure, which depends on the steaming rate. An average pressure of 6 - 8 lbs/sq in. is common for normal working conditions. (The pressure varies considerably at slow speeds - there are four ‘beats’ per wheel revolution - but as the speed picks up the variation becomes very small) The opening to the exhaust is maintained as the piston reaches the end of its stroke (BDC, rotation half a turn = 180º) and carries on with the return past midstroke (rot. just past top dead centre) until it has completed about 75% of the return stroke (rot. about 300º). The pressure average remains low and equal to the blast cap pressure.

4. (Fig 39d, 75% stroke, 300º rot.) The port closes to the exhaust, while the inlet remains closed. This is the start of the pre-compression part of the cycle. In this part, the remaining steam is compressed to a pressure close to boiler pressure and the temperature also increases. It serves two purposes: From the mechanics point of view, the increasing pressure helps to retard the piston and rods which is necessary at the end of the stroke, reducing the load on the bearings. From the thermodynamics side, bringing the remaining steam to boiler steam conditions just before the boiler steam inlet opens, improves the energy efficiency of the cycle.

5. Just before the end of the return stroke, the port is opened to the boiler steam and we reach the start of the cycle as described in Point 1.

36

As the cylinders are double-acting, what happened in the front of the cylinder has to be repeated at the back of the cylinder, but half-a-cycle later, ie about 180º rotation later. This is ingeniously managed by repeating the front piston valve/port details at the back head of the piston valve, but as a mirror image of those at the front. It automatically leads to the required result.

6.5.3 The Piston Valve and Rod The piston valve (Fig 30 I and inset of I x2 scale) consists of two cylindrical steel Heads with cast iron outer Bull Rings, bolted onto the Valve Spindle rod. Their position along the rod can be slightly adjusted with shims during assembly to match the Steam Ports machined into the Steam Chest Liners. The usual proportions are such that with the piston valve in the centre of its stroke, as shown in Fig 30, the outer edges of the two heads should be in line within 1/16”with the outer edge of the steam port, when the engine is at its normal operating temperature. I was told in the SAR Workshop, Pretoria, that the rod expands about 1/32”in length when it reaches that temperature and this should be taken into consideration during cold assembly and final adjustment of the valve gear. This gives one some idea how precise one has to be when working on these big brutes!

This design has one big advantage over the older flat sliding valve (not shown) and that is that the inlet steam is between the two heads: the pressure load of about 22 tons outward on the two heads is balanced by the rod between them. No big force is needed from the valve gear to move the heads backwards and forwards. Leakage of inlet steam past the heads to the exhaust is limited by a set of three or so cylinder rings fitted into grooves on the bull ring. A gland is also fitted around the rod where it leaves the steam chest to be pinned to the Combination Lever (Fig 30K) at the Valve Spindle Crosshead (Fig 30L).

6.5.3 Managing the Valve Spindle Movement If we again look only at the front part of the cylinder with the engine running forward, we note that three of the four port opening or closing functions occur close to the beginning or end of the stroke and that they are at fixed positions relative to the wheel rotation. (Only one function, the closing of the inlet steam, needs to be adjustable.) It follows that one of the ‘fixed’ drives needs to shift the whole valve head assembly close to the front of the liners when the piston is at FDC, and close to the back of the liners when the piston is at BDC. This is the function of the combination lever which is coupled to the crosshead and therefore is exactly synchronised with the piston travel.

What is still needed is a drive that can move the valve heads still further from the position where they were brought by the combination lever, to open and close the ports as needed. The drive mechanism that can do this is the Eccentric Crank (Fig 30M), which is bolted to the protruding end of the crank pin (Fig 30 I) - it is the only place it can fit without fouling the connecting and coupling rods. Its Crank

37 Pin trails the connecting rod crank pin by approximately 90º in forward motion the exact value is determined in the Locomotive Design Office on a Model of the Walschaerts Valve Gear. All the critical items are adjustable which enables the best design to be established by intelligent trial-and-error. The move started by “MM”, was to space the crank so as to obtain as large a ‘throw’ as practical from the eccentric crank pin. This makes for rapid opening and closing of the steam ports which improves power and efficiency.

This drive needs to be ‘managed’ to, firstly, enable the cut-off to be adjustable by the driver. This is where the Expansion Link (Fig 30N) comes into play (or rather ‘work’). It was already used be Stephenson around 1825, but his link was driven by eccentrics which cannot easily supply a large throw, so his gear became obsolete on the SAR in about 1910 when larger locomotives were needed. The first local locomotive with Walschaerts valve gear was introduced around 1896 on the NZASM with the ‘46-tonner’ class from Holland - the Continent started using this Belgian design long before the British could be converted from their traditional Stephenson Link Gear.

How is the cut-off adjustment done? The expansion link is supported by centrally located pins from the frame, around which it can swing - clockwise while the driving wheel rotates from top dead centre to bottom dead centre and anticlockwise while the wheel rotates further from BDC to TDC. In the expansion link there is a curved slot into which is fitted a Die Block, which can slide up or down the link slot as the Radius Rod (Fig 30P) is moved up or down by the driver. The drawing in Fig 30 shows the valve gear in the central position where the action of the die block is not shown; refer to Fig 38 of my model which shows the valve gear set at about 60% cut-off in forward gear. It shows how the bottom of the expansion link is in the full forward position, the die block is halfway down the expansion link slot and that the valve spindle is pushed far forward so that front valve head still has the steam port open to the boiler steam while the back valve head is open to exhaust.

Managing the cut-off is simply done by lowering the die block with the lifting link to obtain a longer cut-off.

The second management function that is needed is to be able to run in reverse.

This is done by lifting the die block past the centre to the upper half of the expansion link: again, the further away from the centre the die block is lifted, the longer the cut-off.

Finally, some further observations on the proportions of the valve gear. Refer to Fig 30 where the valve gear is in neutral and the piston at midstroke: the valve heads are now dead central; the combination lever needs to be exactly vertical.

The aptly named radius rod length from pin to pin centre must be equal to the radius of the expansion link slot. When the piston is at the end of a stroke, and the

38 die block is moved up and down, the top of the combination lever must not move horizontally ie the valve heads must stay in their position.

A last point is that as the valve gear has of necessity to be on a plane further out than the connecting rod and the cylinder centre, the valve spindle centreline is also about 6� outward of the cylinder. This restricts the diameter of the valves to about half that of the cylinders otherwise the steam chest would foul the loading gauge.

6.5.5 Cylinder Protection under Running Conditions Under running conditions other than pulling the load, further devices are needed to ease the motion and prevent damage.

On starting from cold, the first steam to enter the cylinders is partially condensed by the surrounding metal and the cylinders, etc contain air. To prevent damage by compression of the water at the end of strokes, Cylinder Drain Cocks at the bottom of the cylinders and at both ends can be opened from the cab. They are opened as the locomotive starts (or if priming of the boiler is suspected), leading to clouds of steam erupting from them for the first few turns of the wheels. Quite a sight!

When the locomotive coasts downhill, other devices come into play. On the outside of the cylinder steam chest at centre, a large Snifting Valve is fitted. It is a valve which closes when steam under any pressure is in the steam chest.

However, when the locomotive coasts downhill, the valve gear is put into full forward gear and the regulator is closed. The pistons now act in suction for part of the stroke and would pump in smoke and trash from the smokebox, were it not for the snifter. It opens to the outside air if the pressure drops below atmospheric and brings relief.

The two Bye-pass valves on top of each end of the steam chest have an additional function, ie they automatically relieve the excessive pressure built up by the compression stroke of the coasting locomotive.

The last addition is the Drifting Valve operated by the driver. It allows a small amount of steam with its quota of oil to be released to the cylinders, usually used when drifting. The main function is to keep feeding some lubricating oil to the moving pistons and to prevent the cylinders from cooling down too much. Careful drivers also use them shortly before they start with the drain cocks open after a long halt, to preheat the cylinders. I have even experienced it used to start a passenger train smoothly.

6.6

Frame, Suspension and Curve Handling

6.6.1 Frame The function of the Engine Frame of the locomotive is to keep the various moving parts in their correct position even under the high forces experienced under

39 running conditions. Before 1930 most of the SAR locomotives had Plate Frames (Fig 40a) made of two steel plates about 1” thick and maybe 3’6” high, bolted to spacers to keep them at the correct distance apart. Cylinders were of cast iron bolted onto the frames. These frames were adequately stiff in the vertical direction but were too flexible in the transverse direction, ie to resist the forces around curves, particularly for heavier and longer locomotives developed from about 1925 onwards.

Bar Frames (Fig 40b) now took over. They were machined from about 5” thick bar steel, maybe 2’ high. The advantage was that there was more room for a larger boiler, firebox and cylinders, and that the coupling force was now in line with the centre of the frame - no vertical bending. But the cylinders, etc had still to be bolted to the frames. A real disadvantage was that now the vertical stiffness proved too low, but that problem was well solved by fixing the boiler to the frame as shown in Fig 40b. The front of the frame with the attached cylinders was firmly bolted to the smokebox, but the firebox rested on slides which accommodated the expansion of the boiler of about 3cm from cold to hot. Along the main part of the frame it was attached to the boiler by vertical support plates which could absorb the expansion with little stress but gave firm mutual support in the vertical direction between boiler and frame, leading to an extremely stiff vertical assembly.

The final development was the introduction of the Cast Steel Frame (Fig 41), a superb solution made possible by the development of the technique by the General Steel Castings Corp. in the USA during WW2, to cast war tanks in one piece. The system has big advantages: because the steel can be placed in any position and any thickness, an extremely light but strong and rigid frame can be made which incorporates the cylinders, steam chest, smokebox saddle, axle box horns and the cross stays all in one piece. They were introduced with the Cls 24, used on the Cls 25 and its condensing tender, as well as the GMA/M. They gave excellent service.

