Model Engineer Magazine issue 4730 **FREE 20 PAGE PREVIEW!** by Mortons Media Group Ltd

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THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS Vol. 231 No. 4730 17 – 30 November 2023

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HERCULES Marine Engine First featured 100 years ago

Barbados

Railway ride with rum ration

Angle Plate Make your own

7¼ INCH GAUGE AGM Celebrating 50 years

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EDITORIAL Editor: Martin R. Evans Deputy editor: Diane Carney Designer: Druck Media Pvt. Ltd. Club News: Geoff Theasby Illustrator: Grahame Chambers Publisher: Steve O’Hara CUSTOMER SERVICES General Queries and Back Issues 01507 529529 Monday-Friday: 8.30am-5pm Answerphone 24hr help@classicmagazines.co.uk www.classicmagazines.co.uk ADVERTISING Group advertising manager: Sue Keily Advertising: Craig Amess camess@mortons.co.uk Tel: 01507 529537 By post: Model Engineer advertising, Mortons Media Group, Media Centre, Morton Way, Horncastle, Lincs LN9 6JR PUBLISHING Sales and distribution manager: Carl Smith Marketing manager: Charlotte Park Commercial director: Nigel Hole Publishing director: Dan Savage SUBSCRIPTION Full subscription rates (but see page 666 for offer): (12 months, 26 issues, inc post and packing) – UK £128.70. Export rates are also available, UK subscriptions are zero-rated for the purposes of Value Added Tax. Enquiries: subscriptions@mortons.co.uk PRINT AND DISTRIBUTIONS Printed by: William Gibbons & Son, 26 Planetary Road, Willenhall, West Midlands, WV13 3XB Distribution by: Seymour Distribution Limited, 2 East Poultry Avenue, London EC1A 9PT EDITORIAL CONTRIBUTION Accepted photographs and articles will be paid for upon publication. Items we cannot use will be returned if accompanied by a stamped addressed envelope and recorded delivery must clearly state so and enclose sufﬁcient postage. In common with practice on other periodicals, all material is sent or returned at the contributor’s own risk and neither Model Engineer, the editor, the staff nor Mortons Media Ltd can be held responsible for loss or damage, howsoever caused. The opinions expressed in Model Engineer are not necessarily those of the editor or staff. This periodical must not, without the written consent of the publishers ﬁrst being given, be lent, sold, hired out or otherwise disposed of in a mutilated condition or in other unauthorised cover by way of trade or annexed to or as part of any publication or advertising, literary or pictorial manner whatsoever.

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Vol.231 No.4730 17–30 November 2023 668 SMOKE RINGS News, views and comment on the world of model engineering.

669 MIDLANDS MODEL ENGINEERING EXHIBITION John Arrowsmith provides a view of the highlights of this year’s show at The Fosse.

672 FAREWELL TO PERCIVAL MARSHALL How Model Engineer said ‘farewell’ in 1948 to its founder and first and longest serving editor.

674 LNER B1 LOCOMOTIVE Doug Hewson presents a true to scale fiveinch gauge model of Thompson’s B1.

677 RADIAL VALVE GEARS AGAIN Duncan Webster explores the subtleties of valve gear operation.

680 BARBADOS RAILWAY Paul Stone takes a ride with a history lecture and a rum tasting thrown in.

682 THE STATIONARY STEAM ENGINE Ron Fitzgerald tells the story of the development of the stationary steam engine.

686 A METHOD OF MANUFACTURING PISTON RINGS OF THE CLUPET STYLE Martin Gearing exposes the secrets of making Clupet rings.

for details.

692 OBITUARY We remember John Hemmens, supplier of fine models to model engineers.

693 POSTBAG Readers’ letters.

694 A MODEL ENGINEER’S CLOCK Jim Clark uses modern methods to make a skeleton clock inspired by John Wilding.

698 HERCULES – A TWIN CYLINDER COMPOUND ENGINE Chris Walter describes a condensing marine engine first featured in Model Engineer 100 years ago.

702 WORKSHOP TIPS ANGLE PLATE Mike Joseph describes how to make your own angle plate at low cost.

704 A FIVE-INCH GAUGE 0-4-0 PADARN RAILWAY TENDER LOCOMOTIVE Luker presents Fire Queen, a Welsh slate quarry locomotive.

708 50th AGM OF THE 7¼ INCH GAUGE SOCIETY John Arrowsmith reports from the Bedford Model Engineering Society.

