Rollcage tubing size?

For my next speedster, I want to build a kind of rollcage structure for the cockpit (still open top) for a little bit of safety. What size/thickness tubing to people typically use for circle track cars, etc?

For dirt circle track we used 1-3/4" diameter .104 wall mild steel tubing.

dmw56 said:

For dirt circle track we used 1-3/4" diameter .104 wall mild steel tubing.

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I believe thats standard all over. Same thing we use around here too. Good call DMW.

What type material are you planning on using? Chromoly or mild steel?

Doesn't chromoly take some special steps to weld correctly? I have heard something about mild steel being preferable unless something was done. Or am I dreaming.

Don

I used to be an NHRA racer. Most people used mild steel and will be more than good enough. I dont remember what the minimum diameter and wall thickness is but I can look at an old rule book and see. I would build using that size and then if you decided to go to the track you are legal. Just my 2 cents or 3.

http://www.nhraonline.com/contacts/tech_faq.html


This should give you all you need to know. There is a difference on the cages, depending on how fast the car will run.

Great info - thanks fellas.

NHRA requires .118" wall when using mild steel tubing. The spec on .120" wall tubing allows it to be too thin sometimes especially if there is some stretch in the bends. That is why all the fabricators that build roll bars and cages for sale use .134" wall mild steel tubing. Chrome Moly must be TIG welded. It is lighter, stronger, costs a lot more and is harder to bend. Most home builders use mild steel.

I have built many cages for off road trucks including my own and used sched. 40 -1 1/4''. I rolled my rig back in 2000 at 60 mph and never got hurt at all.Cage held up very well and I went end over end ! Not sure how many times........I had my eyes closed! Ha Ha

If I remember correctly schedule 40 1-1/4" pipe is a little larger in daimeter and a little thicker than the required 1-5/8" dia. .134" wall mechanical tubing. Some people think pipe is too brittle but many, like Mr. Gussett have proven otherwise.

Ya gotta go with what passes tech IF you ever plan to take it to the track.....

I definitely don't plan on taking it on any tracks, but I do want a little safety for driving on the highway.

bob w said:

If I remember correctly schedule 40 1-1/4" pipe is a little larger in daimeter and a little thicker than the required 1-5/8" dia. .134" wall mechanical tubing. Some people think pipe is too brittle but many, like Mr. Gussett have proven otherwise.

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1 1/4 pipe has an od of 1.660" and a wall of .140. That might work OK if the od is not too big for the 1 5/8" bending die.

For a JD2 machine, pipe bending dies are available. Probably true for other brands too. I almost ordered the pipe size die instead of a 1 5/8" die because the pipe is so much cheaper than mechanical tubing.

Listen to Pookie and BobW and do it right. Even if you don't think you are going to take it to the tack now, what if you change your mind? They will not let you run with pipe. What happens if you ever want to sell? As far as people proving what works and what doesn't 60 mph isn't really that fast. NHRA makes those rules cause they know what works. In the end it's your decision, but remember it's easier to do it right the first time then it is to go back and cut all those tubes out and start over.

440Clark said:

Listen to Pookie and BobW and do it right. Even if you don't think you are going to take it to the tack now, what if you change your mind? They will not let you run with pipe. What happens if you ever want to sell? As far as people proving what works and what doesn't 60 mph isn't really that fast. NHRA makes those rules cause they know what works. In the end it's your decision, but remember it's easier to do it right the first time then it is to go back and cut all those tubes out and start over.

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I would go with what NHRA and SFI specifies as safe tube not only in case of potential runs at a track, but they deem it safe in the event of a high speed crash, so the safety aspect is there too. Drawn over mandrel tube has better qualities for a safe structure system than pipe. . . .

+2 on what Pookie and BobW said. I have seen the aftermath of sched 40 pipe in wrecks and it litterally will shatter instead of bend. If you wreck your car would you rather spent the extra $200 and walk away from it or save money now and have chunks of 1 1/2" pipe flying around inside your car at a High rate of speed? Your choice.....[

NHRA is happy with either DOM or ERW (electric welded tube). The rulebook does not speak to the use of sch 40 pipe that meets the dimension criteria so I suppose it would pass tech.
I went to the Discout Steel website, the place I buy my material locally. Comparing 1-5/8" diameter, 10 gauge I find 204" of DOM is $99.40. ERW and 1-1/4" sch 40 bare steel pipe are both about $45.00 for 240" lengths. So, no point in using pipe. DOM is a little more than double the price of ERW. Using DOM might add a few hundred bucks to your project, but if the total project is $8,000 then that difference isn't a big deal.

Yeah I agree, I am going to do this one right, not skimp on the safety stuff. I am a big fan of the "when in doubt, overbuild it" mentality. A few extra bucks or a few extra pounds is not worth dying over.