Abstract
By wind-up is meant the twist that occurs in the transmission of a vehicle having several driven wheels but which is not provided with sufficient differentials to ensure equal distribution of the driving torque between the wheels, and which is due to inequalities in the effective rolling radii of the wheels. The first part of the paper discusses the importance of the wind-up phenomena and describes some experiments made on a rig in which wind-up could be developed and the wind-up torque be measured. The results show clearly that wind-up quickly reaches a steady state and that during this phase the effective rolling radii of the wheels change until they become equal.
The second part of the paper describes some experiments, made on another rig, in which the effects of speed of rotation, radial load, inflation pressure, and torque transmitted on the effective rolling radius of a pneumatic tyre, could be determined.
A selection of the results obtained is given in a series of graphs. The most important result is the establishment of the fact that the effective rolling radius of a tyre is a function of the torque transmitted by it and that if this function is known then the wind-up torque can be calculated. The paper concludes with a summary of the results obtained and some suggestions for ameliorating the harmful effects of wind-up.
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