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Forgotten Pioneers - the Grayson Engines In this article, I’ll present a little information on a mostly-forgotten range of pioneering model engines manufactured in London, England during the 1930’s by a long-established firm of toolmakers named E. Gray & Son Ltd. of Clerkenwell Road. Founded way back in 1822, over 100 years before it made its first model engine, this company apparently started out as a supplier of tools, accessories and components to the watch-making and clock-making trades, By the time of which we’re speaking here, E. Gray & Son had become well-established as leading suppliers to the model engineering community. The level of British participation in this hobby was then far higher than it is today - a surprising number of model enthusiasts possessed some basic metalworking equipment such as a small lathe, or had access to such equipment through their places of work. The prevailing level of British involvement in model engineering was sufficient to support the publication of a magazine devoted exclusively to the activities of its practitioners. At the time of which we are speaking, this magazine was entitled “Model Engineer & Practical Electrician”, later shortened to just “Model Engineer” (ME). Established in 1898 by its publisher Percival Marshall, the magazine is still in publication today (2025) under the title “Model Engineer & Workshop”, albeit now owned by Mortons Media Group. The ready availability of low-cost machine tools from China and Taiwan has triggered something of a latter-day resurgence in this long-established hobby. “Model Engineer & Practical Electrician” magazine was joined in October 1933 by a rival publication entitled “Newnes Practical Mechanics” (NPM) which was published by George Newnes Ltd. Although this magazine dealt with a very wide range of do-it-yourself projects, it included quite extensive coverage of both model engineering and the development of the pioneering power aeromodelling movement in Britain. Indeed, it was the best available source of aeromodelling infomation during its first couple of years - "Aeromodeller" magazine did not commence publication until November 1935.
One of Gray & Son's flagship products was the highly-regarded Grayson 3-inch swing screwcutting lathe. They also continued to serve as major suppliers to the British watch-making and clock-making industry, for which Clerkenwell Road was something of a focal point, with a number of horological firms being located there in close proximity. Indeed, a portion of E. Gray & Son’s former premises at no. 19 Clerkenwell Road is still occupied today by the Antique Watch Company (the red-fronted premises in the photograph at the right). Very little information has previously been made generally available on the model engines manufactured by Gray & Son, particularly those used in power aeromodelling applications. By far the best reference that I’ve been able to find appeared in the late Tim Dannels’ ever-informative Engine Collectors Journal (ECJ), Volume 6, Number 3 for Spring 1968. This took the form of a short "Engine of the Month" article by Dr. R. E. Nichol sub-titled “Engines of E. Gray & Son, Ltd.” Dr. Nichol had collaborated with engine historian Alan Denham to ferret out some details of this company’s activities. The ECJ article is reproduced here below at the left.
The Gray company seems to have decided to enter the model engine market in around 1930. They did not design their own engines, since that wasn’t their area of expertise – instead, they produced casting kits and complete engines to designs developed by others who were willing to assign the manufacturing rights on some kind of basis. It’s really difficult to be certain, but it appears from the advertising record that they only remained in the model engine business for around 9 years until the onset of WW2, thereafter returning to their toolmaking roots. Let’s now have a look at what can be ascertained about the various engines produced by E. Gray & Son Ltd. The Gray Engines – an Overview One of the most useful resources for tracking the Grayson model engine range is the series of advertisements that the company placed in "Newne's Practical Mechanics" (NPM) magazine beginning in late 1933 soon after the magazine's October 1933 establishment and continuing on a regular basis throughout the balance of the 1930's. Although this magazine covered a very wide range of do-it-yourself projects, it did include a fair bit of information on the development of power aeromodelling in Britain during the pre-war pioneering era to which the Grayson engines belong. My thanks to Gordon Beeby for drawing my attention to this invauable reference - some really fun reading there! In his previously-cited ECJ article, Dr. R. E. Nichol tells us that the model engine series manufactured by E. Gray & Son included the following models (in order of ascending displacements rather than chronological):
Obviously, all of these engines were spark ignition units. Other models may have existed, but there is no record of them.