712 CLUB NEWS Geoff Theasby compiles the latest from model

689 BUCKEYE COUPLING FOR 5 INCH GAUGE Jonathan Buck creates a set of fully working buckeye couplings for an A4 locomotive.

THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS Vol. 231 No. 4730 17 – 30 November 2023

engineering clubs around the world.

715 CLUB DIARY Future Events.

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HERCULES Marine Engine First featured 100 years ago

Barbados

Railway ride with rum ration

HERCULES twin cylinder compound condensing marine engine (photo courtesy of Chris Walter).

Angle Plate

Make your own £4.95

7¼ INCH GAUGE AGM Celebrating 50 years

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This issue was published on November 17, 2023. The next will be on sale on December 1, 2023.

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Farewell to PM

MARTIN EVANS Editor

DIANE CARNEY Assistant Editor

Percival Marshall, founder of both Model Engineer magazine and the Society of Model and Experimental Engineers (SMEE), died on April 10th 1948, just a few weeks after celebrating the 50th anniversary of the magazine and also, of course, half a century of occupying the editor’s chair. He is, by far, the longest serving, as well as the first, editor of this magazine and it is sobering to reflect that, of all the issues produced so far over 125 years, he edited over half of them. This is possible because, for most of its first half century, the magazine was a weekly publication. It started life as a monthly, rapidly moved to being a fortnightly publication and by the beginning of 1903, by popular demand, had become a weekly. It reverted to a fortnightly publication in 1963 and has been so ever since. I can’t imagine how the Model Engineer staff managed to produce an issue every week! On page 672 we reprint the magazine’s 1948 farewell to Percival Marshall.

FMES/Polly Trophy It is winter coming up and that means the closing date for this year’s competition is nigh! There is still plenty of time for Young Engineers to submit their entry to the competition run by the Federation of Model Engineering Societies (FMES) and Polly Models. It is probably appropriate to add a word or two of encouragement though. FMES and Polly want as many Young Engineers to enter as possible because they want to prove to doubters

Spencer Priddy (2022/23 winner) with Mike Chrisp, FMES vice president.

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this competition, is on March 2nd 2024 at Boscombe Down Aviation Museum in Wiltshire.

Kingston College

FMES that there are still young people who are enthusiastic about model engineering, and who are not only developing excellent engineering skills, but they are taking part in the life and soul of their club. We are not seeking only ﬁnished models as entries, but anything developed by the entrant that demonstrates their learning practical engineering skills (and these days that includes CAD/CNC/plastic printing etc. as well as traditional lathe and hand work), complemented by an explanation of how they are supporting their club and the activities that it is involved with. The closing date this year is 31st December and you can ﬁnd the details, frequently asked questions, application form and examples on the FMES website at fmes.org. uk on the ‘Young Engineers’ page. In case older members think that this is not relevant for them, each entrant needs a club ‘sponsor’ and so if you, as an established and older member of a club, know a young member who should enter, please let them know! The awards will be presented at the FMES AGM, which, for

If you live anywhere near Kingston-upon-Thames in the south-west London area and are looking for a model engineering evening class, you may be interested in the class being offered by the Kingston College Model Engineering Group. The college workshops are well equipped and the group is run by Bryan Ruby, who has been described as ‘an excellent instructor with the patience of a saint’. The class takes place on Thursday evenings. The fees are £130 a term and Bryan may be contacted on 0208-2682824.

Stolen Traction Engine I have received a request to help ﬁnd a Burrell traction engine, stolen from a reader’s house in Mountsorrel, Leicestershire on October 6th. Judging from the photograph it is a fairly small engine, of perhaps 3 or 4 inch scale. The height to the top of the chimney looks like about 70cm. If you spot it somewhere please do let me know.

Martin Evans can be contacted on the mobile number or email below and would be delighted to receive your contributions, in the form of items of correspondence, comment or articles. 07710-192953 MEeditor@mortons.co.uk

Stolen Burrell traction engine.

Model Engineer 17 November 2023

The Midlands Model Engineering Exhibition Highlights John Arrowsmith gives his first impressions of the show at The Fosse.

ollowing on from last year’s exhibition was always going to be an apprehensive expectation by the organisers because of the unknown factor regarding the number of models available following last year’s bumper entry. Whilst numbers were down, which was only to be expected, perhaps the quality overall was excellent and two models in particular were worthy of the entrance money on their own. Good crowds on all days ensured that the organisers were happy, the traders were happy - well the ones I spoke to were - so hopefully that was the case for all of them. Regarding the models only ﬁ e classes did not ha e any entries but the rest made

One of the stars of the show was this magnificent example of an LNER P2 built by John Wilks.

