2 FREE PRO-PLANS! Yellow & Dracan – small electric duoo VOL.66 VOL 66 NO.12 N DECEMBER 2023 www.modelflying.co.uk
RADIO CONTROL MODELS AND ELECTRONICS
Nationals Nation
LOVELY LYRA
STAGGERWING BIPE REVISITED
INC. EURO SCALE MASTER CHAMPS
POPHAM DELIGHTS
SUMMER SHOW SHINES
PLUS II 7-DAY CHALLENGE - DESIGN, BUILD & FLY IN A WEEK II ALBATROS - ARROWS L-39 REVIEWED
WELCOME Editor: Kevin Crozier. Mortons Media Group, Media Centre, Morton Way, Horncastle, Lincs LN9 6JR kcrozier@mortons.co.uk
W
elcome to the December 2023 issue of RCM&E. Wow! Another year gone already. I hope you have enjoyed all the columns, reviews, features and event reports that we have dished up for you this year. There’s plenty more of the same lined up for next year so here’s to 2024! But before then let’s take a brief look at what we have prepared for you in the December issue of RCM&E, starting with our regular columns. In his latest Bench Blog, Tim Hooper returns to his O&R sparkie project and fettles a few accessories using his new machine tools. Then it’s over to Graham Ashby for Kick The Tyres, in which he’ll tell you that success in model flying isn’t about winning, having the fastest or being the best. In Make It Scale, Danny Fenton reports from the British Scale Nationals at Buckminster, incorporating the Euro Scale Master Championship, so he has a bumper crop of scale lovelies to share with us. Next up is Scale Gliding in which Chris Williams resumes his bungee launching experiments. But first he reports from June’s White Sheet scale fly-in. Last, but not least, in Aerobatic Scene, Keith Jackson files a photo report from the F3A Precision Aerobatic World Championships held in Warwick, Australia. All those sleek aerobats are a delight for the eyes! This month’s centre fold Pro-Plan is a two plane treat, with a pair of small electric models for you to
4 | RCM&E
build and enjoy flying. First up is Yellow as Ton van Munsteren redesigns a classic .049 design for electric power and modern lightweight radio control gear. Then it’s over to Terry Anderson and his Dracan, an easy to build canard based on his popular Hanky Planky, which was previously featured as a pull-out plan in RCM&E. Our feature articles start with Lyra Revisited; Adrian Britton’s sporty biplane design is still timeless thirty years after it was first published and here Dick van Mourik describes building an updated version. In Seven Day Challenge, John Hutson gave himself just a week to design, build and fly his latest own design aircraft, resulting in the eyecatching Gemini with its wraparound Warren wing. Finally, despite a busy calendar causing a low trade turnout, our reporter Mike Freeman and other visitors enjoyed some fine flying displays at the popular Popham Model Show. On test this month we have the L-39 Albatros from Arrows Models, who are back with another mini jet and this time there’s an on-board stabiliser! David Ashby puts some LiPos on charge. I hope you enjoy reading it all. Happy Flying!
NEVER MISS AN ISSUE Subscribe to get our best offer
Pre-order your next issue – delivered direct to your door www.classicmagazines.co.uk/issue/RCM
SUBSCRIBE
Save over £2.00 per issue – delivered direct to your door www.classicmagazines.co.uk/subscription/RCM
DIGITAL
Get your digital edition for just £3.99 per issue www.classicmagazines.co.uk/subscription/RCM
PRINT AND DIGITAL The whole package – just £5.50 per issue for a printed and digital version www.classicmagazines.co.uk/subscription/RCM
www.modelflying.co.uk | December 2023
CONTENTS
RADIO CONTROL MODELS & ELECTRONICS I VOLUME 66 ISSUE 12
ONTHECOVER
Photo: Danny Fenton What a week of scale competition was had when the British Scale Nationals, incorporating the Euro Scale Master Championships, were held this summer at BMFA Buckminster. Competitors came from far and wide to compete in glorious sunshine, from Poland, France, Germany and the Netherlands, plus judges from Sweden and France. The hangar was an impressive site with around 50 top scale models on display.
