There seems to be a connection between aircraft landing gear and motorcycle telescopic suspension. BMW equipped two 1935 models, the R12 (photos) and R17, with its hydraulically damped telescopic fork, and also used such a fork from the beginning in developing its supercharged 500cc road racer. Messerschmitt’s M29 airplane of 1932 employed cantilevered telescoping struts to support its two main landing wheels, and at this same time retractable landing gear was becoming a necessity on emerging high-speed aircraft. Telescopic construction combined the stiffness of fair-sized tubes with generous travel and compact internal location of damping systems. Through almost the entire between-the-wars era of 1919 to 1939, motorcycle front suspension had been the girder fork. A pair of girders, usually fabricated from small tubing, extended upward from the front axle to join the steering yoke by means of four short pivoting parallelogram links. Damping—if any—was provided by scissors-type dry friction dampers. The early bugaboo of the girder fork was a “clashing” as the mechanism hit its stops on rough roads. Later, various remedies such as negative springs or rising-rate geometries were added to soften or prevent this. The death knell of the girder fork was the rapid adoption of more powerful brakes in the late 1920s and early 1930s, which placed very concentrated loads on the fork links and their bushings. 
Early attempts to build telescopic forks were criticized for: Low stiffness. I well remember placing a 1950s Triumph front wheel between my knees and finding I could twist the bars through a surprising angle. And they would stay where I had put them! Brake dive. Telescopic forks are pro-dive because, angled as they are, one component of braking force acts to compress the fork. Partly to escape this dive tendency, in the late 1980s independent designer John Britten revived the girder fork, implemented in carbon fiber and using rising-rate linkage (in the mid-1980s, fork dive was shown to actually improve braking by lowering the motorcycle’s center of mass). In 1937, Velocette’s racing engineer, Harold Willis, and his friend, aircraft landing-gear pioneer George Dowty, designed a motorcycle telefork that was not produced until 1949. Both Norton and AJS/Matchless designed teleforks during World War II and were produced once the war ended. US landing-gear specialist Menasco is said to have assisted in the development of Harley-Davidson ’s first teleforks. Landing-gear manufacturers not only had hydraulic damping technology available, but they were able to perform the precision cylindrical or centerless grinding necessary for smooth, low-friction motorcycle fork tubes. Since the 1970s, dozens of ingenious alternatives to the telescopic fork have been built, tested, and even raced. However, the same combination of robust simplicity and long travel that made telescopic suspension struts attractive for aircraft continues to do the same for the motorcycle. 
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