Race Car Reverse Gear Design

Abstract

This thesis presents the design, simulation, and installation of a reverse gear system for the RUSH SR, a lightweight, motorcycle-engine-powered race car that lacks built-in reverse capability. The proposed solution repurposes a high-torque automotive starter motor to drive the car in reverse through engagement with a custom ring gear on the rear differential. Analytical modeling and time-domain simulation were used to evaluate performance under varying loads, including the effect of incline angle on terminal velocity and motor current draw. Simulated results show that the system can reliably move the car in reverse on slopes up to 10° before stalling, with current draw remaining within safe operational limits. The mechanical design includes a new differential carrier, gear coupler, and ring gear, while the electrical system explores both off-the-shelf and custom high-side switching controllers to manage power and solenoid activation. The final hardware was bench tested and installed on a working vehicle. Recommendations for future validation include current-limited incline testing and dynamic vehicle response trials. This modular and cost-effective system demonstrates a practical solution to a common race car limitation while preserving the RUSH SR’s lightweight performance characteristics.