Experimental investigation on the shimmy phenomenon

The dynamic behavior of motorcycles, in terms of out of plane vibration modes, is strongly influenced by relative oscillations that can arise between the front and rear frames around the steering axis. When idealizing behavior for a rear frame mass which is very large compared with the front frame, the shimmy phenomenon takes place. This paper presents a basic experimental investigation of the shimmy phenomenon of a scooter front assembly whose wheel is supported by a constant velocity translating belt. The tests were performed using different sets of parameters that influence the dynamic behavior of the system. For every operational condition, the damping needed to stabilize the system was found by properly adjusting the anti-shimmy damper; the investigation results are mainly reported in terms of damping-speed diagrams.