How to Build a Race Car Layout

Going fast in a race car is all about the engineering.

There are three basic ways to engineer a race car. The first is to stick rigidly to a formula set out by the race sanctioning body, attempting to gain the winning edge by making small improvements wherever allowable. The second way is to try to copy what others have done; while amateurish, this approach can work for those with little understanding of a race car's mechanical subtlety. This is the third way--building your own race car layout.

Instructions

1. Acquire a full set of weight measurements for all components and materials you intend to use. This means primarily the engine, transmission/transaxle, axle, suspension components, wheels and tires, and frame materials.

2. Examine your class rules to see what's allowable, then choose the basic configuration and specs you''ll need to meet the class rules. Configuration can mean front engine-rear drive, front engine-front drive, mid engine, rear engine or any engine placement with all or four wheel drive. Specifications include minimum weight, wheelbase, tire size and aerodynamic restrictions.

3. Find the midpoint between your wheels and place the center of the driver's seat as close to it as possible. For the best feel and chassis control, you should consider the driver's hip bone as the car's "master center," or the point about which everything pivots and functions. The closer you can get the master center to the midpoint of the car's wheelbase, the fewer inertial effects the driver will experience while cornering and braking. This is a huge boon to driver comfort and contributes to the ability to maintain focus during long races.

4. Place the engine, transmission/transaxle, and/or rear axle in entirely in between the axle centerlines--and as close to the driver as possible. Use the weight data you gathered earlier to calculate where the vehicle's center of gravity (CG) will fall relative to the master center; the goal is to keep the center of gravity as close to the master center as possible.

5. Add in the rest of the suspension and chassis components, keeping track of your weight data at all times. You might find it helpful to start two columns of weight figures, one ahead of the master center and one behind. Add anything ahead of the master center to the front column and anything behind it to the rear. The idea is to keep the numbers as close as possible to ensure a perfect 50/50 weight distribution. Keep all components that you can between the wheels to help reduce the car's "polar moment of inertia"--the weight on the extremities that will reduce the car's handling agility.

Tips & Warnings

• When setting up your car's suspension, you need to keep its "roll centers" (RC) "roll axis" (RA) and "instant centers" (IC) in mind at all times. These all important points represent the imaginary places where your suspension pivots around the frame. You want to keep your RA (a derivative of the RC and RA) as close to your master center as possible, preferable engineering the car so the front and rear RCs actually converge on the MC. This is the approach used by some of the most renowned manufacturers in the world (Ferrari, Lotus and BMW among them). When executed properly, this method will yield a race car with outstanding handling limits, a forgiving nature when those limits are exceeded and overall confidence-inspiring handling.

References

• Mira Cerros: Roll Centers
• Circle Track Magazine: Front Roll Center Location - Roll Center Wisdom
• Racecar Engineering: Diffusers Explained
• Baseline Suspensions: Drag Suspension and Engineering