Electric Traction Set for a light car

This paper deals with the feasibility study of a special electric traction wheel-set for a micro-car for disabled customers. In our university department some solutions on the topic had already been developed in the past. The design has not been carried out in a sequential way, but it has been lead in “concurrent-engineering” style and it has been speeded up thanks to the employment of solid modelling. The 3D design technology has helped in a very efficient way to take into account the impact of any modification on any component to the neighbouring items. The following topics have been considered: design for disabled customers, maximum ease of use and low cost technology. This job therefore has coped the main problems related to designing a new car. Some innovative solutions have been proposed and an overall design procedure has been experienced. This paper in particular describes the results of a research activity connected with the study of the general lay-out of such a wheel set. Some different configurations were explored, each showing its strong and weak points. It is to point out that, while the traditional arrangements connected with gasoline or diesel engines were hugely studied, with the electric traction all the wheel sets must be reshaped. In fact too many car designers tend to use the same lay-out used before, wasting much of the potential advantages offered by electric motors. During this study some radically new designs were explored, for example not using any live axle for transmission or trying to use thrust ball bearing for steering axles. In the following a gallery of proposed and studied solutions will be exposed, showing the most characteristic points. We developed the study and design phases starting from some specifications: the group must be composed by electric motor (geared or not), brake, wheel hub, front or rear traction, in case of front traction the group must have steering pivots (attachments for steering rods). This apparatus has been designed to be used in a light car (which is under development in our faculty). However the proposed design may fit even standard city cars. Design goals were: 1) Keeping very low steering radius (intended use in city environment) 2) Absence of traditional suspension system (our light car has some innovative design in this) 3) Respect of Ackermann geometry. Some different design solution have been developed and are exposed in the paper. The most relevant feature is that every wheel has its own motor, so achieving a dramatic reduction in encumbrance.