Software used: Dassault Systèmes SolidWorks, MathWorks MATLAB, Simulia Abaqus 6.11

Equipment used: General milling, turning and other workshop skills, Rolling road dynamometer, vibrations analysis equipment (accelerometer, signal conditioner, impulse hammer, signal analyser)

This project was a group effort of 5 Imperial College 3rd year students including myself to design, manufacture and test the Range Extender Gearbox (REX), a transmission system linking a 250 cc single-cylinder combustion engine to an electrical generator. The motivation of this project was to develop a hybrid propulsion system for the upcoming Formula Student racing vehicle.

Two main tasks were accomplished: the design and manufacture a temporary test rig and transmission for bench testing of a chain drive between engine and generator, and the design of the final transmission.

During the different stages of the project, a number of design concepts were developed through the Quality Function Deployment (QFD) technique. Heat and stress analyses were performed to validate design decisions and optimise the configuration of the gearbox and engine. The final design was 25% below the target weight of 4 kg.

Heat transfer analysis of the gearbox showed that the maximum temperature that the gearbox oil would achieve during a race is 110oC. An SAE80W90 lubricant was found to be an appropriate specification and that it is unnecessary to implement fins or a cooling fan. In addition, Finite Element Analysis carried out on the gearbox yielded a maximum stress of 19.05 MPa, suggesting that the gearbox casing is not in danger of yielding or fatigue failure.

The gearbox was CNC machined in-house from 6082-T651 aluminium. The gears used were customised and required outsourced manufacturing. Finally, an impact hammer vibration test determined three main resonant frequencies of 3800 Hz, 1900 Hz, and 700 Hz and a damping ratio of 0.06. It was determined that the structure would not be subjected to resonance conditions during operation.

All objectives were completed in accordance with project deadlines. A critique found at the end of the report comments on the design and manufacture of components, and provides information on the gearbox for future use.