NHRA-legal roll bar
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The main hoop is normally called the B bar in tech lingo. | The main hoop is normally called the B bar in tech lingo. | ||
| + | ====Side-bar==== | ||
| + | <blockquote> | ||
| + | ''"Side-bar must be included on driver's side and must pass the driver at a point midway between the shoulder and elbow. Swing-out sidebar permitted."'' | ||
| + | </blockquote> | ||
| − | + | This bar welds at the intersection of the B bar/cross bar at the driver's left shoulder and runs downhill diagonally to a point near the driver's left foot. Its purpose is to keep the driver in the car in the event he/she is out of the belts (yep, it happens). If you're planning a swing-out side bar, get yourself a NHRA rulebook. There are several ways to do it, all of them too lengthy to address here. | |
| − | + | ====Cross bar==== | |
| + | <blockquote> | ||
| + | ''"All roll bars must have in their construction a cross bar for seat bracing and as the shoulder harness attachment point. Cross bar must be installed no more than 4" below, and not above, the driver's shoulders or to the side bar."'' | ||
| + | </blockquote> | ||
| − | + | '''Caution: do not install this bar until the driver is seated in the car in his/her normal driving position in the car. And, do not install the side bar until this cross bar is in place.''' | |
| − | + | Maximum protection for the driver will be afforded by installing the cross bar with the top of the bar '''even''' with the top of the driver's shoulders. That's why you don't want to weld this bar in until you have the driver in position. Now, with the cross bar in position, you can weld the driver's side-bar in at the intersection of the B bar/cross bar and be assured the geometric line of pull will be proper on the shoulder belts and the side bar will be high enough to retain the driver in the car in the event of upset, passing the driver midway between the shoulder and the elbow on its way to the floor close to the driver's left foot as dictated above. | |
| − | + | ====OEM frames==== | |
| + | <blockquote> | ||
| + | ''"All vehicles with OEM frame must have roll bar welded or bolted to frame; installation of frame connectors on unibody cars does not constitute a frame; therefore it is not necessary to have the roll bar attached to the frame."'' | ||
| + | </blockquote> | ||
| − | + | For instance, a Chevelle has a full frame, a Camaro is a unibody. If you put subframe connectors on a Camaro, it's still a unibody. | |
| + | |||
| + | ====Unibodies==== | ||
| + | <blockquote> | ||
| + | ''"Unibody cars with stock floor and firewall (wheeltubs permitted) may attach roll bar with 6-inch x 6-inch x 0.125-inch (1/8") steel plates on top and bottom of floor bolted together with at least four 3/8-inch (0.375") diameter bolts and nuts, or weld main hoop (B bar) to rocker sill area with 0.125-inch (1/8") reinforcing plates, with plates welded completely."'' | ||
| + | </blockquote> | ||
| + | |||
| + | You can "sandwich" the floor of the car with these "plate pairs" bolted together, one on top of the floor and one underneath for each connection point and weld the bars to the top plates or you can use only one plate at each connection point and weld the plate to the floor or sill of the car, then weld your bar to the plate. This increases the square inch area of the installation and reduces loading on the floor so the bars will not punch through the floor sheet metal like they would if you just welded the bar straight to the floor or sill. When installing the B bar, you'll want to install it on each side as close to the door as possible, so that the driver will be "inside the box". This will probably require moving the B bar tubing up onto the sill of the car, at least partially. Bend up your 6 x 6 plate to weld it in, so that you are welding it partly to the sill and partly to the floor. '''Do not reduce the size of the plate to less than 6x6'''. You may have to grind the end of the B bars to make them conform to the curve of the plate at the sill and that's OK; you may have to heat and bend the plate to make it conform to the sill/floor and that's OK too, just do what you have to do to make it work according to the rules and you'll never have a problem at tech. Maybe you'll end up with part of the bar welded to the plate at the sill area and part of it welded to the plate at the floor, again, whatever it takes. Grind the end of the bar to make it work. | ||
| + | |||
| + | ====Welding==== | ||
| + | <blockquote> | ||
| + | ''"All 4130 chromoly tube welding must be done by approved TIG heliarc process; mild steel welding must be done by approved MIG wire feed or approved TIG heliarc process. Welding must be free of slag and porosity. Any grinding of welds prohibited."'' | ||
| + | </blockquote> | ||
| + | |||
