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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 3½ 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.

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 2¼ 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 34½" 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.

By this time the tethered car movement was totally speed orientated so he did not attempt a competition car, but produced a semi scale model with another home built engine. The engine was a 5cc diesel that had seen service in Doug's first ever hydroplane, Triton 1. The motor was modelled on the lines of the early Atlas and Sparey engines featured in the Aeromodeller during the 1940s. Machined out of the solid again, it was fitted with a centrifugal clutch and then put into an aluminium chassis.

The chassis had a solid rear end with bevel gear drive incorporated, but the front end featured a most exquisite independent front suspension with lower wishbones and upper rocker arms. The coil springs were mounted inside the chassis and the set up is similar to the ZN units fitted to the MCN grand prix design. The home built wheels were shod with Prestacon tyres and the front wheels had dummy brake drums.

A racing style body was made from gummed paper strip formed over a mould, but in a most unusual way. John’s art teacher made a clay buck, very reminiscent of a Cooper formula 3 car, and each class as they came into the art studio would add more strips of paper until the body was nigh on 3/8" thick.

Tethered car tracks were becoming rare and so Doug improvised by using an area of road outside his home. As he did not have a pylon, his son John was deputed to hold the line, control line style, while the car sped round. Perhaps John could then appreciate why the Americans called tethered cars spindizzies. As with the boats, the car was also subject to rethinks and development and in the course of the year a recoil starter and clutch were fitted, and the engine was converted to glow plug ignition. With these changes the car was capable of 55-60 mph, but I suspect that lack of a track caused the car to be put away in the shed at the end of the year.

The car was to stay there, untouched, for a further 40 years until in July 92 it was ‘taken down to be looked at’. The engine was gummed with castor oil and rusted so it was stripped down, as was the chassis. It was discovered that the self starter clutch was broken so the engine reverted to a centrifugal clutch and hand starting. "The engine started in about 20 pulls but would not keep running." A number of faults were identified and rectified including the left hand rear tyre parting company with the wheel when the engine got on to full song. Whatever Doug tried though, the engine would only run with the glow battery connected and after a series of frustrations put the car away to concentrate on refurbishing the 30cc boat engine.

Interestingly, amongst the various drawings were a set of Atom 5 blueprints, but on the reverse were plans for a 30" hydroplane hull showing the car engine installed. It transpires that this was the original plan for Triton 1 and the engine was built to go into this boat, later being transferred to the car.

What might seem odd is that there are numerous references to speeds, performance and technical details relating to the boats and engines, but never any reference to competition. To Doug Reynolds it was the design and engineering challenge of the hobby that was important, and while he did attend regattas it was as an observer constantly looking for ideas and ways to improve his own boats and engines. When the Fleet Pond was lost in the late 60s, the boats were put away and he turned his attention, skills and sense of purpose to other areas, until his interest was rekindled in the early 90s.

A miniscule 'Roots' type supercharger.

Twin geared interlocking lobes, no doubt intended for the original 15cc engine. Size can be judged be the matchbox.

Another superb example of crafstmanship.

An experimental high-speed, piston valve, uniflow engine for a flash steam hydroplane. Valve gear is driven by a 'scotch crank' which is most unusual. The exhaust ports can be seen half way down the cylinder.

These boats, engines, notes, drawings and photos are an incredible record of one man’s work and passion for modelling and an appropriate reminder of why he was honoured at the ME Exhibition. It was the original intention of OTW to photograph the boats and engines as a permanent record, but our visit turned out to be more of a voyage of exploration. After a cup of coffee and a look at the Model Boats featuring the presentation to Mr Reynolds, it was out to the garden shed where the boats were neatly stacked in cubbyholes.

To see five complete and original boats other than in a collection was a unique experience but the fact that all the discarded parts, props and other items had been retained as well, made the day. A very happy half hour was spent in the loft exploring boxes to sort out material related to the boats and engines. During the course of this it was even more apparent the huge variety of interests that Doug Reynolds pursued.

Electronics, astronomy, and clock making were all in evidence and represented in depth as well. One particular piece of equipment however was of significant interest as it was the prototype of a device that we have all come to loathe or welcome in equal measures.

