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Doug Reynolds: 50years of Model Engineering Excellence

At the 2003 Model Engineer Exhibition, a frail octogenarian was honoured for "An Outstanding Contribution To Model Marine Engineering". George Douglas (Doug) Reynolds was being recognised for the consummate craftsmanship he displayed in his models over a fifty-year period. On show were a number of his engineering projects and three tethered hydroplanes. This was just a representative selection of the superb machine tools, two and four stroke engines, hydroplanes, steam plants and clocks that he had built during his modelling career. Sadly, Mr Reynolds was extremely unwell by this time, and passed away the following November. Luckily his son John has retained all his models, notes, photographs and design material and allowed OTW access to these in order to record and share the exploits of this fine engineer.

Doug Reynolds was born in 1919 and after attending Farnborough Grammar School gained an apprenticeship at Vickers Armstrong at Weybridge, Surrey. Having completed his training as a precision fitter machinist he moved to Aerolex at Camberley. On the outbreak of the second war he was called up on several occasions, but being in a reserved occupation, it was deferred. Finally he joined the REME where he served through to the end of the war having crossed over to France almost immediately after ‘D Day’. By now he had a son, John and daughter Janet, but he was to see nothing of them for a further 4 years as he was transferred to the Royal West African Frontier Force, serving in what is now Nigeria and Ghana. Following his demob, he returned to Aerolex and began his long involvement with model engineering. Space was very limited and he overcame this by installing a 3˝ in lathe in his son’s bedroom and starting work on the first of the projects that were to bring him such richly deserved recognition over 50 years later.

One of the three boats in the display of his work at the Exhibition was the hydroplane ‘Triton 5’ with an exquisite 15cc overhead camshaft four-stroke engine. It was not the first time that this engine had been seen at an exhibition as it was on show at the 1950 exhibition in a boat called ‘Triton II’. Built by Mr Reynolds in 1949, originally as a 10cc motor, this gem of an engine was continually developed over a number of years. The full story of this delightful motor and the boats it powered can be seen by clicking here.

Whilst some builders are content to persevere with just one boat and engine others are far more prolific, and Doug Reynolds certainly came into this category.

His skills were not just limited to hydroplanes and engines, as his workshop equipment included a 2Ľ in screw cutting lathe that he built and a three axis, bench mounted, jig borer that he also constructed from scratch. These two machines alone are worthy of note with the lathe winning a diploma at the 1951 Model Engineering exhibition and the jig borer being exhibited at the Exhibition in 1952.

What is even more remarkable is that not one single casting was used in any of the IC engines he built. Each and every part was sawn, filed and machined from the solid to the drawings he had produced. Only bearings, gears and fastenings were obtained from commercial sources.

Whilst he was developing Triton II, Doug was already working on his next engine. From 1949, the four-stroke engine had been completely superseded by the two-stroke in terms of outright performance although old-fashioned reliability often redressed this difference in performance. From the complexity of the OHC four-stroke motor in Triton II he moved to the relative mechanical simplicity of a two-stroke for Triton 3. Whilst the part count for the new 30cc motor was low, the design was to reflect the very latest practice in high performance engines. The rear rotary valve, loop scavenged engine was very compact with weight kept to a minimum. The crankcase with its large bypass was essentially a sculpted block with front and rear housings, cylinder and cylinder head bolted on. A downdraft venturi with a strangler and a conventional needle valve got the fuel into the motor while a single manifold and silencer took care of the exhaust.

Triton 3. 30" long 8" beam all up weight was 7lb 4ozs.

Diaphragm fuel pump  driven by a worm gear and eccentric on the prop shaft

Doug Reynolds at Fleet Pond with a modified version of the boat.

Some notes do exist relating to the development of the engine.

"Test run made on Nitro Methane Methanol 10% 65% 25% (oil)" "Rotary valve too much overlap new rotary valve made." "New cylinder head fitted, new piston made of cast iron shell with thin sleeve of Duralumin. Deflector top." (An unusual feature was that the deflector was curved to match the piston, rather than straight as on commercial engines.) "Engine performance well improved on old piston also easier starting. Note Glow Plug needs to be set close to piston at TDC to retain heat".

Running the boats RTP usually took place at Fleet Pond, the home of the Aldershot Club, where Jim Bamford who was to became a lifelong friend was registered as AT1 and Doug as AT2. Before a pylon was installed, it was son John’s happy lot to have to stand in the middle of the pond acting as the tethering point. Engine testing was slightly less fraught but an even wetter experience. The boats were run up, either in a tin bath in the garden, or in the adjacent local river, where Doug would fire up the motor with the boat between his knees and wind it up to full revs with John strategically placed at the bow in case the boat escaped.

Although the boat was destroyed at some stage, the engine from Triton 3 survived. Having retired in 1984 Doug was heavily involved in other pursuits, but returned to his modelling roots in 1992 by systematically working through all his surviving boats and engines, reconditioning as required, making changes where he considered it desirable and bringing all the motors back to good running order.

Throughout September 1992 the 30cc motor underwent major surgery to try and address some of the problems that had been evident in its early days. After an overhaul, a new piston with a conventional deflector was fitted along with alterations to the head to match. Several experiments were tried with differing positions for the glow plug and eventually a completely new cylinder head was machined up.

A new silencer was tried and over an intense few days numerous trial were carried out to get the engine running properly. Vibration was noted as a continuing problem. Doug Reynolds pondered over the difficulties he was experiencing with this motor and during August 96 tried a number of further modifications, each meticulously recorded and analysed.