34 Regulars 8
SWITCH ON
This month we celebrate the 50th Anniversary of Deluxe Materials
24 PILOTS’ PICTORIAL
Reviews
12 L-39 ALBATROS
Arrows are back with another mini jet and this time there’s an onboard stabiliser. David Ashby puts some LiPos on charge
12
Send us a picture of a new or favourite model and it could appear in our regular readers’ models gallery
71 COUNTERPOINT
A selection of new gadgets, kits and bits for you to buy
92 GOING PLACES
Our list of model shows, events and competitions for you to visit over the next few months
94 MARKETPLACE
Sell off your unwanted airframes and engines or maybe buy a few new ones
95 NEXT ISSUE
64
Take a look at what’s coming in the January ‘24 issue of RCM&E
98 PARTING SHOT
Mike Freeman captures a jet’s close encounter with terra firma
86
6 | RCM&E
www.modelflying.co.uk | December 2023
288
42
Features
Columns
42 LYRA REVISITED
Adrian Britton’s sporty biplane design is still timeless thirty years after it was first published. Dick van Mourik builds an updated version
64 SEVEN DAY CHALLENGE
For his Gemini design project John Hutson gave himself just a week to design, build and fly his latest own design aircraft
72 SUBSCRIBE…
18 BENCH BLOG
Tim Hooper returns to his O&R sparkie project and fettles a few accessories
28 KICK THE TYRES
Ask Graham Ashby and he’ll tell you that success in this hobby isn’t about winning, having the fastest model or being the best
34 MAKE IT SCALE
Danny Fenton reports from the British Scale Nationals at Buckminster, incorporating the Euro Scale Master Championships
... and receive Ronny Barr Profiles - British Two Seaters: British Two Seaters of the Great War FREE
74 AEROBATIC SCENE
86 POPHAM 2023
Despite a busy calendar causing a low trade turnout our reporter Mike Freeman and other visitors enjoyed some fine flying displays at this popular southern model show
18
74
Keith Jackson files a photo report from the F3A Precision Aerobatic World Championships held in Warwick, Australia
58
free pro-plan
48 YELLOW
Ton van Munsteren redesigns a classic .049 design for electric power and modern lightweight radio control gear
58 DRACAN
Terry Anderson offers up an easy to build canard based on his popular Hanky Planky design
All reasonable care is taken in the preparation of the magazine contents, but the publishers cannot be held legally responsible for errors in the contents of this magazine or for any loss however arising from such errors, including loss resulting from negligence of our staff. Reliance placed upon the contents of this magazine is at readers’ own risk.
December 2023 | www.modelflying.co.uk
RCM&E | 7
SWITCHON
Get in touch...
kcrozier@mortons.co.uk
DELUXEMATERIALS CELEBRATES50YEARS As 2023 ends we celebrate the 50th Anniversary of Deluxe Materials, the UK based modelling adhesive and finishing goods company whose products are used by modellers across the world. In this special edition of Switch On we ask John Bristow, who with his wife Vivienne started Deluxe Materials from humble beginnings all those years ago, to give us
some background on the history of their thriving company and to gaze a little into the future to see what this great British success story has in store for the modelling community in the future. Right: A small selection of the best-known Deluxe Materials adhesives used by aeromodellers across the world.
John and Vivienne celebrate success at an early model power boat endurance race meeting.
Q. Many congratulations to you and your team, John, on reaching such an impressive milestone anniversary. Please can you tell us a little about how Deluxe Materials came into being? A. It came into being by accident really. I was a keen modeller and loved working with materials and modelling. I was self-taught, having been giving the confidence to work with metal and wood in school, and I had an inquisitive mind that wanted to know how things worked and how chemical and physical changes affected how materials behaved in the real world. I had degrees in engineering (lubrication) and chemistry that took me into real world applications. Vivienne also had a science degree and was able to help and encourage. I got my first full time job after an article I wrote on amateur rocketry for the Cranfield College of Aeronautics caught the eye of an ex-pupil of the college. This job took me into the world of adhesives resins and composites where a curtain was raised on this whole exciting industry and where the rule books had yet to be written. At the same I was dissatisfied with products available for my
8 | RCM&E
Irvine Engines team at a presentation to Ron Irvine (centre).
