cyrus Posted January 9, 2006 Share Posted January 9, 2006 Here is my rollcage. How have others hook bar D at the floor? It will hit my seat right now. And yes, I drafted this myself. Quote Link to comment Share on other sites More sharing options...
johnc Posted January 9, 2006 Share Posted January 9, 2006 Any bar attachment to a unibody structure requires a plate. Typically these plates are at least made of .080" thick mild steel (.095 is more typical) and are bent (or cut and welded together) to tie into more then one panel on the unibody. For your "D" bar I would make the plate so it spreads the load to the floor pan and the rear bulkhead. Probably 5" wide with 5" on the floor pan and 5" up on the bulkhead (5" x 10" plate with a bend in the middle of the 10" length). Make sure its welded all the way around the perimeter where it contacts the unibody and bar "D" has a tight, normal, fit to the plate. Weld bar "D" all the way around where it contacts the plate making sure you get good penetration on both parts. Quote Link to comment Share on other sites More sharing options...
BringIt Posted January 9, 2006 Share Posted January 9, 2006 I think it has to be 1/8th Inch Plate and has to be a minimum of 6" X 6" square or 8" x 8" square. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 9, 2006 Share Posted January 9, 2006 Instead of the D bars I would run a diagonal from behind the driver's head to the passenger's floor. It looks like the purpose of the D bars is to provide more support to the hoop to keep it from folding over on impact. This is also what the diagonal does, but more efficiently. Careful with your shoulder bar. You may find that it won't allow the seat to go back far enough. Check Austin's (240hoke) post about his roll bar. He has the diagonal, and the part of the shoulder bar that goes behind the seat is bent rearwards maybe 3" to allow more room for the seat. I'm anticipating having to do the same on my car. The main hoop should really have 4 bends in it. The reason being if you make the sides come straight down you'll be 4 or 5 inches inside the side of the car, just due to the way the car is shaped. There was another guy who posted pics of his main hoop who did it with two bends like in your drawing there and I think he was going to redo it. In the event of a side impact I think whatever you hit would contact your seat and you well before the cage got involved if you did it like your drawing. If you are doing dimensions in your drawing, check 74_5.0_Z's album. He has a jpg with the specs on the main hoop. I used that drawing to have my main hoop bent. Had to be modified slightly because I used 1.75" tube, but it was extremely helpful. Last thing and I'm sure this is a result of the cad program, not the design, but the main hoop needs to be one tube, and not have joints. So I'm thinking your bends have a seam on either end of the bends because the program makes it that way, and that you aren't actually going to have 5 pieces of pipe in the main hoop (top, sides, and bends) because that wouldn't be legal by any sanctioning body AFAIK. Quote Link to comment Share on other sites More sharing options...
Psykovertible Posted January 9, 2006 Share Posted January 9, 2006 my dad's is legal and his is shaped just like that. the "d" bars go from the corner of the crossbar behind the seats to frame rails for the tie-in. Quote Link to comment Share on other sites More sharing options...
johnc Posted January 9, 2006 Share Posted January 9, 2006 Read the 2005 NHRA rule book and yes, 6" x 6" x .125" plate is the minimum for any tube attachment to the unibody. Quote Link to comment Share on other sites More sharing options...
katman Posted January 10, 2006 Share Posted January 10, 2006 my dad's is legal and his is shaped just like that. the "d" bars go from the corner of the crossbar behind the seats to frame rails for the tie-in. Legal doesn't mean good. jmortenson is right. Also, the crossbar up front you'll want to locate as close to the top of the tranny hump as possible, and don't forget to pad it above your shins. Quote Link to comment Share on other sites More sharing options...
tube80z Posted January 10, 2006 Share Posted January 10, 2006 Also, the crossbar up front you'll want to locate as close to the top of the tranny hump as possible, and don't forget to pad it above your shins. Just curious, why is that? Cary Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted January 10, 2006 Share Posted January 10, 2006 Just curious' date=' why is that? Cary[/quote'] I have read enough Katman posts to venture a guess: to protect you from a side impact in that area. If the cross bar is up in the dash, it won't prevent the whole underside from being pushed into the tranny tunnel. Quote Link to comment Share on other sites More sharing options...
katman Posted January 11, 2006 Share Posted January 11, 2006 That's correct. Although after I wrote it I got to thinking that for drags it proly doesn't matter that much. My background is for road racing, and our big fear is being t-boned. In a t-bone the inboard force on the door bars will push the bottom of the A-pillar bar inboard, and the floorboards are near worthless for preventing this. To help we put the cross bar low, and run a tube to the firewall. Because of the horizontal bends in the firewall at your feet it has some lateral stiffness and is a big help redistributing the side forces. The floorboard at the forward edge of the door, however, is a big soft spot. I've seen it crush up toward the tranny tunnel, and I've actually seen the A-pillar cage bar punch through the bottom in a big flip. Of course I've also seen a Z split the floorboard and tranny tunnel on a diagonal from just behind the driver's feet to behind the shifter hole. Now that was a wicked hit (damn Don Panoz and his concrete wall at turn 12!) but the driver's lower extremeties were unhurt. Say, I think we stopped 5 feet short of winning that race come to think of it.... Quote Link to comment Share on other sites More sharing options...
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