A model of the tension and transmission efficiency of a bush roller chain

This paper describes an improved chain link tension model for a simple two-sprocket roller chain drive. The model includes modified versions of previous models of the tension in the chain links, together with a new model for low-slack span tensions. The model allows the tension of a link to be calculated at any point in the chain drive more quickly and for a wider range of tight and slack span tensions than before. A new chain efficiency model is formulated, based on the losses due to sliding friction. Coupled with the chain link tension model, this can be used to predict the transmission efficiency of a chain. Experimental work undertaken on 0.5 in pitch industrial roller chains and bicycle chains has demonstrated that the chain efficiency model is accurate for moderate and high torque transmissions. At low torque, losses due to impact, adhesion and/or vibration become more significant and impair the accuracy of the model, particularly for heavier, industrial roller chains. The chain efficiency model enables certain design trade-offs to be carried out, such as the selection of the size of the overall system to achieve the right balance of transmission efficiency and weight.