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up with some outstanding examples of the model engineer’s art. The most striking model of the show was the 10¼ inch gauge model of Gresley’s P2 Cock o’ the North built by John Wilks, who sadly died last November. This was an outstanding model which displayed all the Gresley characteristics, including the Lentz poppet valve gear, Kylchap exhaust and the ACF1 feedwater pump. It was as built in 1934 in the semi streamlined form. It has three cylinders and a TIG welded steel boiler. Positioned at eye level in the main hall it was a real eye catcher (photo 1). The other outstanding model was in the competition and won both Class 8 for internal combustion engines and the Chris Deith Memorial Trophy awarded for the best working engine in the show. This model of a 1927 Delage 15.S.8 GP engine was built by Mike Sayers and was the unanimous choice of the judging panel (photo 2). No commercial castings were used in this engine - everything was either machined from the solid or fabricated. Other classes also had some excellent models and Bruce Harvey’s 7¼ inch gauge LNER N2 locomotive was a case in point in Class 3. Fitted with condensing gear, it worked as well as it looked and I saw it in action at the 7¼ Inch Gauge AGM at the Bedford club

Another star of the show was the Delage 15.S.8 GP engine built by Mike Sayers.

3 Luke Mason won the Young Engineers class with this lovely little Stuart S50 mill engine. recently (photo 8). All the other exhibits in Class 3 were also superb models and they will be covered in my next report. All the competition classes had really excellent examples on show and provided a real challenge to the 14 judges. The display classes were a little disappointing not because of the quality on show but because of the numbers on show. It would be a real boost to the organisers if the classes could be better supported. Remember any show is only as good as the quantity and quality of the exhibits on show and I know there are some really good examples of all sorts on engineering models

669

An excellent example of a WW11 armoured car was on the Welwyn Garden City display.

A large scale sailing barge built by Tony Judd.

This 4 inch Burrell traction engine was started by the young man in the driving seat when he was 15.

Winner of Class 3 Locomotives was this LNER N2 condensing tank built by Bruce Harvey.

Another example of superb locomotive building skill was this 5 inch gauge GWR pannier tank by Alan Crossfield. A superb example in 1½ inch scale of an Allchin Royal Chester traction engine built by Dennis Lambe. out there. So perhaps next year, model engineers everywhere will respond to this request and put on a really great show for

670

everyone to enjoy. Remember we have already lost the London shows. I don’t know yet about the Northern show but

if that doesn’t materialise next year the Midland Exhibition will be the only one of its kind in this scale left in the UK. You all know the old adage ‘Us it or Lose it’ - I rest my case m’Lud.

As I said at the beginning over all this was an excellent show with very reasonably priced catering and drinks, free parking and plenty to see. Hopefully next year there will

Model Engineer 17 November 2023

MIDLANDS SHOW

A 5 inch gauge dual tank wagon by Guy Harding.

11 The lady herself, Cherry Hill with her engines and Duke of Edinburgh trophy.

An unfinished 3½ inch gauge LMS 0-6-0 ‘Jinty’ by Richard Folwell.

This superb example of a horizontal mill engine was built by Cherry Hill in 1962.

This 10¼ inch gauge LNER J11 0-6-0 ‘Pom Pom’ was built by Daniel Floyd in 3 years.

The 100-year old 15 inch howitzer built by Admiral Sir Reginald Bacon was part of the SMEE display.

www.model-engineer.co.uk

be some added attraction as well to provide an extra element for your enjoyment. Finally, I think I should mention that this year marks the 125th anniversary of Model Engineer magazine but coincidentally it is also the 125th anniversary of the Society of Model and Experimental Engineers (SMEE) and they put on a tremendous display of their work going right back to their origins and the 100 year old Howitzer built by Admiral Sir Reginald Bacon, who was chairman of SMEE at the time, was a wonderful example of early 20th century model engineering. Fully refurbished by SMEE member John Clarke, it looked an outstanding

model of the time (photo 13). The other notable visitor to the exhibition was 96-year old Cherry Hill who is still a SMEE member and who had on display three of her prizewinning models, her book by David Carpenter and the Duke of Edinburgh Trophy which she won a number of times. It was a really lovely moment when she posed for photographs with her models on the SMEE stand (photo 14). I hope these few words have whetted your appetite and you will look forward to reading about the exhibition in more detail in future issues of Model Engineer. To be continued.

