The William Douglas Motorcycle Factory in Kingswood, Bristol reconverted and developed its engines as Douglas dedicated to the construction of engines for light aircraft.

“Douglas”

-In the assembly of the Parnall Pixie light aircraft, we see the inertial flywheel of the engine and the chain reduction transmission for the propeller.

-The Douglas engines have been mounted on many aircraft of the time from 1922 until 1935 when the brand was taken over by Aero Engines Ltd continuing under the new aegis.

"On the Parnall-Pixi"

-We can start with the 500 cc that had simple ignition, and had two horizontally-opposed cylinders. In 1923 it obtained altitude records in its category during the meetings of Hendon and Lympne.

“Douglas”

-Another characteristic was that the cylinder fins were parallel to it. Most engines had two carburetors.

-The 500 cc was rated at 10 hp at 2,500 rpm and 17 hp at 4,000 rpm. The weight of this model was 50 lbs. It was very popular.

-The 600 cc gave 18 hp and was known as the "Douglas Dot". It was built between 1923 and 1927.

-The 737 cc was known as the "750" giving 22 hp at 3,500 rpm and 30 hp at 5,500 rpm. It was seen on the Parnall-Pixie II, Vickers Vigit, and DH-53 Hummingbird.

-Another engine was the "Douglas Digit" giving 22 hp at 3,000 rpm. It was built between 1925 and 1932.

"Douglas 750 cc"

-Mixing production with Aero Engines Ltd. engines, there is the Sprite giving 23 hp at 2,380 rpm, and 24 hp at 3,150 rpm. It was manufactured between 1936 and 1937.

-It was geared, had simple ignition on the Mk.I and double ignition on the Mk.II. It was installed on the Tipsy S-2, Helmy Aerogypt, Gordon Dove, BAC Drone, and the Pou-du-Ciel.

"Boxer with different fins"

-The Douglas "Dryad" that gave 36 hp at 3,000 rpm and 40 hp at 4,000 rpm or 52 hp at 4,500 rpm was from 1932.

-It was also built with double ignition by Weir just before Douglas closed, in 1932. It has been seen on the Weir W.1 autogyro (Cierva C-28).

-For the Weir W.2 autogyro, the 40-50 hp Weir Flat Twin was manufactured from 1933 to 1935. It was designed by CG Pullin (see) and GE Walker.

-Already in Aero Engines they made the 1.5 lts, ​​known as the "engine of 1'5 lts" with Douglas base and giving 38-40 hp at 2,800 rpm.

-It weighed 110 lbs with gear and simple ignition, and it was built between 1936-1937.

From Appendix 6: Engines such as the 25 hp Douglas Mk II shown below were manufactured at Aero Engines Ltd., in Kingswood, Bristol.

"Douglas Mk II"

-This model had a displacement of 750 cc and was quickly surpassed by the Mk III.

-We show the 500 cc "Flat Twin" from Douglas Motors Ltd, in Kingswood.

"Douglas from 1923"

-From the famous boxer-type motorcycle engine,which has been adapted toward the years 1920/30 on light aircraft, we now show the curious logo of the company.

"The Scotsman on the logo, carrying the Douglas sign"

From Appendix 7: A clear picture of the Dryad with front and side views, one in top perspective, and a gearbox.

"Douglas gearbox"

"Douglas engine without gear"

"A small Douglas 4 HP from 1915"

From Appendix 9: Below we see the 24 hp engine installed on an Avro 558 with a chain drive that gives a small reduction rate.

"Foto del Avro con Douglas-Motor"

From Appendix 10: Manufacturer of engines and motorcycles. Their horizontally-opposed cylinder engines were common in industrial uses, cycle, cars, etc and aviation could not be missed. The flywheel and clutch assembly was eliminated.

"From a Douglas ad"

"Another Douglas model"

"Douglas flywheel details"