hobby, racing model boats, and I wanted to make better ones. So, I developed a heat conducting silicone rubber that would not burn away with engine heat. Then I found our first valued customer in Irvine Engines, later to become part of Ripmax here in the UK. Q. Most RCM&E readers will be familiar with your products by using them to build model aircraft. But as we can see from the nearby picture you started your own modelling career as a marine modeller racing model boats. Can you tell us a little bit about your racing background and what that trophy was for? A. Model boats was the entry point as they were more affordable than model aircraft. I will remember to my dying day the thrill and smell of starting a diesel engine in my first model boat. Boats required only two channels operating rudder and throttle. I bought one of the first ten OPS 60 marine engines, which started me in racing. The trophy is for winning the 1978 World Model Powerboat Endurance Racing Championships, a special trophy awarded by the IMPBA of Indianapolis.
Q. In the next picture we see some well-known faces from the Irvine Engines team, including Ron Irvine at the centre. Ron was instrumental in suggesting Deluxe Materials’ first adhesive and then going on to act as your UK distributor for many years. What was that glue and how did your relationship with Ron develop? A. That glue was Speed Epoxy 4 minute. Ron had an instinct for what was needed in the marketplace and offered valuable advice as we developed further products, including Speedbond and Aliphatic Resin. The relationship soon became one of mutual respect and trust. We owe much to Ron and Margaret Irvine and their team, including Ken Morrissey. Q. More recently, when Irvine Engines were incorporated into Ripmax’s distribution network, you went on to have a long and fruitful relationship with that leading British distributor too. And following recent developments you have remained faithful to them. Such loyalty from suppliers is highly prized and valued by distributors. Can you tell www.modelflying.co.uk | December 2023
Above :Some specialist machinery is needed to manufacture Deluxe Materials products. Here we see caps being added to Roket Card glue bottles. Intended for the fast assembly of card models this glue also bonds balsa wood, paper, and card to most plastics so it would have a use in flying models that use those materials too! Left: Behind John and Vivienne there’s a very loyal team. Right: Past RCM&E Editor David Boddington samples the wares at a model show.
us a little of what is planned for your UK distribution going forwards? A. Distributors have been an important part of the development of our company, and we value long-term relationships where we work together for the benefit of both sides and our aim is for this to continue. Ripmax have played a major part in encouraging us in, for example, product development and ideas, notably our Power Model Oils. Q. Back to the early days of Deluxe Materials, can you tell us a little more about the early challenges of building your business? A. The main challenge was that we had to do everything ourselves with little experience and limited resources, although we had plenty of ideas. Everything was more difficult in the early days - no internet, no good computers enabling in-house design work, administration and communication. We remember designing adverts with Letraset and hand drawn images!
