DOM vs ERW for roll cage. (Page 1 of 3)

We're running a heavier car, and my cage builder (who builds cages for NASA, SCCA, and BMW club cars) still very, very heavily recommended DOM even though it was twice the price.

DOM

Thanks for the input everyone, I will probably proceed with the DOM!

It's a shame....IMO ERW should be allowed, but with greater wall thickness and gussets....easier to get good welds with a thicker tube and cheaper. Just bend with the seam in and you're fine. This obsession with cage material strength is weird...much more likely to fail at bad welds or in the HAZ than in the tube itself, especially if the cage is properly triangulated and gusseted. NASCAR was running 50MPH over Lemons speeds 50 years ago with black pipe welded with oxy/acet and AC stick and I don't recall many cage failures even then, with some horrific superspeedway wrecks...The difference in price would go a long way towards a  HANS....

Has anyone ever seen a cage fail ERW, DOM or otherwise?

The last time we had this discussion RobL posted a pic I can't seem to find of a halo bar crushed down on to the seat.  that said I've never seen something like this happen in person, and I can't imagine the impact that caused that, IIRC he didn't know the story behind the pic either, for all we know a tree fell on the car. 

That said our cage is ERW, thicker tubing than the rules require,  it was significantly cheaper and if jimeditorial and FJ40Jim are right, no less safe than anything else.  I know ours was put in right so I feel perfectly safe with it.

The worst cage failure I've seen was in a Mustang and it had nothing to do with the type of tube used.  The builder failed to strengthen the floor with pad and the base of the cage punched four holes in the floor when it landed on the roof.

Correct me if I'm wrong, but the Lemons rules on cages is simply the MINIMUM safety requirement.  Want to add forward braces to the front firewall to make it an 8-point cage?  Go ahead.  Want to add four bars at every corner of the halo?  knock yourself out.  Heck, run a diagonal from the the top of the main hoop, just right of the driver to clear the helmet and run it all the way to the base of the leg on the front passenger floor.

We just received our ERW cage kit yesterday and I plan on adding a number of extra tubes to make it as strong as possible.

If i remember correctly this car is in the east and went off at a high rate of speed then hit the berm at the end of the runoff and was thrown up into a very large tree branch which caused this roof damage. The driver was trapped in the car because it forced his head forward and down so tightly that it pinched off his wind pipe and he blacked out and eventually had to be resuscitated. Because of this you now see a lot of the BMW club cars have installed support tubes right next to the drive and just forward of the driver also. Race tracks in the east are beautiful but if you reach the trees they are not so beautiful.

Pendejo

I just don't see the huge difference in price between DOM and ERW..    Maybe its because I buy so much tubing, but the price diff for me is 10-15%   at low quantities(<200ft).    In reality DOM costs me less because I buy it 1000+ ft at a time..  A low quantity of ERW would cost more per foot.  There is no ERW in my shop, I don't use it.

    DOM is stronger, the cold working of the tube adds a lot of toughness, I don't have my strength tables here in front of me, but  I know the strength difference is significant.   

    One of the main reasons that SCCA, NASA and others have gone to DOM only is its accuracy and concentricness.   Oft times when you measure the thickness of ERW you get variations that will give you a measurement under the required thickness, oops, fail.  Most DOM is spot on (within 2 thousandths)  while ERW usually varies from .111 to .131 on a .120 wall thickness tube.   

     Yes, cage design and weld quality are more important, and we are cracking down on crappy, lumpy, cold welds.     

  DOM has become the standard in road racing and We (Lemons) recommend it strongly in our rules..   Please use it if you can. 

  I just called around NoCal as a consumer, not giving my business name and asking for 100ft of 1.5 X .120 ERW and 1.5 x .120 DOM..   the price difference varied between $.65 to $1.23 per foot..   An average car with Minimum Lemons cage will use 60ish feet, a car with added bars will use up to 100ish feet.  So I see the price difference as about $40 to $110...  Not that bad of a hit to use the right stuff.     

-John

My cage builder has had the same thing happen and told us that he no longer builds any ERW cages.  Split amongst 5-6 drivers, the extra $100 or so for DOM is a no-brainer.

That's the one.  He lost it cresting the blind hill just before The Bitch and I've seen many offs at that part of the track.  SCCA allows for mounting plates to be a maximum of 144 sq. inches.  For those of you, like me, who have rusty floors...fix them well and then add another layer to help spread the load so it doesn't punch through.