To explore how NASCAR race cars are built, we visited Bill Davis Racing in High Point, NC.
This shop buys its frames prefabricated from a frame supplier. The frame consists of a structure of round and square steel tubing of varying thickness. The bulk of the structure surrounds the driver. This part of the frame -- the roll cage -- is made of the thickest tubing and is designed to stay together, protecting the driver during any type of crash (see How NASCAR Safety Works for details).
The front and rear sections of the frame, called the front clip and the rear clip, are built from thinner steel tubing so that they will crush when the car hits another car or a wall. In addition to being collapsible, the front clip is designed to push the engine out of the bottom of the car -- rather than into the driver's compartment -- during an accident.
When the frame comes into the shop, the firewall (the metal panel separating the engine compartment from the driver's compartment) and floor panels are welded in, along with various mounting brackets for things like the engine, suspension, seat, fuel cell and body.
The next step is building the body and installing it on the frame. This process is amazing -- almost every part of the body is made by hand from flat sheet metal.