The design process started by utilizing the constraints given by the customer. Some of the main constraints that were encountered were the size of the electrical motor and the correct positioning of the wheel. All steps of the design process were followed to obtain the best possible solution to the problem. A total of 3 months was devoted to obtaining the right design that would suit the needs of the customer.

Before making a decision on the design, different possibilities were explored.

After three months of work we obtained the following design as the best solution to the problem given to us.

This final design was submitted to the client for approval in December of 2001. After some review from the customer we obtained a final approval with some minor changes to the design submitted. these minor changes can be seen on the picture below. These minor modifications include the use of an of the shelf hub instead of a custom fabricated one, the use of tapered bearings that are included with the hub and the repositioning of the back plate in the axle for ease of removal. The axle plate was placed in front of the strut so the whole assembly can be removed without having to disassemble the whole thing. This make use and removal of the wheel mount more user friendly.

The final design is composed of a fixed axle, a fixed motor mock up, a rotating hub with two tapered bearings, a hub adapter to couple the unit to the wheel and a back plate welded to the solid axle aft of the strut. The axle, motor mock up and back plate were built by the machine shop at school. The hub, hub adapter and tapered bearings were bought from a mail order catalogue.

After the design was finalized all parts were modeled using PRO-E software. This allowed the design to be adaptable and to obtain all correct dimensions before any material was bought. The following drawings were used for test fit and then were taken to the machine shop for fabrication.

Whole assembly in PRO-E

Axle

Hub

Image of all parts used for rear wheel mount.

All parts put together (click to enlarge)

Parts in better detail. Center picture shows motor mock up attached to laid in machine shop.

The hub ordered for the wheel mount was the same hub used for the front wheel assembly. This simplified drastically the machining and assembly time needed for the project. Safety was one of the biggest concerns when designing the rear wheel mount. By using a hub that was designed and tested before hand we knew that a great deal of safety was achieved. All parts machined in the school's machine shop were machined using cold rolled steel. This material was used because of it's strong characteristics, low price and the ease of machining. Special emphasis was placed on the exact dimensions of the motor mock up. The actual electric motor weighed 17.27 Kg. and the mock up ended up weighing 17.40 Kg. The dimensions of the electrical motor and the mock up are almost identical even though the design and calculations for it never intended it.

The electrical motor bolted directly between the wheel and the strut. In order to achieve including a hub, axle, adapter and bearings on the same space the motor mock up had to be bored so the hub and adapter would sit half way inside the motor mock up. The following picture shows this in greater detail. (Click image to enlarge)