6.6.2 Axle box Guides and Suspension The Axle boxes of the coupled wheel sets fit into the Horn gaps (Fig 40b) of the frame. The axle boxes are subjected to backwards and forwards forces by the piston and cylinder, which they need to transmit to the frame with as little ‘banging’ as possible. At the same time they must be able to move vertically where the track is uneven, eg over points or when the locomotive cants round a curve. It means there must be a little play between axle box and frame and that wear will take place. To provide for these demands, adjustable Shoehorns much broader than the horn are fitted to the frame as shown in Fig 42. An American design of a spring-loaded self adjusting shoe horn was successfully tried out on 15CA No 2828 and was subsequently used on all the Cls 25 engines, eliminating regular adjustment by the running shed staff.

40 A clamp, called a Hornstay, is fitted under the horn to close the gap, thus preventing the axle box from dropping out under extreme conditions, but more importantly, to strengthen the frame against vertical bending.

In the modern motorcar, an independent spring system for each wheel is taken for granted - the exact opposite works best for the locomotive. Why? Firstly, the maximum wheel load prescribed from the track’s point of view is critical - only a small fraction of extra load will lead to considerable extra wear, particularly when negotiating points which are inherently bumpy. So the demand is that if there is a slack or a bump in the track, ensure that the change in wheel load is spread as far as possible to the other wheels. This led to the introduction of the Compensated Spring Gear (Fig 43). Each axle box has its own spring, but the springs are not directly attached to the frame: they are hung by Spring Hangers from Compensating Beams which in turn are supported at their centre by the frame. The system is even extended to the bissel bogie under the firebox. Only the first and last hangers’ ends are pinned to the frame. If any wheel rides over a bump, most of the extra spring compression is transferred and distributed to the other wheels, thus limiting overloading onto parts of the track.

Note however that the compensation does not extend from one side of the locomotive to the other: Modern locomotives are already prone to roll due to their high centre of gravity and a very large overhang over the track: a 10’ broad loading relative to a 3’-6” track gauge. Cross Compensation would make the roll much worse

6.6.3 Negotiating Curves One of the most exciting events when one first joins the driver and fireman on the footplate is when the locomotive has picked up a nice turn of speed along the straight and heads for the first fairly sharp turn to the left. You are behind the driver on the right and as the curve comes close he shouts “Hou vas!” and suddenly the track disappears to the left - but the locomotive is still charging straight forward- - - . OH NO! WE are going to derail - I knew he was going too fast. Then Bang! The front of the locomotive swings hard to the left and disappears from your sight as you get flung to the right and hang on for dear life to the handrail. Phew, we made it after all, Praise be to God! By the time it has happened ten times you take the curves hands free and wonder what all the fuss was about - well, not quite, it will always be exciting.

So how does it all work - how can you fit a locomotive with a 37’ long wheelbase, of which 16’-6” (the four coupled wheel pairs) is fixed, onto a sharp curve? After all, on the 300’ radius curve, the sharpest your Cls 23 will encounter regularly on the Hex River Pass, the curve will be 7” away from a 37’ long straight line (the engine wheel base), and 1½” away from the line between the first and last coupled wheels. The answer is, it won’t fit, (Fig 44A), unless you do several of the things listed in Fig 44 B.

41

Let us first look at the locomotive: a) The Front Bogie and the back Bissel Bogie are made to shift sideways. The front bogie is kept in its central position on a straight track by two springs attached to its turning pivot and supported at their ends to the frame. When the bogie enters the curve, it turns enough to keep the wheels in the right direction, but most important, the springs are pressed from their central position and start to push the engine frame sideways, near to the front of the locomotive. This starts the slewing action needed to negotiate the curve without too much sideways force on the first coupled wheel. It also explains why the locomotive is about a third of its length into the curve before it really starts curving itself. The Bissel bogie also has a lateral spring system rather like the front bogie. In some of the last locomotives there are also roller supports on the bissel axle boxes which increase the weight load on the outer axle box with a corresponding reduction on the inner axle box, to reduce the tendency for the outside wheel to climb over the rail as shown in Fig 44A. b) The Coupled Wheels can be adapted as follows: the leading wheel pair’s axle boxes can be given an additional lateral clearance in the horns of 1” either way (Fig 44 (2)), and the third wheel pair (which tends to run close to radially on a curve), is made flangeless and , if necessary, slightly broader than normal(Fig 44 (4)).

Note: The calculation of the position of a locomotive’s wheels on a curve is fairly complicated, but it is well explained in “MM”s ‘Annale’, Ref 8. Copies can be made available on request. 5 Regarding the track, the Chief Civil Engineer collaborated to incorporate the following changes as standard practice: c) The rail gauge is slightly widened on sharp curves up to a maximum of ¾” on curves with a radius of less than 700’ (Fig 44 (1)). d) A Checkrail (Fig 44 (5)) is fitted at the same height but next to the inner rail to check the sideway’s movement of the wheels when the flat inside of the flange of the inner wheel rubs against the checkrail. This limits the tendency of the outer wheel of a wheel pair to climb over the outer rail when it is forced at an angle against it. e) Super elevation (canting) of the track is applied (Fig 44 (3)) to the extent that the outer rail is 4½” higher than the inner rail.

One last comment: Scheffel’s brilliant invention at this time to make four-wheeled bogies negotiate curves with both the axles in a radial direction did not have an equivalent for tender 6-wheeled or engine bogies. So we shall leave it at that.

5

Should there be interest in this paper it could be published as a special issue of ULOLWE - HBH

42

6.7

Lubrication

Lubrication will always be remembered as the hallmark of the engine driver: whenever the train is stopped for a period, we see the driver checking around the locomotive, oilcan or grease gun in hand - the mere fact that it had to be done so often shows that it very often was a problem. In fact, the final limitation to the steam locomotive up to the Cls 23 lay in its broader sense, in friction. The problem lay on the one hand, in not having enough friction between coupled wheels and rail on starting or emergency braking, and on the other, in often having too much in the overloaded rod, crosshead and axle box bearings or even more so, between piston and cylinder - the Hot Box Syndrome.

Rod bearings have been dealt with, but not piston sliding in the cylinder. Up to the Cls 24, cylinder lubrication was done by feeding a small amount of boiler steam over a container with boiler water and engine oil (all at boiler pressure) and letting the oil float to the top of the water, drop by drop, where it was swept away by the steam to the cylinders. The flow rate had to be regularly adjusted by the driver peering through small, often murky glass portholes. The problem was not solved until mechanical lubricators were used on the Cls 25 and the GMA/M. Now there certainly was enough lubricant around - or was it too much? (Fig 45). That combined with the increased or complete use of roller bearings, reduced friction, vastly improving the reliability of steam locomotives.

The story is told how one of the new Cls 25NC’s was standing unmanned on the level at Paarden Island, Cape Town’s running shed, one very windy day. Loco and shed staff was used to leaving locos without any brakes on, as there was enough friction to keep them quiet on the level, but in this case the South-Easter was at its spectacular best and when the foreman looked out, the locomotive was slowly beginning to move and picking up speed. With enough running and yelling, he managed to get the staff to grab some scrap sleepers and to throw these onto the track between the wheels to eventually bring it to a stop right down the yard.

Another regulation was put on the books by next morning.

Usually it is assumed that a locomotive of the Cls 23 type has a rolling friction when in a running condition of at least 4½ lb/ton. If the wind touched 60 km/hr, it would only move the cls 25 locomotive if its friction was as low as about 2½ lb/ton.

6.8

Tender

The tender’s main function is of course to carry the water and coal supplies in a way accessible to the loco. If the grate is mechanically fired, the tender must also house the screw conveyor and the steam engine to drive it (Fig 46). Quite important is that it was the only part of the locomotive to have vacuum brakes in the pre-war years. Drivers did not like to make use of the steam actuated brake on the engine; it had almost an on-off type of action. After the war all engines also had vacuum brakes, which operated together with the vacuum brakes on the rest of the train.

43 The coal ‘bunker’ on the modern tender was shaped with both sides and the end plate sloping as can be seen in Fig 2. This made it easier for the fireman, it was not necessary to Trim the coal except when the last little bit was needed. The Mechanical Stoker’s layout of a Cls 25 can be seen in a sectional drawing in Fig 46.

Of interest is the simple but effective way of feeding the coal to the Conveyor without clogging it: the top of the conveyor slot is closed by a set of movable Slides before the coal bunker is filled with coal. The coal can be easily hand shovelled to start the fire and when the steam pressure is sufficient to start the conveyor, the fireman takes a rod with a claw at its point, sticking the claw into a hole in the edge of the first slide. With a smart pull it is moved forward opening a gap through which the coal in the front of the bunker starts pouring in. It stops when the coal heaps up to the slot at about 45º as shown in the drawing - there is enough coal to feed the screw without clogging it. It works well, except that the coal is crushed too much for efficient burning!

The screw with coal moves towards the firebox door up an Intermediate and an Elevator Unit (pipes with swivel and telescopic joints). The coal drops onto a Distributing Table just inside the firebox. The fireman has charge of a set of five Jet Valves which actuate the jets in the table which blow the coal into the centre or any of the four corners of the firebox. He also has a valve which controls the speed of the engine driving the conveyor. It requires a lot of practice to handle it well.

In section 6.4, mention was made of the advantage to couple the tender so directly to the engine that the two would act as one body as far as damping the backwards and forwards oscillation of the locomotive is concerned. Where the coupling is fitted, is shown in Fig 46 and the details of its construction in Fig 47. At the bottom is the Intermediate Drawbar, a solid bar with an oblong hole at each end through which the two coupling pins are fitted. Before the pins can be inserted, the Compression Spring above it has to be compressed by another locomotive or heavy jacks. The spring is strong enough to resist the compressive part of the oscillation cycle, ie the drawbar remains solidly coupled. Only during shunting or coupling operations can the compressive load become so high that the load on the drawbar drops to nil and the engine and tender can move a bit closer within the limits of the oblong holes in the drawbar. There is therefore no danger of the drawbar being buckled or of the engine being slewed to one side. The design also accommodates the relative lateral movement between the back end of the engine and the front part of the tender when, for example, they negotiate the S-shaped track on moving from a sideline to the main line. The Cushion Buffer Button which transmits the compressed spring’s load to the Engine Drag Box can slide over the drag box face without losing the spring load. You become aware of this when you see the tender moving about 6” to one side and then the same to the other side while peculiar groaning noises come from under your feet, as the loco negotiates the points to the main line. (This is in addition to the bumping noises from the wheels as they pass over the gaps in the points). The cushion effect also helps a bit to dampen slewing of the locomotive.

