High-Performance Rear Differential Mounting & Chain Tensioner

Both rear differential mounts withstand the motor’s pulling load and the differential’s vibration during operation.

Rear diff mounts assembled to chassis

1. Project Scope & Challenge

Objective: Design a lightweight, high-stiffness mounting assembly for the vehicle's rear differential, capable of transmitting $240$ Nm of motor torque while integrating a precise mechanism for chain tensioning.

Role: Mechanical Design Engineer & FEA Lead

Tools: SolidWorks, ANSYS Mechanical, Hand Calculation, GD&T.

2. Analytical Modeling & Load Derivation (First Principles)

Before beginning CAD geometry, I performed static analysis to determine the governing loads. Ideally, the differential assembly behaves as a rotating shaft subjected to immense radial loads from the chain drive.

Torque Conversion: Calculated the wheel torque and chain tension based on a 5500 RPM motor input and the specific gear reduction ratio.
Free Body Diagrams (FBD): I idealized the differential assembly as a supported beam to resolve the reaction forces at the bearing locations. Through summing moments and forces, I identified a critical Radial Sprocket Force = 7.843 kN.
Bearing Selection: Using these calculated radial loads, I selected the appropriate ISO bearings (63/28 and 6011 series) to ensure the bearing’s life exceeded the vehicle's race duty cycle of 200 hours.

3. Mechanical Design & Eccentric Tensioning

The primary design challenge was maintaining axle parallelism while allowing for chain stretch adjustment. A static mounting hole would not suffice.

Eccentric Mechanism: I designed a custom eccentric bearing housing interface. By rotating the eccentric rings, the differential center axis moves fore/aft relative to the chassis, allowing for precise chain tensioning without compromising the perpendicularity of the drivetrain.
Topology Optimization: The mount geometry was iterated 5+ times. I focused on removing material from the "web" sections of the mount (neutral axis) while reinforcing the load paths between the bearing race and the chassis mounting points (clevises).
Geometric Dimensioning: Calculated precise hole distances and tolerances to ensure the eccentric mechanism would not bind under thermal expansion or chassis flex.