Aviation Engines

Siddeley (Later Armstrong-Siddeley)

Originally formed out of the Siddeley-Deasey Motor Car Company, due to the intervention of the UK Government in preventing the Royal Aircraft Factory from producing any aircraft engines for commercial use from 1917.

Many projects were under way at the time, and Major F.M. Green (ex-Royal Aircraft Factory) was given the job of sorting out the BHP engine, which in its redesigned form became the Siddeley Puma.

Once the Puma was finished and available for production, attention was turned to the RAF3 engine, a small 14-cylinder twin-row radial design which held considerable potential in the view of the company's engineers. Those involved in the engineering side at the time included S.D.Heron, considered at the time to be leading expert in combustion and cylinder design. Heron was to become world famous through his design expertise in internal combustion engines, and has contributed many books and papers on the subject. He was also involved on engine projects in the USA at the same time.

The new engine became the Jaguar, and as it's output was increased from 300bhp (with 5" X 5" cylinders) at the start of testing, to over 400bhp (with 5.5" X 5" cylinders) it became obvious that the crankshaft was suffering from the lack of a centre bearing between the two rows of cylinders, and this was a major factor in preventing development of the engine long-term.

Another engine under development was the Tiger, which was an in-line V12 used as a development tool for various throw-offs. In 1920, this engine was producing 420 bhp, but it never reached production maturity and remained a development project.

The only other significant engine at the time was the Cheetah, a 7-cylinder radial with 5.25" X 5.5" cylinders. This engine produced up to 425 bhp and was to provide a run of steady business for the company, although a number of other engines came and went without significant numbers being produced up to the 1950's.

Multi-row radials were produced by the company, and although successful from a technical view point, they did not find acceptance in the commercial market: Deerhound and Boarhound were two typical engines out of this period. Boarhound did not actually fly, as the company did not have the resources to get it into flight condition.

The Lynx was developed from the Jaguar engine, and used half of the Jaguar mechanics, this eliminating once and for all the centre-bearing crankshaft problems which had dogged the Jaguar from it's inception. The centre-bearing issue also cropped up at Bristol, with an engine designed by Roy Fedden.

The company eventually ceased production of aircraft engines, as mergers in the industry eventually led to only Bristol and Rolls-Royce being left with the resources to develop new designs, and the gas turbine was about to make those two into one..

A lot of other engine makers were to contribute staff and designs into the Siddeley company, one of which was BHP

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