Q. Things are a lot different now about your business premises. Please can you tell us a little more about your units near Basingstoke and how products are made, packaged, and distributed there, both for the UK market and for export too. A. Yes, things have changed a lot in the 50 years we’ve been in business, from a small flat in Barrow in Furness to the full-blown business premises we have today. We now employ eight people and we distribute to over 50 countries worldwide, as far as Japan in the East to the United States in the West. Our brand management is controlled from our premises in Basingstoke. In these premises we control the flow of production in and out and carry out in house product development. As we develop our own products and work closely with major chemical companies, we completely understand and have confidence in our products and how they work. We not only have the ability but, perhaps more
Deluxe Materials often have stands at major model shows. Here John and Vivienne meet the Paysant-Le Roux’s at the much-missed Sandown Model Symposium. December 2023 | www.modelflying.co.uk
importantly, we have the passion. Q. Another picture shows a machine adding caps to bottles of glue. Can you buy such machines off the shelf or are they made specially for tasks such as this? A. At the beginning we improvised with the help of engineer friends who were able to modify or build simple machines for us. We even inherited a simple machine for folding and crimping metal tubes. This was found in an engineering storeroom and had been used previously for sealing tubes of glue sold by Woolworths for repairing plastic macs! But to answer the question, machines can be bought off the shelf or have them made to specification. We do now use outside packaging companies for larger runs, though we pack smaller runs in house. Q. You are very proactive in marketing your products. Although your website and social media are obviously very important, you still
John does the rounds promoting another great Deluxe Materials product. Here the management team at Sussex Model Centre get the low down on Eze Tissue. RCM&E | 9
Q. It is also good to see you supporting model shows and model shops by taking show stands and visiting retailers to show them new products. Do you find that such a hands-on approach still brings dividends in this website orientated age? A. As manufacturers it is vital that we know our end consumers and meet our dealers. We use shows to do market research and to receive ideas from users. Personal contact brings us far closer to our customers and has far more value to get real insights. We can also carry out product and sales training. Q. You are well known for continually developing new modelling adhesive and finishing products. Long may that continue.What are the major milestones in product development that you recall? A. Some important milestones: First 4-minute epoxy. Speed Epoxy was important before CA became widely used. Super ‘Phatic! was a unique product and important as it was fuming free and nonbrittle and gave us our entry into the US. Development of environmentally products such as Eze Dope, Eze Kote and more recently the world’s first environmentally friendly model jet oil. We remember being encouraged by David Boddington to do this sort of work. Q. It’s not just aeromodelling products that you are famous for.Can you expand on just a few of the other model markets that you are most active in. A. Model railways is an important market for us, where we have developed and several products such as Track Magic, which improves electrical conductivity, and novel ballasting adhesives, Ballast Magic and Ballast Bond. For plastic modelling we have developed safer, fume free plastic glues and, most recently,
10 | RCM&E
Lo
we
vaporati
o
n
value offering a printed catalogue and spreading the word via ‘how to’ articles and advertisements in magazines, including RCM&E. Can you expand on your thoughts regarding print versus digital marketing? A. A good question. Both are important and they are not mutually exclusive. Digital can be used to impart a lot more information and can be widely accessible. Printed material has an appeal in that it is nice to look through a brochure or read one of the excellent magazines in print rather than on screen. The UK is fortunate to have several hobby magazines - RCM&E, Aeromodeller and others. Our brochure delivers both print and digital in the form of QR codes, which allow our customers to find advice on product choice and use with the aid of videos.
Minimal odour
Milestones in Deluxe Materials product development over the years.
Deluxe Materials are widely used in other modelling disciplines. Here the finishing touches are made to a WW2 diorama using Making Waves, a clear setting, water based, low odour resin.
Precision Plastic Glue with our uniquely designed bottle with an enclosed applicator. We also produce doll house products, notably Tack Wax for temporary holds of miniature pieces in place, which is also used by railway modellers to hold figures in place and by aeromodellers for holding small servo screws on screw drivers. Our scenic products such as Aqua Magic for artificial water, Scenic Snow and Scenic Rust are used in railway, diorama and doll house making. Q. Do you sell into non-model and industrial sectors too? A. We haven’t sought out these markets, but our products are used in electronics, film making and by several manufacturers. Our Power Model Jet Oil is being used by Gravity Industries, who manufacture jet packs for personal flight. Q. Can you tell us anything about new products that we can expect to see on model shops shelves in 2024 and beyond?
Vivienne and John demonstrating Deluxe Materials products at a recent UK model show.
