Abstract
During experimental work on flexible belts running on pulleys of small diameter, the loss of speed of the follower arising from the elasticity of the belt was observed to be considerably greater than would be normally expected. It was also noticed that this loss of speed depended on the mean tension of the belt and the diameter of the pulley. The usual type of belt material does not follow a linear elastic law for strains in the direction of its length, the elastic modulus being relatively low at low tensions and when in compression. On the assumption that compressive stresses can be neglected, the resulting stress distribution is found to account partly for the experimental results. In addition the material has a relatively low transverse compression modulus, and the surface compression causes an additional slip loss which would be negligible with an isotropic material in all practical cases. The examination is applicable to V-belts when the effects producing radial movements are of greater importance because of the amplification by the groove angle. For both kinds of drive the relative influences of the component losses on efficiency are discussed, and conclusions can be drawn on the suitability of materials for small pulley drives.
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