DOM vs ERW tubing ID?

I have a car with a rollcage installed when I got it. Racing organization rules now require DOM-only construction. Is there any way to tell what this cage is contructed from, without cutting it? Texas Parts Guy

Reply to
Rex B
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Welded tube should have a relatively noticeable seam in it. It may or may not be visible through the paint, good stuff will not show the weld seam. It may or may not have a weld flash on the inside, again, good ERW will have the flash removed.

I'd suggest using some paint remover on a section of the tube that is not near a weld. Do NOT sand or grind it off. The ERW should have a noticeable blued section about 3/8" wide down the tube with a tiny ripple line in the center of that.

If none of that works, you still don't know if it really is DOM. Only way I know of is to slice out a section, polish it, and etch it. DOM has a weld seam but it has been refined through the drawing process, quite noticeable when etched (the grain around the weld is much smaller than the rest of the tube on DOM)

Prov> I have a car with a rollcage installed when I got it.

Reply to
RoyJ

How do the racing inspectors tell? Ask one. Bob

Reply to
Bob Engelhardt

Reply to
David Billington

Seamless (CDS)is just that: round stock that has been pierced down the center: Metal content: they send round stock though some rollers that roll off to the sides, creates a sorta void in the center. Then the process is the same as DOM except that degree of cross sectional reduction is MUCH greater.

DOM is welded then drawn. Total cross sectional reduction is quite small, which keeps the tolerances pretty tight. Wall thickness on seamless is pretty sloppy. Drawing the tube does a lot of good things: better tolerances, grain refinement, and work hardening for better strength.

These are the US trade designations. But they can cause some confusion because seamless is drawn over a mandrel.

Most race rules > I read your post with interest and have seen those in the US refer to

Reply to
RoyJ

Reply to
David Billington

DOM is usually double the price of EW, Seamless is double the price of DOM. In the US, DOM is acutally a more uniform product than CDS with the same strength numbers.

A lot of the bias against EW stock comes from the old days. Current production from top mills is extremely good product. Picture 2" diameter x .065" wall tube bent on a 2" inside radius with the weld seam on the outside of the bend. Now picture that done 1000 times in a row with no splitting.

For reference: Hot rolled electric weld ASTM A-513 Type 1 Cold rolled electric weld ASTM A-513 Type 2 Welded and Drawn over mandrel (DOM) ASTM A-513 Type 5 CDS ASTM A-519

Cheers.

David Bill> I'll have to enquire with the local steel stock holder about DOM as I

Reply to
RoyJ

Find somebody with an orthoscopic camera. Dril a small hole and insert the camera into the tube.

Reply to
Ernie Leimkuhler

RoyJ wrote in article ...

Reply to
Bob Paulin

SCCA changed it this year to require DOM.

||> Most race rules in the US call for the DOM product, not seamless.

||I have several rule books from several oval-track organizations in my shop. || ||While many mention "seamless tubing", I cannot find a single one that ||specifically requires DOM. || ||Even my NASCAR Cup rule book states: || ||"20-17.4 Round, magnetic steel tubing 1-3/4 inches by 0.090 inch minimum ||seamless roll-over bars are compulsory for the basic roll cage (diagrams #4 ||and #5), and must be NASCAR approved. Aluminum and other soft metals not ||permitted. Roll bar connections must be welded." || ||Admittedly, Cup car builders would prefer to use DOM over ERW, but in the ||USA, ERW is considered to be "seamless", and - in spite of the previous ||poster's statement - ERW would be acceptable since NASCAR does NOT ||specifically require DOM. || ||And, the rule also puts to rest another old wives' tale in that the only ||NASCAR requirement is that the roll bars be welded - not TIG welded, not ||MIG welded...just welded. || ||Again, chassis builders will use what they believe to be the best process ||for their own application. || ||Bob Paulin - R.A.C.E. ||Race Car Chassis Analysis & Setup Services

Texas Parts Guy

Reply to
Rex B

||In article , Rex B || wrote: || ||> I have a car with a rollcage installed when I got it. ||> Racing organization rules now require DOM-only construction. ||> Is there any way to tell what this cage is contructed from, without cutting ||> it? ||> Texas Parts Guy || || ||Find somebody with an orthoscopic camera. ||Dril a small hole and insert the camera into the tube.

