Moparts Tech Archive
Drag Racing Tips
Rollcage kit, tips on installing it?
I want to do everything right...and by the NHRA rulebook for a 9 sec car(which I just ordered a new copy of). The tools I have already are:
How close to the roof of the car can I install the bar and still weld it all the way around? Any tricks to do this?
Oh...and whats SFI rollbar padding? I saw it at Alstons....when is it required?
A tubing notcher will be a big help, but not absolutely necessary. As for how close you can get it and still weld it depends alot on the size mig gun you have.
Biggest suggestion I can make is to tack it all before you start welding. The front cage part there are a lot of tricks to get it all welded but unless you have done a few, I wouldnt recommend trying them because you will end up with a real mess.
A board member here cut holes in the floor plates, and through the floor, allowing the hoop to drop down so he could get to the top easier. I thought that was a good idea. Make sure and protect or remove the glass from spatter
I'm mostly done with an Alston 14pt MS cage and 4-link back-half in my 67 Dart. I've never done it before either and there's a few great tips I got from Moparts over the last year. Pay heed to any advice from Richard, he builds racecars for a living and has given me and lotsa folks great help. To get the cage tight to the headliner and still welded all around: trim/fit the main hoop, a-pillar bars, and windshield bar tight into the headliner and tack them all together, then drop the whole unit thru holes in the floor to enable full welding.
For a stronger mount than floor plates: make "outriggers" of 2x2 box tubing going from the front framerails to the rockersills, and from the subframe connectors to the rockersills. The main hoop stands on the rear outriggers and the a-pillar bars stand on the front ones. On my Dart, these were about halfway thru the stock floor. I fitted them but didn't weld them, then fitted the cage onto them as described above. Then I pulled the outriggers out and dropped the cage thru those holes to fully weld, then lifted it back up, put the outriggers back in and welded them in, then welded the cage onto the tops of the outriggers. It passed NHRA certification, and of the 22 "professionally" built cars in line ahead of me, 9 of them failed. I will e-mail you some pics of this layout.
I didn't get a tubing notcher, I just used a chop saw followed by a carbide burr bit in an air die grinder. Took a lot of trial and error sneaking up on a good fit, using a grease pencil to mark where more grinding was needed.
I'm doing the tin work now and I've found 1/8" steel rivets are quite a bit stronger than the 1/8" aluminum rivets normally used.
For a 9sec car I think you will need a dash bar, and probably rockersill bars too, despite the rulebook its the tech inspector's discretion and if he considers your firewall and floorpan modified, he will want them. They are easy to fit and add useful rigidity/ safety anyway.
Also make sure the subframe connectors are NHRA spec for frame/ cage: 2x2x.058 box or 1-5/8x.118 round minimum. Lotsa people use 1.5x2x.125, not big enough though overkill on wall thickness. If you can have the sub connectors piercing the floor and welded to it, it will be stronger.
When i bought my CE kit, it came with tubes a little shorter than i wanted, due to some modifications of my own to make it a full chassis. So i had new tubes made for some of the cage. Don't be afraid to find a local chassis builder that will bend you up some custom tubes if the kit comes up short anywhere in your estimation. You will be looking at this for a long time after its done, so take your time and be sure it is exactly the way you want it, or as close as you can make it!
On my dart i welded a tab on the back brace , then put a fenderwasher on a long bolt through the seat back and through the tab. My seat rests against the tube that the tab is on. If yours would be forward of that a bit, be sure the bracket you build will support the seat very well in case of an impact from the rear, so the seat ( and your back!) doesn't get impailed by the bracket, if you can visualize that. This meets the rules.
From my experience with Div 7 tech guys, if you have an 'after market' seat you will need to find a way to secure it to the backbrace/bar of the cage. They all grab the seat and push on it to make sure it doesn't flex/wiggle. You can weld a plate with holes to a tube welded to the back brace and drill holes thru the seat to attach. Also use a thick plate or puck to secure the safety harness (5 point belt) tie down point to the back brace. Use triangular tabs to strengthen this joint if necessary. This is for the top belts go to one bracket style, not the wrap around the bar type. You don't want that joint to break in the event you get into a nasty situation.