Model-Based Compensation and Uncertainty Analysis of Support Bearing Losses in a Chain Drive Dynamometer

Efficiency testing of chain drives has received renewed attention in recent years from sectors including elite cycling, e-mobility and automotive engineering. This is because of a desire to maximise performance, reduce energy consumption and minimise wear rate at a component level. In particular, chain and lubricant manufacturers have developed test rigs that replicate transmission drives in order to measure the efficiency and wear behaviour of the chain and sprocket. Most test systems are dynamometers that either apply representative torques to the input and output sprockets (Transmitted Power Measurement) or replicate loads in the articulating links by tensioning the whole chain drive (Frictional Power Measurement). Each method has advantages and disadvantages with respect to measurement uncertainty. One challenge that both methods have is the requirement to isolate torque transducers from the shear loading induced by chain tension. A common solution to this involves mounting each sprocket on a shaft supported by a set of bearings. However, these bearings introduce parasitic losses which must be accounted for if absolute values for transmission losses are to be deduced from the raw data. A comparison is made between two commonly used models of bearing frictional moment. One is given by a major bearing manufacturer and the other is the most referenced model from the literature. The effectiveness of each model for predicting parasitic losses is discussed for a transmitted power measurement dynamometer application. The effectiveness of each model to for predicting parasitic losses is discussed for a full load chain drive dynamometer application.