Cage
FINDING OR BUILDING A ROLLCAGE
Before you put in a rollcage, you've got a decrepit $500 hooptie. After you put in a rollcage, you've got a thoroughbred competition machine. Really. And hey--as a side benefit, that rollcage might even prevent your heap's rusty scab of a body from collapsing right onto your head. Assuming you built it correctly.
Don't know what "built it correctly" means, exactly? Overwhelmed by the prospect of bending tubes, cutting metal, welding seams, and getting hot flaming sparks up your corn chute? Well then, you've got other options.
1) Use a professional cage builder/installer. Go to your town's local race shop or competition fabricator, drop the car off empty, and pick it up a few days later with a rollcage in place. This can cost a ton, or be shockingly cheap--it pays to shop around and get referrals. There's a huge spread on pricing, and it's not always associated with quality.
If you choose this route, make sure that both you and your builder understand LeMons' cage requirements in advance: A lot of roundy-round and drag-racing series don't build their cages to anything approaching roadracing standards. Whether you're doing the fabrication or handing it off to a pro, it's your butt (and your entry) on the line in the end. Make sure they understand what the LeMons rules dictate.
2) Buy a Pre-Made kit. One alternative to a scratch-built cage is buying a pre-made kit. These can be great, but all kits are not created equal. Pre-made cages from high-quality builders like Kirk Racing and AutoPower tend to be jigged, bent, welded, and sized precisely to your particular car; expect to pay $500-600 or more for one of these than for a generic, one-size-fits-none cage. And just about everything cheaper ($250-$400 range) turns out to be the latter, unfortunately, even if the company claims that it's specially made for your car. By the time you're done modifying and fixing and re-shaping a one-size-fits-none cheapier cage, you'll have spent more than you would have getting a good one to start with. Also avoid kits sold as "drag cages" or "street cages." These rarely meet the requirements for wheel-to-wheel roadracing.
3) Buy a Tubing Kit. Halfway between a real kit and pure DIY, these offer raw tubes that have been cut to approximate lengths. It's then up to you to bend, weld, and grind stuff accordingly.
4) Go with a known quantity. A couple of cage manufacturers consistently deliver good stuff: Autopower, Kirk Racing, Chase Race (WA), and Full Tilt Fabrication (MA) are all recommended. If you're in the SF Bay Area, Chris Overzet and Mitch Parella (510.526.5003) can build and install custom setups.
NOTES ON CAGE DESIGN
Cages should fit the cabin's original contours as closely as possible, but should also contain as few bends as possible. Obviously that means some tradeoffs. Stripping out the interior always gains you more room and more options. Removing the dash makes things even easier.
Use common sense when designing your cage. Bars that are too close to the driver will diminish both safety and comfort; avoid unnecessary curves or bends, since straight tubes are always the strongest; verify that your drivers can still get in and out of the car in a hurry; make sure the tops of your team's helmets are comfortably lower than the top of the cage (at least two inches' clearance is a good rule of thumb). Again, this is car racing, not rocket science.
When visualizing your cage, imagine it made out of dried-out spaghetti. Now picture a fat dude perched right on top, pushing against the sides, or rocking it back and forth. Wherever the spaghetti breaks first is the weakest part of your layout. Return curves and compound curves are especially bad (and virtually always unnecessary). Use straight lines wherever you can, and triangulate wherever you can't.
LeMons' most basic cage requirement calls for at least six major mounting points to the car: two where the front hoop meets the car, two where the main hoop meets the car, and two where the main-hoop backstays (two straight reinforcing tubes connecting the top of the main hoop to stout mounting points at the rear) meet the car.
The windshield hoop and main hoop should be connected with at least a pair of straight tubes running as close to the roof's edges as possible. The door bars should run across the door opening between the front and rear hoops to protect the driver from a side impact. When positioning the door bars, try to balance impact protection and ease of entry/exit--the only thing worse than getting T-boned is not being able to bail out in a fire. Cutting out the stock inner doorskins will get you a lot more room to design safe but accessible door bars. Vertical reinforcing bars that tie the horizontal door bars together, and/or connecting the horizontal door bars to the rocker sill, are also good ideas.
