The Hotchkiss V twin Engine

Hotchkiss History and Notes

The National Rally this year was remarkable in bringing together every surviving variant of BSA V-twin light car at one event (as far as I know there are no V-twin vans in existence), and this provoked considerable interest about the cars and also about the Hotchkiss engine. It seemed worthwhile reviewing the known history of the Hotchkiss engine as far as is known, particularly after Peter Nicholls launched a desperate appeal for more material!
I was sufficiently motivated to do some digging into the background of the Hotchkiss company and involvement with BSA. The following notes on the Hotchkiss Company are largely taken from "The Flatnose and Bullnose Morris" by Jarman & Barraclough.
Hotchkiss et Cie started life in the Franco-Prussian war in factories at Saint Denis and Levallois-Perret in the Seine district of France. The story is that when it looked like the factory at St. Denis might be overrun by the Germans in the Great War, production was hurriedly transferred to a new factory in Far Gosford Street, Coventry.
On the face of it this appears a simple story, but there are some aspects which remain intriguing: St. Denis is in the northern suburbs of Paris. Levallois-Perret is also in the northern suburbs, about 2.5 miles South West of St Denis. The Germans did come near to Paris in the first few weeks of the war, but following the Battle of the Marne in September (the war started in August 1914), the Germans were driven back to lines which remained static until the end of the war. Had Hotchkiss needed to move they would have needed to move both of their factories, and extremely quickly, to avoid the anticipated fight for Paris. I am not sure what time they arrived in England, although it seems to have been in 1914, but if it was in hasty flight from the German guns, then they would not have had time to build their own factory, furthermore, following the stabilisation of the lines in 1915, any further relocation was probably abandoned.
The Hotchkiss factory in Far Gosford Street is still there today. For those visiting Coventry, a trip around the city ring road will lead past the building outside the ring road between the A444/M69 and A45 turnoffs on the North East corner. The building was for many years government offices, but was recently sold to Coventry University, and redeveloped. It now sports two additional floors on the roof of it's original 4 story brick factory block, characterised by their white Grecian pillars and the new arched roof. The building is sometimes referred to as a Government building, and this name seems to precede its office use, suggesting that Hotchkiss may have taken over or leased an existing factory.
In any event by the end of the War Hotchkiss were well established in Coventry, with a full order book for arms. It is said that the factory had produced 50,000 machine guns. Coventry had been very busy during the War. W.O.Bentley was building his BR1 rotary aero engine in the Humber works, several streets away, and the larger BR2 engine at Daimler's, half a mile across town, which was also producing guns, and there would have been considerable collaboration under wartime controls between all of the other industry in the city.

