Whether you're purchasing...
Whether you're purchasing a new car or looking to get into racing on the cheap by buying used, a sharp eye can help you determine the quality of the chassis you will be purchasing.
Sure, the usual stuff you think of when you talk about racing safety is important-critical even. We're talking about your helmet, seat, and five-point harness, head-and-neck restraint, and even the fire bottle. But none of those are the most important when it comes to keeping you in one piece in the event of a hard wreck. Not even close.
And if you race any amount of time, it's not a question of if, but when you're going to be involved in a hard wreck. You can be as careful as you like, but that still doesn't account for the other competitors on the racetrack with you. So what is the most important safety component, you ask? It's the car that surrounds you.
A properly built race car goes a long way in protecting your body from the forces involved in a violent collision. This includes both dissipating energy before it gets to you and keeping damaging objects-such as other race cars flying by at high rates of speed-from getting to you. We recently visited the shops of Leavitt Racing to talk with both Steve Leavitt Sr. and Jr. about the finer points of constructing a safe race car. Leavitt Racing has built NASCAR Sprint Cup and Nationwide Series cars for years and has begun expanding its focus on Saturday night-level racing chassis.
The information they provided should be invaluable for anyone looking to either repair an existing car, build their own, or purchase a car-either new or used.
This can be more difficult...
This can be more difficult if you're inspecting a painted chassis, but the most important thing is to check the quality of the welds. Most Saturday night cars will have MIG welds (as opposed to the more labor-intensive TIG welding method), and when done well are very strong. The weld bead should be consistent with minimal to no spatter. There should also be a bit of a color pattern radiating out from the weld, as you can see here. This shows that the welder used plenty of heat so the weld should have good penetration into the tubing. If you don't see this, there is the potential that the weld bead can simply be sitting on top of the metal and the joined pieces of tubing can be easily broken apart in the event of a wreck. Finally, notice that there is a single weld bead all the way around. This is a sign that the builder took the time to notch the tubing precisely and there is a good, tight fit. If you see beads on top of each other or beside each other, you can probably assume the welder is trying to fill in
One thing that veteran chassis...
One thing that veteran chassis builder Steve Leavitt says many fabricators neglect to do is chamfer the ends of the tubes to be welded. A good chamfer will encourage a good, deep penetration of the weld bead.
For comparison, this is an...
For comparison, this is an unchamfered piece of tubing. The notching work is good, which provides a nice, tight fit, but you can see how it would be easier for the weld bead to simply sit on top of the tubing this way.
Take the time to inspect how...
Take the time to inspect how the 'cage is attached to the framerails. On a Street Stock where the 'cage often must be welded to sheetmetal, there should always be a large metal plate welded between the end of the tubing and the sheetmetal to keep it from ripping off. And even on a purpose-built race chassis like this, the ends of the tubing should never be simply welded to the framerails. Leavitt says he's seen the tubing be ripped right off the framerails in a hard hit-even if they were welded properly. By adding a gusset wherever a part of the 'cage connects to the framerail, he can significantly increase the surface area of the weld-and the strength of the connection between the 'cage and the frame.
This shot shows the driver's...
This shot shows the driver's door bars. Notice the two vertical braces supporting the bars right at the location of the driver's hips and legs. You could use less tubing (and save a little weight) by connecting the braces to the bottom bar, but Leavitt points out that this won't help the driver much. In the event the driver takes a hard hit from another car right in the side, that car's bumper will probably hit right about the second bar up. That's why these braces are there.
Whenever possible, Leavitt...
Whenever possible, Leavitt never has a tube simply end in a 90-degree joint with another tube. Instead, he will brace it with another tube on the other side, as you can see from many of the tubes in this 'cage. You will also notice lots of triangulation going on here.
A straight piece of tubing...
A straight piece of tubing is a lot stronger than one that is bent, even if the work has been done on a mandrel bender. Although lots of bends are necessary on a racing chassis, Leavitt says he tries to keep as many straight pieces of tubing as is possible. As an example, he points to the downward sloping bar on this truck chassis. Racers must put a piece of Lexan between the bottom of this bar and the top of the truck bed, called the "Romeo Window." On the right side, this window can keep the air from hitting the spoiler, so Leavitt must bend the tube to minimize the area. This isn't as big a deal on the left side, however, so he's able to leave it straight.
Leavitt points to the area...
Leavitt points to the area just behind the crossmember where most rear clips will bend. He says it's rare that a hit at the back of the car will damage the center section of the chassis. "Once you get past the rear suspension pickup points," he says, "about the only thing we're doing back there is holding up the fuel cell, so it's easy to create a crush zone that will protect the rest of the car."
This is a joined area of a...
This is a joined area of a rear clip that has been replaced. Instead of welding two pieces of tubing end-to-end, the better method is to weld a butt plate to the end of the tubing after the old clip has been cut away, and then attach the new tubing to the end of that butt plate as you can see here.