44

6.9

Vacuum Brakes

I still have memories as a child of going with my parents by train down the Hex River pass at night. My brother and I shared a coupé. My dad had explained to me about the pass that it was very steep (It was before a gradient of 1 in 40 meant anything to me) with lots of sharp turns, and that we would pass a memorial for the soldiers who had died in a train derailment in 1914 because the brakes had failed. This had me very worried but I was too scared to say anything - I was however determined to stay awake and to make sure that we came through the pass unscathed. One thing that I remember clearly as I peered through the window is seeing the whole train crawling down a curve with the locomotive headlight showing the way, but then an unexpected wonder: a brilliant shower of sparks around every wheel of the coaches: it made me completely forget the memorial and the dangers. In later years I learnt that the brakes were cast iron brake blocks pressed hard against the steel wheel rims by the Vacuum Cylinders, and that during a long application the blocks got so hot that sparks could form.

Incidentally the coefficient of friction reduces under those conditions, so that the driver had to apply the brakes a bit harder. Nowadays composite blocks are made of a plastic and filler mixtures (Asbestos no longer allowed!) which has a higher friction and a longer life - they still act onto the wheel rim. The Blue Train is an exception: it has disc brakes, smoother and quieter, but probably more expensive.

While we are still close to the Hex River Pass, by the time I was a student on my way to Maties, I became aware that on the way down that there is a section of the track between the steep sections which was level: the reason is to give the driver a section where he could release the brakes and steam lightly. The brake release was called the Regeneration of the Vacuum in all the vacuum cylinders. The brake force comes from a cylinder with a piston (Fig 48). When the brakes are off, there is a partial vacuum on both sides of the piston and the piston drops to the bottom of the cylinder. This partial vacuum is generated by an ejector in the locomotive’s cab and piped by the Train Pipe along the full length of the train. To apply the brakes, the driver allows some air to enter the train pipe, the vacuum becomes smaller and this lower vacuum is piped to the bottom of the cylinder only. The piston is pushed up which applies the brake.

The top of the cylinder is also connected to a ‘reserve’ Vacuum Chamber so that if there is a slight leakage past the piston in spite of the Rolling Ring seal, enough vacuum is retained to handle the brakes. However, if the brakes are applied hard for a long time such as down the Hex River Pass, problems might arise (Remember the Memorial!) Hence the level section halfway down the pass.

The vacuum brake is a British tradition; it performs adequately but because the pressures are relatively low (about 10 lb/sq in) the cylinders have to be large. With the Continental system using compressed air, much smaller cylinders are sufficient and response times are much shorter, but far more attention is needed to ensure that the train pipe joints are well made and correctly tightened.

45 This brings to a close the summary of how the steam locomotive worked. One is painfully aware that it is not complete and also, that for many readers it will be confusing - too many new ideas compressed into too little space. Try to concentrate on the little incidents on a second reading and skip the engineering details!

Now for some memories of several personal experiences in trying to solve problems experienced on the SAR and a private Narrow Gauge line to Port Elizabeth, while I was in the CSIR doing research in the Strength of Materials field.

7.

Problem Solving for the Railways - Personal Experiences

During the period 1954 to 1964 while I was at the CSIR in the Strength of Materials Division of the NMERI there were several projects on our list that originated from railways. They all had some interesting aspects which I would like to share with all ‘Friends of the Rail’.

But first of all let us try and recapture some of the background of those times: those were the days before computers had developed to the stage that engineers could use them as day-to-day tools to calculate exactly what the stress pattern was in their designs. With slide rules and log books we could only do so for very simple shapes. We were just beginning to appreciate that holes, sharp notches or rapid changes in cross-section caused much higher stresses than the mean values we calculated - they could lead to early failures, particularly under repeated loading. Let us remember how the first jet-powered airliners, the Comets, had several disastrous accidents and had to be scrapped round about this time. The cause was the explosion of the fuselage which was kept at close to atmospheric pressure when it flew at heights approaching 30 000’. The designers had unwittingly used rectangularly shaped windows in the fuselage, and did not appreciate that extremely high stresses acted at the square corners when the cabin was placed under this pressure. Cracks formed after a relatively small number of cycles, triggering the explosion after a few years of service.

It was my choice to concentrate on experimental stress analysis techniques to determine actual stresses on models or prototypes, using the capital that became available to invest in repeated loading testing machines with loading capacities up to 100 tons. Particularly valuable was the recently developed SR-4 Strain Gauges and their Multichannel Recorders. Fig 49 shows strain gauges ‘cemented’ (The generally accepted American term for ‘stuck on’) onto rails. The strain gauge is very simple: it is a flat coil of thin alloy wire wound around a paper slip and cemented between two more thin sheets of paper (Fig 50). Their resistance was usually 120 Ohms.

When the gauge was stuck onto a metal object which was then subjected to stress, the object would strain accordingly and so would the strain gauge in the direction it was cemented. (If you did not know in which direction the main strain would be, you used a Rosette of strain gauges close to each other, usually with an angle of 45º to each other. From those three readings you could calculate in which direction

46 the main strain was and its magnitude). The open secret of the gauge was that as the whole gauge strained with the metal below it, the wire did the same: if, for example, it was a tensile stress/strain, the wire would become accordingly longer but also smaller in diameter, the overall percentage change in its electrical resistance being usually twice as much as the percentage change in strain. We called this a Strain Gauge Factor of 2. An important development at that time was made by the electronic engineers who developed compact portable instruments that could comfortably measure strains with an accuracy of 5 parts per million! (If you had a strain gauge cemented lengthways onto a ¼” (6mm) diameter steel rod, you could reach this 5 micro-inch per inch reading if you pulled it with a force of only 7 lbs). Another big advantage of these strain gauges was that they could be connected electrically in ‘bridges’ so that one could get a reading of the average of the two, or of the difference between the two. Returning to the ¼” steel rod, if two gauges were cemented lengthways onto the rod, but exactly at 180º to each other, it would accurately measure the tensile load on the rod even if there was superimposed bending or eccentric loading. Similar ‘tricks’ could be used to measure only the amount of bending (by connecting them differentially) or twist (with gauges cemented at 45º to the longitudinal axis), etc.

If these ‘bridges’ were cemented onto a component, to be tested under running conditions, the readings from the bridges could be calibrated beforehand by applying known loads to the component in a testing machine. When the component was being tested in practice, it would be convenient to take the readings from these different bridges so that clarity could be obtained as to what conditions lead to maximum loads and how they relate to each other in time and magnitude. The detail stress analysis in the ‘danger’ areas at ‘notches’ or changes in section can then subsequently be obtained accurately in the laboratory, with the component back in the testing machine and some strain gauges in the critical sections.

It takes some time to master the art of the strain gauges: choosing the right type and length - the smallest are more liable to problems - preparing the surface for cementing - which of the four cement types would be most suitable for this job which recorder - what speed and sensitivity settings, etc., but the results are worth it. Without them, the problem of the connecting rod fractures on the first Cls 25 locos dealt with in Section 7.1 would not have been solved.

7.1

The Case of the Fractures of the Unbreakable Connecting Rods

Connecting rods were always prone to failure, as was already mentioned at the end of Section 6.3, so when the Cls 25 had to be designed, the SAR was very happy that Murray Franz became available to improve the 15F connecting rod design: they would both be of the same length of 7’ 5” between pin centres and the loads would be only 7% more on the Cls 25. Murray had just returned from England where he had worked on the strength design of aircraft: he knew far more than any of us did in 1951 about stress analysis and all were happy that now, for the first time, there would be an unbreakable connecting rod on a SAR locomotive, the

47 Cls 25. The locomotives were placed in service during 1953. The first failure took place in Sept 1954 and in the following 12 months another 5 followed. The Metallurgy Section of the SAR checked the steel - it was a Mn-Ni-Mo-Si steel (EN 13), hardened and tempered - and found it in order. The position of the start of the fatigue failures is shown in Fig 51. What was most unusual was that the fatigue failures all started on a fillet between the flange and the web of the rod, three near the big end and three near the small end. The only type of loading that causes a maximum stress in such fillets is torsion of the rod as a whole, a type of loading not previously taken into consideration in the design of a connecting rod.

A first prognosis was that torsion was the culprit, that it came about because of tilting of the locomotive over points or curves and because these new-fangled Timken double-taper roller bearings had no play to absorb this tilt. What confused the picture, however, was that not all of the cracks were at an angle of 45ยบ to centreline as would be expected if there was a dominant shear stress. The matter was urgent so it was prudent to combine the SAR team with the CSIR team to solve the problem - we had suitable big testing machines in our laboratory. A spare connecting rod was delivered to the laboratory even before the contract was signed and my team got stuck in to cement all the strain gauges at the right places.

We put in bridges along the length of the rod to measure longitudinal, lateral bending, vertical bending and torsion loads - three of the latter to be able to check one against the other or if there was a failure in the gauges: life is tough on a steam locomotive. The 6 bridges were calibrated in the testing machine. We could just fit the rod in the testing machine for the longitudinal load, but how do you apply torsion? The answer lies in an X, just visible in Fig 52. (Sorry for the poor quality of the reprint, it was all I managed to get from the CSIR archives of reports. The original photo was good but the negatives remained with the CSIR and they are not readily available any more). The drawing in Fig 53 makes it clearer. While the two diagonal beams press down onto the rod clamps and twist the rod, the twist deflection is measured by four deflection gauges fixed to a separate pair of unstressed clamps. The twist load is calculated from the compression load shown by the testing machine and the bridge output read from the strain gauge meter at the same time.