Will it fit through a 3/16" hole? Texas Parts Guy

Reply to
Rex B

Sorry, I misspoke in saying that DOM was required in the US. I was trying to differentiate between true 'seamless' and other.

But any race rules that require "seamless" should indeed actually be enforced as true seamless. ERW has a both a visual and metalurgical seam that has different characteristics than the rest of the tube. DOM has the remnants of a seam that can be found but it is not significant. It may be a nit but I take strong exception to rule books that come up with their own interpretations of common standards. Leads to arbitrary rule interpretations that usually favor the old guard that 'know' the rules.

But 'most' ERW available in the US is much lower carbon than the equivalent DOM tube. Combine that with the work hardening that goes on with DOM and you get typical specs like these: ERW at 55k/40k/20% (Tensile/yield/elongation % in 2") DOM (1020/26) at 80k/70k/10% DOM (1035) at 90k/75k/10%

These are DIFFERENT materials! 50% higher tensile and half the elongation gives you a material that tends to snap rather than bending or stretching. You better know what you are buying/using when you have mission critical assemblies. I might mention that you have a completely different HAZ zone when welding DOM and common ERW. If you don't believe me, weld up two samples, cut and polish the cross sections, and run a rockwell test across the joints.

Which brings me to a real rant: When I used to buy a full 40,000 pound truckload of ERW tube, I could specify anything I wanted and get it with a mill spec that was performed on the physical tube in question. These days, when I buy enough for one car, mention 'mill cert' and the clerk goes blank. I walk out the door with no clue what I just bought. Thank goodness the race specs I deal with call for much heavier stock than is required for our low speed off road cars. Everybody gets stuck with the same weight, strength is not an issue.

Cheers.

Bob Paul> RoyJ wrote in article

Reply to
RoyJ

On Tue, 06 Jul 2004 14:52:01 GMT, RoyJ wrote:

||Sorry, I misspoke in saying that DOM was required in the US. I was ||trying to differentiate between true 'seamless' and other. || ||But any race rules that require "seamless" should indeed actually be ||enforced as true seamless. ERW has a both a visual and metalurgical seam ||that has different characteristics than the rest of the tube. DOM has ||the remnants of a seam that can be found but it is not significant. It ||may be a nit but I take strong exception to rule books that come up with ||their own interpretations of common standards. Leads to arbitrary rule ||interpretations that usually favor the old guard that 'know' the rules. || ||But 'most' ERW available in the US is much lower carbon than the ||equivalent DOM tube. Combine that with the work hardening that goes on ||with DOM and you get typical specs like these: ||ERW at 55k/40k/20% (Tensile/yield/elongation % in 2") ||DOM (1020/26) at 80k/70k/10% ||DOM (1035) at 90k/75k/10% || ||These are DIFFERENT materials! 50% higher tensile and half the ||elongation gives you a material that tends to snap rather than bending ||or stretching. You better know what you are buying/using when you have ||mission critical assemblies. I might mention that you have a completely ||different HAZ zone when welding DOM and common ERW. If you don't believe ||me, weld up two samples, cut and polish the cross sections, and run a ||rockwell test across the joints. || ||Which brings me to a real rant: When I used to buy a full 40,000 pound ||truckload of ERW tube, I could specify anything I wanted and get it with ||a mill spec that was performed on the physical tube in question. These ||days, when I buy enough for one car, mention 'mill cert' and the clerk ||goes blank. I walk out the door with no clue what I just bought. Thank ||goodness the race specs I deal with call for much heavier stock than is ||required for our low speed off road cars. Everybody gets stuck with the ||same weight, strength is not an issue. || ||Cheers. || || ||Bob Paulin wrote: || ||> RoyJ wrote in article ||> ... ||> ||> ||>>>>SNIP ||>>Most race rules in the US call for the DOM product, not seamless. ||>>

