What’s Under the Skin?
Written by John Davison · January 21, 2004
Or, how “stock” are stock cars?
NASCAR NEXTEL Cup racers are only “stock” cars in name. This writer recently had an extended (and unsupervised but approved) visit to the HaasCNC Racing shops. There we had the opportunity to look at the skeleton under the skin at Ward Burton’s new NetZero Chevrolets.
When Bill Ingle, crew chief for the team parted company with us, his instructions were to call him if we needed anything. Then he went back to his office and let us wander around the shop with no restrictions on what we looked at or photographed. Quite a change from some of the bigger teams, where nearly everything is shrouded in a cloak of secrecy.
Stock? Well, they do start with stock rectangular and round steel tubing. That and lots and lots of flat sheet steel. Toss in a few hundred hours of very skilled labor by fabricators and sheetmetal experts and a rack of raw material like this one becomes a finished race car just a few weeks later.
The basics: NASCAR racers are all based on a custom-built tube frame chassis. The main frame rails are about 2×4 rectangular steel tubing. Welded onto the main rails is a maze of steel tubes serving variously to support the engine, suspension and fuel cell. The center of the car is the most complex by far, with the roll cage serving to support the driver’s seat and to protect in an impact. The seat is mounted to the roll cage and not the car’s floor.
This is in contrast to the original days of NASCAR when cars had to be “strictly stock” and replacing nearly any significant part resulted in disqualification of the car. In today’s NEXTEL Cup world, use of unapproved parts can cost more than losing the race. In recent history, drivers, crew chiefs and even owners have lost money and points if a car was found with “unapproved” parts on board.
The main frame rails are doubled on the left-hand side as shown here. The curved tube above and to the left of the main rail is part of the diagonal bracing to protect Burton.
Both right and left sides of the car have a quartet of tubes (the right-hand side shown here) intended to protect from intrusion in the inevitable crashes. These bars are bowed out so that an impact will try to straighten them before they collapse inward, adding a bit more strength and protection.
All these tubes are tied together for stiffness. Visible in the photo above are a couple of spots where the junctions between tubes are reinforced with gussets. These little pieces of plate add significant strength to the joints. The base of the main hoop is reinforced even more with the addition of a “box gusset” as shown here.
Stiffness in a chassis is the key to consistent handling. Without a stiff chassis, the suspension engineers are just chasing their tails like a Jack Russell terrier on methedrine. The stiff chassis allows engineers to design a suspension that willkeep the tires planted squarely on the track. Or, at least, plant the tires squarely on the surface in the turns, where traction is most important in winning races. Teams build extensions to the frame for the front suspension to mount on. Here’s the lower front suspension mount on one of the Haas cars.
As the recent articles in SportsCar magazine explain, tire traction makes the difference. Springs are very stiff, compared to road race or street springs, with shock absorbers even stiffer. At one time, teams would run really odd spring and shock settings on superspeedways to let the rear suspension settle down, putting the rear spoiler a bit out of the airstream. Lately, the rules have specified springs and shocks that keep the cars more level. Teams still seek to lower the front ends to keep air out from under the cars as much as possible.
When it comes to hanging the bodies on the chassis, there’s at least as much art and magic as science. But before the bodies can be placed on the chassis, they have to be constructed. Nearly the entire body starts as flat pieces of sheet steel. Through a laborious process of hand labor, these flat sheets are converted to the sleek curvaceous bodies we enjoy watching on the track. Many teams build even the hoods and trunk lids on the cars. One team of Chevrolets is rumored to have run a car with a Ford hood and a Dodge deck lid and still had the car fit NASCAR’s templates.
Compound curves are formed by the use of “English wheel” tools, rolling flat sheets into shapes that are recognizable as the street car they’re supposed to represent. The front lower fenders 
and front valence were all one piece on the Haas cars we saw during our visits. The rest of the front fenders were made of three pieces, extending all the way back to mid-door.
The nose and tail of the car are NASCAR-specified fiberglass pieces. Rear fenders, from about mid-wheel opening extends forward to meet the front panel, and is also made of several pieces, as is the roof.
What’s stock on a Nextel Cup “stock” car? We’ll get back to you on that one.
Comments
One Response to “What’s Under the Skin?”
Got something to say?
You must be logged in to post a comment.
I am a teacher working on a unit that involves vehicles that are fuel efficient, safe, and aerodynamic. Could students post questions here to be answered by someone for class? We need email contacts for this unit. Thank you for your help.
Melissa