Harley-Davidson XA
Brakes | Drums front and rear[1][2] |
---|---|
Tires | 4.00 x 18[1][2] |
Wheelbase | 57.5 in (1,460 mm)[1] |
Fuel capacity | 4.1 US gal (15.5 L; 3.4 imp gal)[1] |
Oil capacity | 2 US qt (1.9 L)[1] |
The Harley-Davidson XA (Experimental Army) was a flat-twin, shaft drive motorcycle made by Harley-Davidson for the US Army during World War II.[4]
Development and production
During WWII, the U.S. Army asked Harley-Davidson to design a specification of a motorcycle much like the
In 1943, the XA's leading link fork[1][2] was replaced with Harley-Davidson's first telescopic fork.[4]
Similar motorcycles in other countries
From 1942, the BMW R71 would serve as the basis for the IMZ-Ural and KMZ-Dnepr M72 (U.S.S.R./Russia), and from 1956 the Chang Jiang CJ750 (China) which likewise pressed it into military service though parts should not be considered interchangeable across marques despite visual similarities.
Cooling
According to the American Motorcyclist Association's Motorcycle Hall of Fame Museum, regarding the World-War-II-vintage Harley-Davidson XA, which has an opposed twin engine — "Mechanically, the large cooling fins stuck straight out in the breeze, reportedly keeping the XA’s oil temperature 100 °F (38 °C) cooler than a standard Harley 45."[4] The latter was a transversely mounted V-twin, in which the air stream cannot reach the cylinders, especially the rear cylinder, as efficiently as a longitudinally mounted flat twin. The use of "transverse" and "longitudinal" here follows motor car convention based on crankshaft alignment. However, with motorcycles the convention is based on width - hence cylinder orientation. Therefore, a flat or v-twin with left and right cylinders is transverse but with front and rear cylinders it is longitudinal.
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1942 Harley-Davidson XA on display at the California Automobile Museum
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Harley-Davidson XA engine
Related projects
Though the XA motorcycle was "dead" as far as the military was concerned for full-blown production, both the side-valve and overhead-valve versions of the XA engine were explored according to Jerry Hatfield in his 1990 book "Inside Harley-Davidson" published by
See also
References
- ^ ISBN 0-7603-0326-6. Retrieved 2012-08-05.
- ^ ISBN 0-8734-9949-2. Retrieved 2012-08-05.
The XA was a BMW clone machined to American dimensions and fitted with H-D tanks and fork.
- ^ ISBN 0-7603-1541-8.
In addition, the XA was the first production Harley to feature front and rear suspension.
- ^ ISSN 0277-9358. Retrieved 2012-08-06.
Mechanically, the large cooling fins stuck straight out in the breeze, reportedly keeping the XA's oil temperature 100 degrees cooler than a standard Harley 45.
- ^ "BMW Group Classic".
External links
- Army Tests Experimental Shaft Driven Motorcycles September 1942, Popular Science