Guide to Baja Suspension
This guide is intended to be an intro and complement to Racecar Vehicle Dynamics, not a replacement. This page is a collection of specific insights in regards to designing a Baja suspension that should serve as a useful study aid in reading of Racecar Vehicle Dynamics and other suspension documentation.
In a single sentence, the goal and purpose of suspension is to distribute reactive forces in a way desired by the driver. This is done through the use of linkages, springs, and dampers. Links limit motion of the wheel to a single path and very stiffly resist (until they break) any forces not in line with this path. Springs will apply forces normal to the direction they are displaced. Dampers will apply forces normal to and based on the velocity they are displaced.
Parameters of Interest:
- Roll Axis
- CG Location
When tuning its especially important to consider the car as a whole when making changes.
- Weight Distribution
The process for determining geometry suggested on pg 618-621 of Racecar Vehicle Dynamics was implemented in Solidworks as follows: 1. Create an adjustable model of Frame with mounting points of Rear Suspension, CV axles, and add in sketches of control arms, shock and cv axles. a. Ensure that limits of shock and CV axle are appropriate. (Limits are approiate if at full compression the bottom of the frame is 4.5” (the max compression of tires in use and at full extension the CV axles can still go down another ½” before hitting their hard limit.) If limit is not appropriate use the following procedure. i. Put ride height at full compression or extension. ii. Set the height of the inner mounting to driven, adjust the length of the shock to its overall length at that travel limit, make the shock driven again and the height driving. iii. Put ride height at opposite limit. iv. If the shock isn’t yet at its travel limit, the shock needs to be closer to vertical and adjust the horizontal mounting accordingly. v. If the shock has gone past its travel limit, it needs to be more horizontal, so adjust the horizontal mounting accordingly. vi. If shock is already horizontal or vertical at either end of travel, then it can not be adjusted any farther 1. If the shock is horizontal, links are too long. 2. If the shock is vertical, links are too short.