Rollcages are an important piece of the puzzle of a racecar build. So many people buy a mail order pre-bent cage setup, pay some random dude with a welder to do inadequate welds, and show up at events. I've seen too many mediocre quality rollbars and rollcages, especially in the last few years as welders and equipment costs are getting pretty low.
Recently, Mike from Red Mist Automotive sent me a bunch of pictures of his most recent rollcage fabrication project for another friend of mine and Gridlife participant, Nick Rowan, so I thought I'd share those and my thoughts on the topic.
Mike does excellent work and I was happy to share these pics with you, and do a series of articles on how to approach rollcage building/how to review a cage for those purchasing a car that is already built, etc. Fabrication of a rollcage or rollbar setup requires some expensive tools still, and a bit of knowledge of how you want it to turn out, and WHY you want it the way it should be. There are a lot of "styles" of rollcage (specifically door bar setups), and we won't get too into the varying types of door bar setups in this article, instead, we'll talk about how to approach overall design, and why you should definitely consider hiring a professional (like Mike) to build one if you are AT ALL confused about what you want the outcome to be.
My first few rollcages (rollbars actually) sorta sucked. Everyone does a few turd setups before getting semi-proficient, I'm sure, but my friends and I bumbled through a few, because, well, we were lacking knowlege. I had a good welder, that was a plus. I did not have a real Mandrel pipe bender, that was not a plus (those cheap ones at the store are not mandrel benders. they crush the tubing, distorting it a bit, and ARE NOT FOR BENDING ROLLBARS WITH). I bought a pre-bent rollbar kit (a "drag style" kit), and started putting it in my hatchback. What a terrible idea (this was 12 years ago, don't judge too harshly, it has since been chopped out of the car).
First, you need a proper material to build out of. ERW (electric resistance welded) tubing is NOT WHAT YOU WANT for any road race cage, and all the cheap pre-bents are made out of this stuff usually. ERW is not as strong in compression, bending, and all the other forces you subject a rollcage to when flipping it over and crashing into stuff, and it has been known to split wide open down the seam (I haven't seen this , or pics, but supposedly its a thing). DOM (drawn over mandrel) tubing is the normal standard for rollbars and roll cages, and it isn't much more money than ERW material, so, don't cheap out here. SCCA, NASA, and almost all other sanctioning bodies spec DOM and specifically outlaw ERW.
Proper benders are expensive (Pro Tools, JD2, etc), and they take practice to use....and practice means you are going to mess things up. Education costs money, and you either spend it on time, material and equipment, or bring your car to a pro. This really is as simple as that. You should not be doing a rollbar if you cannot do it correctly. Buy a bolt in, save your pennies, sell the bolt in when you have saved up a few thousand, and let a pro build something proper for you.
Basic layout of a rollcage intended for racing is something you should spend a lot of time designing and planning. Do not just jump into this. Many message boards and forums have enormous threads dedicated to pictures of rollcages and to discussing the theory and execution of fabricating them. Read, look at pics, then read and look at more pics. Racecars find all sorts of things to hit out on the racetrack, including each other. Every year I spend a few minutes at an event somewhere and think "how did that car get up there!?". Racecars will find places to crash and things to hit that you'd never in your wildest dreams imagined were crash-into-able. Every time I build a rollbar or Rollcage setup (I'm not a pro), I spend more and more time thinking about how I want to lay things out and how the rollcage will survive a potential impact, from many directions. I visualize the car from overhead, and in 3D space, and mentally slide it into things in all directions, and think about how the cage will distribute the loads sustained from these impacts. Racecars can hit things hard, from anydirection, so with a full cage build, don't leave unsupported areas nowadays.
Cage design isn't always about throwing more steel at the car, but properly done, more bars and gussets can be better, obviously. Triangles are the strongest shapes in a roll cage as well, and thus, connecting "nodes", the points of intersection in tubing, can really stiffen and strengthen a build.
More steel and labor costs more. Simple as that.....but... more steel sometimes means the setup is difficult to exit and enter for the driver, and that is a giant issue as well. Why? Well....if exiting the car is difficult on a sunny day when you shut the car down and take your helmet off in the paddock, how tough is it going to be to exit the vehicle if something (or yourself) is on fire, and your helmet is on , and your head-and-neck restraint is still on , and cars might be zooming by you still because the corner worker didn't see it yet, and has yet to wave a yellow flag? Worst case scenario sometimes happens.
Ease of entry and exit into the car MUST be a priority in my opinion. Fire is very real and very scary. Mid way through a build, before you get into the door bars, one should practice exiting the car, with the door closed and open, and be sure they aren't building a trap for themselves. Planning for an easy exit also results in a cage that is easy to live with!
Mike can be reached at Red Mist auto, 139 Industrial Dr, unit A, Gilberts, Illinois. 847-428-6610. Redmistauto.com . Shoot him a facebook message or call. Redmist also offers a huge variety of parts, and can do full builds and even tube chassis work. Mike himself is also a Nasa Tech Inspector, for your annual tech inspection needs.
If you've got roll cage or fabrication pics you'd like to share in future articles, send them to firstname.lastname@example.org along with descriptions of the build, and we'll potentially use them in future articles! Thanks for reading.