This week: Suspension

This week in Baja, we had to get the car ready for technical inspection.  What that means is that all of the rules of SAE, the society of automotive engineers who sponsors the competition, must be met by our car.  The remaining items for us include a lot of small things, including car numbers, as well as various other aesthetic parts.  All of the sub team leads are double checking all facets of their systems for any way that the car will not be acceptable according to SAE rules.  The first thing that happens at competition is technical judging, not only to make sure that the car is safe to drive, but also to score our car based on our design decisions.

On the note of design decisions, it is easy to get lulled into the idea that our car is the only concept of vehicle that can be realized.  Upon arriving at competition, you rapidly realize how many design variations there can be.  Variations in suspension alone make no two cars alike.  The most basic option is double A-arm suspension, as pictured below.

Source: http://www.carbibles.com/suspension_bible.html

The part with the circular hole on the right side is called the upright.  The upright is the part that attaches the suspension linkages and also where the wheel attaches.  The idea of any suspension is to have the wheel move along a predictable arc when the suspension articulates from hitting a bump.  Bearings attach the A-arms to the upright so the wheel can stay somewhat vertical as the suspension moves up and down.  This introduces the concept of dynamic suspension geometry, where an angle of the tire, called camber, can help dig in during turns.  Suspension theory can get very complicated; the list of contents on the Wikipedia page for suspension is intimidating enough to make a young engineer question his career choices.  Thought that is the case, the basic idea is relatively simple: to have the wheels able to cushion the impact of bumps on the road.  Additionally, the suspension should react desirably to weight transfers during turning, accelerating, and braking, as should sound familiar to anyone who has driven a road car.

Wikipedia Suspension Article
http://en.wikipedia.org/wiki/Suspension_(vehicle)