The Grayson design was based upon that of an earlier boat engine designed by one F. N. Sharp, who had been The Sharp engines were developed through a succession of variants, culminating in the Model B6A which was originally built in 1931 as a 25 cc unit but was subsequently refined into the 30 cc variant of 1935 illustrated here. The 30 cc displacement reflected the expectation that the engine would be used to power tethered hydroplanes. Mr. Sharp had evidently reached some kind of arrangement with E. Gray & Son which allowed them to draw very heavily upon his design. Presumably some kind of compensation was involved – possibly a royalty payment on units sold. There was nothing underhand about this situation - Sharp’s design involvement was openly acknowledged in a number of the earlier advertisements for the Grayson engines. As previously stated, his name was also attached to the offerings from other companies as well.
The production version of French’s design reached the market in mid-1933, being offered as the Grayson Special (hence “Grayspec”) model. Although designed primarily as an aero engine, it was offered in both aero and marine configurations (both air-cooled), also being available both complete and in casting form. As far as I'm currently aware, this engine was the The appearance of the Grayspec initiated something of a trend among British manufacturers. Before the end of 1933, the London model goods supply firm of A. E. Jones had released their well-made but expensive 14.5 cc Atom Minor unit, while J. Hallam & Son of Poole in Dorset followed in early 1934 with their 13.5 cc aero model. In 1935, Rogers & Geary of Leicester joined in the fun with the 18 cc Comet aero engine. The Grayspec was priced at what sounds like a remarkably reasonable £3 17s 6d (£3.88) for the aero version and £4 2s 6d (£4.13) for the flywheel-equipped air-cooled "marine" variant. However, we must remember that the price of one of these engines would have represented over a week's wages for the average British working individual in 1933. Puts a little perspective into latter-day engine prices, doesn't it?!?
Sets of castings, materials and blueprints were also available at a price of £1 1s 0d (£1.05) for both aero and marine engines, with castings and blueprints for the carburettor also available at 4s 9d (£0.24). A presumably matching 18 in. dia. airscrew cast in elektron alloy was also available at a price of 10s 6d (£0.53). Clearly, this was not a high-speed engine! The Grayson OHV four-stroke model continued in concurrent production at this time, still being offered in displacements of 25 cc and 30 cc and remaining available in both “standard” form with aluminium alloy castings and a “lightweight” version with elektron castings. The “standard” engine with aluminium alloy casings was offered at £7 5s 0d (£7.25), with the lightweight version based on elektron castings selling for £7 15s 0d (£7.75). A basic set of castings and blueprints was available for 12s 6d (£0.63), while for a price of £1 5s 0d (£1.25) one could buy a complete kit comprising castings, materials and blueprints. Both models were still being advertised at the same prices as of 1935. However, as 1936 approached, British model engine manufacturers had come to appreciate the fact that many prospective aeromodelling customers were put off by the challenge of constructing, transporting and storing the very large models needed to accommodate the Grayson, Jones and Grayspec aero offerings. The advent of smaller motors like the enormously influential 0.359 cuin. (5.88 cc) Baby Cyclone from 1935 America had Hallam & Son had reacted promptly to this market trend by bringing out their 6 cc Nipper in late 1935. Gray & Son were a little slower to react to the situation, but they eventually did so by introducing a 3.5 cc two-stroke model called the Grayson Gnome in Unfortunately, the Gnome does not appear to have been a commercial success. Its appearance was evidently overshadowed by the simultaneous April 1937 introduction of both the 3 cc Hallam Baby (essentially a down-scaled rendition of the Nipper) and the 2.31 cc Rogers & Geary Spitfire (basically a scaled-down Baby Cyclone). The Gnome continued to be advertised along with the other Grayson models on a somewhat sporadic basis almost right up to the onset of WW2, but I suspect that by that time the company had lost interest in pursuing its model engine production activities and was simply attempting to liquidate existing stock, actual manufacturing probably having ceased quite a bit earlier.