New rotary valve, a completely new twin jet RC type carburetter, and more work on the head, different balance factor for the crank. At last the engine was running as he wanted it and with a long venturi fitted to the carb, the engine would be run regularly. A 30cc racing two-stroke bolted on to a board and running with no load must be an impressive sight.

Whilst on the two-stroke theme Doug produced two more racing engines, one for the 15cc ‘B’ class and a 10cc for the ‘C’ class. Jim Bamford, his club mate and friend, devoted much time, energy and effort to producing competitive flash steam hydroplanes as well as competing with IC engined boats. The most successful of these was ‘JAB 3’ with a George Lines inspired engine. The George Lines rear rotary valve ‘Sparky’ motor was by far the most successful 15cc engine of the time and won innumerable races as well as becoming the most copied engine in hydroplane history. Doug Reynolds set about building a similar motor and for once he mirrored the techniques used on the original as that too had been machined from the solid.

The engine was unusual in that it had 360 degree transfer and exhaust ports that involved milling ten transfers up the inside of the cylinder bore and then cutting ten exhaust ports immediately above them. A lapped iron piston was all that sealed the transfer ports. These engines are all instantly recognisable through the twin silencers bolted directly to an angled exhaust belt. Doug Reynolds put his engine into a more streamlined version of the Triton 5 hull, and this became Triton 7.

The 10cc motor is a very different matter. Whilst the 15cc class was dominated by engines based on the ‘Sparky’ design, the ‘C’ class was the province of the American Dooling and McCoy motors. These were very fast, but expensive and difficult to obtain and the Dooling in particular was very fragile, as its die cast crankcase would easily blow apart if it took in any water. Many competitors set about building replicas of the Dooling and some of these were very successful, but they did require complex patterns and cores for the castings.

Continuing with his normal method of production, Doug Reynolds machined his Dooling replica from the solid and overcame the difficulty of reproducing the bypass by using a technique from the past.

Instead of special tooling and machine set ups, the transfer passage is machined into a separate piece of material and then bolted to the side of the engine. With a steep downdraft venturi that puts the fuel straight on to the big end this was a very handsome engine.

This hull for the 10cc motor represented a radical departure from the style Doug had been using as can be seen from this photo. As well as sponsons, there is a secondary step behind the engine, which is most unusual.

Judging by the large weights bolted to the transom the boat was lifting too much at the rear end.During the early 1960s,new hulls were constructed for the 10 and 15cc two-stroke engines.

Both hulls are reminiscent of the later Lines designs that dispensed with a skeg and had an after step with the prop shaft coming out through the transom. Towards the rear of the deeper 10cc hull can be seen an aluminium fin that aids the boat getting away by counteracting the torque reaction from the prop. This was a modification that was used on several of his boats. No bungee launches for Doug in those days! During 1996 this engine also had a bit of a make over with a new venturi and needle valve being fitted. A large lump of lead on the transom of the 15cc boat indicates that the back end was somewhat 'lively'

No names or numbers. The later 15cc and 10cc boats in their current condition.

If you consider that this represents an incredible output, with everything having to be machined from the solid there was yet another major engine building project, a 30cc overhead cam four-stroke for an ‘A’ class boat. Although this engine was again machined from the solid it shared little in common with the previous 15cc OHC motor. The crankcase was split vertically and very short allowing a very short and stiff crankshaft to be fitted. All the other engines he built had overhanging cranks, but for this one a twin flywheel motorcycle crank was constructed. The camshaft was chain driven with the 2:1 ratio sprockets being hand made and the rocker arms using ball races as cam followers. Most unusual for an engine of this size was the piston which was lapped cast iron. This compromised the combustion chamber shape somewhat but was probably done for expediency as one of his work colleagues at Aerolex, Ted Barton, was a precision grinder, and in a recent conversation he recalls grinding and honing several cylinders and pistons for Doug.

The engine was mounted in a 34˝" long hull with outrigger sponsons. These were later removed and adjustable aluminium side planes fitted, as on Triton 2. Several modifications were made to the engine during its life, including a range of different venturis, needle valves and jet arrangements. The hull suffered the ravages of time, but in a joint effort between Doug and son John an exact replica was built and a jig constructed so that the engine could be run on dry land. The engine was also given some attention at this stage and another twin jet R/C type carburetter made and fitted to give better throttle control than a needle valve. Along with the notes detailing the work on the engine is a calculation and admission that with the bore and stroke dimensions chosen; the engine is around 25cc and not 30cc as originally indicated.


Triton 6.  30cc Overhead camshaft motor.


From a modern perspective it is very difficult to understand how so much time could be devoted to building engines and boats as well as all the development that went on besides, but it seemed to be the norm for the enthusiasts of the period. Doug’s output was not unusual in the tethered boat world and is indicative of the way the balance between employment and free time has changed over the years. Racing was so much more than just the boats and engines as the very best were no good without props and making these was an essential skill for any competitor.

Doug Reynolds spent a great deal of time analysing blade shapes and profiles, using mathematics to come up with appropriate designs. To aid manufacture of the props a jig was made and then for comparisons a sophisticated prop gauge was built. In a historic hydro article published in Model Boats in 1997 a prop gauge made by Ed Kalfus in 1939 was illustrated. In the next issue was a letter and picture from Doug showing the similar gauge he had made in 1950 along with a range of props he had produced.

This almost concludes the story of the hydroplanes and engines, but as mentioned in the introduction Doug Reynolds did not confine himself to hydros and IC engines, although how he found the time is remarkable. While still working on Triton II, the 30cc two-stroke engine and Triton 3 in 1952, he embraced another discipline, that of tethered cars.                                                                                                                                         next page

 CopyrightOTW 2007