A.We are working hard on new products for 2024 but we prefer to wait until we are happy with these to announce them, usually at the time of the Nuremberg Toy Fair. Last year we did the research on what products were needed and this past 12 months we have been busy developing them! Q. Thank you for taking the time to answer our questions. Here’s to another 50 years of Deluxe Materials! Is there anything you would like to say to our readers as a send-off into your next decade? A. You should expect a lot from us in the next 10 years and we hope that as model hobbies evolve, we can create the relevant products that you will enjoy using and thus live up to your expectations. In short, we want to continue to earn the respect of modellers for all that we do and be talked about in a positive way. If you are one of our customers, we say thank you. If you are the person that shares the same ambition and vision maybe you could be the person that will help us on this journey. www.modelflying.co.uk | December 2023
L-39 ALBATROS Arrows are back with another mini jet and this time there’s an on-board stabiliser. David Ashby puts some LiPos on charge words & photos » David Ashby
Y
ou don’t need me to tell you that EDF jets have come of age over the last few years and if there’s one type that has outsold the rest then it’s this, the mini jet. The appeal is obvious; they look and sound good and fly well. They are pretty affordable and easy to transport while avoiding fussy and costly retractable undercarriages. Tony Nijhuis has helped to popularise the mini jet segment thanks to an extensive range of balsa selfbuild designs but if ‘foamy ready-to-fly’ is your preference then Arrows Hobby have become a very popular source. This new offering joins their 50mm range that already includes a Viper Jet, BAe Hawk and T-33, not forgetting the slightly larger 64mm F-86 Sabre and Marlin. If you’re new to electric ducted fan jets then note that size here (50mm, 64mm etc.) denotes the ducted fan diameter. Power systems are identical across the 50mm models and this L-39 follows suit.
The 50mm models now come with a Vector stabilisation system installed. It’s the board by the XT60 plug.
The familiar 2627-size 4500kV outrunner powers all the 50mm models.
Say hi to Arrows’ new mini jet. Pretty, eh?
12 | RCM&E
www.modelflying.co.uk | December 2023
TESTING, TESTING | EDF scale jet
Above: Canopy lines are required, me thinks.
Although Arrows jets have shipped with a factory-fitted stabilisation unit to some overseas markets that hasn’t been the case with models distributed in the UK. Until now that is, because all models in the range now arrive with a switchable Vector unit in situ. More on that later. Like its peers this one is a three-channel machine (aileron, elevator, throttle) moulded using EPO foam and is very nicely finished. A large canopy hatch reveals a generous battery/ receiver bay and a sheet of self-adhesive markings provides the option to decorate the model in one of five national insignia. I popped some Czech roundels on mine.
AIRCRAFT TYPE
The L-39 is a popular subject for models and no stranger to the foamy EDF jet genre. The big one is built in the Czech Republic by Aero Vodochody and they’ve produced a lot of ‘em, some 2900, making it the most widely used jet trainer in the world. It first flew in 1968, so it’s been around a while, long enough for some examples to find their way into private hands. Some are even raced at Reno.
ASSEMBLY
Getting it together is a 10-minute job. The stabiliser is glued to the fuselage and while the manual suggests CA, I prefer UHU Por, which is nicer to use and works very well. You’ll need to centre the servo then either adjust the clevises or release the pushrod grub screw retainer to adjust the pushrod length. Thread locking that grub screw is a sensible measure while you’re at it. The on-board Vector unit (stabiliser/gyro) sits on a shelf under the canopy hatch. Hook its lead to your fifth channel, allocate a threeposition switch and you’re ready to go. It’s switchable in flight, offering three options: Stability Mode - the unit levels the model whenever no control inputs are detected. This is the mode I use for take-off and landing. Dynamic Mode - adjustments are made to correct for movements not made by the pilot, such as cross winds, gusts etc. Direct Mode - ‘off’ in other words, the unit making no intervention.
“Like its peers this one is a threechannel machine moulded using EPO foam and is very nicely finished” December 2023 | www.modelflying.co.uk
RCM&E | 13
“I’ve flown the model with both 3S and 4S batteries and 4S LiPos are my preference”
DATAFILE Name: Model type: Manufactured by: UK distributor: RRP: Wingspan: Fuselage length: All-up weight: Wing area: Wing loading: Power system:
Connector type: Functions (servos): Required to fly:
14 | RCM&E
L-39 EDF jet Arrows J.Perkins Distribution jperkins.com £174.99 659mm (26”) 808mm (32”) 480g 8.8dm2 (136 sq.in.) 54.5g/dm2 50mm 11-blade fan, 2627-size 4500kV outrunner, 30A ESC, 3S 1300-1600mAh LiPo XT60 Ailerons (2), elevator (1) 3S 1300-1600mAh LiPo & receiver
There’s something about jets with tip tanks, they’re more animated somehow.
www.modelflying.co.uk | December 2023
TESTING, TESTING | EDF scale jet
I always use Stability Mode for launching and landing.