||> ||> ||> ||> I have several rule books from several oval-track organizations in my shop. ||> ||> While many mention "seamless tubing", I cannot find a single one that ||> specifically requires DOM. ||> ||> Even my NASCAR Cup rule book states: ||> ||> "20-17.4 Round, magnetic steel tubing 1-3/4 inches by 0.090 inch minimum ||> seamless roll-over bars are compulsory for the basic roll cage (diagrams #4 ||> and #5), and must be NASCAR approved. Aluminum and other soft metals not ||> permitted. Roll bar connections must be welded." ||> ||> Admittedly, Cup car builders would prefer to use DOM over ERW, but in the ||> USA, ERW is considered to be "seamless", and - in spite of the previous ||> poster's statement - ERW would be acceptable since NASCAR does NOT ||> specifically require DOM. ||> ||> And, the rule also puts to rest another old wives' tale in that the only ||> NASCAR requirement is that the roll bars be welded - not TIG welded, not ||> MIG welded...just welded. ||> ||> Again, chassis builders will use what they believe to be the best process ||> for their own application. ||> ||> Bob Paulin - R.A.C.E. ||> Race Car Chassis Analysis & Setup Services

Roy Good information, thank you. The way I understand it DOM is required for the main roll hoops, but probably not for the door bars and longitudinal supports. Would it make more sense from a safety standpoint to use ERW in some areas? for example, a NASCAR-type door protection might benefit from some bending to absorb energy. Texas Parts Guy

Reply to
Rex B

When did they change and for what class? usually they have a thicker wall ERW equivalent.

Reply to
Brian

||When did they change and for what class? usually they have a thicker wall ||ERW equivalent.

2004 GCR, announced in FasTracks sometime in 2003. Existing cages grandfathered, new logbooks require DOM

18.1.6. Material: A. Seamless, or DOM (Drawn Over Mandrel) mild steel tubing (SAE 1010, 1020,

1025) or equivalent, or alloy steel tubing (SAE, 4130) shall be used for all roll cage structures. Proof of use of alloy steel is the responsibility of the entrant.

Looks to me that, as another poster said, ERW is often called "seamless", then this paragraph would seam to allow ERW. look for a future "errors & omissions" addendum.

||> ||> Most race rules in the US call for the DOM product, not seamless. ||>

||> ||I have several rule books from several oval-track organizations in my ||shop. ||> || ||> ||While many mention "seamless tubing", I cannot find a single one that ||> ||specifically requires DOM. ||> || ||> ||Even my NASCAR Cup rule book states: ||> || ||> ||"20-17.4 Round, magnetic steel tubing 1-3/4 inches by 0.090 inch ||minimum ||> ||seamless roll-over bars are compulsory for the basic roll cage (diagrams ||#4 ||> ||and #5), and must be NASCAR approved. Aluminum and other soft metals not ||> ||permitted. Roll bar connections must be welded." ||> || ||> ||Admittedly, Cup car builders would prefer to use DOM over ERW, but in ||the ||> ||USA, ERW is considered to be "seamless", and - in spite of the previous ||> ||poster's statement - ERW would be acceptable since NASCAR does NOT ||> ||specifically require DOM. ||> || ||> ||And, the rule also puts to rest another old wives' tale in that the only ||> ||NASCAR requirement is that the roll bars be welded - not TIG welded, not ||> ||MIG welded...just welded. ||> || ||> ||Again, chassis builders will use what they believe to be the best ||process ||> ||for their own application. ||> || ||> ||Bob Paulin - R.A.C.E. ||> ||Race Car Chassis Analysis & Setup Services ||>

||> Texas Parts Guy || ||

Texas Parts Guy

Reply to
Rex B

||When did they change and for what class? usually they have a thicker wall ||ERW equivalent.

and reading further, there is this:

"Note: ERW tubing is not permitted in any car registered with SCCA after of

01/01/2003."