| + | If you're not an expert welder, then hire a professional. It'll be the cheapest wages you'll ever pay for a nice roll bar installation. Nothing is cheezier than bird-crap welding. And don't even think about grinding any welds on the car. Hire a pro. If you fit up all the bars in the car and tack them in, the pro welder won't be there long doing a proper job. If you have fit the bars properly, there won't be much room at the roof to weld completely around the B bar/rear brace connections, so you may as well plan on gusseting these. Use 1/8" (the rule calls for 0.110" minimum) chromoly or mild steel flat plate of a triangular design with the long (unwelded) side of the triangle measuring at least 1 3/4". Use two gussets at each rear brace (four gussets in total) and you'll be bulletproof. By the way, NHRA now allows these rear braces to be bent (one bend only) to a maximum of 30 degrees '''(needs confirmation)'' so that the guys with street/strip cars can retain the back seat in the car for double dates and such. Most guys will run the rear brace bars from the B bar intersection back at a shallow angle to the roofline and then make a turn down and through holes in the package tray to the trunk floor, where the bars are terminated on 6 x 6 plates which are welded to the trunk floor. Now, you know what's going to happen don't you? Some guys from down off the farm are going to hear about this new lax interpretation of the rule from a buddy who didn't tell them about the "one-bend-only" part of the rule and they'll run the rear braces back from the B bar right up against the roof and make a 90 degree turn through the package tray and then another turn to terminate the bars on their plates somewhere on the trunk floor. Multiple bends in the bars will allow them to kink-up and will render them incapable of preventing the B bar from "lozenging" forward or backward. And the problem will be that there is little or no tech inspection at most drag strips, so they'll get away with it until they get to Firebird and get trailered. Then they'll raise a stink with the front office about how they passed tech at Podunk Dragway. You either have a race car or you have a street car -- '''make a decision!''' | ||
| + | |||
| + | ====Roll bar padding==== | ||
| + | <blockquote> | ||
| + | ''"Roll bar must be padded anywhere drivers helmet may contact it while in driving position. Adequate padding must have minimum 1/4-inch compression or meet S.F.I. Spec 45.1. All cars running 180-mph or faster, S.F.I. Spec 45.1 mandatory."'' | ||
| + | </blockquote> | ||
| + | |||
| + | Whether you think so or not, seat and shoulder belts stretch when you're flippin' and rollin', so make sure you've covered all your bases here with every possible place your helmet could make contact with the bars. | ||
There is no restriction on improving a rollbar into a rollcage, even though you must use 1 3/4" minimum diameter tubing for a rollbar and can use smaller 1 5/8" for the rollcage. Just build onto the existing rollbar material with your new 1 5/8" tubing. Also, there is no restriction on using 1 3/4" material for the entire rollcage. There is just a 1 5/8" minimum for a rollcage and 1 3/4" minimum for a rollbar. You could even use larger material if you want to, you just can't use smaller than the rules call for. Of course, there has been much hoopla about the choice between mild steel and chromoly. Mild steel is less expensive than chromoly and can be migged or tigged in. Chromoly is more expensive to buy and must be tigged in. A car with a moly bar or cage may be easier to sell. | There is no restriction on improving a rollbar into a rollcage, even though you must use 1 3/4" minimum diameter tubing for a rollbar and can use smaller 1 5/8" for the rollcage. Just build onto the existing rollbar material with your new 1 5/8" tubing. Also, there is no restriction on using 1 3/4" material for the entire rollcage. There is just a 1 5/8" minimum for a rollcage and 1 3/4" minimum for a rollbar. You could even use larger material if you want to, you just can't use smaller than the rules call for. Of course, there has been much hoopla about the choice between mild steel and chromoly. Mild steel is less expensive than chromoly and can be migged or tigged in. Chromoly is more expensive to buy and must be tigged in. A car with a moly bar or cage may be easier to sell. | ||
| − | This article was written pursuant to the 2008 NHRA Rulebook and will be updated in the future. | + | This article was written pursuant to the 2008 NHRA Rulebook and will be updated in the future. |
| − | + | ==Related resources== | |
| − | http://wescoperformance.stores.yahoo.net/racingbelts.html#hardware | + | *[http://wescoperformance.stores.yahoo.net/racingbelts.html#hardware Link to seat belts, shoulder belts, crotch belts and hardware] |
[[Category: Good articles]] | [[Category: Good articles]] | ||
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