Ring motor front wheel for electric motorcycle applications

Abstract

This thesis examines the design process of a ring motor meant for replacing the front wheel of an electric motorcycle for performance benefits such as traction and additional acceleration. Gas motorcycles are unable to power the front wheel without some degree of mechanical complexity, but electric machinery is not subject to the same constraints because it can be integrated within the wheel itself. The ring motor is designed by first using calculations and verifying the performance through various simulation software such as Motor-CAD, and a thermal test for heat pipes is performed. A concept for packaging it is presented at the end.

The machine is designed as a permanent magnet synchronous motor with an outer rotor. Minimizing weight while retaining performance was achieved by using various means, such as increasing the number of poles to reduce the rotor thickness and using finite element analysis to examine the flux density. The lack of coupling between teeth allowed the stator to be thinned greatly, but the active region is quite heavy because of the usage of materials much denser than aluminum.

The design of a 40 kW ring motor is described based on constraints given by the original wheel and tire used. The final design required lowering output power to 32 kW due to heat issues, but it is quite viable and efficient enough for practical usage. The packaging concept shows a possible way to enclose the active portion while integrating cooling as well.