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Farewell to

Percival Marshall From Model Engineer, M.E.2449, April 29th 1948

‘P.M.’ (photo by W.J. Bassett-Lowke). he quality that makes a man memorable takes many different forms. Eminence in the big affairs of the world; distinguished work in science, law, or the arts; heroic action in an hour of danger; statesmanship, administrative ability, even the dull power of accumulating money, may raise his name above the common level. But there is another and kindlier fame that wins no

672

headlines in the daily press; it shines, nevertheless, with a steady light, clear and unmistakable and inspiring. It is a quality of life, endearing and enduring—the gift of making friends; and that gift Percival Marshall possessed in the highest degree. He did great and lasting work in a special ﬁeld of engineering hich he made his own; yet we who knew him and talked with

him day by day would set an equal value upon that genius for friendship which was the outstanding characteristic of his personality and his career. He gave, in the New Year’s Day issue of this journal, something of the story of his life. Born in London on December 31st, 1870, his early training was in good hands, for the professors at the historic Finsbury Technical College, through which he passed, were men of mark in the eighties and nineties—many of them pioneers in electrical and mechanical engineering. He also attended courses of study at the Birkbeck Institute, the Manchester Technical School and the Victoria University, afterwards gaining experience with several wellkno n firms as apprentice, impro er, fitter and machinist He spent some months as a lathe hand in a French factory. With a scholarship, technical diplomas and other honours he considered that he was all set for the life of a skilled practical engineer. The fates, however, had different views. Perhaps we should more correctly say that his own energy and decision steered him in a different direction e had a definite desire to get his ideas down on paper and like many another young man he found eventually that free-lance writing opened the way to an editorial chair; rather surprisingly, he became editor of a photographic magazine. Then the idea of starting a popular engineering paper captured him and Percival Marshall, carrying that idea over many difficult hurdles, heeding

Model Engineer 17 November 2023

PERCIVAL MARSHALL

no doleful prophets, published the first issue of his o n monthly, the Model Engineer and Amateur Electrician, in January, 1898, when he was 27 years old. Warned that he would be lucky if he sold 500 copies; told that model engineering was ‘dying out’; he faced with his calm smile all the usual gloomy comments that enterprise attracts he first t o numbers sold out at once and had to be reprinted and today the circulation of the ‘M.E.’ is counted in tens of thousands a week. Thus, then, began the main theme of Percival Marshall’s acti ities for the ne t fifty years, a theme with endless variations, delightful to himself and to his innumerable readers. His heart was in it and if at any time he heard some derogatory remark that relegated model engineering to the toyshop level or attempted to lower its standing by limiting its scope to a passing amusement for boys, ‘P.M.’ would demolish such criticisms in one of his rare onsets of severity. In fact, this class of loose comment, still occasionally to be heard, was the one thing that could bring him as near to ‘blowing off’ with the pressure of resentment as any of us have ever seen him. He was cross with it; it annoyed him and he refuted it admirably, advancing argument after argument that left his opponent no escape. He would point out the vital part that model making plays in almost e ery scientific and industrial development, from the small ‘hook-up’ of the laboratory to the giant tanks and wind-tunnels of the largescale experimental test or the ‘mock-up’ of a new type of aeroplane. But apart from this essential aspect, he would say, what about the sheer pleasure of building a beautiful bit of mechanism with one’s own hands —the recreative aspect, as evidenced at the Model Engineer Exhibition, where ships and clocks and engines of every kind in miniature, made by postmen and taxidrivers and those interesting people known collectively as