Following peace, however, orders dried up. The Works Manager, a Mr Ainsworth, had modern production facilities and a good engineering team, but no work. The rumour apparently "got round" that Morris was looking for engines, and Ainsworth and M.Benet, the Managing Director from Hotchkiss in France were at Morris's door to make an offer to make engines, to Morris's designs if preferred. Morris had acquired the manufacturing rights to his American Continental "Red Seal" engine. Hotchkiss offered to copy the engine and Morris did not offer a deposit or any "up front" funding deal. Even though Hotchkiss had never reportedly made an engine, Morris had a good deal, with no financial commitment, and if things went wrong the Continental "Red Seal" supplies would have presumably just carried on. Perhaps this indicates how desperate for work Hotchkiss actually were.
Hotchkiss produced samples in July 1919, and production started in September 1919. Bearing in mind the War only finished in November 1918, this was rapid progress.
V-twin owners may wish to note that the Continental engine had always suffered clutch slip from oil leaking past the rear main bearing seals. The Hotchkiss engine was designed with a two plate wet cork clutch, attributed to Morris himself as a solution to the problem, and the copy was so close that the complex oil seal, no longer needed, was retained.
By 1922 Morris had started to acquire some of his suppliers and build a single large business. Hotchkiss were largely dependant on Morris's orders, but were also making the V-twin engine for BSA, and another engine for a Scottish firm called Gilchrist. Some armament manufacture was also continuing.
Morris was planning a large increase in production, and it seems that Hotchkiss's capacity and interest in diversification was limiting these plans, so for a number of reasons Morris made an offer for the plant.
By May 1923 Morris owned the plant. It had reportedly cost him £349,423. Negotiations had apparently been going on for some time, with one motor trade journal reporting that the new company would be called Morris-Hotchkiss Limited as early as January 1923. It is reported that at the Eighth Annual Dinner of Hotchkiss et Cie in February 1923, Morris announced it would be called Morris Engines Limited. (This incidentally puts Hotchkiss's move to Coventry at around 1914).
Mr Ainsworth, the Works Manager, stayed with Hotchkiss, and a Mr F.Wollard, from E.G.Wrigley & Co Ltd was appointed Works Manager, and under him all existing contracts, other than those for Morris, including some residual gun contracts, were completed and terminated, and the company went on to increase Morris engine production by 66, eventually moving to larger premises in the North of the city, where it remained until closed as part of the cut-backs of the British Leyland consortium in the 1980's.
An interesting sideplay is that of W.O Bentley. He is one of the few designers of the period to have written about his life. Before the Great War, W.O Bentley, an ex-railway apprentice and engineer, who had moved to a career in cars, decided, along with his brother to buy out a London dealership selling the french DFP car. They found the middle of the three models was susceptible to tuning, and promoted the car heavily by a strong competition programme. Bentley tells the story of visiting DFP in France and seeing a small alloy piston ashtray on the Managing Director's desk, a demonstration sample from a local foundry. His DFP competition cars had been suffering with piston failures, and Bentley was prompted to get DFP to contact the foundry and get some pistons made. These gave the DFP a competitive advantage which remained until the outbreak of war. No other manufacturer at this time appeared to be using alloy pistons, and Bentley was sent to Rolls Royce, where the use of alloy pistons was incorporated in aero engine design.
Bentley also tells the story of hearing that one of the 1914 Mercedes Grand Prix cars had been in a London garage at the onset of war, and he led a small raiding party to "requisition" it for the war effort. The vehicle's engine was closely studied, and British aero engines featured many of the design aspects of this engine.
Where does this leave BSA? The designer of the original light car engines is still unknown. Hotchkiss could well have acquired designs or skills from the local workforce, and in one book the V-twin engine is described by a contemporary journalist as having design similarities with RAF aero engines.
The first known occurrence of the Hotchkiss engine is a magazine review in the early 1920's in which the engine was tested. Hotchkiss had made two prototype engines, and installed one in an early "narrow track" Morris Cowley, in the hope of tempting car manufacturers to use the engine in light cars. The use of a Morris as a test bed vehicle may well reflect the company's involvement with Morris. Articles in magazines of the period tend to be rather more friendly than is normal today. I suppose that in those days if it ran at all it was a success, whereas today our expectation is greater, so it is difficult to judge the actual performance of the engine. It would seem that BSA were keen enough to purchase the engine, and it's design rights, and consequently the BSA light car appeared in 1922.
Clearly if BSA were to continue selling their light car past the end of 1922, they would have been forced by Morris to make their own engines, if they were not already doing so. I am not clear when the design rights for the V-twin passed to BSA. Could it be that this was the final settlement agreed by Hotchkiss/Morris to terminate the contract?
At this time the engine does not appear to have differed significantly from the original prototypes, although evidence is rather scanty. One interesting fact however is that almost every part on the original Hotchkiss engine was redesigned by BSA for the launch of the Trike in 1929. One reason may be that although they had bought the design from Hotchkiss, they had never tooled up for production. Perhaps the purchase of Hotchkiss by Morris was the final nail in the coffin of the BSA Light car, and faced with a need to make their own engines, and with increasing competition, decided to close the project.