Gouws of the SAR and I travelled with the calibrated rod stowed on the Dynamometer Coach, No 60, down to Touws River where Engine 3508 was ready for the rod. Engine 3508 had already developed two flawed rods with only 130 000 miles service. The biggest problem with the strain gauge tests was connecting the large number of leads from the strain gauge bridges on the rod to the multichannel recorder made available for the test by the SAR. The best we could do was to pull a rubber pipe over the leads and to clamp it to the combination lever on its way to the running board and back to coach 60. In practice, it did not last longer than about half an hour with the loco working hard before some of the wires started failing. (Why is it that a specialist on fatigue failures like me, experiences more fatigue failures with his own equipment than anybody else?) Anyway, we did manage to get all the recordings we needed within about two weeks and could

48 submit a clean report at the end of all the tests. Even the highest stresses were well below the fatigue strength of the rod.

The highlight of the test was my first opportunity to be on the footplate of a Cls 25 locomotive and experience the thrill as the giant pulled away at full power, picking up speed against the gradient like I never experienced before. I did miss the sharp exhaust beat as it was a condenser but the fire roar and the vibration was there even better than on the Cls 23. It was also the last trip I had on the footplate.

The main results of the tests were: • Yes, there was a significant torsional load on the rod when the locomotive cants: the biggest effect was when the locomotive pulled a full load over the set of points running from a branch line to the main line. At a speed of about 24 mph (The allowable limit is 20 mph!) the cant was almost 2º either way and when the locomotive was pulling hard the rod was subjected to nearly the same degree of twist.

• The torsional twist was so high in spite of play in the crosshead and bearings, as the high connecting rod push or pull loads cause the play to be taken up by wedge action: an end load of 94 000 lb was measured on the connecting rod!

• The maximum stress was found with the loco pulling hard over the set of points and was not in the fillets where the flaws had started, but on the flanges near the big end, due mainly to the combined effect of end load and lateral bending due to about 0,35” eccentricity of the end load. To a lesser extent there was also stress due to cross bending under torsional twisting (The eyes at the end of the rod restrain the I-section from twisting in the normal torsion way: instead, there is some cross bending stress on the flanges next to the eyes). From where the eccentric loading? It is not easy to believe, but it was clearly shown to be due to elastic bending of the crank pin and the whole wheel assembly, solid as they might appear - well, 47 tons is a big force.

• The maximum stress of 25 000 lb/sq in. was in any case considerably less than the expected fatigue limit of over 30 000 lb/sq in., so Murray Franz’s design was vindicated. It seemed that stress was not the primary cause of the failures.

Just imagine how I felt when these results became clear. Where was my mistake?

I spent several sleepless nights checking and rechecking all the calculations, and was at least thankful that the three torsion bridges were consistent within a few percent. Gouws and I could not come up with any logical explanation, unless . . . .

Next morning I tackled my good colleague ‘JP’ Hugo, our metallurgist, and asked him to please find something wrong with the material (in spite of Dr Reissner’s conclusions), and slipped him one of the specimens of the failure. I had a guilty feeling as I, being only 28 years young, did not like to risk asking the big bosses in the SAR to approve of this step which was in any case outside my brief. Next day JP turned up with a gleam in the eye and ‘borrowed’ another specimen. Within two days it was clear: somehow the rods had been welded in the flawed fillet area after its heat treatment, and before it was finally machined (no superficial sign of

49 any change in the metal - until you etched it). We as engineers all know that welding highly stressed heat-treated steel is a disaster.

The finding was reported to the ACME Dr Douglas immediately via our boss Dr Roux, leading no doubt to consternation that the SAR had not spotted the cause but also relief that the manufacturer of the rods, Henschel und Sohn, would have to rectify the fault. JP and I never had any direct formal recognition for the solution of the problem from the SAR. What we did hear was that the slip had taken place during a night shift machining operation at Henschel. To the milling machine operator who had to mill the inside of the flange of the connecting rod, it was a first experience that the flanges were slightly tapered and not parallel; also that the rod was made from a heat-treated steel. He made a slip in milling the flange and took a cut which was too deep. He seemed to pick this up soon enough but about 10 rods were involved. He got his pal the welder to quickly fill up the missing material and then re-machined the rods, without realising the damage that had been done. All one can say is that the welder did a perfect job: no pitting or slag inclusions to catch the eye.

One last thought: courses in Strength of Materials always start off with stress as the culprit to be watched and that strain is caused by stress - strain is handy to measure the stress. Here we have a case where a strain is the cause of a stress, superimposed on the stress due to loading forces. One can speculate that the many cases of connecting rod failures in other engines were due to this extra unrecognised stress from the torsion. The natural reaction to the failure would have been to ‘strengthen’ the rod by thickening the flanges of replacement rods, which would reduce the tensile/compressive stress, but due to the extra stiffness, would greatly increase the stress on the outside of the flange when the rod is forced to twist through the 2º (Although stiffer, it will still not be stiff enough to restrain the locomotive’s cant). It could perhaps also increase the eccentricity of the end load and therefore increase the lateral bending stress. So the ‘stronger’ rod can be expected to fail quicker. As steam locomotives were on their way out and no new locomotives were ordered after 1954, this aspect was no doubt never followed up. However, the Cls 25/25NC locomotives were never fitted with connecting rod safety straps!

7.2

Case II: The Fractured Blower Turbine Blades

The Cls 25 condensing locomotive, as the designation tells us, does not blow the exhaust steam through the chimney to the atmosphere - it is piped to the oversize tender where the steam is condensed in a large assembly of small copper pipes arranged as the side walls of the tender. To ensure sufficient cooling of the pipes, large fans are fitted as part of the roof of the tender - they draw air through the side walls over the pipe nests. The fans are driven by a steam turbine driven in turn by the incoming exhaust steam: The faster the steam comes in, the faster the turbine and its fans run. A similar turbine is fitted into the smokebox to drive the

50 Blower Fan that draws the air through the grate and boiler and exhausts the smoke through the chimney.

Within about 10 months of service 26 cases of failed turbines due to fractured blades had been experienced on blower turbine rotors (Fig 54). The blades are fitted into a groove machined into the rim of the disc. A sectional view of how blades are carried in the rim is shown in Fig 54. The turbines run up to speeds of 6 000 rpm for the blower turbine, the centrifugal load reaching more than a ton per blade and there is substantial vibration as well as shocks if there is priming, etc.

The blower turbines were all rebladed with blades with a core thickness of 14mm (Fig 54 e) in place of the original 7mm. The alarm bells went off, however, when the rebladed turbines had their first failure, again after only three months. This is where the CSIR was asked to find the cause and suggest a solution. This involved both Metallurgy and Strength of Materials. We came up collectively with the following: • All the fractured and cracked blades inspected had failed due to fatigue starting in the fillet at the back (trailing) edge (Fig 54 d 7 e), which carries the brunt of the centrifugal load.

• The material appeared in order.

• Fatigue testing the 14mm blade up to the centrifugal load was sufficient to start a crack at the same position as found in the failed blades, within about 100 000 cycles. (This was an extremely long test: we could only use our new 30ton Mohr & Federhaff load alternator at 30 cycles per minute.) This would amount to about four years service on the locomotive if it was accepted that there were about 100 cycles of full speed of rotation dropping to less than a third of full speed (about 10 % of the centrifugal load) per day of service and for 250 days per year. The failures occurred far quicker than that, showing that the other factors were significant, but the point was that even if these factors could be eliminated, failures would in any case lead to the demise of a generation of turbines every 5 years or so in spite of the reblading with blades of double the root size.

• Stress analysis of the blades was difficult because of the small radii of the blade root where the crack starts, but measurements with Stresscoat, a brittle lacquer, and strain gauges of 1/16” in length, combined with data from the newly published book, Stress Concentration Design Factors by R E Peterson, gave a good estimate of the stress values to be expected for the two designs of blade. The 14mm blade is 11% heavier leading to a correspondingly higher centrifugal load, the stress concentration factor where the cracks start is about 30% higher and the tendency to ride on the back ledge is also higher, which taken together leads to about the same stress in both the 7 and 14 mm blades! Fatigue tests confirmed these findings.

Here again we find an almost classical case of how doubling the size of a component prone to failure leads to no improvement in service life.

Release of the report on this investigation to the SAR, who promptly sent copies to Henschel, led to an invitation - or could it be taken as an instruction - to visit

51 Henschel in Kassel, Germany. It was my first visit by air to Europe, flying in the noisy old radial piston engined DC-7B, which needed its four stops along the way at Salisbury, Nairobi, overnight to Khartoum watching the flames streaming from the engine exhausts, then to Rome, before landing at Frankfurt after an exciting flight over the Alps - 24 hrs all told. They picked up my remains and drove me to the grand Schloss Hotel at Kassel looking down on the Schloss garden where a large water stream was allowed to cascade down once every Sunday. Hundreds of quiet, demure citizens gathered there to view the scene, then just as quietly returned home afterwards. From the Schloss you could just see the border of East Germany, maybe 10 km to the east. It was an elite hotel where I felt rather unsure of my position but I did manage to make them understand that I would appreciate a plate of porridge for breakfast.

Next morning the discussions started, led by Herr Prof. Dr.-Ing. Ehrenhaber Roosen, chief designer of the Cls 25, and Herr Oberingenieur Hany. As soon as they found that I could (sort-of) speak German that became the language of negotiation. It was quite a struggle for me. Roosen contested my findings, Hany being more careful. They won the first round when they pointed out I had quoted ‘Petersen’ when he really was ‘Peterson’ (p.37). They had found the book but were not really interested. Roosen was strongly of the opinion that the problem lay in priming when the drivers opened the regulator coming full speed downhill in advance of a steep climb ahead. I agreed that there were factors over and above the centrifugal loading but their attempt to strengthen the blades by doubling the neck was futile as they increased the stress concentration. What could they offer to improve the situation? I offered to sit with them to do the stress analysis.

