DOM vs. HREW

[davido]

Scott's done a lot of reading. I'm interested in discusion between well read/educated people....

What say you Scott, Andy, Doug, Grayson, or anyone else who knows.

~dso

[Doug Krebs]

I'm going to try to find the thread that came up on this on CK5.

Here is some crap i found:

ERW is a 1010 steel, DOM is 1020. The 10 and 20 represent the amount of Carbon in the steel. The higher carbon
content make the steel much stronger. Yield strength on 1010 is around 45,000 psi and DOM is around 70,000 and 4130 is around 90,000. So you can see the strength difference. Also, DOM is "work-hardened" or forged if you will. The Steel itself becomes denser and the surface tougher.


DOM is a process and means "drawn over mandrel". Typically you use DOM when you require precise thicknesses in the ID, OD or wall thickness of a tube. Hydraulic applications come to mind. It is not seamless but is made from sheet steel, rolled and electric resistance welded and finally, DOM'ed. DOM is a cold process. Most typically it is made from low to medium carbon steel. Often a low carbon steel application is preferred because of it's ability to be formed easily. The higher the carbon content, the harder it
becomes to bend. Typical tensile strength of DOM tubing is in the 60-75000 range although some increase can be gained with a 1040 steel base rather than the more common 1020. 4130 Tubing is often referred to as "Chrome Moly" tubing. This jargon term is derived from the chromium and molybdenum concentrations present in the metal itself, which run in the area of .80-1.10 for Chromium and .15-.25 for Molybdenum. typical tensile strength for this material is 95000 - 110000 PSI however it can range as high as 225000 by heat treatment. It is good to
remember that the higher the tensile strength, the more brittle a metal becomes so you need to find a balance. A good balance for 4130 would be somewhere in the 145000-15000 PSI range.

Just stuff i found real quick, some where there was a huge discussion about this. I'll try tommorow

[Fredo]

Well, as far as I know, HREW is cheaper than DOM, but isn't as nice as DOM. HREW has a seam weld, as does DOM, but DOM is taken a few steps further and as far as I can tell, it's basically like a heat treating and then it's rolled over a die to counteract the welding and cold working abnormalities for a straighter stronger piece of tubing. But as far as strength goes in cages and other automotive applications, HREW will sufficiently do the job except for like steering columns (saftey sake) and driveshaft tubes. I know some organizations such as NHRA require DOM to be used in many classes simply because those cars could hit a wall at 250+mph, but in the case of many SCCA classes, they don't require a cage to be built of DOM. Now if I was building a purely competition rock buggy were I would be getting into areas with large drop-offs, I would probably use DOM, but for the kind of stuff we all do and even for the occasional rock competition, I would probably go with the HREW.

I guess if by this post you're asking which one is better, definitely the DOM, but it just depends on the application. I plan on putting a cage in my camaro and perhaps even in a scout, but I haven't decided if I'm going to fork over the extra cash for DOM....so I guess to me, it's a matter of how serious you are going to be depending on that piece of tubing to do what you are asking of it.

[Cajun]

I'm on my way out the door to go hunting, so I'll post more info. later.

However, for the life of me, I can't figure out why people try to skimp on cage building. You're designing and building something that has 1 purpose...TO SAVE YOUR LIFE and the lives of your passengers. This seems easy to me, DOM is stronger than HREW, so use it.

While super cool, (and light) I believe that "chro-mo" is overkill for just about everything but a pure competition vehicle.

For the record, the cages on the vehicles that roll out of my shop will use exclusively DOM on the support bars.

Like I said, I'll post more later, this has been discussed ad nauseum on the PBB.

[Krawler68]

THree cages and the only one i ever felt SAFE in was my DOM one...

[redcagepatrol]

do a search on POR, the last time I read about it, (before I bought the HREW) I read everything above except about the different types of steel used.

From my understanding, there is a MINIMAL strenth difference between DOM and HREW and that the difference is mostly with the tolerances (that don't matter in cage building). The cage strength will come down to the CAGE DESIGN and the WELDING, not the type of tubing used. The minimal difference in strengeth will not matter if you build the cage correctly and weld it without defects (or large gaps Doug).

In conclusion, there is NO reason to get DOM unless you like a smooth ID and have extra money to spend. the strength difference does not matter, only the cage design and welding techniques.

[Krawler68]

kinda like glad lok... let's roll my **** down a hill and then your ****... whose rig would you feel more comfortable inside? I for one would NOT want to take a tumble in an HREW cage if I could help it... not to say it won't work...but why buy a Forkin' Klune V and then be cheap on a cage?

[redcagepatrol]

it's NOT being cheap, it't having a brain and being smart about it. The way you are talking, you would be stupid for using DOM and not true tig welded chrome-moly tubing.

You don't have to have 40 spline axleshafts on a 2000lb rig. There is a reason God made brains. Overkill is not the answer.

[Krawler68]

gun drilled 40 spline axles on a 2000 lb. rig WOULD be my first choice, kick ass bullet proof design, low weight...and YES I think a tig welded Chro-Moly cage would be a good choice... however I DO belive that might be overkill.

My point is if you want a strong cage that will hold up to a massivew thrash endo roll, I'd rather KNOW I have the best I can afford rather than being a cheap biatch and saying HREW is good nuff'.


I remember you used to justify pipe as a cage material... boy were those the days :Flipoff2:

[Cajun]

.120 HREW,1 roll, backwards onto roof:



I'm certain additional bracing would've helped, but some of that stuff flattened, not so cool. I don't know if DOM would've held up any better in the same situation, but it's food for thought.

I'm looking for pics of DOM failure, but I haven't found any.

[Cajun]

Another pic


Here's the link if those don't show up:

http://www.pirate4x4.com/forum/showt...&highlight=DOM

[Cajun]

This would be the ad nauseum that I mentioned earlier...

http://www.pirate4x4.com/forum/showt...&highlight=DOM

[redcagepatrol]

I have read the thread on the POR, overall they agree with me. The bent cage is due to a TERRIBLE design. A horizantal bar supported by another horizantal bar??? No upward bars on the outside? What would you expect , gaurentee DOM would have done the same but alot more money would have been wasted.

[froader03]

now hold on a minute there, cowboy... DOM is unarguably superior in composition (read: stronger). let's say you build identical cages out of each. rocks will much sooner take a toll on HREW leading to more little nicks and dents. don't stop me if ya think I'm wrong here... hell, I'm not even gonna go any further... I agree with andy and doug. the value of a cage can never be more than the people it protects. I agree that proper construction is essential in any case, but you can't honestly say that saving money (even if more than a little) is the SMART way to go. DOM is more durable and safer, especially in the long run when your cage has taken some hits, rollover or not.

you get what you pay for and if you don't pay for it now you'll pay for it later my friend...

[Krawler68]

Forget what I said earlier...upon conferencing with Scott I think that it would be best for you to use either old 2 3/8" TK70 drill pipe (because i can get it for you for free)... or a Bunch of mitre cut square tubing (.095 wall cause Square tubing is SOOOOOOO much stronger).



DOM sucks because it's about 1.50x more expensive and is hard to purchase... I would never use this inferior part on anything I built...not when cheaper things are SO much superior...

Get the point?