(apparent typo is theirs)

Rex

||> ||> Most race rules in the US call for the DOM product, not seamless. ||>

||> ||I have several rule books from several oval-track organizations in my ||shop. ||> || ||> ||While many mention "seamless tubing", I cannot find a single one that ||> ||specifically requires DOM. ||> || ||> ||Even my NASCAR Cup rule book states: ||> || ||> ||"20-17.4 Round, magnetic steel tubing 1-3/4 inches by 0.090 inch ||minimum ||> ||seamless roll-over bars are compulsory for the basic roll cage (diagrams ||#4 ||> ||and #5), and must be NASCAR approved. Aluminum and other soft metals not ||> ||permitted. Roll bar connections must be welded." ||> || ||> ||Admittedly, Cup car builders would prefer to use DOM over ERW, but in ||the ||> ||USA, ERW is considered to be "seamless", and - in spite of the previous ||> ||poster's statement - ERW would be acceptable since NASCAR does NOT ||> ||specifically require DOM. ||> || ||> ||And, the rule also puts to rest another old wives' tale in that the only ||> ||NASCAR requirement is that the roll bars be welded - not TIG welded, not ||> ||MIG welded...just welded. ||> || ||> ||Again, chassis builders will use what they believe to be the best ||process ||> ||for their own application. ||> || ||> ||Bob Paulin - R.A.C.E. ||> ||Race Car Chassis Analysis & Setup Services ||>

||> Texas Parts Guy || ||

Texas Parts Guy

Reply to
Rex B

snip

Can of worms question!! In theory, you would like to have some controlled crush areas to absorb energy. In practice, it's real hard to get it to work. Take the door question: what is the thigh door tube fastened to? If the answer is the main frame cage that should not move in an incident, then you might want some bending to go on. If the mounting is to some area that has some give, I would want the thigh bar to be as strong (rigid) as possible to avoid contact with the driver.

Sometimes I even hate to weigh in on the question: I'm not sure that the average small builder has the resources to really go deep into the issues of crush zones for crash protection. That's why the rules committees just mandate reasonable standards, everyone has to play by the rules.

As for energy absorbtion you might want to ponder this: The area under the stress/strain curve is the energy absorbtion. In a nutshell ERW at 55k/40k/20% (Tensile/yield/elongation % in 2") has more energy absorbtion capability than DOM (1020/26) at 80k/70k/10% ie 40k x 20% is bigger than 70k x10% Of course trying to keep the frame intact enough to move 20% is a big deal!

Reply to
RoyJ

Ernie probably meant arthroscopic camera. Eg see

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I think the usual arthroscopic and endoscopic cameras are in

5 to 10 mm tubes (to fit thru standard 5 mm and 10 mm trochar ports) so 3/16" (4.7 mm) would be on the small side. But 4 mm endoscopes exist, and I think 3 mm also but don't know for sure.

The scope view in an endoscope is typically at 15-30° to the scope axis which would allow you to see about half the inside wall, opposite the entry hole. To see the wall on the same side you might need a flexible scope. Google on "inspection scope".

If you have 2 holes, shine a white LED into one of them and take a picture through the other, with a close-focussing camera. I've taken pictures through quarter-inch openings and gotten ok results, but lots of cameras won't focus close enough.

-jiw

Reply to
James Waldby

It did in my knee ------

Reply to
nospam.clare.nce

||In article , Rex B || wrote: || ||> I have a car with a rollcage installed when I got it. ||> Racing organization rules now require DOM-only construction. ||> Is there any way to tell what this cage is contructed from, without cutting ||> it? ||> Texas Parts Guy || || ||Find somebody with an orthoscopic camera. ||Dril a small hole and insert the camera into the tube.

I guess you could bore a 1.5" hole in the floorboard under the "foot" and run a colonoscope through it too ;) Texas Parts Guy

Reply to
Rex B

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