www.model-engineer.co.uk

‘ordinary’ can be seen and admired? How ‘P.M.’ loved this Exhibition! In the year that saw the birth of The Model Engineer, he had founded also the Society of Model and Experimental Engineers, which has influenced the formation of over a hundred local clubs and societies with similar aims at home and a road he first Exhibition was held in October, 1907, and though for a time it was biennial it has become now a remarkably successful annual event, a rallying point for model enthusiasts everywhere, as all our readers know. There, amid the unique display of talent in true craftsmanship, ‘P.M.’ was ‘at home’ indeed to a host of friends; and many of us remember with pleasure his happy little informal speech on the occasion of the 21st birthday of the Exhibition in 1946. Although it is natural to lay strong emphasis on the work by which Percival arshall as chiefly kno n, his other interests must be remembered. One of these was his early association with the Junior Institution of Engineers, to which he was elected in October, 1886, becoming a member of the then ‘Committee’ - later the Council—in 1887, ‘at the age of e held the office of Chairman of the Council for two years (1900-1902). But apart from engineering he did a great deal for technical journalism. This followed partly, no doubt, from his family link with publishing; he was a nephew of Sir Horace Marshall, K.C.V.O., P.C., J.P., M.A., LL.D., Governing Director of Horace Marshall and Son Ltd., who was Lord Mayor of London for the year 191819. Percival Marshall took a leading part in creating the British Association of Trade and Technical Journals, which later was amalgamated with the Periodical Trade Press and Weekly Newspaper Proprietors’ Association. He was Executive Chairman of this larger body from 1928 to 1943, when he was elected vice-president.

To this work he devoted much of his spare time, attending committee meetings regularly and being responsible for many suggestions affecting the well-being and prestige of technical journals in this country. For some years he served on the Council of the Empire Press Union, and, in kindred activities, made more than one visit to Canada and the United States. He had been a member of the Press Club for over 30 years, was a trustee of the Press Club Fund and at one time lunched there almost every day, spending half-an-hour or so afterwards over a game of bridge in the card-room. In June, 1929, his own publishing business of Percival Marshall & Co. was by arrangement amalgamated with that of the Electrical Press Ltd., since when the two have been carried on successfully as a single organisation. For the last few years he had relinquished the more onerous duties of editorship, leaving them in the hands of a loyal and competent staff which had carried on, and will continue to do so, the tradition so finely and firmly esta lished y the leader they knew so well. His recreations were such as one would expect in a man whose nature was tranquil, contemplative, and philosophic. olf and fishing took first place he was a prominent, member of the ondon ress olfing Society and followed Bernard Darwin as captain in 1912; he was also an excellent shot, winning a silver cup at Bisley. And now we have to say farewell … to a pioneer, an engineer, a philosopher; a man upright physically and mentally; a man who was ‘valiant for friendship’; a man of wide experience and alert of thought. With quiet humour and kindly wit, Percival Marshall moved among us for many good years, smiling, encouraging, steadying and it is hard to realise that we shall not see him again in the old familiar places. The farewell was unexpected, for though he had not looked thoroughly well of late he was busy at his letters—

nearly always written with his own hand—and his charming ‘Smoke Rings’ with his beloved pipe, almost to the last. He left his ofﬁce early on arch th and did not return. The end came peacefully and without pain on April 10th. To us he was always ‘P.M.’ and we may close on a note of gratefulness that we have walked for a little way along the journey with one of whom it can be truly said, as of another pioneer, that, apart from his work, remains ‘that best portion of a good man’s life, his little nameless and unnumbered acts of kindness and of love’.

The above obituary for Percival Marshall appeared in the April 29th issue in 1948, just after the magazine had celebrated its 50th anniversary. His death had been announced in the previous issue (April 22nd – yes, Model Engineer was weekly then!) with the following words. ‘By his death the hobby of model engineering has lost its best known and certainly its most loved personality. Many thousands of letters from readers all over the world have told how much his kindly wisdom and philosophical style have been appreciated; the friendly personal touch so typical of ‘ours’ is the result of years of guidance from his editorial pen. ‘For some months Mr. Marshall had been in poor health but continued to write his Smoke Rings until the middle of March this year and none of those who were privileged to work with him ever heard him complain. ‘His death is a great loss to our hobby and a deep personal loss to those who were in daily contact with him. His life’s work was well done and the movement, to the growth of which he was so devoted, will carry on to greater strength because of the sure foundation upon which it was built by him.’ ME

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LNER B1 Locomotive PART 32 – THE CAB FITTINGS Fig 121

Steam chest pressure gauge

Vacuum gauge

Boiler pressure gauge

Doug Hewson presents an authentic 5 inch gauge version of Thompson’s B1 locomotive.

Left hand gauge frame

Right hand gauge frame

Live steam injector steam valve

Exhaust steam injector steam valve Carriage warming valve

Blower valve

Carriage warming gauge

Vacuum brake ejector Steam brake valve for engine & tender

Continued from p.645, M.E.4729, November 3

Coal watering clock

Reverser Isolating valve for steam brake cylinder Steam sanding gear Cylinder drain cock lever

Carriage warming steam reducing valve Vacuum reservoir Drain cock lever

Backhead layout.

