February 1, 2009

Rating A Rollcage
When buying or building a race car, one of the most important things to consider is the rollcage. The 'cage is akin to the foundation of a house-don't buy either one with problems. When assessing a used race car, don't get distracted by long lists of trick goodies and speed parts, that stuff all bolts on and off-a rollcage is forever, good or bad. If you are building a new car, you've got pretty much one shot to get it right. The first thing to consider about a 'cage design is whether it meets the basic rules of the sanctioning body you intend to race it in. If it has all the minimum required tubes, and is made from the correct material (some groups require at least DOM mild steel), next check to make sure it is legal for the intended class. Many classes restrict the points where the rollcage can be attached to the chassis, so make sure you won't have to cut any bars out to meet the rules. It can be costly to adapt a car built for drag or circle track racing to road racing, as there are often big differences in rollcage standards that make crossing over difficult. For example, drag racing rules typically differ greatly in the design of side impact door bars and diagonal supports in the main hoop, as well as allowed material. Finally, try to assess the overall quality of the construction. Are the bends well made, do the tubes fit tightly to the interior, and do the welds look like they were done by a pro or a guy with a tube of bathtub caulk?

Avoiding Common Rollcage Problems

  • Wrong material: SCCA and NASA require all newly constructed rollcages to be built with drawn-over-mandrel (DOM) mild steel, and will not certify rollcages made from electrostatically-welded (ERW) tubing, which is common in street and drag cars.
  • Wrong size tubing: Most sanctioning bodies specify a minimum outside diameter and tubing wall thickness based on the minimum weight of the car. Make sure the rollcage meets these specs.
  • Missing or illegal bars: Some classes restrict rollcage designs to a maximum number of chassis attachment points, and they may have specific rules regarding the construction of main hoop braces, door bars, diagonals, roof and dash bars, and other features. Make sure you have a rulebook with you when inspecting an existing rollcage or getting a quote from a builder.
  • Poor weld quality: Not only is bad welding as unsafe as it is unsightly, if it's really bad, your car may not pass tech. A word of advice: Building rollcages is not a good way to learn how to weld.
  • Incomplete welds: This is one that trips up a lot of people. NASA requires all welds to be completed 360 degrees around the circumference of the tube; SCCA only requires 270 degrees.
  • Poor design or construction: Even if a rollcage meets all the basic rules and specs for its intended class, there is a big difference between one that is really good and one that is just adequate. In addition to safety, chassis rigidity is a beneficial side effect of a good rollcage.
  • Poor condition: Beware of rust or heavy corrosion, or signs of previous impacts.