The idea behind building a race car is to travel from point A to point B as quickly or as fast as possible. To accomplish this, there is a need to make the car as light as possible, and make sure that it still maintains a certain degree of safety. One way to increase safety actually adds weight to the car, but the safety benefits far outweigh the negative affect of the additional weight—adding a rollbar or rollcage…
There are a lot of companies that supply prebent rollbars and cages like the one we will be installing from Rhodes Race Cars (RRC). But, unlike our RRC cage, most are a “universal” fit. These sometimes require that the installer do major modifications to the bars, which can far exceed the capabilities of the do-it-yourselfer. Not only does a “bar” or “cage” add an immeasurable degree of safety, but it also adds to the car’s ability to reduce elapsed times, but we’ll get into that later.
We did a lot of research to find a company that could build a rollcage for our 2014 Camaro, and guarantee that we would be getting a quality component. Rhodes Race Cars have been delivering race components to winning teams for years, and since we have received great feedback from our readers about the company, we knew that they were the right choice to build our cage.
You Have Choices
When contacting RRC, you will have a few choices to make in regards to the style and materials used to build your rollcage. When it comes to materials, you can choose from either mild steel, DOM (Drawn Over Mandrel) steel, or chromoly. A mild-steel cage will definitely be less expensive than one made of chromoly, and unless you’re looking to eliminate every ounce of weight from the finished car, the added expense might not be worth it to you. A 10-point chromoly cage will save roughly 50-pounds over one made with mild steel, but will cost roughly $350 more.
Mild Steel, DOM, Or Chromoly?
Mild-steel tubing begins as a flat sheet of steel that is formed into tubing and is then welded by a process called Electric Resistance Welded.
DOM stands for Drawn Over Mandrel, and it is actually ERW tubing that has gone through a second process that shapes and smooths the tubing. This insures the walls are more uniform, which makes the tubing stronger.
Chromoly is a steel alloy that incorporates both Chromium and Molybdenum. Chromoly is stronger and lighter than both mild steel and DOM steel.
Both the NHRA and IHRA have standards that must be met in order for a rollbar or cage to be certified and considered legal. If the welded joints show any visible porosity, shoddy workmanship, or evidence of the weld being ground, it will not pass inspection. Therefore, the actual install should be completed by someone with a knowledge of the rules, and the ability to weld the cage to the satisfaction of the sanctioning body.
We are fortunate that we have a guy in the tech shop that is capable of properly doing the install for us, so all we needed was to get the proper cage for our application and put it in place. In our application, saving weight is a big requirement, so we chose RRC’s chromoly cage, part number 11-1534. This 10-point cage will make sure that the driver is safe, help launch the car perfectly, and make sure the car is legal to run our estimated mid-8 to low 9-second e.t.s.
Making It Hook
When completed, Project COPO Tribute will have a Moser straight-axle conversion underneath, but a car needs more than a great suspension to win races. Since the Camaro is a unibody design, we need to control chassis flex. Chassis flex is caused by force applied by the engine and drivetrain that initiate body flex, which wastes energy. When launching the car, you want the engine and drivetrain’s energy to be handled by your suspension. If the chassis is flexing, you have reduced control of how the suspension components are working.
When we outlined the plan for our COPO Tribute, we weren’t planning to weld the entire body together. So, by adding the cage and a few other chassis-stiffening devices, we can create a body that is rigid, and allows the suspension to properly do its job. Not only that, but the driver will be protected in the event of a crash.
A Rollbar Or Cage
Every cage is vehicle and driver specific. Differences in vehicles and the driver’s build have a dramatic effect on if the installed cage is NHRA legal. – Josh Rhodes
We’re sure you have heard the words rollbar and rollcage thrown around when describing the visible pipes that are welded together inside a race car’s interior, but there really is a difference between the two. NHRA rules require that any full-bodied car running an elapsed time between 11.00 and 11.49 seconds in the 1/4-mile must have a rollbar connected to the car with at least six contact points. A contact point is any location where the bars contact the car’s body or frame. A rollbar usually includes one main hoop, two rear-support bars, and a driver and passenger’s-side door bar. Stepping up to a rollcage is mandated when any car is running the 1/4-mile at an e.t. of 10.99 seconds or quicker, or if it is traveling faster than 135 mph. A cage adds to a rollbar, a minimum of a roof hoop, which connects to the top of the main hoop and surrounds the front of the interior. This “halo” bar is supported at the front by two down posts located near the windshield, and these connect to the floor near the front door bar contact points.
Since our plan is to build a car that can consistently run the 1/4-mile somewhere in the realm of eight to nine seconds, we definitely need to install a cage. There are many places that can build and install a custom rollcage, but we felt that we could install a kit ourselves, and that would also give us the opportunity to show our readers some of the focal points of what is involved when installing one.
According to NHRA rules, when mounting a rollbar or cage to a unibody car like our Camaro, we need to attach the rollcage tubing to 6-inch by 6-inch by .125-inch thick steel plates that are solidly welded to the floor and/or rocker area. While this is sufficient for the rules, we did take things one step farther. When building a unibody-style car for racing, one of the first things you can do to stiffen the body is to install subframe connectors like we did.
There are many companies that make frame connectors, but we chose to fabricate our own from square tubing. We tied the front and rear frame sections together, and then even added outriggers at the rear, to give additional support to the rollcage.
Welding a rollbar or rollcage into your car takes more than just a stick welder and a prayer. If you are not comfortable with your welding skills, hire a professional. Nothing looks worse than a badly-welded rollbar. What’s more, any grinding on the cage material or the welded joints will render the cage illegal for sanctioned racing.
All 4130 chromoly tube must be TIG welded.
Mild steel can be welded using either a MIG or TIG process.
All welding must be free of slag and porosity.
The quality of the materials used, and your workmanship, will ultimately determine the strength of the car’s chassis after the cage is installed. When fitting the tubes during cage construction, notching all tube ends that will be welded is a must. When fitting each pipe, a small gap (1/16-inch maximum) between each pipe is acceptable, and will actually help to maximize weld penetration. You can also chamfer each notch to improve the weld quality. Make sure the car is properly supported when installing your rollbar or cage. If you have the car on a lift with no support at either end, the front and rear of the car could sag while it is hanging from the lift. If you weld the bars in place with the car sagging, you will never get it straight. This will definitely cause chassis tuning and handling problems.
Since our Camaro will be traveling the ¼-mile in roughly eight-seconds, the car and the rollcage must meet certain certifications as mandated by the NHRA. To get your rollcage certified, you need to contact one of NHRA’s inspection team members, and set up a time and location so they can inspect the car. In short, there are minimum standards that must be adhered to.
When an NHRA inspector checks your car and rollcage, he inspects each weld, does a sonic test of the tube material, and makes sure each connection point of the cage meets regulations. Once the inspector approves the rollcage, he will apply a non-transferable, dated sticker on the passenger side of the cage’s main hoop. The sticker is tamper proof and cannot be removed.
Unfortunately, there was no way that we could cover every aspect of the rules and regulations regarding a rollcage or rollbar installation, there are simply too many variables that will dictate each installation. You’ll need to follow the NHRA rule book to get those, but hopefully we have provided a general overview so you have a good idea what it takes to properly install a rollcage into your car.