Next time a phone call elicits a response that the person you are calling is not at home, so please leave a message after the tone you will be listening to a direct descendant of the very first reel-to-reel, recording, answer phone, developed by Doug Reynolds. He had left Aerolex and joined Southern Instruments as a mechanical development engineer and was responsible for the device that would become the answer phone and could also be used for recorded announcements. The worldwide patents for this are still in his name. With a tape cassette almost a foot long and hard-wired thermionoic valves this was an impressive machine to say the least, and interesting to compare with its modern digital counterpart.

The tale of the visit does not quite end there as it was decided that one of the engines had to be started. Triton 6 with the OHC 30 was selected, as this was known to run, but two immediate difficulties manifested themselves. A lack of a glow battery and fuel that was goodness how many years old so a trip to the local model shop was called for. The shop is no more than a couple of miles away but a 44 mile return journey is necessary if going by car, but luckily a short ferry trip could achieve the same end. The fuel was somewhat of a surprise as five litres of 10% nitro was handed over gratis. Support your local shop. Back on the ferry, a quick charge of the battery and a sausage roll and we were in business, or so we thought.

Vigorous tugging on the starting cord produced nothing except a reddening of the face. Yes there was fuel, but as the tank had sprung a leak the contents were slowly draining into the hull. What about the plug and a glow? Ah no glow, try spare plugs, dead, take one from another engine, yes a glow, well more like a sunspot for a second or so and then a stark realisation. The battery was not a Nicad so it was knocking out 2 volts and knocking out plugs with equal speed, so with our tails between our legs we retired for a cup of coffee.

Triton 6. Replica hull built by John Reynolds.

30cc Overhead camshaft motor.

Not being able to face fighting our way through the local football supporters for a return trip to the model shop we reluctantly gave up the idea and set to photographing and recording the whole amazing collection. Considering that all the engines, boats and the car that are illustrated and described here and all the development that were done on them, originally occupied no more than eight years is a testament to the skills and unremitting hard work that Doug Reynolds devoted to his his modelling.

OTW is extremely grateful to John and Jackie Reynolds for their hospitality and our thanks go to John for all his help, advice, reminiscences and for sharing the collection and information with us.

Doug Reynolds - Update


The recent discovery of Doug Reynolds’ photo album has proved a most exciting ‘find’. Not only has it provided original photographs to add to the existing pages, but more importantly it has provided vital information about the development of each of the Triton boats.

The photos, helpfully captioned and dated, have also identified more hulls in the series that were previously unknown, as well as more fascinating material about Doug’s general involvement with model engineering and tethered hydroplanes.


Triton 2 was the first of the hydroplane series detailed in the Model Engineer, yet it seemed strange that there was no Triton 1. It was thought that a line drawing discovered on the back of a Westbury engine plan may have been for an earlier boat, but there was no evidence that it had ever been constructed until the discovery of the album.

A series of pictures showed Triton 1, with the same 5cc diesel engine that was to be used later in a tethered car. The hull matched the line drawing found on the plan, and so Doug Reynolds’ engine and boat building proved to have started earlier than his family had previously believed.

Triton 1 was based on the Westbury 24" hydroplane design, constructed in traditional lines with frames and stringers. The single step hull was unusual in that the front plane was rounded, rather than flat as was more common. The diesel engine was still in its infancy and this 5cc version was based on the early Atlas and Sparey designs.

Being a diesel, there was no need for batteries or ignition components, and with an integral tank, the result was a very simple installation. The relatively low power of the engine and resultant performance may well have been the spur that led to the well documented Triton 2 and it’s sophisticated four stroke engine.

An excellent illustration of the volume of work that Doug Reynolds put into his tethered hydroplane activities.

Triton 5,6,7 are shown here along with 15 and 30cc four stroke motors, 10, 15 and 30cc two strokes. The assorted spares represent just a tiny fraction of what Doug produced during his modelling career.

Triton family with 'outrigger' sponsons. 1957 GDR and Triton 6. 1957 Triton 6 'on the wire' at Fleet Pond in 1960

Thanks to John Reynolds for the loan of this fascinating archive of photos and cuttings.

 CopyrightOTW 2007