An LED on the unit indicates which mode has been selected, although it’s easy to surmise by moving the model and watching the control surfaces. The manual provides suggestions for control surface deflections and the C of G should be easy to strike with a bit of battery shifting, although my packs do need to sit towards the back of the battery bay to achieve this. Do note that the manual specifies a 3S 1300mAh pack and you’ll struggle to hit the C of G with a 3S 2200. Throw in the weight penalty and, like me, you’ll find the model struggles to get away cleanly after launching.
Plenty of room for the battery, although you may find that it needs to sit towards the back of the bay to hit the C of G.
December 2023 | www.modelflying.co.uk
Wing servos get protectors to deflect bumps when landing.
I’ve flown the model with both 3S and 4S batteries and 4S 1600-1800mAh LiPos are my preference. That size 4S pack records 400W and 28A peak, albeit right up to the ESC’s rating.
FLYING
Let’s talk about the Vector gyro first. I launch underarm and it usually gets away cleanly, but it only takes one clumsy launch… Which is where Stability Mode helps by keeping the wings level for the first couple of seconds when speed is building. It’s not a nasty model, far from it, but in Direct Mode a wing drop is always a risk when it’s moving slowly.
These 4S 50C 1800mAh packs are my preference. Perhaps the straight wing is a little draggier compared to, say, the BAe Hawk, but it just seems to fly better with the extra cell. RCM&E | 15
“The Vector unit is a useful inclusion especially when landing and taking off” What’s not to like?
As I say, it’ll fly on three cells but seems just a tad uncomfortable, fidgety even. Stepping up to 4S transforms the performance and the difference in flight times isn’t so bad either; I still record 3.5 or 4-minutes on the timer
with careful throttle management but the improvement in speed and smoothness is unmistakeable. Dynamic Mode isn’t intrusive and Direct Mode seems little different. In both cases big,
smoothly flown manoeuvres are just lovely. It feels as if you’re flying a far larger model and all the while the 11-blade fan makes a very nice noise. Don’t be tempted to max out your elevator and aileron deflections until you’ve tried the suggested rates. You may find the low rates (8mm +/-) perfectly fine. In both cases they exert a powerful effect, so I use 25% exponential to improve the feel. Landing is straightforward when the gyro is engaged, although the finish to my third flight wasn’t pretty. It was a calm day as I approached in Direct Mode, slowed down a bit too much and watched the model flick. Thankfully it recovered just before the ground arrived, so I got away with that one. Stability Mode for landing then; the gyro keeps the wings level as the speed bleeds away and it arrives every time without incident.
ALL UP
Neat finger holds provide launching grip although underarm is my preference.
16 | RCM&E
This is a nice addition to Arrows’ quiver of mini jets. It’s surprising how each model in the range has its own flying feel even though they’re all around the same size and have identical power systems. The Vector unit is a useful inclusion, especially when landing and taking off, but don’t go thinking that Stability Mode suits a beginner as that’s far from the case. These little jets are for confident intermediate and experienced pilots who want a fuss free, grab ’n’ go sport jet.
www.modelflying.co.uk | December 2023
That ancient Ohlsson & Rice sparkie rears its head again this month and gets some fancy accessories for today’s flying fields. Read on…
O&R SPARKIE MODS Tim Hooper returns to his sparkie project and fettles a few accessories words & photos » Tim Hooper
R
egular insomniacs might recall my struggles with getting a vintage spark ignition engine running a couple of episodes ago. The rather stylish 1940s Ohlsson & Rice .23 was built in the US and found its way to me via my mate, Ian Easton. Getting it to run again was quite a saga and took several weeks, during which it got through three ignition systems and a couple of fuel recipes before it burst into life, which was a major cause for celebration I must admit! With a modern CDI system replacing the ancient points and coil ignition set up, and with the leaky tank topped up with a gloopy mix of Coleman’s camping fuel and syrupy SAE 50 engine oil, the O&R has proved to be an easy starter. True, it’s not the world’s most powerful engine but it will spin a 10 x 4 prop in a relaxed kind of fashion and should be happily adequate for a lightly loaded vintage model.
