NHRA-legal roll bar
(New page: 5 OR 6 POINT ROLLBAR CONSTRUCTION (NHRA LEGAL) This topic will cover a 5-point roll bar as opposed to a roll cage. Most fellows these days will go ahead and build a cage while they have t...) |
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H. "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." 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 6 X 6. 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 o.k., you may have to heat and bend the plate to make it conform to the sill/floor and that's o.k. 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. I've trailered more than one car for reducing the plate size. Then, after I've asked them to fix it and they show up again with the same lame installation, I send 'em home. | H. "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." 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 6 X 6. 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 o.k., you may have to heat and bend the plate to make it conform to the sill/floor and that's o.k. 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. I've trailered more than one car for reducing the plate size. Then, after I've asked them to fix it and they show up again with the same lame installation, I send 'em home. | ||
| − | I. " 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." If you're not an expert welder, then for heaven's sake, 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 again, I've trailered more than one car for crappy 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" flat plate of a triangular design with the long (unwelded) side of the triangle measuring at least 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 (I believe) 30 degrees so that you 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 turds 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. I can see it coming. 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 and I'll have to write a report supporting my decision. I can just see it coming. In my humble opinion, NHRA should have left the rule as it has been for 50 years. You either have a race car or you have a street car, MAKE A DECISION!!!!!! | + | I. " 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." If you're not an expert welder, then for heaven's sake, 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 again, I've trailered more than one car for crappy 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 (I believe) 30 degrees so that you 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 turds 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. I can see it coming. 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 and I'll have to write a report supporting my decision. I can just see it coming. In my humble opinion, NHRA should have left the rule as it has been for 50 years. You either have a race car or you have a street car, MAKE A DECISION!!!!!! |
J. "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." 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. | J. "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." 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. | ||
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