In Roosen’s autobiography (Ein Leben für die Lokomotive - 1976) he mentions my visit but does not say anything about my point of view, he only says that he made the remark “half in desperation and half sarcastically, why don’t we fix all the blades like the last blade to be fitted - with taper shank bolts”. The point was that apparently none of these blades had broken so far, a fact of which I was not aware.

As I recall, it was Hany who came along with some taper pins maybe 4 or 5mm in diameter, and who suggested that between every blade foot, a hole be drilled through and reamed to a taper; then the taper pin be forced in and riveted over on the other side (Fig 54 f). This would force the blades together so that vibration and shock effects would be reduced, and how about the centrifugal load? From Peterson it appeared that it would reduce the stress concentration by a factor of two to three so I agreed that it would be most promising in spite of the thinner foot. If they could make up a sample ready for my tests, I would take it back and could give them an answer within about a week. They could also take the case to Dr Gassner at Darmstadt who, from his publications, was in my opinion the best authority on fatigue testing under simulated service conditions. This was accepted so Roosen took me in his beetle to Gassner - what a clean, precise setup! Gassner was a little careful and did not commit himself other than to say that he was booked up and did not see his way clear to do such a test with his Schenck machines which would take even longer than in my M & F load alternator. Roosen

52 was a good host by this time taking me for a round trip along the Rhine past Wetzlar, the home of my Leica camera, before coming back to Kassel.

It was time to return but all the flights were booked up. Eventually Henschel paid up and booked me in First Class! The weather had become quite bad but we took off in any case and headed for the Alps. What a trip - we found ourselves in the worst storm I have ever experienced during a plane trip. Everyone was strapped down tight, including the flight staff and meals shoved back into their racks.

Lightning all around us, then FLASH/BANG! The lightning struck the plane on the wing. Lights out for a while, but the plane kept going on its extremely bumpy way, and then we gradually cleared the storm and found our way to Rome, where we palefaces were shakily led to the waiting room. It took two hours to clear up the mess and check the plane. Some of the shocks were bad enough to break off the tops of glasses stowed in partitioned racks, but we could continue after some minor repairs.

The final chapter was that back in Pretoria the Hany specimen performed well in its fatigue test (Fig 54 b). This conversion was then done on all the blower turbines with good results. Eventually somebody suggested using broader sheet metal vanes welded to the rim and this was the final answer. Nobody said how such a contraption could be balanced; this was probably after I had left the CSIR, I was not asked to follow up the case.

Another aside: while I was there I picked up a general news letter from Henschel jnr. to his staff, expressing his regret that it was necessary to reduce staff as the orders for locomotives had dropped - they had started too late to change over to diesels. So for them the writing on the wall was many years earlier than for the SAR.

7.3

Rails

The story of Loubsers and Rails starts in about 1927 when my dad “MM” got involved in the question of how the then main line rail of 80 lb/yrd should be upgraded to what became the 96 lb/yrd rail (Fig 55). Apparently rails had been found with cracks in the lower fillet. “MM” did some tests on a section of 80 lb/yrd rail and became aware of the high stresses when the rail is subjected to high lateral flange loads as a locomotive rounds a curve, so he proposed that the web be not parallel, but become slightly broader at the bottom and that the lower fillet have a bigger radius. Otherwise it is a slightly scaled-up version of the 80 lb/yrd rail. In some mysterious way the test rail piece found its way into dad’s workshop after the tests - I still have it, it makes a good anvil.

In view of the damage caused by the wheels at rail joints, it was decided later to convert from 40’ to 60’ long rails which could still be packed onto specially built 60’ long flat coaches for transport, thus saving a third on fishplate joints. The need to cater for temperature driven expansion and contraction could still be handled.

53

By the time I landed in the SAR, things had changed a lot. It was already standard practice to weld three lengths of rail together in the workshops using the flash-arc process: two rails placed end to end at a time are gripped near their ends, while a strong welding current source is connected to the two ends. The rails are pushed towards each other until the electric arc starts, when they are moved a fraction away from each other until the arc starts to melt the ends. Then the current is turned off and simultaneously the two ends are quickly forced together with a load of many tons. The rails are now firmly welded together, only a flash from the molten steel shows where the joint is. This flash is easily machined away, leaving a smooth joint with hardly a trace of where the weld was. Thus rails of 180’ length became available. They could be transported a few at a time along the centre of three of the 60’ trucks, but were only restricted as far as lateral movement is concerned on the central truck; they were free to slide sideways on the outer trucks when the train went round curves. The fatigue strength of these joints is practically as good as that of the unwelded rail, provided that the correct welding procedure is used. Only a fatigue test in repeated bending can readily check the effectiveness of the welding procedure.

As the CSIR was the only laboratory that had fatigue testing machines of sufficient capacity (Up to 100 tons on the Amsler pulsator), the SAR turned to us to do the tests and link them with stress analyses as well as checks on the metallurgical aspects by JP Hugo’s Metallurgy sub-division.

Investigations at the CSIR started with the fatigue strength of thermit welded rails compared to the fatigue strength of the unwelded rails. The question was also asked whether superimposed tensile or compressive end loads influenced the fatigue strength.

A thermit weld is made by placing the rail ends to be joined close to each other, then fitting a ceramic mould around the gap, filling the mould and gap with thermite powder (a mixture of mainly fine aluminium powder and Fe 3 O 4 powder also used in incendiary bombs). On ignition, a temperature of 2600ºC is reached and the iron oxide is reduced to molten steel, which fuses the two rail ends together. The outside of the weld is very rough with a sharp fillet (Fig 56). We did not expect any good results. The tests confirmed this: • The fatigue strength of the unwelded rail in vertical bending was 45 000 lb/sq in. End loads had no significant effect on the fatigue strength.

• The fatigue strength of the thermit welded rail was only 25 000 lb/sq in.

Superimposed end load tensile stress of 10 000 lb/sq in dropped the fatigue strength still further to about 20 000 lb/sq in.

• Stress analysis showed that the weld shape led to a stress concentration factor of about 1,4 and the metallurgical examination of the weld also indicated defects such as small cracks, shrinkage cavities, lack of fusion, and a poor structure.

54 The importance of these tests is that a clear answer as to the anticipated life of the welded rail can be obtained within a few weeks instead of watching specimens built into the track over a period of years.

Over the years, several types of rail and rail weld were tested in fatigue for the SAR - it almost became a routine test, although we always kept a close watch for any unusual evidence. One such an interesting observation is shown in Fig 56 b, where a thermit welded old rail with a fishplate hole next to the weld was subjected to bending while coated with brittle lacquer. It shows cracked lacquer with diagonal lines around the hole in the web. This is due to shear stress which occurs in a web when the rail (or an I-section girder) is subjected to bending. It is common knowledge for engineers that a hole in a part subjected to a tensile load has a stress concentration factor of 3. What is less well known is that under shear conditions, the factor increases to 4! It explains why rails bolted together with fishplates often developed these 45º cracks, particularly if the bolts were left loose and the rail end was exposed to impact shear loads as the train wheels climbed onto the projecting rail end.

Two more interesting facts were picked up during this work: the first is that the temperature differences, to which rails are subjected between day and night in areas of clear sky such as the Karoo, are far greater than one would expect. The rail is clear off the ground and well insulated from it by the sleepers. In the daytime, the sunlight can push the temperature of the rail up to about 40º higher than the air temperature, while at night the bright steel radiates heat out to the open sky and its temperature can drop to about 20º less than the air temperature it is by far the coldest body you will see as you look around you. That is why rail sleepers have to be so well anchored into the ballast to handle the expansion and contraction loads.

The second and last is the strange way that a long rail deflects as a heavy wheel rolls over it, as shown in Fig 57. It is well known that a wheel depresses the rail as it moves over it and the load is taken by the sleepers - most of it by those closest to it. What is not so well known is that further along the line, there is a marked tendency for the rail to lift up over a short distance. The best way to accept this apparent contradiction is to look at rail sleepers and imagine how they have to push their part of the rail up to support the wheel’s weight. In fact, if it were a short rail, the ends either side of the wheel would bend up considerably and point over the horizon. But as it is a long continuous rail, the further extension of the rail eventually pulls the rail back to its normal height. To put it another way, if you want a warning signal to tell you when the first wheel of the train is coming, you can put a light switch on the foot of a rail - the first indication that you would get is when the switch is pushed up. Incidentally, the same happens to our made roads. Failure of the concrete or tar roads is to some extent due to the tensile stresses induced ahead of particularly heavy vehicles. Concrete is far happier to handle compressive stresses. We are now far away from the subject of rails, so it is time to stop.

55

7.4

Dynamometer Tests on the Narrow Gauge Railway

Why do dynamometer tests on a narrow gauge (NG) railway line at all, and if so, why ask the CSIR and not the SAR to do it? Well, the NG line concerned was the private PPC Company’s line from their lime mine near Hankey, to their cement works in Port Elizabeth. They (George McEwan) did ask the SAR to do it, but the reply was that they do not have a NG dynamometer coach, maybe the CSIR can help. And why the test at all? They needed new and bigger engines and were opting for a diesel but did not have the data to specify what was needed, so could we help? Yes, we would love the challenge and got stuck in.