18 | RCM&E
However, I felt that the engine could benefit from a few external mods to make it more user friendly and replacing the cracked plastic fuel tank was top of the list. Yes, I could probably have sourced another plastic tank but I thought this would be a good opportunity to improve my turning skills by making an aluminium replacement tank on the lathe.
ORDER OF WORK
Taking measurements from the old plastic tank and jotting them down on a notepad seemed a good place to start, to produce a rough sketch and a plan of action. As with any machining project I’ve tackled so far there’s a fair amount of mental exertion involved to finalise an order of work prior to physically attacking any actual metal. I realised that the main hurdle to overcome when hewing a tank from solid aluminium bar
would be to leave the internal, central pillar intact. Creating this pillar would call for a bit of lateral brain strain on my part as I couldn’t just drill out the internal cavity with a centred drill. Thinking cap on. The old legend about creating a sculpture of an elephant from a block of stone by simply removing any material that doesn’t resemble an elephant sort of applies here, in that I had to hollow out a solid ali bar but leave the middle bit well alone. Just putting the bar in the lathe and attacking it from the end with a trepanning tool (which I haven’t got anyway) seemed fraught with potential problems, mostly to do with the tool pressure required and compounded by the limited grip of the chuck’s jaws, given that the available 35mm ali bar was too fat to fit down the centre of the chuck to gain stability.
www.modelflying.co.uk | December 2023
BENCH BLOG | Column
The digital read-out computer on the mill allowed me to create a circle of 16 holes. I really only needed eight, as it turned out.
The cracked and leaking fuel tank needed replacing. I opted to turn one from solid ali bar. The sketch gives a clue to its complexity.
MILL & DRILL
In the end the solution was to lop off around 55mm from the end of the bar and mount this vertically in the mill, using a V-block to keep it secure and centred within the vice jaws. The next step was to utilise the digital read-out’s computer and to program in a bolt circle of 16mm diameter. My idea was to drill out a ring-shaped cavity and so, as a sanity check, I pecked out a series of 16 holes with a 3mm drill, all to a depth of 26mm. Then I moved up to a 6mm drill and it became clear that those 16 holes were an unnecessary luxury, so I drilled every alternate station to give a widening circle of eight overlapping holes. The final round of drilling with a 9mm bit resulted in a roughly octagonal cavity, with just enough clearance to allow the use of a miniature boring bit. So, the hollowed chunk of ali was removed from the mill and installed on the lathe in the three-jaw chuck.
for a bit of lateral thinking in that my boring bar isn’t designed to face the other way i.e., towards the centre of the piece, and won’t work that way. The solution was to run the lathe in reverse and to position the boring bar on the far side of the central pillar. This let the tool operate at its optimum orientation. As the pillar slimmed down with each successive pass of the tool, I let the cutting depth become progressively lighter to avoid bending or fracturing the pillar as it neared the desired 6mm diameter.
Using a 9mm drill I succeeded in creating a continuous ring-shaped cavity, which was necessary for the next operation.
A LITTLE TIP
Here’s a little tip I picked up online: instead of letting the chuck’s hardened steel jaws squeeze directly on the soft aluminium I fitted little scraps of soft copper sheet to the jaws to act as protective buffers to prevent leaving unsightly marks. So now you know. With the chuck spinning at 500 rpm, I introduced the little boring bar into the drilled cavity and gently brought the cutting tip into contact with the outside of the cavity. As the drilled surface wasn’t uniform there was a certain amount of noise and buffeting caused by the interrupted cut, which progressively lessened as the surface became smoother. When the cavity matched the desired 27mm in diameter I set about machining the ragged looking central pillar down to size. This called
December 2023 | www.modelflying.co.uk
Transferring the fuel tank to the lathe let me bring a miniature boring tool into play to enlarge the drilled cavity. Frequent measurements were taken.