So where did the engine come from? People have speculated on a heap of spare aero engine cylinders lying around after the Great War having an engine designed to use them, and there are other stories of previous cyclecar engines. Hotchkiss are most unlikely to have had a stock of aero engine parts left on the shelf, but appear not to have been in a position to design an engine themselves without outside help. They certainly would not have been involved at all in engine design prior to or during the 1914-18 period. The design of the twin may well have followed the launch of the Morris engine in 1919, giving a time slot of 1920-21 for engine design.
As far as can be ascertained no records have survived, but by looking at the design and other period sources, it is possible to make some informed guesses. All of the variants of the Hotchkiss engine have common features, and those of most interest are it's cylinder head design. The engine has a hemispherical combustion chamber with inclined overhead valves, and on the early engine there was clearly provision for two spark plugs, one on each side of the head. In the later light car engine, only one plug was fitted, and in the trike engine the position of the plug was altered to sit between the valves.
The valve timing on all of the twin variants appears to be the same, and incorporates large valve overlaps, as in a modern car. In fact the valve overlap is larger than some moderns, and would equate to a mildly tuned modern engine. For its day this arrangement is remarkable. You have to remember that BSA was making motorbike engines with simpler side valves into the 1930's and even the BSA 4 cylinder engines are relatively conservative in terms of head design. Fred Hulse, and presumably much of the BSA design team were busy with munitions in the Great War. His name is apparently associated with several patents to do with guns. In any event, had the BSA design team been associated with the early Hotchkiss design, you would expect the concepts to be carried over into motorbikes, and they aren't.
Clearly there were designers in the Coventry area who by the end of the war would have had considerable experience of aero engine design. W.O Bentley did not work on his own and teams of engineers would have been both on his and other engines produced in the area.
All of the V-twin head design points to an engine designed for high performance - yes, you may scoff at its 4.5:1 compression ratio, but early fuels were not good and all air-cooled engines have low compression ratios, because of their poorer cooling. The last VW air cooled flat four engine, made for their Transporter van, has a compression ratio of 7.4:1, compared with an "A" series-engined Rover Metro with compression ratios of between 8.4-10.3:1

(the highest comp'ression ratio is for the Economy HLE variant). Vintage engines were sometimes prone to valve burning and breakage, as a result of poor metallurgy and unleaded fuels. Perhaps this also explains why having designed a high performance engine, it's potential was immediately choked by the complex induction manifold used on all of the twins. We do not know who designed the V-twin engine, and we may never know, but we can make some informed guesses. The only place where engine design progressed to overhead valve high performance engines was in aero engine design, and then it is hard to imagine the designer preparing such an advanced design without considerable experience of high performance engines.

HOTCHKISS DEVELOPMENTS

History

When I first joined the B S A Front Wheel Drive Club in the 1970, after I bought my 1934 Vee Twin trike, I found my car described as having a "Hotchkiss Engine". The rumour was that Hotchkiss had designed the engine for BSA. There was a story too that the engine had been made to use up spare aero engine castings left over after the war, although I thought this highly dubious. Over the years this story has intrigued me and slowly as time has passed, more details of this rather peculiar engine have emerged.

