Abstract
A new transmission index based on a static force analysis, the joint-force index, is presented. The joint-force index is an improved transmission index for mechanisms which support external loads. No other transmission index in the literature predicts the effect of specific external loads on the force transmission, even though mechanisms that are subjected to external loads are very common. The joint-force index provides a meaningful transmission guideline regardless of the complexity of the mechanism. Planar four-bar linkages as well as complex planar linkages of six or more links may be evaluated using the joint-force index.