RCM&E | 19
With the lathe running in reverse, I was able to use the same tool to form the tank’s central column. This would be drilled and tapped to accept a 3mm mounting screw.
The bottom of the cavity was cleaned up by eye, letting the tool gently ease away the conical marks left by the earlier drilling, to yield a cavity 27mm deep. I didn’t want to go any deeper as that would be beyond the reach of the engine’s existing fuel pick up pipe.
GOING OUTSIDE
With the tank’s innards pretty well sorted, I started on the outside surface and turned the diameter down to 31mm. This gave an unnecessary wall thickness of 2mm but it allowed me to machine a fine rebate around the top of the cylinder to house the tank’s original top plate. The lower majority of the tank’s exterior was thinned down further to give a wall thickness of 1mm to save a bit of weight. The tank hangs on the engine’s inlet tube when installed so any extra weight is liable to add extra strain to the tube in actual use. The penultimate operation was to drill and tap the centre of the pillar to accept a 3mm screw.
With the interior finished the outside of the tank was turned down to minimise its weight - and to look pretty too!
PARTING OFF
Lastly, the tank had to be parted off from the parent chunk of aluminium bar. This is always a bit of a stressful process, especially as the only tool I have that’s long enough to reach the centre line of the tank is some 3mm wide, so there’s a fair amount of material to remove. This leads to high tool pressure on the piece, which in turn leads to the risk of dislodging the piece from the chuck as it’s spinning, potentially destroying it in the process. Needless to say, I took the parting procedure very gently, using a brush to frequently apply cutting oil as the tool bit deeper, until the tank dropped away from the parent chunk of ali. The underside of the tank was a little scored with concentric circles but nothing that a polish on a piece of 240 grit wet and dry paper couldn’t sort out.
ENGINE MOUNT
With the new tank sorted I turned my attention to the way the engine mounts to a model. Now, some O&R engines had conventional beam
Completed tank alongside its predecessor. It was an interesting machining exercise that taught me several new techniques.
20 | RCM&E
mounting lugs on the sides of the crankcase and some didn’t. Mine doesn’t and relies on the three through bolts that hold the crankcase together to act as a radial type mount. The problem is that the hanging fuel tank is in a terrible location as it will conflict with just about any sort of firewall. On my test stand I had to use a vertical piece of 3mm aluminium sheet as a mounting plate at the rear of the crankcase, with the tank hanging behind it. Not ideal for use in a model. Just why some of these engines don’t have beam lugs is something of a mystery, although O&R did sell a cast radial mount that doubled as a fuel tank. So maybe that’s a partial reason why. Those tanks are pretty rare these days and anyway I wanted to try something a bit different. After mulling it over for a day or two it eventually struck me that I could use the three crankcase screws to secure a pair of transverse mounting bars to the front and rear of the crankcase. These bars would extend from the sides of the engine so it could rest on conventional hardwood bearers. So far, so good. The engine’s original bolts would need replacing with longer items to cope with the thickness of the new bars so the original 1/8” screws were replaced with M3 x 40 metric items from the bits box. The two transverse bars each measure 46 x 6 x 6mm and were sawn and milled from a handy scrap of aluminium. They’re nearly identical except that the bolt holes in the front bar were drilled for clearance whilst the matching holes in the rear bar were drilled undersize at 2.5mm and then tapped to receive the rear ends of those 3mm bolts. The ends of the bars had their ends drilled vertically to accept the actual mounting bolts. Each bar also needed their central portions relieving with the mill to clear the crankshaft and fuel tank. The end result looks simple enough, it’s true. But there was a fair amount of planning
www.modelflying.co.uk | December 2023