laxking012

Was looking at cages on S&W website for my 1991 s10, there's EWS and DOM mild steel. I've always heard DOM is stronger and better, but on website it says "Do not recommend DOM tubing for drag racing applications". Why is that and should I just get the EWS?

zipper06

Technically there's almost no difference, the EWS is made from flat plate and electrically butt welded 1010 mat'l, the DOM is 1020 mat'l and cld draw over a mandrel and seemless, the carbon content is in the same range on both.
They both have 80,000 PSI tensil strenth and 70,000 PSI yeild strenth.
The EWS is cheaper to produce so it sells for less. They are both rolled on ther OD for consistent dia.
I would buy the DOM for the price difference and be sure to get .134 wall because there's up to .007 tolerance on the wall thickness and it could fail NHRA's .120 wall specification.

Zip.

TheYellaBrick

This is what you're seeing on the S&W website

Available in 1-3/4 x .134" EWS wall tubing or 1-3/4 x .083 Chrome Moly wall tubing or 1-3/4" x .120 wall DOM tubing. Do not recommend DOM tubing for drag racing applications. Photo is for clarification purpose only, actual part may vary."

What they're saying is that the DOM kits that THEY(S&W) offer comes ONLY in .120 wall. NHRA requires .134 MINIMUM and S&W has .134. only in EWS.

DOM is more consistent in wall thickness and stronger as it is cold worked into one piece where EWS has that pesky weld joint.

You could build one(or have it built) in 1 3/4" .125 or .188 DOM.


DOM Steel Tube (Drawn Over Mandrel)

Product Description:

DOM is actually not a type of tubing, but a process that is applied to tubing after it is initially constructed. It is Drawn Over a Mandrel...which "cold works" it, giving it more exact dimensions relative to the inside and outside diameters, a smoother finish, and better alignment of the crystal lattice structure. Although it is almost always referred to as a SEAMLESS tube, technically it is NOT seamless tubing, and it started life as some sort of EW (electric welded) tubing. During the manufacturing process, the weld line becomes nearly undetectable, thus it is referred to as SEAMLESS. It is considered a high strength, high quality tube, and is normally constructed from SAE 1020 or 1026 steel. DOM is commonly used in the manufacturing of race cars and motorcycle frames.

1020 is normally used in the manufacturing of small-diameter or thin-wall DOM steel tube. 1026 grade is normally used in the manufacturing of DOM over 2" OD, with walls heavier than .156". Depending on the diameter and/or the wall thickness, you may receive EITHER 1020 or 1026.

http://www.stockcarsteel.com/dom-ste...-over-mandrel/

laxking012

Not saying your wrong, but I'm pretty sure in the 2012 NHRA rulebook I have, it says min. .118 mild steel for roll cages?

curtisreed

Pretty sure you are right about that. What can happen is the .120 wall might not sonic test thick enough. It is way more consistent being drawn but it will still vary slightly. Just the chance you take with using it on a cage.

Zip, can you get .134 wall DOM?

On a side note it is pretty cool to watch them make DOM tubing. I have toured a tubing manufacturing facility before.

Curtis

zipper06

No Curtis, i cannot get .134 wall 1 3/4" DOM it only comes in EWS tubing but i still like the DOM @.120 wall. I know it's a gamble. The NHRA rule book says 1 3/4" X .118 min wall and that's the reason the roll cage mfg. will only sell EWS .134 wall, they have to guarentee it will pass certification.

Bottom line is the tolerance of DOM for 1 3/4" DOM is +.002/ -.004 and could very well fail a sonic test.
Below is a wall thickness tol. chart which shows all the tol.

Zip.

curtisreed

I wasn't sure so I thought I would ask.

markdunlap

The .120" wall thickness material can stretch and decrease in wall thickness when it is bent, and become less than NHRA specs. The NHRA inspector will go for the outside of a bend first thing to see if he needs to continue the certification.

Are you sure .134" material is not available in DOM?

TheYellaBrick

These guys have 1 3/4 DOM in .125 and .188;

http://www.stockcarsteel.com/dom-ste...-over-mandrel/

zipper06

Looking back, i haven't worked steady in the machine shop since 2008, but ENJ/Earl M. Jorgenson used to have DOM 1 3/4"X.134 wall tubing and i just looked at their website and they still have it listed, i didn't get a price, but probably in the neighborhood of $3.50 per foot in 1018/1026 steel.

Zip.