FSAE Chassis Tuning

Bearcats Electric Racing has only ever had one reliably running car. However, while the car was reliable, it wasn't fast. The car never won any awards in its season due to persistent handling issues and lack of driver talent. EV3's handling issues stemmed from certain design choices that were not ideal for the car. For example, EV3 would push hard into corners, but feel loose coming out of corners. Even though the car seemed like it was designed to oversteer, we struggled with low speed understeer. 

Solution

Approaching our third race in EV3, I realized that we needed to make a change to the handling of the car if we wanted to be competetive. The team that designed the suspension of this car assumed that lifting tires was detrimental to the handling of the car, do they included a primary and a secondary spring on each damper to maintain contact with the ground. In reality all this did was provide more of an anti yaw moment in the form of drag on the inside rear tires. So first step was removing the secondary spring. We were able to machine spacers to make up the compressed length of the spring and allow more consistent loading of the tires. The second big change we made was removing preload from the differential. This served the same purpose of lowering the anti yaw moment from the drag on the inside tire. Unfortunately we had to tear apart the diff and manually phase the pinions to tune the diff, which ate up all of our time for testing and tuning before the race. All of our tuning had to be done at the race. At the track, we set up the alignment to be relatively nuetral and adjusted toe for oversteer/understeer tuning. Our driver had experience in gokarting, so he quickly asked for the car to be looser in low speed. After constant tuning and adjustment we managed to set a good time and land ourself on podium. That day we got 2nd which was the first trophy for not just that car, but for the team in general. 

What I should have don differently

• While our driver requested for the car to be looser, we only had one run where he didn't hit any cones. So next time I probably should have made the care more stable until we got one or two clean runs in.

• Testing time before the race would have been a good idea.