9/32

1 11/16

1/8

Two #54 holes for 12BA bolts

61/64

5/32

7/32

Silver solder tube to backplate

1 7/16

Silver solder tube to backplate

1/8

Fig 122

To fit inside elliptical hole

9/32

18SWG plate

31/32

Silver solder Use 10BA screws to fit latch plate to fire hole door including washer

19/32

3/32 pin 3/64 taper pin

#51 hole

r1 5/32

5/32

3/16

5/8

9/16 5/8

1/4

1 7/8

r7/16

Stop

1 9/16

7/32

Hinge vertical

16SWG strip

9/16 15/16

Elliptical

1/8

3/16 21/32 1

5/32

Stop

Use taper packing behind parts of hinge

1/4

5/32 7/32

2 3/8

Slot holes in bar x 1/16”

18SWG strip

1 7/16

Former For Fire Hole Door

11/64

7/32

Former For Fire Hole Door Opening

Firehole door.

674

Model Engineer 17 November 2023

LNER B1

229

230

Part of the back plate of B1 61306 (photo courtesy of John Thompson).

231

232

Back plate of Geoff Moore’s 8303. e ill no make a start on the ca fittings s can e seen from the dra ing fig 121) I think ha e made a good sta at the fittings, although not all of them ha e descri ed all the essential ones at least and some hich aren t e ill make a start on the fire hole door fig 122 his is mounted on a hinge that is mounted on the sloping ackplate ut the hinge that is ertical other ise it ould e ery difficult to open ha ing to open it uphill t has the typical flap in its centre and the usual way to carry out the firing is to fire under the flap am not sure ho most folks fire a inch gauge engine ut may e they open the door hen Ballan Baker uilt his he copied the design e actly as on oung had designed it

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Back plate of Ballan Baker’s K1.

B1 back plate undergoing repair. and, one day, as shunting coaches ith it at illing and found it a delight to dri e firing it under the flap found it quite amena le to sho el coal on like that so think you ill find that acceptable too. It is the same on Brian pthorpe s B Brian has a acuum rake fitted on his ackplate ut took this photo efore Ballan had fitted his either of them are the correct type of e ector the proper ersion ut they ha e used the ersion as fitted to on oung s they oth ork of course ould make a start ith the former for the elliptical plate for the ack plate and if you make the former plate inch thick you can also use it as a filing ig to achie e the correct thickness ou ill need to make the ack plate from s g steel plate to gi e it a it of su stance and the flap can e made out of

the same material. Photograph 229 shows the fire hole door on and this photograph shows all of the its hich am going to mention in the te t here is a chain on the door catch ith hich to open it he catch at the bottom is obviously nutted on the ack of the ack plate cleading ne of my o n photographs photo 230) sho s Ballan s hich ha e happily dri en on a num er of occasions his does of course sho the fire hole door o this photo 231) is a photo of eoff oore s on shed at illing, also sho ing the fire hole door from the ack ut eoff s is a it more complete than Ballan s as it has a acuum rake e ector in the ca and eoff has fitted the correct t o ater gauges in his ca ust thought that

you might like to see the ne t photograph photo 232) as it is one of the B s undergoing a ma or operation on its oiler with the bottom part of the ack plate eing rene ed t has also had pre ious operations done efore that around the top end too ust thought ould sneak this photograph in photo 233) for you as this is my friend ohn Bruce s rather larger ack plate in as it is ohn s inch B hich he is uilding ould tackle the door hinge ﬁrst and this needs t o pieces of s g plate rapping around a piece of inch ar and then cutting ith a slitting sa to ﬁt ust nicely into the t o rele ant parts ou ill then ha e to arrange to set the t o parts of the hinge up to match the slope of the boiler ack plate so that the pin is

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233

234

Fire hole door frame (photo courtesy of John Thompson).

John Bruce’s 7¼ inch back plate.