The last article

In the first part of this article I described how Hotchkiss had evacuated their one factory from the German advance in the autumn of 1914 and had taken up residence in premises in Coventry, eventually building up a considerable workforce and production capacity. At the end of the war the factory was left high and dry with no orders for guns and a desparate search began for other work. The Works Manager, Harry Ainsworth, and some of the main Hotchkiss management managed to secure work from Morris to make a copy of the American Continental engine for the Bullnose Morris, eventually turning out 100 engines per week - a respectable production in their eyes. Attention then turned to broadening the orderbook, and Hotchkiss produced a Vee twin engine prototype. Two were built, one being run on test beds and the other fitted to a narrow track pre-war Morris Oxford and used for sales demonstrations. Subsequently several manufacturers including BSA purchased small quantities of the engine, BSA's powering the 1922 RWD Light Car, A firm called Stoneleigh also used the engine in a short-lived light car design, and one of these remains in the Coventry Science Museum. By 1922 other events overtook Hotchkiss. Morris wanted to start a huge expansion of his t short notice to talk about this subject. During the discussions, Peter Cook produced further information and this has led to more information being tracked down. The following notes set out my current knowledge. The Clue Just before I presented my talk at the AGM, Peter Cook handed me a fax he had been sent after a talk with some people he had met at the National Rally. They had been researching a book about a Motor Industry personage, who they were reluctant to name, but were only prepared to send Peter the following extract: "The only important job I can remember, we did was an air - cooled twin cylinder 90 degree engine, for a light car. This was done for Hotchkiss Et Cie, a firm in Coventry. The Hotchkiss factory had been established during World War 1 to make machine guns for the British. The engine had cast iron cylinders with the cylinder and barrel in one piece. The valves or were inclined at a very considerable angle in a hemispherical combustion chamber, this being a very similar to later aircraft engine designs. The valve gear was enclosed and lubricated. The valve gear lubrication was supplied by the crank case breather, breathing being brought up the push rod housings into the rocker boxes and then vented through the rocker box covers. The exhaust ports were on the front of the cylinder and the valves were fore and aft in each cylinder. The enclosure of the valve gear was definitely copied from a Swiss motorcycle engine, of which I was aware of prior to 1914. I am not sure of the Swiss used crank case fumes to lubricate the valve gear. However, to the Swiss goes the credit for this feature, which later became a standard practice on aircraft engines. On aircraft engines, a course, we did not rely on crankcase fumes to lubricate the valve gear. Incidentally, the outlet for the crankcase fumes up the pushrod tubes was the only be breathing supplied to the crankcase. The engine was manually started, and on the starting crank was on the camshaft. A decompressor was fitted which lifted in the exhaust valves slightly when starting. Starting it was very easy by swinging the crank: I believe the decompressor was automatically released when the crank was released. An attempt was later made to obtain starting with the starting crank on the crankshaft but this proved impossible. If one got one cylinder over top of dead centre on the compression stroke, the crankshaft ran away with one. Solid aluminium Pistons were of course that it, since there they were the only piston type I knew that could be cooled in an air-cooled engine. Later, this was to be the cause of considerable controversy, as will be discussed. Manufacture of the first experimental engine started at a Hotchkiss. Surely thereafter Green closed the consulting business, and I was transferred to Hotchkiss." This was extremely interesting, but who was "I" and who was "Green"? Several people commented that Green engines were used in early aircraft, but no-one at the meeting knew much more, Time to search the bookshelves! There are two Greens involved in engine design in the period. Their work overlaps and so there is doubt as to which one is referred to, although as you will see, I have my suspicions. I am grateful for the information gleaned from Harald Penrose's works on the British Aviation industry and publications of the Rolls Royce Heritage Trust concerning the Coventry Parkside site, and Armstrong Siddley. I am particularly grateful to another member of the Rolls Royce Heritage Trust - Mr David Williams, who in discussions with Peter Cook, our Club Chairman, at the 1999 National Rally was able to provide unpublished information forming the key to solving the problem.

Gustavus Green (1865-1964) was the founder of the Green Engine Co. The company manufactured engines for airships and some early aeroplanes. All seem to have been in-line liquid-cooled engines, and they gained a reputation for reliability. Their engines also had a reputation for being low-powered and heavy, and unsuitable for aircraft design. At an early stage in the War, Green engines stopped being used for aircraft. They were switched for use in CMB's (Coastal Motor Boats - Motor Torpedo Boats or MTB's today) where their use was more successful. Manufacture of engines appears to have continued into the 1920's when he is said to have retired, his son becoming a test pilot for Armstrong and AVRO.

Fred Green (Born 1882) is a more interesting character.