What is needed for such a test is to record the locomotive traction force (Or at least the drawbar force, as was done with SAR coach 60 tests at Laingsburg), the speed, brake application, also the train’s location vs gradient and curvature along the line. We had a portable (Battery operated) 12 channel recorder suitable for strain gauges, so we used a coupling hook and cemented a strain gauge tension bridge on a grove cut in it, calibrating it in a tensile testing machine. This took care of the drawbar force from whatever locomotive would be used (Also for the future diesel)(Fig 58). Speed was indirectly measured with a coil around a magnet, positioned by clamp on the loco frame so that we obtained an electric pulse from the coil as the big end passed close to it every revolution of the driving wheel (Fig 58). At the start of the test we measured how far the loco travelled per revolution so that we could determine the speed of the loco from the recorder chart which was set to run at a fixed speed. As a check we also recorded a pip every minute from a clock. On another channel, coded pips were recorded to place when certain incidents occurred, e.g. engine slipping; stopping for a signal, etc, of which written notes were kept. Space was a bit of a problem but in the end we three made ourselves at home on the back of the tender (Fig 58). Our SAR experience at Laingsburg helped a lot to plan the tests and they went well The biggest task was that the original record had to be ‘translated’ into a new record with the position on the line as the longitudinal scale and speed and drawbar pull on a convenient mph and lb. scale, which took some time. However, the data was satisfactory for PPC to draw up the diesel specification. When the diesel arrived (I had already left the CSIR by then) it went through the same test procedure as before and was found satisfactory.

One interesting result was that the initial force to start the train on a level track was far greater than normally accepted for trains. For the 3’ 6” gauge trucks of those days, a value of 4½ lb/ton is normally found; in these tests, the value was 8 lb/ton for loaded trucks and as high as 15 - 20 lb/ton for empty trucks. One can only surmise that the alignment of the bogies and the track was not up to the SAR norms for the 3’ 6” track.

As mentioned above, these tests were the last I could manage as far as Railways and locomotives were concerned; thereafter I was so fully tied up with the Atomic Energy Board and UCOR that I never got involved with trains again, except for

56 one or two trips by Friends of the Rail and the like, and one very Grand Finale, the inaugural trip in 1972 of the (then) new Blue Train (As designed by brother Kobus with some input no doubt from his wife Rita) to Kimberly and back - a wonderful experience to remind one why locomotives are needed, even though no steam locomotives are involved!

Appendix A

Locomotive and Tender Numbering Systems Each steam locomotive has three numbers: The Class, the Individual and the Maker’s Number. The first two are prominently displayed on the oval red Number Plate, one on each side of the cab (just visible in Fig 4 & 11 top). The individual number is the large central number; the small one under it is the class. Well below the Number Plate is a small plate with the maker’s name, his serial number and the date of manufacture.

Individual numbers are unique per locomotive; the individual number is the loco’s name: a number such as 3211 is spoken as thirty two - eleven, and never as ‘three two one one’ On ordering a new batch of the same type of locomotives, a block of new individual numbers and the class number were allocated, eg the first batch of locos with 5’- 3” diameter wheels was allocated the Class 23, Numbers 2552-2571, and the repeat order 3201-3316, retaining the Cls 23. The tender’s type number consists of two letters eg EW for the class 23 tender, and they have the same individual number as the loco.

Class Numbers reflect further information, eg: 19. A number without letters means that it is the first batch of a new type of rigid frame steam locomotive, or a further batch of the same type (Fig 1).

19A. Indicates a batch of loco’s basically the same as the cls 19, but with a few changes, in this case the wheel diameter was changed from 4’-6” d into 4’-3” to reduce weight for lighter branch line work.

15AR. A 15A loco reboilered with (in this case) a standard No 2 boiler.

S, S1, S2 Shunting locos. (No bogie wheels) (eg Fig 3) G. Garratt locomotives, ie a central boiler pivoted onto two engines (Fig 9).

GM. The 13 th Garratt class GMA. The same as the GM (suitable for 60 lb/yrd track), but with, in this case, cast steel frames instead of bar frames.

GMAM. The GMA with increased water and coal capacity, for main line working (Fig 9).

57

MA, MB - MJ1 Mallet locomotives (eg Fig 12). Not to be confused with the previously mentioned ‘M’.

Other Types of Locomotives eg: • 7E2. The seventh type of Electric Unit, second variation.

• 34-214. Class and individual numbers combined: Diesel loco No 214 of class 34. Diesel loco classes start with 30.

• NGG 16. Narrow gauge Garratt locomotive, class 16. The last of the line.

Let us not get involved in pre-Union, harbour, experimental, etc,etc---

Appendix B Eleven Representative SAR Locomotives These notes introduce 11 locomotives which were chosen as relevant to the later more detailed discussions as to what made the steam locomotives work well -or not so well.

19 and 19d (Figs 1 & 2) The class 19 was the first SAR locomotive designed by my father “MM”. It was in response to an unusual request by the Chief Mechanical Engineer, Col Collins, in 1926 when “MM” had only been one year in the service - it was the CME’s prerogative to design new locomotives himself. The cls 19 was to replace ageing loco’s (eg cls 6,7,8 ) for branch line working on 60 lb/yrd track. It was a brilliant design that proved so effective that the basics were retained for 23 years, when the last order for 19D’s was placed. “MM” was CME then and introduced the larger ‘Vanderbilt’ torpedo shaped tender (“Die Perdeby kolewa”) on 6-wheeled cast steel ‘Buckeye’ bogies, and vacuum brakes on the engine. It proved reliable, effective and powerful; it is still the preferred loco by Rovos Rail and on the George - Knysna line. A large (by branch line standards) fire grate (36 sq ft) combined with big cylinders and long travel cylinder valves worked wonders. Note also the change in cab design: the cab floor is higher and extended towards the tender - there is no floor attached to the tender any more.

The fireman now has one stable footbase from which he can do his stoking. Total number of engines ordered was 336 (19-19D).

S1 Shunter (Fig 3) “MM”s wartime design to suit local manufacture. Simple but powerful. Only low speeds are involved so that small driving wheels could be used, reducing the weight to the point where bogies could be eliminated. The adhesive weight was the same as for a main line locomotive such as the 15F, which meant that the S1 could on its own easily without slipping “lift” and shunt a train

58 dropped in the yard by the 15F. There was weight to spare so that a large standard boiler (Cls 12AR) could and was fitted.

24 (Fig 4) “MM”s last design. Intended for very light (40¼ and 45 lb/yrd) branch line work, particularly in the then SWA. It was the first SAR loco to use a light but strong cast steel frame integral with the two cylinders, boiler saddle and supports (Fig 41) dealt with in section 7. The lighter frame enabled a shortened version of the 19D boiler to be fitted - extremely powerful for such a “small” locomotive.

This called for a larger than normal bogie under the firebox.

Raimund participated in the first trip of the Cls 24 with an ore train through the Kruger Park from Palaborwa to Komatipoort on the now defunct “Selati” line. Quite an experience to sit on the front cowcatcher at dawn and see a family of cheetahs scrambling off the track as the driver blows the whistle! 100 locos were ordered but they had a limited life as all the light branch lines were upgraded soon afterwards. As far as I know, no problems were experienced with the 2-8-4 wheel arrangement - after all the loco was used at low speeds.

16E (Fig 5) Chief Mechanical Engineer Allen Watson’s proudest design - the only SAR locomotive with 6’- 0” diameter wheels. Intended for the early “Blue Train” and other expresses, it reached 72 mph on test with a light load. The revolving cam (RC) valve gear with poppet valves was good at high speeds, but strangely enough was found wanting on Watson’s 15E with four coupled wheel sets, which developed about 10% lower tractive effort when starting a heavy goods train than its later model, the 15F with Walschaert’s valve gear. This I can confirm from working the dynamometer recording table during the 1949 traffic tests in the Karoo.

The new standard 3A boiler of the 16E, with its 62½ sq ft fire grate, could produce enough steam for a large power output but the cylinders were too small to make use of it. This can be deduced from the engines low Tractive Effort - see Table B1, column 7, compared with that of the 15F (18% more) with the same boiler capacity.

The 15F could in any case reach 60mph, the maximum allowable. It sadly led to the 16E’s relegation to minor duties. The new Blue Train was too heavy! Why were larger diameter cylinders not used? Read all about it in section 3 on loading gauge limitations.

15F (Fig 6) (See also 16E above). The standard main line loco 1938-1955 altogether 254 ordered. As mentioned above, it proved suitable for both goods and express service on the main line. However, the 3B boiler with its large square grate, the rounded ‘Wooten” water space design and the long fire tubes led to high maintenance costs. It was also prone to “pulling the fire”. These will be dealt with in section 5 on Boilers. Mechanical stokers were fitted as soon as these became available - grates over 60 sq ft in size require too much stoker effort for hand firing.

59

23 (Fig 7) this was CME Day’s proposal to improve still further on the 15E/F. Day wanted an improved larger boiler and 5’-6” driving wheels, but this would have taken too long to design, and WW2 was on its way. He had to compromise by using the standard 3B boiler of the 15F and wheel sizes limited to 5’-3” diameter.

Even they proved to be too large, the longer frame causing increased transverse flange forces on curves. The higher boiler pressure with corresponding increased cylinder loads also led to higher stresses in the frames. Fatigue cracks developed soon in the frames near the cylinders. Repair by welding was ineffectivewithdrawn about 1970.

The boiler had the same problems as that on the 15F. When the tests on the 3B boiler were planned in preparation of the design of a better boiler for the cls 25, the best section was from Laingsburg, a water station, to Pietermeintjies. The steady climb was long enough to get reliable test results. As this was the ‘home’ of the Cls 23, one of them, No 3211, was chosen for the tests in 1949.

On the plus side of the Cls 23 was the bigger tender which made travelling through the dry Karoo much better, but there again the design of the six-wheeled bogies with their bolted construction proved too light: the forks guiding the axle boxes permanently deformed outwards, placing excessive end loads on the SKF self-aligning roller bearings (Fig 8). This led to their early failure at the end of the WW2, when no spares were obtainable. Brother Kobus saved the situation by rapidly setting up production facilities to make replacement “Isothermos” axle boxes in the SAR Workshops. (Raimund had been told to check what was causing the problem. He joined the breakdown gang at midnight in the middle of a snowstorm at Pietermeintjies (the coldest part of the main line), where a failure had occurred. The gang lifted the failed tender, leaving me to crawl under it with my tape measure to check dimensions, before their actions led to further deformations. They withdrew quietly to their fire so as not to be disturbed by my chattering teeth. Anyway, the surmise proved correct and the Loco Drawing Office (LDO) got cracking on designing stiffeners for the bogies).

