Development of a design tool for modelling and optimisation of the Milner CVT

The Milner continuously variable transmission (MCVT) is a traction drive transmission based on rolling contacts analogous to those found in angular contact roller bearings. The MCVT is applicable to very high power density applications or those with demanding packaging constraints, due primarily to the existence of multiple traction contacts on each of the rolling elements. This paper details the application of a design of experiments approach to optimising the design of the MCVT. An Analytical model including the contact mechanics and Elasto-hydrodynamics of the traction contacts has been developed and interrogated using design of experiments. Furthermore, the results of the technique have been applied to develop a design tool based on multi dimensional response surface models of pertinent transmission performance criteria. The use of the design tool is then demonstrated to derive future geometry iterations of the MCVT based on the tradeoffs between efficiency, ratio range and transmission life requirements. Inputs to the design tool include geometry parameters, number of rolling elements, design torque and speed ratings and required traction coefficient. Outputs from the design tool include assessment of ratio range, spin effects, traction efficiency and material stress levels.