Overhead Cam Engines

The Dyak

The Dyak was a water-cooled, six cylinder inline engine, with a single aluminium block. The cylinders had a 120mm bore and 130mm stroke, giving a capacity of 8.8 litres. It had a single overhead camshaft, operating two valves per cylinder. There were two Claudel-Hobson BZS.38 carburettors, two ML magnetos and a direct drive to a Remy propeller. The weight of the engine in running condition was 745lbs and the power output was 100h.p., at 1,200r.p.m. A starting handle was also included so that the pilot could start the engine from the cockpit. Sunbeam quickly received an order for 160 engines, but non had been delivered by the end of 1918. The order was put on 4 months notice of cancellation, due to the end of the war. Some were delivered, but the number is not known. This was a bad time for aircraft engine manufacturers, because the large wartime military orders ceased, and large numbers of aircraft engines were sold off, at a fraction of their original cost, by the Aircraft Disposal Board. This made it almost impossible for manufacturers to sell new engines. The Dyak was one of the casualties. Dyaks were included in the Aircraft Disposal Board's list and so Sunbeam only produced a small number of them. A Dyak is preserved at Stockman's Hall of Fame Museum, Queensland, Australia.

Aircraft Fitted with the Dyak

Aircraft Make and Type Number of Engines Ordered
Avro 504K biplane 11
Submarine Scout rigid airship 17
Japanese Navy Airship No.1 2
Japanese Navy Airship No.4 2

The Sikh

Development work on the Sikh began at the end of 1918. It was a big, slow engine for use in airships, large aircraft and seaplanes. The Sikh was a water-cooled, V12, with a 60 degree 'V'. The bore was 180mm and the stroke was 210mm, giving a capacity of 64.113 litres. There was a single central camshaft, that was housed in the crankcase, at the base of the 'V'. It operated six valves per cylinder, via rockers and push rods, there were 4 Sunbeam-Claudel carburettors, and 4 twelve-cylinder magnetos. The propeller was geared to 920 r.p.m. and the engine delivered 800h.p. at 1,400r.p.m. Tests began in May 1919, and the engine was displayed at the Paris Salon and at the 1920 Olympia Aero Show. The engine passed the Air Ministry tests and a great deal of interest was shown, but no orders followed. 

Coatalen also developed the Sikh II. It was basically half of the original Sikh, using a single bank of 6 cylinders and was intended for use in airships. The Sikh II was water-cooled, with six inline cylinders and developed 400h.p., at 1,400r.p.m. The cylinders had a bore of 180mm and a stroke of 210mm, giving a capacity of 32 litres. The single camshaft in the crankcase, operated six vertical valves per cylinder, and the dry engine weight was 1,120lbs. There were two Sunbeam-Claudel carburettors, two six-cylinder magnetos and the propeller was geared to 920r.p.m. Unfortunately all military airship development came to an end after the war, and so no Sikh IIs were sold.

In 1928, when work was in progress on the R.100 and R.101 airships, Sunbeam decided to produce a more powerful Sikh engine, in the hope that many airships would now be built. The new engine, known as the Sikh III, was a water-cooled V12 engine, with a 60 degree 'V'. The cylinders had a bore of 180mm and a stroke of 210mm, giving a capacity of 64.113 litres. There were two camshafts which operated 5 vertical valves per cylinder. The engine weighed 2,760 lbs dry, and delivered 1,000h.p. at 1,650r.p.m. It was shown at the 1929 Olympia Aero Show and was the largest engine on display. When the R.101 crashed in October 1930, the British airship programme came to an end, and as this was the only suitable application for the engine, none were sold, only prototypes were built.

The Pathan

In the late 1920's Coatalen started experimenting with his first diesel aero engine. Diesel engines seemed to offer a number of advantages over petrol engines for aviation use. They have a lower fuel consumption and a less volatile fuel, which was particularly desirable for use in an airship. Coatalen had gained a lot of experience in designing diesel engines for road vehicles and so a diesel aviation engine was a logical step forward. Work on the engine, which was basically a modified Dyak, began in 1928, and by July 1929, the new engine was on display at Olympia. 

The Sunbeam stand at the Olympia1929 Aero Show.

The engine was water-cooled, with six inline cylinders. The cylinder bore was 120mm and the stroke was 130mm, giving a capacity of 8.8 litres. The engine delivered 100h.p. at 1,500r.p.m.and was fitted with a new type of fuel injection, which allowed the engine to start from cold, without any other assistance. The engine never went into production, only prototypes were built. When the British Airship Programme was cancelled, there was no further demand for engines of this type.

The 2,000 HP Sunbeam

Sunbeam's 200m.p.h. land speed record had been broken several times by 1929, and the company decided to try and break the record again, by producing a car that could travel at over 250m.p.h. As with the 1,000h.p. Sunbeam car, it was decided that the new car would be powered by an aircraft engine.

The car, called the Silver Bullet would provide an ideal test bed for such an engine, which would need to be much more powerful than in the 1,000h.p. car. The decision was taken to develop a new engine that could deliver 2,000h.p., and the car would be powered by two of them. The new engine was a V12 with two banks of cylinders set at an angle of 50 degrees, to make the engine more compact. The cylinder bore was 140mm and the stroke was 130mm, giving a capacity of 24.02 litres. The engines were supercharged, using a large centrifugal blower, that was geared to rotate at 17,000r.p.m.

The engines had an unusual cooling system. The usual radiator was replaced with an 11.5cu.ft ice tank and a one gallon mixing tank in the nose. The ice tank had to be filled with 5.5cwt of ice after each run. Because the land speed record was being broken so often, the car was built at a rapid pace. Work went on around the clock with day and night teams.

The car was first shown to the public on 21st February 1930 and Kaye Don was to drive the car on the record attempt. The attempt took place at Daytona Beach, in Florida and the car arrived on 8th March. Due to the haste in which the car was built, the engines had never been properly bench tested and numerous problems appeared.

Louis Coatalen arrived on 16th March and the record attempts began. The car performed very badly and was difficult to control. The fastest speed attained was 186.045m.p.h., although the car did break the American record for 5 miles at 151.623m.p.h.  After the team returned home, further attempts were made to improve the car, but by then the Sunbeam Car Company was in a poor financial state and so little work could be done. Only two of the engines were built, and they were never fitted to an aircraft.

This was Sunbeam's last aero engine. A little while later, Louis Coatalen left the company and returned to France.

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