ckkrause

I'm curious...does anyone have any actual data, from a roll over, that any of the roll bars failed in any way or added to someone's injury. I guess I would be most curious to hear about any autopower failures as they are taking the most abuse... anyone?

-CKKrause

James Achard

Well, the last two I saw at a shop were ERW. Maybe old stock but in stock no less.

James

944Cup

Autopower DOM cages are also legal for NASA and PCA Club Racing.

docwyte

You have to specify that you want DOM tubing and pay extra for it from Autopower.

Geo

Definitely old stock. I did check their web site.

Like I said, I'm no fan of Autopower or bolt-in cages for that matter. I didn't mean to be harsh, but I did want to make sure the facts were straight on this matter.

Geo

Would you go to an ice cream stand that has vanilla and chocolate and just say "I want an ice cream."?

And of course you have to pay extra for DOM. First of all the ERW is discontinued and being heavily discounted. Then there is the fact that DOM is more expensive.

kurt M

True but not everyone might know that there are different materials to make a bar from. They just want an ice cream, they don't know if it is made with organic hand squeezed milk or not.

I had to install an A.P. bolt in bar in a 911 for someone that bought one cheap on flea bay. Everything was just a little off and had to be tweaked to make it fit. The main hoop pads bolt to the thin floor pan when there are nice strong points nearby. I made welded up shelves that went to hard points to help hold the main hoop. In the end it would have taken less time to make a bar than I spent but it was a stronger install that orginaly intended.

Rob S

Please pardon my ignorance, but what is ERW? It is my understanding that Autopower made "alloy" cages and bars a few years back, and that the alloy was an option and was more expensive than DOM. I was of the impression that the alloy being used by Autopower was Cr-Mo. True? I understand that Cr-Mo steel was allowed by the sanctioning bodies at the time to have a thinner wall section than DOM steel (hence would be lighter in total weight). It's also my understanding that it in Autopower's case, their cages and bars weren't necessarily made with a thinner section (i.e., may have been of the same thickness as DOM). Cr-Mo is a stronger material than DOM steel, and more expensive, though trickier to weld proplerly. I was told that it was difficult for sanctioning bodies to approve Cr-Mo at tech inspections, because it had the same outward appearance as DOM, but required a chemical analysis. Isn't that why DOM is now required? It wasn't that "alloy" was inferior -- it was just too difficult to verify the existence of. Can anyone further enlighten me as to whether I have this straight, what happened to Cr-Mo as a cage/bar material, and of course, what ERW is?

RedlineMan

Hey Rob;

In the strictest sense, DOM (drawn over mandrel) refers to manufacturing process, not material type. It would be more correct to say mild steel DOM.
...Lest I be accused of being picky.

ERW (electric resistance welded) is a rolled, welded seam tube that most people thumb their noses at.

I would imagine the easiest way to verify CR would be to grind it. I have never fooled with it to tell you the truth, but I would guess it offers a distinctive spark as does each type of ferous metal. However, grinding some guy's cage in tech might tend to provoke ill will.

Der Professor or Geo might know the sanctioning of CR better.

Bull

It does offer a distictive spark as I recall from my days with bike frames.

Geo

CrMo is indeed still legal in the SCCA.

Also, while CrMo does require special welding techniques, I read (I think it might have been here even) that the FAA does NOT require quenching of CrMo under a certain thickness (cage thickness is thinner than the minimum). While the FAA is certainly not a sanctioning body, I would personally accept their standards for welding for motorsports.

DOM is also a welded tube. My understanding is that drawing over the mandrel makes the tube more uniform however.

RedlineMan

Well...

This is where James should chime in, as he has done all that fancy book larnin on welding and materials and such.

I have NOT done all that fancy book larnin, but I am fairly comfortable in stating that you would NEVER want to "quench" CR. Any time you artificially speed the cooling process, you stand to "shock" the metal. How you quench certain alloys of steel can either make them hard, or BRITTLE. In the case of CR, it is most decidedly the LATTER!

I think you meant to say stress relieve it. Further, the process and facilities required to truly stress relieve CR are so highly specific as to make it a moot point. It is my understanding that most CR applications do not actually require any overly special processes. It is my assumption that as long as you do not overheat the weld area that it will be fine. Or as one guy told me, "if it don't crack when you weld it, it won't crack!"

James?

Geo

Yes, whatever it is that's special about welding CrMo. I always get that stuff backwards. Drives the guys at work nuts as I work for a company that finishes tubing for oil & gas down-hole use. You'd think I could get the terms straight. All in good time I guess.