Rollcage tubing size?

[uzaree]

I build a lot of roll cages and tube chassis. I get the 1.75" x .120" DOM for $50.00 a stick to my door only because of the amount I work with. SFI specs use 1.625" but also say the larger dia the better for them. So 1.75" will work great. That spec is the 25.5 SFI spec.

 

[RPM]

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.

The price of the DOM is .49 per inch and Chrome Moly is only .59 per inch and you will have about 1/2 the weight in the car. Weight in the roll cage can be an important thing to think about as it is high in the car and it raises the center of gravity.

http://secure.chassisshop.com/partdetail/41-158-083/

 

[cantwell.colton]

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.

Houston has a lot of really good metal yards so shop around - dont know if youll even end up paying all that much really.

 

[Pookie Bros]

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.

[cl Good deal my man.

 

[Unkl Ian]

Chrome Moly is only

Chrome Moly requires specific methods to be welded correctly.
Done incorrectly, results in brittle welds, that can fail when you need them most.

Mild steel is your best bet.

 

[RPM]

Chrome Moly requires specific methods to be welded correctly.
Done incorrectly, results in brittle welds, that can fail when you need them most.

Mild steel is your best bet.

It should be tig welded.

 

[bob w]

I have purchased two pre-bent unassembled 12 point cages from Chris Alston's Chassisworks. They are NHRA legal and are made from 10 gauge ERW (not DOM) mechanical tubing. The cages are available in Moly but the company highly encourages the home builder to use the mild steel because it can be easily MIG welded. Tator (on RRR) bought pre-bent cage parts from Morrison. Same thing. His is certified to 8.50.
If you can find DOM for reasonable money, fine, if not ERW is just fine.
My local supplier has lengths of material up to 12 feet long in the "shorts rack". About half price. I have to check regularily to score some materials.

 

[TubularFab]

In the sportscar racing world no sanctioning bodies allow ERW. You really don't want to be wondering if there was an inconsistancy in the welding process at the tube mill! If you supply large loads into ERW it is going to fail at the weld seam - there's no way around it. An average cage on a sportscar with doorbars, etc is going to take about 100ft of tubing. At roughly $1.00 more per foot than ERW a $100 investment is a no-brainer.

If you're new to tube bending then buy some ERW and practice. It is cheaper! Get the tubes fit the way you want, then duplicate them in better tube.

The good thing about cromolly is the 120,000psi tensile strength lets you run thinner walls or smaller diameters to achieve the same strength as mild steel DOM and therefore save weight. Most mild steel filler rod (mig or tig) is only going to be 70,000psi. If you get true cromolly filler it will match the tensile strength of the tube - but it HAS to be heat treated after the welding or you get a very high tensile strength and BRITTLE weld. In a wreck this is really bad - all the joints snap apart. So, the best work-around is to use the 70,000psi mild steel Tig filler and make sure the joints are done very well. The 70,000psi blends with the cromolly to result in about 100,000psi strength in the weld and retains some ductility without any post weld heat treatment.

 

[Unkl Ian]

I wouldn't bet my life on that.

Without the proper pre-heat, brittleness
will also occur either side of the weld.

 

[Unkl Ian]

It should be tig welded.

With the correct filler and pre-heat.


No cutting corners with that stuff.

Toby Tobias Sr was killed when his Chrome Moly chassis came apart.
Brad Doty was paralyzed when it Chrome moly cage came apart.

Mild steel bends in a crash. Like it should.

 

[sir woosh]

Used 1 3/4" for my street car. Still plenty of room in the back seat. Foam padding saves bruised heads. Helmet hook sleeved with a rubber finger offers protection too. And a chuckle or two................

 

[cantwell.colton]

just go to craigslist - materials - type in "pipe" in search - you live in houston - theres drilling well pipe EVERYWHERE
http://houston.craigslist.org/mat/1930393672.html
try that guy - 30ft sticks