235

vertical or use a piece of taper packing he proper ay is of course to make the hinge ith a taper in it ha e sho n the pin ith a collar on oth ends retained y a taper pin as that is hat it looks like on the photograph he flap needs to e a ery good fit in the ack plate as this controls the top air to the fire f the engine is getting near to lo ing off ust open the flap a notch and then that might ust drop the pressure enough to stop it t the centre of the flap there is the ad ustment for the flap in the form of a little arced quadrant and this ought to e case hardened so that you

can ust flick it open ith your trusty firing sho el and then if you feel the need to close it you can then ust lift the catch ha e also sho n a little stop hich should e sil er soldered to the inside of the ack plate to pre ent the flap from going o er centre he actual door catch is formed from a inch strip of s g steel strip and to gi e it its proper shape it needs shaping as sho n t has a couple of slotted holes in it so that can e lifted up to open the door he catch for the door is ust a utton and if you make it the correct shape it should ust click shut and if it doesn t it ill e intensely annoying, can assure you ha e also used some more photographs of ohn s hich he sent me of his B and the first photo 234) is the fire hole door frame s you ill see he has also used some lost a castings for that. Photograph 235 shows the completed article n the left foreground of photo one can t help ut notice ut there are some goodies from dam ro, like the proper lu ricators for the B hich he also produces in inch gauge To be continued.

NEXT TIME More on the cab fittings. Complete fire hole door photo courtesy of John Thompson .

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Model Engineer 17 November 2023

Radial Valve Gears Again

PART 13 – BAKER’S VALVE GEAR

Fig 77 Duncan Webster sheds light on what is often seen as a complex subject.

Continued from p.632 M.E.4729 November 3

Baker valve gear – outside admission. his gear was invented by Abner D. Baker sometime in the early years of the 20th century. The version about to be described should more correctly I think be called BakerPilliod, the Pilliod bit being the company that sold complete valve gear assemblies for use on locomotives. It was popular from about 1910, particularly in the USA, but fell out of favour and the later American locomotives reverted to Walschaerts. Its main claim was that it did away with the wear to sliding surfaces on the expansion link and could easily be maintained by just replacing bushes and pins. The Pilliod Company supplied standard sets of gear, the idea being you could take the whole thing off and replace it with a refurbished set much more quickly than repairing in situ. Later versions had needle roller bearings.

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Fig 78

Baker valve gear – inside admission. The arrangement for outside admission valves is shown in ﬁg , for inside admission in ﬁg . The similarity with Walschaerts is clear; the inphase motion is derived via the union link/combination lever and the outphase motion is driven from a return crank.

Here the similarity ends. The expansion link and its associated lifting link etc. are replaced by a system of levers, links and bellcranks as will be shown. It is not the easiest thing to describe, so please excuse my step by step approach.

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Fig 80

Fig 79

Gear connection lever with point m unrestrained.

Fig 81

Pilliod design of Baker’s valve gear. In ﬁg we have the combination lever at the lefthand side and the return crank drives the bottom end of the gear connection lever (GCR) via the eccentric rod. The top of the GCR is connected to a bell crank kjh, which pivots on a ﬁ ed point j on the gear frame. The other (vertical) arm of the bell crank is connected to the combination lever at e. If we now rotate the axle, nothing will happen to the bell crank as the GCR will just swing to and fro and point m will move in an arc

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centred on k. However, if we force point m to move in an arc whose centre is displaced from k, as shown in fig , point k will be driven up and down and the radius rod eh will drive the combination lever. The magnitude of this motion is governed by how far the centre of this curved path is offset from k. How this is achieved is shown in fig 1 - point m is suspended by radius bars mn from the reverse yoke np, and the reverse yoke pivots on a second fi ed point p on the

Gear connection lever with point m constrained. gear frame. If the reverse yoke is positioned such that k and n align, e are in the ﬁg situation and as the reverse yoke is moved away from this position we get more and more outphase movement. All very nice you might think and in his article in Model Engineer ( 21) LBSC says ‘…Baker valve gear is, in my humble opinion, the best outside radial valve gear ever invented…’. I have in my possession a booklet produced by the Pilliod Company (ref 22) which gives all dimensions of the gear - they must have had a good patent lawyer! LBSC must also have had access to this as his design is an exact 1:16 model of one of Pilliod’s, the only difference being about 0.005 inch where LBSC used a fraction measurement instead of a strange decimal, no doubt in keeping with the ruler and centre punch methods available in 1945. In the analysis that follows I have used LBSC dimensions except where noted. Now for the problems! LBSC recommends that the throw of the return crank should be three times the full gear valve travel and in his design for Juliet 2 (ref 23) the return crank radius is 0.647 inch and the big end is only 0.75 inch radius. This is a lot more than would be used in a Walschaerts setup. Readers will remember the problems of eccentric rod angularity described in part 7 (M.E.4724, August 25). Here they will be a lot worse. It will be noted that point r is set back from the line through k and m. This might be thought to be backset as described

