building a roll cage

captainrb · 05-06-2008, 08:58 PM

Good Day I have been doing allot of reading/research about building and installing a roll cage in my '73 911. I have previously installed coil over shocks and was warned about reinforcements required for the front and rear shock towers after I had already bought the shocks. I have found a Fab/welder guy to assist me in the rear shock reinforcement project. the front shock towers have already been completed. In my research I have noticed a difference of opinion about weather you place the car on jack stands and properly leveled. Or you can just let the car stay on the wheels. While welding in the roll cage. My logic tells me that it is better to have the car on jack stands(level) ..so that after the welding is done the car(shell) is in the proper position. but have read on this forum that people do install roll cages while the car in sitting on the suspension (engine out). which way should I go.. can anyone tell me the correct way to have the car when installing the rear shock support and the roll cage I plan to install at the same time. The roll cage will connect to both the front and rear shock towers. So that all the suspension points are connected as a unit.. Looking for help !!
Thanks Captain R.B.

Mo_Gearhead · 05-07-2008, 04:12 AM

Would be easier to work on with the car up on jack stands, sitting level and solidly supported. The cage (of course) should be fitted and tack welded everywhere FIRST ...then once all is assembled/solidly tacked, go back and complete your welds, moving around the car so no one area is stressed by excessive welding heat. This is critical, especially on a uni-body car without a solid frame or full tube chassis.

Could be done with the car on its suspension without problems (I assume), just not the way I would do it.

Plavan · Plavan's Garage

I would only weld in a cage when the car in on the ground supported by its own suspension. No jack stands.

gestalt1 · 05-07-2008, 07:17 AM

i guess it would be ideal to corner balance the car first, then weld it in while its on the tires. jack stands are not that level, many times the car is really resting on 3 of them and the fourth has much less weight on it. i would also put some blue tape at a few points with a marker dot on them so you can tape measure a few diagonals as you are welding to make sure the cage is not putting tension in one direction etc..

i've not done this so it might be worthless info in reality.

toddu · 05-07-2008, 01:22 PM

What are the details on your motor? Sharp looking...

Todd

metalracer · 05-07-2008, 06:26 PM

I don't think it matters much at all, whether to have on its for or on stands. Like previously mentioned, the tubes must all be cut, fitted, and tacked together before you start welding. Any good welder will do that anyway. The most critical thing is GOOD TUBE FITMENT so that when the welds cool and shrink distortion is minimized. You don't want the tubes to be pre-stress or pre-load the chassis when you're done. I've done several cars now, on there feet or on stands. I even did one mounted on its ends on a rotisserie. Whenever possible, weld the A-pillars to the cage, same with the B-pillars. All of them came out with no effect on corner weights, fenders, doors and all panels fit the same when I finished. If I may, I would also like to suggest using DOM steel tube. Chrome-moly is best for the pros and regular seam welded tube is dangerous and not legal in any racing organization.

Best of luck!