The number of examples of the various Gray & Son model engines which were manufactured by the company or were constructed from castings by home builders is now impossible to determine. All The company survived the WW2 years, resuming its model engineering supply business thereafter but not returning to the model engine manufacturing field. They were still promoting the Grayson lathe along with a wide range of associated tools and accessories. By 1953, the company had relocated its operations to 12-14 Clerkenwell Road after a brief interim residence at no. 3 Clerkenwell Road (which may have been merely an office address). They were still advertising in this vein in mid-1956. As of 1959, they apparently remained active as suppliers to the watchmaking trade, rebuilding the combined premises at 12-16 Clerkenwell Road (now known as Grayson House) in that year. I have no information regarding their subsequent activities or their long-term fate. Having set out what is recorded about the model engine manufacturing activities of E. Gray & Son, it remains for me to provide a description of the various model engines that they produced. In doing so, I wish to acknowledge the fact that some of the images which appear here are derived from those presented by the Miniature Engineering Museum (MEM) operated by Paul & Paula Knapp. Their photo gallery is well worth a visit by anyone interested in model engines! Images of some truly amazing examples of the model engineer’s craft may be found there. My sincere thanks to Paul and Paula! The Grayson OHV Four-stroke Engines
As of the early to mid-1930’s, tethered hydroplanes were the sole all-out model racing category being practised, since tether car racing and control-line speed contests still lay in the future. To give some idea of the levels of performance then viewed as competitive, F. N. Sharp won a Bronze Medal in the 1930 Model Engineer Speedboat Competition at a speed of 27 mph using one of his own four-stroke engines in his boat "Mona". The fastest hydros were then pushing 40 mph. At this time, four-stroke engines pretty much ruled the roost in the prestigious 30 cc tethered hydroplane racing category along with their flash steam compatriots, which actually held all the records up to 1936 - it took over forty years for the two-strokes to catch up!
The engine used mechanically-activated overhead valves and a ringed light alloy piston. It relied on oil-bath splash lubrication internally, with manual lubrication being applied to the exposed valve gear. It was equipped with a float chamber carburettor along "full sized" lines.
In the “standard” marine version of the engine, the components were produced in the materials described above. A “lightweight” marine version was also available in which components 1, 4, 5, 6 Finally, the “aero” version of the Grayson dispensed with the heavy flywheel, also featuring elektron castings throughout with the exception of the forged aluminium alloy conrod. This unit must have weighed considerably less than the “standard” marine model, but I don’t have any actual figures. The complete kit of castings and materials which was available to would-be constructors of these engines included the illustrated castings, blueprints, piston rings, finished timing gears, all necessary nuts and bolts and sufficient materials to complete all other components. Examples of the Grayson engines appear to be very rare these days – I’ve never seen one myself in the metal. I have no way of knowing how many examples were either manufactured by E. Gray & Son or were build by home constructors. However, the engine was apparently used quite widely in various categories of power boat modelling. Given the company’s toolmaker background, I would expect the examples made by Gray & Son to be of quite high quality, while that of the homebuilt examples would doubtless vary somewhat depending on the skill of the constructor. The Grayspec 15 cc Engine
The Grayspec engine was basically a standard two-stroke sideport spark ignition engine of a type that was to become very familiar. It featured an open-frame timer. With a bore of 1.0625 in. (26.99 mm) and a stroke of 1.00 in. (25.40 mm), it was a short-stroke engine having an actual displacement of 14.53 cc (0.887 cuin.). It weighed in at a not unreasonable 16 ounces minus the ignition support system (typically around 4 ounces at the time in question). Initially, all light alloy castings were formed in elektron alloy, underscoring the evident expectation that the engine would be used primarily in aero service, hence encouraging minimum weight. The conrod was a drop forging in aluminium alloy. The elektron cylinder jacket enclosed a cast iron liner. The domed light alloy piston was fitted with a single ring. At some point, the material of the castings was switched from elektron to aluminium alloy. Reportedly, examples built around aluminium alloy castings as opposed to elektron are somewhat more commonly encountered today. This suggests that the change to aluminium castings was made fairly early on.