A horizontal harness-mounting bar behind the driver is generally the best (and sometimes the only) place to anchor your shoulder straps. Keep in mind that the shoulder-strap anchors must be even with, or no more than 15 degrees below,the point of seat entry. Position your harness bar accordingly.
Finally, you must have one main-hoop diagonal support--the simplest way to accomplish this is to run a clean, straight tube from the driver's-side top corner of the main hoop to the passenger's side bottom cage-mounting pad at a more-or-less 45-degree angle. This bar will likely intersect your harness bar; you can make either the diagonal or the harness bar from two pieces to deal with that intersection, but the finished two-piece section must still form a very straight, very clean line.
TUBE TYPES
A single, continuous piece of tube, properly bended as needed, should be used for all major cage elements. This means if your main hoop comes up a few inches short, just build a new one that actually fits--don't try to extend it with short bits of tube grafted onto the ends. Spliced tubes, hoops made from multiple intersecting sections, and damaged tubes scavenged from other cages are always a no-no.
Bear in mind, all tubing isn't the same. Purpose-built rollbar tubing (the only thing we allow) is a whole lot stronger than muffler pipe, water pipe, or electrical conduit, and you won't find it at the local hardware store. This is special-order stuff. We highly recommend seamless, drawn-over-mandrel (DOM) mild steel rollbar tubing. A cheaper but much less robust alternative is seamed (commonly called ERW) mild steel rollbar tubing. While LeMons allows either type, we feel the extra cost of DOM tubing is peanuts in light of the additional safety it buys. Want to be smart? Use DOM.
Rollbar tubing also comes in various sizes. The measurements that matter for our purposes are outside diameter (O.D.) and wall thickness. This is usually expressed as [O.D. in inches] x [wall thickness in inches]. For cars under 3000 pounds as raced, LeMons requires a minimum of 1.50" x .120" or 1.75" x .095" cage tubing. For cars over 3000 pounds, the spec grows to 1.75" x .120" or better.
MOUNTING POINTS
Cages can be bolted or welded to the car. Welding is stronger, and all welds should be clean, deep, and as close to fully continuous as possible. If you're using bolts, they need to be Grade 8 or better and big enough to handle the job. You'll also need equally sturdy backing plates on the opposite sides of the mounting pads.
Bolted or welded, sturdy mounting methods are required at every junction between rollcage and car. Usually, this means creating robust mounting plates where the tubes join the body or frame; you might even have to reinforce the area around the mounting plates to guarantee suitably sturdy attachment. And remember, as the tubes travel down toward their attachment points, they should be kept as straight as possible—any bends near the attachment points can significantly compromise strength. Under no circumstances should reverse bends be used under the dash--either run the tube straight down and accept the cramped access, or take out the dash (ie, do it right).
TUBE BENDS
All bends should be smooth and consistent and show zero abnormal crimping, crushing, stretching, narrowing, or other weirdness. These visual markers point to improper materials or handling, and will get you rejected in tech. The typical Harbor Freight bottle-jack bender isn't nearly strong enough to properly bend rollbar tube of LeMons' required diameters. A good, professional-grade hydraulic bender using the correct dies and reasonable radii is the least that you'll get away with. If you've got access to a professional mandrel bender, so much the better.
CAGE PADDING
Wherever any part of the driver's body might contact the cage during a crash, that area must be securely covered with high-density, purpose-built rollbar padding. You'll have to find this stuff from a speed shop—the pipe padding they sell at Home Depot won't do bupkis.
FINAL THOUGHTS
Once you've got the basic cage in place, we recommend adding extra diagonals and gusseting to increase overall strength. You can't really go wrong adding more strength, and nothing makes Friday tech inspection more pleasant than not having to scramble to find cage tubes and welders at 6:30 pm.