previously but it is nowhere big enough and anyway was always the same no matter how long the eccentric rod. Back in part 5 (M.E.4722, July 28) I introduced the error caused by a curved slide in Hackworth/Joy type gears. In those the valve rod only moves through a few degrees but here the radius bar mn will move through a much larger angle (+/- 20 degrees or so) and so the error ill e signiﬁcantly higher. A few inches ago I said ‘If the reverse yoke is aligned such that k and n align...’. This implies that km and mn are the same length but on neither LBSC drawings nor on Pilliod is this the case. LBSC has mn = 0.875 inch, km = 0.75 inch. The best that can be achieved for mid gear is that m, k and n are in line but movement of the GCR will still give some outphase motion. The mathematical model to be described later shows this to be of the order of 0.01 inch at k, rather more at h, so the LBSC instruction to ‘set the GCR in such a position that the valve spindle does not move…’ is impossible. This oddity is discussed at length in ref 24, so I don’t intend to belabour it here. It will be noted that at mid gear the reverse yoke is not vertical at mid gear and the bell crank arms are not at right angles. This is on both Juliet 2 and a rather faint drawing of a full size locomotive in the Pilliod book. I suspect these two oddities are an attempt to correct the other errors. The sliding block of Walschaerts, which I count as two pins, has been replaced

Model Engineer 17 November 2023

VALVE GEARS

Fig 82 Program output – forward gear.

then calculate the distance between m and n. The error is the difference between this distance and the real length of mn. The Python language has a function optimise.newton() which makes this straight forward. Trigonometry then allows the position of h to be calculated but then we need the Newton Raphson method again. We guess the height of g above the centreline, calculate the horizontal position of g and the positions of s and e using seeker and interpolation. The error is then the vertical distance from e to the valve centre line. Output from the program is shown in fig 2 (Juliet 2 forward gear), and fig (reverse gear). They are not good, especially at shorter cut off. The curved line at mid gear shows the effect of the mn km difference. How much they could be improved by using the methods in ref 24 I don’t know - as I have no intention of using this gear I leave it to others. At least with this model one can examine the motion of every pin rather than ust the final valve motion. It may be that it works much better for inside admission - I’ve not tried it and of course it could be worse. To be continued

REFERENCES Ref 21. Baker Valve Gear for 3½ inch Gauge Locomotives, LBSC, M.E.2283 February 8 1945 Ref 22. The Baker Locomotive Valve Gear, Pilliod Company 1951

Fig 83 Program output – reverse gear. y ﬁ e pin oints, so there is a lot more potential for slop affecting valve events. The mathematical model is the most difﬁcult so far We can easily calculate the

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position of n dependent on the reverse yoke angle. Working out where b, d, c and o are as the crank rotates is simple trigonometry, then it gets hard. The Newton Raphson

method has to be employed twice. First imagine that link mn has been removed and guess the vertical height of pin k, then the position of m can be calculated and we can

Ref 23. Juliet With Outside Valves, LBSC, M.E.2655 April 10 and M.E.2658 May 1 1952 Ref 24. The Geometry of Baker Valve Gear, Arthur Sherwood, Engineering in Miniature Vol. 8. Acknowledgement to John ag e or fin ing co ies o re s an .

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Barbados Railway 1

Paul Stone takes a ride on the St Nicholas Abbey Heritage Railway.

Winston takes a break to soak up the sun (photo courtesy of St Nicholas Abbey).

No free rides on this railway! he Caribbean island of Barbados had 24 miles of narrow-gauge railway between 1881 and 1937 linking the capital and port of Bridgetown with the towns and sugar plantations in the north of the island. onstruction of the ﬁrst line began in 1887 and

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The start of the journey.

A free history lesson is included. opened in 1881 to a gauge of feet inches he ﬁrst locomotives to run were a 2-4-0 tender locomotive built by Avonside and a 2-6-2 side tank locomotive built by Vulcan Foundry. By 1896 the track on the east coast had deteriorated due to corrosion from sea spray and storm damage. After

an assessment a decision was made to rebuild the line to a gauge of 2 feet 6 inches, which would better suit the tight curves. New locomotives were ordered from Baldwin USA. The railway continued in operation until closure in 1937 due to a lack of maintenance and declining trafﬁc he

Model Engineer 17 November 2023