The engines of this well-known motorcycle brand were adapted for use in light aviation.

“Logo de H-D”

“Harley Davidson”

-Long and Pickle adapted these engines, but they were not the only ones. And above all, with the first models. Starting with the 9 and 15 hp to reach the 25 hp, as we shall see.

“Harley-Davidson, 25 hp”

llevando el H-D de 7-9 HP, provisto de una cadena de transmisión y posible reductora.

-In 1923 it was fitted on a Mummert Sportplane.

-In 1932, the H-D model "74" engine is converted with a reduction gear of 2 to 1 for the Miller aircraft.

“Harley-Davidson, installed”

-The adaptation that was missing was the Mignet Pou-du-ciel, which admitted all types of engines, because it had basis for any bench. (Aubier-Dunne, Train, AVA, etc.).

-In 1934, the Harley Davidson 2V in the photograph is installed. It had a displacement of 500 cc and gave 25 hp at 4,000 rpm. It had reduction gear.

From Appendix 6: Certain Harley Davidson engines have been more adaptable for small aircraft than others.

-Those from 1920 to 1950, for their simplicity and crankshaft output to the outside, have been better than the more sophisticated ones.

“1000 cc prototype from 1915”

“Engine details”

-As in most engines of the time it had side valves, until the arrival of WWII.

-Later, cylinder-head valves would be common.

-The crankshaft output was simple too. As we can see below.

“Later model 2V engine”

“Ad for WWII surplus motorcycle engines”

-Like the above ad for surplus material, and through army auctions, these engines were sold at really affordable prices, which led to the use of these engines in multiple activities.

-Precisely the one shown in the ad, due to its balanced and symmetrical architecture, was suitable to be applied in aviation, as we can see in several examples of previous texts of this A-Z.

-We also observed that between 1937 and 1946, this was the one mounted on motorcycles. We suppose that they were spare engines from WWII.

“Enlargement of the H-D engine from the years 37-46”

-Sometimes the thick Harley Davidson cylinders are confused with the Anzani 2V ones when the photographs are not very clear.

-More H-D engine applications are being found.

-Both in flying machines and snow or water gliders.

“Snow glider with H-D engine” (PiP)

-In these three examples we see the same engine model, two cylinders in V and somewhat big.

“H-D engine and propeller on a boat” (PiP)

“Experiment with H-D engine, tank included” (PiP)

-The engine shape without transmission, and for its PTO -power output or Power Take Off- has awakened the imagination of many people.

"Relatively modern H-D engine"

-We located two more Harley Davidson engine installations. In this case it is done with modern Twin-cam engines (see also Hog-Air).

-The first one is half installed, as we see in the illustration below.

“Aviation-adapted Harley engine”

-We see the tubular bench in detail, together with the front plate to support the reduction gear.

“Another Harley Davidson application”

-Here is another system for mounting the engine on the aircraft structure. The pair of top braces attract our attention .

"Photo courtesy of Hog-Air"

From Appendix 7: Motorcycle engines have been flying as we have seen in the main chapter. We now see a preparation on the JD engine model.

“The JD with propeller”

-And the surprise of the author has been locating a rocket engine built by Harley-Davidson on behalf of the US Navy. It was used for aircraft "drone" or "target" shooting practice.

-It is the LR-64, of which were made more than 5000 units for three decades from the mid-1960's. It ran on liquid fuels.

“Assembly with main and cruise rocket engine”

From Appendix 9: We found a Harley Davidson motorcycle engine with built-in propeller.

"Aspect of the whole"

-Another motorcycle engine of this brand that was converted for its use in aviation, was the 24FE model shown below. Its cylinders are soiled by burned oil that has been overflowing from the rocker lubrication.

“HD 24FE”

-At an aeronautical museum in Czechoslovakia, this 25 hp motorcycle engine is exhibited. It was allegedly used on a light aircraft.

“Harley-Davidson V2 engine”

-I am getting information from this brand's motorcycle-engine applications.

“Half-cowled H-D engine”

“H-D engine with gearbox and higher propeller”

"H-D engine with gearbox and lower propeller"

-Both gears in the last two photos are by chain. The one in the first picture looks like an engine with direct transmission.

-The last photo appears in the main text, less clear.

From Appendix 10: Thanks to my partner JGA, I receive an extraordinary engine achieved by coupling two Harley-Davidson motorcycle engines in a new crankcase or block.

-In 1920, builder Al Lepsch from Wisconsin made a Heath Parasol airplane and used this engine to power it.

"The curious double H-D engine in X"

-Each cylinder couple has its own magneto. In fact they are two separated old 61 cu. in. engines, that have been assembled together with their own magnetos.

-According to information comments, it would ran softer, with hardly any vibrations. They also offer the possibility of joining 71 cu. in. engines of that time.

-We we can see the coupling plate for the propeller.