Early Beginnings

Fred Green (Born 1882) was a Daimler Man, and in Coventry in the early years of the Century that was a title of some prestige.
Daimler Men always went to work in shirts and ties, no matter what their job. They always looked neat and tidy, and saw themselves as a step above other workers in the Motor Industry, after all, only their cars were good enough for Royalty.
Fred Green was a graduate taken on by Daimler and earned a reputation working in their engine design department in the 1900's He is described as a tall, hook-nosed man with a rather abrupt manner and a tendency to talk with his head held back and glancing down his nose. He later appears to have gained respect for his expertise, although his mannerisms may have counted against him on occasions.
In 1909 Fred Green met Mervyn O'Gorman, who had been newly appointed as Superintendent of Aeronautical Work at Farnborough, taking over a balloon shed and airship workshop. The discussion ended with Fred Green being offered the post of Chief Design Engineer at what was to become the Royal Aircraft Factory at Farnborough.
Around the same time another Coventry man was making an impression on the world: John Siddley (born 1866) is described as a small and fiery individual, perhaps not without good cause. From being a champion cyclist for the Humber Cycle Co he had joined the design team, and then moved to a career in tyre manufacture. His interest in cars around 1900 led to him selling his interests and in 1902 formed the Siddley Autocar Company, badge-engineering French Peugeot cars, and was successful enough for an offer to be made for the business by the Wolseley Tool and Motor Car Company, after Siddley asked them to build engines to his own design for his company in 1903.
Wolseley subsequently made cars and buses badged as Wolseley-Siddley until 1909. The relationship was not always easy, Siddley falling out with the Wolseley Designer and Works Manager, Herbert Austin, who left after a row in 1905 to set up his own business at Longbridge in Birmingham.
The Deasy Motor Car Manufacturing Co was founded in 1906 by Captain H Deasy. Captain Deasy had a controlling interest in the Swiss Martini car company. The Company took over the factory and land of the Iden Car Co, which was in receivership in Parkside, Coventry. The site included premises leased to the Velox Motor Works, the Maudslay Motor Co and a small chocolate factory.
Deasy got off to a very shaky start. Early cars were unreliable and prone to breakages even by the standards of the time, but in 1909 John Siddley joined the company as General Manager, and by 1910, cars bearing the name "Siddley-Deasy" were being produced and started to earn a reputation for quality and reliability. Most of the parts were manufactured by suppliers, the firm being primarily a assembler.
In 1912, a further wholly-owned company was established by the now Siddley-Deasy Car Co called Stoneleigh Motors Limited. This firm was to offer light cars and commercial vehicles, although very limited production was apparently undertaken, the company finally disappearing with the onset of the Great War in 1914.

The Great War

With the onset of war, Siddley-Deasy started to take on engine production, building engines designed by the Royal Aircraft Factory at Farnborough. Production took off in 1915 and the company expanded, taking over more of the Parkside site.
During the War, Green and his team continued at the Royal Aircraft Factory at Farnborough, their last design being the SE5 fighter, which was acknowledged by many as one of the best allied fighters of the war. The factory came under increasing criticism for inefficiency by commercial manufacturers and despite the continuing conflict, the Government decided to close the factory in 1917, putting the design team out of work.
Siddley saw an opportunity and Major Fred Green, his new Protégé John Lloyd - a stress engineer, and S D Heron, one of the engine design team, joined Siddley-Deasy. They brought with them work on developing air-cooled radial engines and the outline of a replacement for the SE5A fighter eventually known as the Siskin.
Fred Green is reputed to have personally completed the drawings in a room over a Coventry laundry shortly after joining the company - office space was at a premium!

Peacetime

Siddley had been closely associated with Vickers Armstrong during the war, and in 1919 the Company was merged with Armstrongs, the outcome being Armstrong Siddley Cars, Managing Director John Siddley, and the Sir W G Armstrong Whitworth Development Company Limited, the latter rather grandly named company being housed in a small shed on the London Road in Coventry and intended to be the centre of aircraft production.
Green and his team appear to have remained at the Parkside works and ran both car and aeronautical design. Siddley and Heron fell out in 1919 over Siddley's interference in engine design, and Heron left for Wright's in the USA. He was replaced by S M Viale - an engine designer who had worked for Gwynne's making Clerget rotary engines during the war, and had experience of alloy piston and head design. Not much is known about him, but he seems to have been able to avoid Siddley's interference or divert it.
By this time, whilst car production was starting to climb, aircraft work was in the doldrums. There was a surplus of military hardware from the war, and the civil aviation business had not yet been invented. Almost all flying up to this point had been in combat. The design team in particular appear to have found themselves twiddling their thumbs.
One project undertaken was the design of a cinema film projector, which perhaps shows the desperation to find opportunities. The country was bankrupt after the war and wages were cut by employers year on year to seek profitability.

