An English motorcycle engine that has been adapted in the US for several small helicopters, or rather, gyrocopters or autogyros.

-The 650 cc, 40 HP (40/46 HP) engine on the Adams Wilson XH-1.

"Bensen Gyrocopter"

-On the Bensen B-9 "Little Zipster" model.

-Other engines found in outboard motors such as Mercury, Johnson, and Evinrude have also been tested on this gyrocopter model.

From Appendix 6: In the first half of the 20th century, attempts were made to adapt several motorcycle engines for light aviation.

-Among them, those from Triumph.

-At least the Tiger 100, Tiger 100C, and Thunderbird 6T models were adapted.

-They gave 30, 46, and 44 HP respectively.

“34 HP Thunderbird Model”

-The Triumph in the photo is a 649 cc engine and delivers its power at 6,200 rpm.

“Adams and Wilson helicopter with a Triumph engine”

-The 650 cc, 40/46 HP Triumph is the engine used on this helicopter, also known as the Hobbycopter. From 1958.