GMAM (Fig 9)(Die Gammat). The most modern (1954) and most successful of the SAR Garratts. Basically the same as the pre-war GM, ie of the same wheel, cylinder and boiler size, but modernised with cast steel frames integral with cylinders, vacuum brakes on the driving wheels, mechanical lubricators and roller bearing axle boxes. It is the same as the GMA, allocated to branch lines with 60 lb/yrd track, but with increased water and coal capacity, for main line working (hence the extra ‘M’). A total of 150 were ordered. Like the GM, an auxiliary water tank was trailed by them. The advantage was better adhesion and longer trips before watering. They still suffered from coal shortages due to a limited coal capacity of 14 tons, compared to the Cls 23 with 18 tons even with a slightly smaller fire grate.

Raimund was sent as the Northern Transvaal System’s representative to participate with the Test Section’s crew (The same as he had joined at Laingsburg) in commissioning the first GMAM, No 4051, including the trip from Waterval

60 Onder to “Boven”. The load was the same as handled by a ‘double-header’ 15AR pair, which is a stiff test. Some months before, a GM was sent to Waterval Boven for the training of drivers and firemen on the handling of Garratts with mechanical stokers, two new experiences for them. What went wrong I did not hear, but before we came a local crew had to cope with a stalled GM (low boiler pressure?) in the tunnel between “Onder” and “Boven” while hauling a load up the gradient.

Both driver and fireman died on the spot due to asphyxiation. It was against this background that we started with our full load from Waterval Onder. The GMAM had steamed well so I requested the chief to allow me to join them in the cab on the trip. We made a good start but I soon found it advisable to climb into the coal bunker and trim the last bit of coal into the mechanical stoker’s conveyer screw, otherwise who knows? Garratts never have enough coal! She had incidentally been running up the bank at 19 mph, with the regulator fully open, at full boiler pressure and the cut-off set at 60%, a remarkable achievement. On arrival at Boven, we found that the piston rods looked overheated and had turned blue, in spite of adequate mechanical lubrication. Working her too hard or are there too many superheater elements? I never heard the full story as I left the SAR shortly after.

25(condenser) and 25NC (Fig 10) . The last and the largest non-articulated steam locomotives on the SAR. The engine part with the driving wheels, cylinders and valve gear were the same basic size as on the 15F, but Timken roller bearings were used on all axles, shafts and even on all rods. Mechanical lubricators took care of all moving parts including the valves and pistons. A massive cast steel frame integral with the cylinders was supplied by the General Steel Castings Corp from the USA. They also provided the cast steel frames for all loco and tender bogies.

A larger boiler was designed, based on the Laingsburg boiler tests of 1949/50 (See section 5). The extra weight meant that a 4-wheeled back bogie had to be used.

The 25NC performed exceptionally well, a ‘clamp-down’ became necessary to stop drivers from regularly running up to 70 mph on the Karoo main line. The condensers worked reasonably well but the maintenance was high. They were all converted to non-condensers in due course.

26 (Fig 11). In 1981 a last attempt to increase the efficiency and power of the 25NC was made under the supervision of David Wardale. Loco 3450 was rebuilt to include many features, as quoted in the literature (Refs 11, 12 & 15). Raimund has no direct information on the cls 26 other than a TV shot showing her slipping badly on starting with a load - in spite of an improved sanding gear. The improvements included: • Converting the boiler to Porta’s gas-producer combustion, increasing the number of superheater elements and damping the flow through the other tubes at low power levels. The details are dealt with in section 5, Boilers.

• Increasing the boiler pressure. No specific value has been quoted, but 240 lb/sq in is a good guess.

• Lengthening the smokebox and introducing a double chimney Lempor exhaust.

(Double chimney exhausts had already been used before on some of the 25’s).

61 • Adding a feed water heater between the two chimneys, heated by the exhaust steam • Increased steam chest size plus valve gear improvements to cope with lubrication at the higher temperature • Fitting compressed air sanding gear • Increasing the tender coal capacity by 2 tons It was claimed that the coal consumption was reduced by 35%, the water by 20% and the maximum power was increased by 50%. Apparently the maintenance staff had problems in handling so many new types of equipment so that some were abandoned in due course. The feed water heater and its pump were amongst these.

In the end, the improvements were not sufficient to warrant further conversions.

Why not? The 26 could not comfortably ‘lift’ a significantly bigger load than the 25, as the adhesive weight had remained substantially the same. The extra power would give an increased speed, but that was not the basic limitation of the 25. The 25 could already run the Trans Karoo at speeds up to 50 mph up the bank from the Orange River and well over the 60 mph limit for the Blue Train elsewhere. The good improvement in economy was welcome, but the potential savings for the limited life still left for the steam locomotive would, I think, not cover the cost of the conversion. If not satisfied with this opinion, try to struggle through The Final Verdict

The Final Verdict: No verdict without sufficient evidence, in the case of Steam vs Electric/Diesel! To assist in this Case, the most relevant data of the eleven steam locomotive types mentioned above have been given in the Table B1, together with those of a contemporary Electric and two Diesel locomotives. A further Table B2 was prepared from Table B1 in which the data were used to calculate and compare the maximum load of a train that could just be ‘lifted’ up an incline of 1in 100, such as is found on the Kimberly - De Aar main line, and the maximum horsepower available to handle a train of 3000 tons up this gradient. In both these cases allowances have been made for the weight of the locomotives, which absorb a pro rata amount of the available tractive effort as well as horsepower. The comparisons have been made on the basis of double header Cls25 and 26 locos versus double and triple headers Cls 6E1 units as well as Cls 34 diesels, as the handling of heavy loads is a priority.

There are problems in comparing with the Cls 26, as no reliable data comparable with those of the other locos were available to me. Reasonable assumptions were that the loco total weight as well as the weight on the driving wheels had remained the same as the 25NC. The changes could hardly have influenced them by more than about 1%.

The tender weight was increased by 2 tons to allow for the extra coal capacity. The tractive effort was increased by 240÷225 to allow for the higher boiler pressure (factors such as wheel and cylinder sizes were not changed). The Horsepower

62 increase is debateable: Ref 15 quotes “-dynamometer --on some of these tests more than 4000 hp was achieved--”, which appears well founded. Ref 12 is general and appears to quote a more optimistic press release stating “Compared to the Class 25NC, the Class 26 has 35% reduced coal consumption, 27% reduced water consumption and 50% increase in maximum drawbar horsepower.” The ‘drawbar horsepower’ is derived from indicator horsepower and only has meaning if the train load is given. Furthermore, are the other savings cumulative values over a long period with different load conditions, or the best values for a particular condition? On what values for the Cls 25 are they based? The following approach is suggested for reasonable comparisons.

As mentioned above, the power is best expressed as the Indicator (or Cylinder or Tractive Wheels) horsepower, which is an independent power value from which drawbar (ie Load) horsepower can be simply calculated, as was done in Table B2.

Also, what was the comparative horsepower value for the Cls 25 - I have not seen it published anywhere? The approach followed is the following:From Ref 1, a good prediction of the power expected from the Cls 25 was obtained from a reliable source: the leader of the Laingsburg Cls 23 boiler tests. Raimund confirms from his participation in these tests that the Cls 23 reached a 3000 maximum cylinder horsepower under passenger train running conditions. The class 25 has a 12% bigger fire grate area, and some further boiler improvements such as the higher boiler pressure would increase the output by a further factor of about 1,04. This leads to a reasonable maximum cylinder power output of 3500 hp for the 25NC. Assuming that the maximum drawbar horsepower for the Cls 26 was achieved with the same train load as for the Cls 25, then the increase percentage would also apply to cylinder horsepower. Applying the quoted increase of 50% leads to 5250 cylinder hp for the Cls 26. This cannot be reconciled with the value of “more than 4000 hp” from Smith and Bourne. Also, a “35% reduced coal consumption” would imply a boiler efficiency approaching 80%, which is hard to accept even with improved burning, as the temperature of the superheated steam was increased: the smoke outlet temperature would also increase leading to some reduction in boiler efficiency. As a compromise, a value of 4500 cylinder hp for the Cls 26 was used in Table B2, a figure which is probably still on the high side.

In Table B2, values for Locomotive Weight (which include tender or auxiliary water tank) and Maximum Sustained Horsepower (a term vital for comparison with the Electric Locos) were taken from Table B1 and multiplied by the number of locos. The available Tractive Force to start the whole train with locos was taken as the Tractive Effort times the number of locos, except for Cls 26, where this value was reduced slightly to correspond to a friction value of 28%, already a dangerously high value.

The “Load Lifted on 1 in 100 gradient” is calculated on the basis that the gradient effect amounts to 20 lb/ton, and total friction and other losses to 5 lb/ton, a total of 25 lb/ton. The netto load in tons, which can be lifted, is then derived by dividing

63 the Tractive Force by the 25 lb/ton, and subtracting the weight of the locomotives.

A reasonable way in assessing how effective the horsepower values are, was to calculate in the same way what the available drawbar horsepower would be if the locos were hauling a 3000 ton load.

The Verdict is then that three Cls 6E1 Units or Cls 34 Diesels would have to be used to have the same horsepower available under typical passenger train conditions (assuming the optimistic power value for the cls 26 holds), but that the load that they could then lift would be 1,7 resp 2,1 times as much. Even then, the two Cls 26 locos would need double the number of footplate staff. This analysis does not take factors detrimental to the steam loco such as delays to take on water/coal and maintenance costs into consideration, or the factor of fuel or capital cost. Case dismissed.

