A race car’s roll cage is more than just a safety feature. It’s a structural design that can help prevent serious injuries in the event of a crash. Cages can protect occupants from being thrown around the cabin, and they can also prevent the vehicle from rolling over or getting crushed. Having a well-built cage can mean the difference between life and death in a crash.
A basic layout for a race car’s cage should be carefully planned out and then fabricated. This is not a project to take on lightly and it should be done by a qualified welder. While there are kits available, this is a good time to consult with a professional welder to have them make your cage and ensure it meets the rules of your racing organization and the regulations of your racetrack.
There are two main types of tubing that can be used for a roll cage: mild steel and Chromoly. Mild steel is available in EWS, HREW, and DOM (cold drawn seamless or drawn over mandrel). DOM offers the best value for money with higher tensile and yield strengths than EWS or HREW tubing. Chromoly is more expensive but it offers increased strength and durability.
While aluminum has been discussed for use in a racecar’s bygga bur cage, it’s not allowed by any racing organization we’re aware of. The reason is that it has a very low yield strength and can be easily flexed and bent. It’s also difficult to weld due to its brittleness. Stainless steel is another possibility but it’s very expensive and requires the use of shielding gas during welding, which can be a challenge for the average garage builder.
The type of tubing to be used in the roll cage will depend on the class of racing you plan to do. Consult your sanctioning body’s rulebook for this information or call the track to speak with a tech inspector. For example, a tech inspector at the New Hampshire Motor Speedway can explain the differences in requirements between NHRA and WORCS sprint car racing.
A bolt-in kit can be an option for a lot of people as it’s fast and easy to install, but it will not be as strong to withstand the rigors of racing collisions as a welded cage. JEGS has both mild steel and chromoly tubing that is available for those building their own cages.
When choosing the material to be used in a roll cage, cost and weight are important factors. Chromoly is more expensive but has greater strength and ductility than mild steel, so it’s a good choice for the high-speed, heavy impact racer. Mild steel is less expensive but it has lower tensile and yield strengths, so it’s a good choice if the budget limits what can be spent on the cage.
Lastly, the location and how the cage is tied into the vehicle’s sills should be considered. Some builders choose to simply hang the cage off of the floor pan, but this can be prone to tearing in a hard impact. A better method is to tie the cage into the vehicle’s boxed sills, which are much stronger than the floor pan.