Enter Hotchkiss

By 1920 Hotchkiss, just across the road from Siddley-Deasy were in a much stronger position. As a result of some smart work by Harry Ainsworth, who had made Morris an offer he could not refuse, the firm were turning out all of the "Bullnose" Morris Oxford engines they could make, although their dependence on a single customer must have made them uneasy. There seems to have been an approach to Armstrong Siddley to design a light car engine for Hotchkiss, although how this came about is unclear. In any event the Siddley design team set out to design the engine. Most of the Siddley car engines up to that time had been bought in from other suppliers - many were from Daimler, and the firm's designers would have had little or no automotive engine design experience at that time. They did however have considerable experience at designing aero engines, and their old RAF research into air-cooled radial engines was off the shelf and being dusted off. An air-cooled Vee Twin must have seemed the safest and most familiar route to choose. Valve gear enclosure was said to be based on the design of a pre-war Swiss motorcycle engine (An old Deasy connection?).
There seems to have been a close liaison for a time between the two companies. After the first two engines were built, one being fitted to a 1914 Morris Cowley test vehicle and the other used on the test beds, Armstrong Siddleys appear to have revived the Stoneleigh Motor Co and bought back some engines to use themselves. The first Stoneleighs were given a single central driver's seat but later developed into a conventional light car. One survives, but like the BSA light car, the buy-out of Hotchkiss my William Morris in 1921-22 seems to have spelt its death-knell.
One of the design team appears to have transferred to Hotchkiss to follow through the design. The identity of this person is unknown, but S Viale appears a good candidate, since his name disappears from the history of Armstrongs and aviation design from this point on.
With the buy-out by Morris, Hotchkiss did not finish making cars. Harry Ainsworth and probably other members of the British works moved to France, where Ainsworth is credited with masterminding the successful range of 1920's Hotchkiss cars. It is tempting to wonder whether the anonymous transferred engine designer went with him.

Enter BSA

BSA of course were the other engine purchaser, for their Light Car. It is perhaps ironic that pre-war 1913 Stoneleighs were said to be virtual copies of the BSA light car of the period! BSA also appeared to stop using the Vee Twin engine at this time. Peter Cook has uncovered entries in the minutes of BSA meetings suggesting that a licence fee was paid to Hotchkiss throughout the 1920's, presumably for the continuing rights to the design. By 1929 this must have been quite an embarrassment, so hauling the engine out of the plans and using it would have been a good tactical step, and ensured work for the BSA design office. Perhaps this explains why BSA did not just use a JAP engine like Morgans.
When the Vee Twin trike was constructed in 1929, the engine, whilst being very similar to the original, had been extensively redesigned by BSA, suggesting that whatever rights they had to the design, they probably had never had much in the way of patterns or tooling.

In Conclusion

In the first article I wrote, I proposed that the Vee Twin was based on aero engine design. It appears that it was actually based on the Royal Aircraft Factory research work on air-cooled radial engines during the War, was dusted off and taken off the shelf by Armstrong Siddleys as a quick way of designing an engine. The work did not end at this point. Armstrongs built a series of very successful radial aero engines during the 1920's. Most used enclosed valve gear designed on the same basis as the Vee Twin, and continued the development of the work carried out at Farnborough in the War. John Lloyd went on to become a senior designer at Armstrongs/Hawker Siddley in the 1920's and 1930's.
Fred Green appears to taken an increasingly back seat role, eventually retiring in the 1930's but returning briefly to work for the 1939-45 conflict.
The candidate for the design of the engine is not one single person, but appears to be a small group of people. John Lloyd probably figures prominently in the scene, as does Viale. The author of the note found by Peter Cook appears to have been Stan Heron, who decamped to the USA and whose unpublished biography is held by a major US corporation.
There is still more uncovering work to be done, and most of the Armstrong Siddley records were lost in the bombing of Coventry in the second World War, however I appear to be very near the bottom of the mystery of why my BSA, unlike all other BSA cars and motorcycles had a "Hotchkiss" engine.