But - what about the other alternatives for BIG steam locomotives? Why not articulated locos like the Mallets? Yes, if we look at Fig 12, we find that the world’s biggest steam locomotive was indeed a Mallet. The Mallet articulated design calls for splitting the engine part into two halves, each with its own cylinders, valve gear, etc. The front half pivots around the rest, and also supports half the total loco weight, so that it can adequately contribute to the total power output. Boiler size remains a limitation, particularly if the loco has to be able to negotiate sharp curves - the boiler front will project outwards só far that it needs to be tapered. It does not, however, have the limitations of the Garrett loco which has to carry all its coal and some of the water on the engine part. The ‘Big Boy’ had at least 50% more tractive effort than a Cls 25 double header, but only the same horsepower. It would not have been suitable for sharp curves. Our experience with Mallets was poor on the whole: double expansion (‘Compounding’) was used, but only the last orders had superheaters (See the MJ, Fig 12) and even the later models had troubles, one being broken boiler tubes as the boiler was too long. Somehow the SAR abandoned the design in the twenties.

I have no further information but that the ‘Big Boy’ did not save even the American steam locos.

Now take a breather before we carry on with the details of what made the locos work - or not.

B7 Table B1 - Locomotive Power Data S t e a m Cl

Loco Year

T r a c k lb/ yrd

Max. Axle Load toncwt

Drivi ng Wheel Sets - Dia

Cyl inder Num ber Bore ”x Strok e”

Trac tive Effort lb f

Driv ing Wheels total Axle load t-c/lb f

Fric tion Fac tor %

B o i l e r Press ure lb/sq

Grate Area sq ft

Estimate d Max. Hp.

Total Mass short tons

64

219”x 26” 224”x 26” 418½” x26”

27 600

45 - 4 101280

27%

in 200

36

1800

145

31 850

55 - 7 124 040

26%

200

36

1800

171

49 430

106 - 16 239 360

21%* *

200

56,6

2700

237*

223¼x 25 224”x 28” 224”x 28” 224”x 28” 224”x 28” 224”x 28”

38 000

74 - 8 166 660

23%

180

42

2000

157

35 820

59 - 14 133 730

27%

210

62½

2800

187

42 340

74 - 10 166 880

25%

210

62½

3000

205

43 200

72 - 10 162 400

27%

225

62½

3000

241

45 360

74 - 5 166 320

27%

225

70

3500

250

48 380*

74 - 5* 166 320

29%*

240*

70

252

420½” x26” 422”x 26”

60 700

122 - 3 273 620

22%* *

200

63,2

4000( 15) 5250( 12) 3000 +

78 650

144 - 17 324 460

24%* *

200

74½

3600

236

-

49 460

196 030

25%

-

-

2950

98

24

1948

40¼

11-10

451”

19D

1949

60

13 19

454”

GO

1954

45

13 - 8

854”

Mai n S1

Line 1947

96

19 18

448”

16E

1935

96

20 19

372”

15F

1938

96

18 15

460”

23

1938

96

18 14

463”

25N C

1955

96

19 - 6

460”

26

1981

96

19 - 6

460”

GM AM

1954

81

15 14

854”

GL

1929

96

18 14

848”

Elec tric 6E1

Unit s 1985

96

21 17

448”

Die sels 35

1972

60

34

1971

96

13 645 190 181 520 25% 1430 10 36” 18 661 150 248 680 25% 2600 10 40” ** Calculated on the basis of loco/auxilliary tank with full supplies included.

* Estimated value

292*

91 111

Table B2 - Locomotive Performance Comparisons Ref

1

Loco s Cls x no

Staff on locos

Loco Mass ton

25N

4

500

F

Tra ctiv e For ce

F

1

90

<1

Load lifted on 1/100 Gradie nt short tons 3630 -

F

<1

Max sustaine d Cyl. Hp

7000

F

0,8

Hp. for 3000 t Load

5810

F

0,8

65 Cx2

700

2

26 x 2

4

504

1

95 000

1

3

6E1 x2

2

196

2,6

99 000

1,1

4

6E1 x3

2

294

1,7

148 500

1,6

5

34 x 2

2

246

2,0

122 300

1,3

6

34 x 3

2

369

1,4

183 500

1,9

500=31 30 3800 504=33 00

1

9000

1

7470

1

3960 196=37 60 5940 294=56 50

1,1

5900

0,7

5550

0,74

1,7

8850

1,0

7970

1,07

4900 222=46 80 7340 369=69 70

1,4

5200

0,6

4810

0,64

2,1

7800

0,9

6950

0.93

Note: The Factor F is an indication of how much better the other alternatives are relative to 2 x 26 locos, ie a factor less than 1 shows that alternative is poorer than the 2 x 26. All tons are short tons of 2000 lb.

An Addendum on Fuel Costs: Fuel costs can be roughly compared between Steam and Diesel Locomotives as follows: The Steam Loco is about a quarter as efficient as the Diesel (Overall efficiency about 6% and 25% resp.)

Compare 1 ton of coal used by the steam loco at a (high) price of R400 with the diesel equivalent. The heat value of the coal is taken as 14 000 and that of the diesel fuel as 19 000 BTU/lb. The Diesel will therefore need ¼ x 14/19 x 2000 lb of diesel oil, or 368 lb = 167 kg of fuel. At a specific gravity of 0.9, this equals 186 litres. The basic price of diesel is about 3 R/litre.6 The Diesel’s fuel cost for the same power output at the driving wheels is therefore R 557/400 or 40% higher than the steam’s.

Fuel costs are not as important as one feels instinctively. The two Cls 25s dealt with in Table B2 hauling their 3000 ton load up the gradient will reach 30 mph.

The firing rate will be 170 lb/hr per sq ft of grate x 70 sq ft x 2 locos = 12 ton/hr. At 30 mph this amounts to 12/30 or 0,4 tons per mile, a cost of R160 per mile. They are, however, moving 3000 tons, making it 5,3 cents per ton-mile. How much does my petrol bill amount to for my car of 1,5 tons doing ten km per litre? At 5 R/litre, it would be about 30 cents per km, or 50 cents per ton-mile.

Any more questions?

6

'Fuel cost values are those applicable in 2005'.

66

Appendix 1 Summary of Robin Barker’s View of the Origin of the 4’-8½” Rail Gauge Robin Barker gave Raimund a three-page paper at the last U 3 A session on “Our Steam Locomotives”. The title is BRITAIN’S (not so) PECULIAR RAIL GAUGE (© Copyright: Robin Barker, Pretoria 2003).

It is based on references JB Snell: Early Railways, & OS Nock: Encyclopedia of Railways and after consultations with Philip Brooks of Wylam Historical Society, Andy Guy of Beamish Open Air Museum and Philip Atkins of the National Railway Museum, he sorted out some conflicting information on how ‘wheel’ and ‘rail’ gauges had been quoted in the period before and up to the time inner wheel flanges became the standard. He puts forward a strong case that the development started from 18 thC horse-drawn coal carts that ran (more or less) on the stone block strips. It seems that these wheels were conveniently spaced 5’ apart as measured from outside to outside.

When cast iron became available at the turn of that century, the collieries started using plateways of cast iron. Robin puts forward a case that they were L-shaped strips and that they were screwed onto the stone blocks with their vertical flanges on the outside- this gave the ponies more room to move. The cast iron strips were brittle and were very short-lived.

When malleable iron became available, the Wylam Colliery 5-foot outside flanged plateway was rebuilt by engineer William Hedley, probably by bolting thick malleable iron strips in a vertical position to create what became known as an Edge Railway.

The edge had no flange; instead the wheels were given outside flanges he thinks.

This railway misleadingly retained the five-foot gauge designation. (Note by Raimund: I am speculating that the initial conversion of the wheels could have been done by merely clamping a disc of about two inches greater diameter to the outside of the wheel - the wheel position on the axle could have been left unchanged. Naturally, the wheels would soon have been changed for solid flanged tyres when the better shape proved necessary) Robin came to the conclusion that the distance between the iron plates remained the same (see sketch), regardless of what the track gauge was now called. As the disadvantages of outside flanges became clear (Wheels are more easily dislodged and bumped off the axle with outside wheel flanges as is also the case with inside rail flanges), the Wylam Colliery railway was converted in 1862 to inside wheel flanges, leaving the track basically as it was. This meant that the gauge of the track as measured from inside edge to inside edge became 4’-8”, soon to be adjusted to 4’-

67 8½” for added clearance. This accorded with Stephenson’s design and was retained as the British and American main line gauge.

In short, the point made is that the 4’-8½” rail gauge was a logical consequence of starting off with a nice round figure of 5’-0” spacing (outside to outside) of the flangeless wheels of their precursors running on stone block strips.

Figures FIG 1 & 2

68

69

FIG 3 & 4

70

FIG 5 & 6

71

FIG 7 & 8

72

FIG 9

73

FIG 10 – Class 25 & 25NC (1953 – 1955)

Fig 11

74

75

Fig 12 Local & USA Mallets

76

Fig 13

Fig 14

77

Fig 15 & 16

78

Fig 17

Fig 18

79

Fig 19

Fig 20

80

Fig 21

Fig 22

81

Fig 23

Fig 24 Cab of GMAM 4051

82

83

Fig 25

84

Fig 26

Fig 27

85

Fig 28

Fig 29

86

Fig 30

87

Fig 31

88

Fig 32

Fig 33 Loss of White Metal after Overheating

89

Fig 34 & 35

90

Fig 36 & 37

91

Fig 38 â&#x20AC;&#x201C; Model of a Walschaert Valve Gear

Fig 38 - Settings

92

Fig 39

93

Fig 40 & 41

94

Fig 42

95

Fig 43

96

Fig 44

97

Fig 45: Class 25 Overlubricated

Fig 46

98

Fig 47

Fig 48

99

Fig 49

Fig 50

100

Fig 51

101

Fig 52

Fig 53

102

Fig 54

103

Fig 55

Fig 56a

Fig 56b

104

Fig 57

Fig 58

105

Steamloco Images

106

107

Photographs7

7

Some are better than those in the text – these are from the slides that accompany the “talk” when delivering the paper.

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

And thatâ&#x20AC;&#x2122;s all Folks! I sincerely hope you enjoyed this special edition. On a personal level I learnt a lot! Our special thanks to Dr Loubser and Mr Les Pivnic.

Kind regards, Hennie Heymans

131