For another thing, the carburettor which was intended to be used with this engine was equipped with a float chamber along “full sized” lines. This carburettor was equipped with both a conventional needle valve and an air intake control to facilitate the engine’s operation at varying speeds for An example of this variation is to be seen in the superb example of the Grayspec which is featured at the previously-cited Miniature Engineering Museum (MEM). The example of the Grayspec which appears on that site is clearly a home-built example made by some unknown but highly competent constructor. It is built up from aluminium alloy castings as opposed to the elektron used originally. Note that the builder has chosen to use a conventional model engine spraybar carburettor rather than go with the original Grayson float-chamber design. The builder has also added a neat bolt-on exhaust stack. The Grayspec was described in very general terms in a brief article which appeared in the March 1934 issue of NPM. However this reference adds nothing to our knowledge of the engine beyond what has been summarized above. In particular, no performance indications are provided. Once again, I have no idea how many examples of the Grayspec ended up being built in total. All I can say is that the engine is mega-rare today – I’ve never so much as seen one myself! The Grayson Gnome 3.5 cc Model
From this commentary we learn that the Gnome had bore and stroke figures of 5/8 in. (15.875 mm) and 3/4 in. (19.05 mm) for an actual calculated displacement of 3.77 cc. The engine's weight was not reported. The only performance indication was the suggestion that props in the 8 in. to 9 in. dia. range appeared to be a good match. The Gnome was a basically conventional sideport spark ignition engine of its day. It featured the usual cross-flow loop scavenging with an external bypass which was sealed by a flat plate secured by two screws and was presumably supplied with mixture from the crankcase via a piston skirt port. Like the other engines from this manufacturer, its carburettor incorporated both a needle valve and an air intake control. Like its Grayspec predecessor, it featured an open-frame timer.
That’s about all that I can tell you about this extremely elusive pioneering model engine from pre-WW2 England! If any reader knows more, let’s hear from you!! Conclusion The rarity of the engines produced by E. Gray & Son is such that few of us will ever so much as see one, let alone own one! Still, that’s no reason to let this pioneering model engine marque sink into the quicksands of history to be lost forever. The odd example undoubtedly does still exist, and it’s only fitting that there should be some accessible record of the company which made them. Hope you agree!! __________________________ Article © Adrian C. Duncan, Coquitlam, British Columbia, Canada First published December 2025 |
According to Dr. Nichol, the company began advertising its model engine casting sets in 1930-31, at which time they were characterizing their 30 cc offering as the “Grayson speed boat engine”. This implied that the engine’s primary anticipated use was powering tethered hydroplanes in the 30 cc class, then the Blue Riband category in that genre, in which four-stroke engines and flash steam powerplants predominated. The "standard" castings were formed of aluminium alloy, but a set of lightweight castings was also offered in elektron alloy (a very lightweight magnesium alloy), creating a variant said to be “suitable for model aircraft”. Clearly, they built model airplanes BIG in those days! 
While Gray & Son were getting their Sharp-based Grayson four-stroke model into production, an individual named Lionel French was working on the development of a lightweight 15 cc two-stroke model powerplant designed primarily for aero applications. Gray & Son reached a manufacturing agreement with French, presumably similar to that which they had negotiated with Sharp. 
first lightweight two-stroke model aero engine to be offered commercially by
The final advertisement for the Grayson model engine range appeared in NPM in July 1939 (left). Thereafter the company returned to a focus upon its toolmaking roots, with the flagship product being an upgraded Grayson 3½ in. screw-cutting lathe along with a wide range of model engineering tools and accessories. They were presumably involved in war-related production of some kind, but I have no information regarding that side of their activities. 
It’s amazing how many present-day modellers believe that the four-stroke model engine was a development of the 1970’s and beyond! In reality, the use of four-stroke model engines to power both model boats and model aircraft goes way back into the first decade of the 20
This engine was doubtless introduced in mid-1933 in response to the obvious need for lighter powerplants for use in aeromodelling applications. Although it was offered in an air-cooled marine version with flywheel, it would appear that its primary envisioned use was in power aeromodelling. 
The Grayspec presented several quite unusual features. For one thing, its conrod had a roller bearing big end. A similar feature was to be found on the far later 
As stated earlier, this engine appears to have represented E. Gray & Son’s final attempt to crack the mid-1930’s model aero engine market before they returned to their toolmaking roots. Almost no information on this model has ever been published – all that I've been able to find is a commentary on the engine which appeared in the 
The most noteworthy feature of the Gnome was its method of mounting. The crankcase had no mounting lugs at all, either beam or radial. Instead, the engine featured a large integrally-cast externally-threaded spigot protruding from the centre of the integrally-cast backplate. A flat cut into the top of the unthreaded full-diameter portion of this spigot provided a reference plane for stability, and the threaded reduced-diameter portion of the spigot protruded rearwards through the front bulkhead of the aircraft. A large T-nut threaded onto the spigot from behind to clamp the engine tightly against the bulkhead. A somewhat convoluted and inconvenient mounting system, it must be said! Hopefully the accompanying drawing by Alan Denham will make this arrangement clear. | |