For longer than I can remember I have wanted to do this, and I finally scheduled time for it, so here it is! The thread to end all debates!

Marlin Crawler USA HREW Bumper Steel vs. Competitor's DOM Bumper Steel

The motivation for this article is because I feel there is a misunderstanding of the term "DOM". It seems that many people in this industry believe that the term DOM automatically equals a material that is more dent resistant than HREW. The truth of the matter is that DOM (Drawn Over Mandral) and HREW (Hot Rolled Electric Welded) are simply manufacturing processes used to produce a final product. This article is not going to go into the manufacturing details between the two as there are many sites available for this. Rather this article will prove that DOM does not mealy equal "more dent resistant."

The core source of confusion is that the performance of a material is largely dependent on the type of material itself and not the manufacturing process used to create it. If we were to compare apples to apples, then we might find one process to be superior in certain tests than another, but because not all material in this Toyota market place is made equal, we should find a problem with the status quo.

As we will see, simply put, an orange is not an apple.

Point in case: Marlin Crawler uses bumper tubing that is made via a HREW process whereas a competitor uses bumper tubing that is made via a DOM process. The difference is that the Marlin Crawler bumpers are built from high quality genuine USA steel whereas the competitor's bumpers are built from an unknown material.

To further motivate this article, the competitor's website states,

"DOM steel is far stronger and dent resistant when compared to HREW tubing"

"DOM is known for being stronger and more dent resistant when compared to electric welded material."

It has always been my own personal conviction that our USA steel is superior to the competitor's steel, regardless of the process used, but to this date this has not been proven. So let's jump right in and get dirty! I will be conducting two tests: a Rockwell Hardness Test to see which material is more dent resistant, and a Direct Loading Test to see how each material reacts under pressure.

Rockwell Hardness Testing

Marlin Crawler USA HREW Sample	Competitor's DOM sample

Shown to the left is a cut-out sample of our USA steel HREW tubing, and to the right is the competitor's DOM tubing sample. Both samples have an 1-3/4" outer diameter and have a wall thickness of 0.120". Two small pieces of equal size were cut out very quickly using a plasma cuter in an attempt to avoid elevating the temperature of the material. To ensure an accurate comparison, both pieces were cut within seconds of one another by the same person using the same cutter. Please note no heat marks are present at the cut lines on both samples. Additionally, as seen below, 5 individual trials were done as far away from the edges as possible to avoid heat affected areas.

5 trials of Rockwell Hardness testing each

Marlin Crawler USA HREW sample	Competitor's DOM sample

What is a Rockwell Hardness Test? It is a test that determines the hardness of each material by measuring the depth of penetration of an indenter, comparing a major (large) load against a minor (small) load. The higher the number, the harder the material, and therefore the higher resistance to deforming (dents).


Rockwell Tester and class-B indenter used

The Rockwell Hardness tester used was a Louis Small Service Diamond Hardness Tester model number 8B serial number 5751, and was last calibrated on May 27th of this year. The indenter used was a SUN-TEC 1/16" B-scale Carbide indenter, serial number 090104W and was manufactured on March 2nd of this year. All testing was performed courtesy of the California State University of Fresno's Mechanical Engineering Department in Fresno, CA.

To ensure accuracy, the two samples were loaded concave up and tested on their smooth inner surface. We ran 5 trials each to make sure we are getting consistent readings from the material. You be the judge:

When we tested our USA HREW steel material, the results were as follows:




When we tested the competitor's DOM material, the results were as follows:


There you have it!!! Obviously DOM does NOT mean it is more dent resistant!! You must have a high quality steel if you wish to have a dent resistant bumper!!

Here are the two materials compared in a bar graph, including an average bar at the far right:


So the average Hardness of our HREW material is 81.3, compared to our competitor's DOM material which is only 74.3. Therefore their DOM, which they advertise as being "far stronger and dent resistant when compared to HREW tubing" as well as claiming to be "known for being stronger and more dent resistant when compared to electric welded material" is actually softer and weaker than our HREW! Our USA HREW steel is 9.4% more dent resistant than their DOM material. This didn't surprise me as I know that we are talking about two different steels and we are proud of the material performance of USA steel!!

It's not hog-wash: USA Steel really is good and that is why we run it on our trucks!

Nice going! Its neat to see results like this. 

Now to play the devils advocate. 
What if the dent or rock slides on the seam of HREW tubing? VS Seamless DOM?

I don't doubt that your steel is stronger but just thought I would ask. Don't worry every piece of prefabbed steel on my truck is from marlin and thanks cause Ive given them a beating!

Thanks for the write-up BigMike.  It's nice to see how these tests are done and nice to confirm agian that Marlin puts out superior products.

i wonder what the competitor thinks of these results?

that would be interesting to hear their rebuttal.... but then again, that's what pirate is for

When bending HREW, it is common practice to have the seam on the inside of the bend. Therefore the seam will be on the back side of any impact.

freds40 is correct and I just verified this on all of our front and rear bumpers and our rock sliders.

BigMike

Don't forget, to compare apples to apples you need to compare the same rated steel in both HREW and DOM. It's the steel not the process.

freds40 is correct and I just verified this on all of our front and rear bumpers and our rock sliders.

BigMike

What made me think of this is on one of my sliders the weld was on an exposed area of the bent part of the slider. When we installed it my buddy and I discussed this and put the slider on weld side up. Otherwise I usually dont come up with good questions. Hahaha Thanks for the input!

how about some bend tests on a longer piece of tube..... reading all this makes me wonder why we use DOM on links??

Don't forget, to compare apples to apples you need to compare the same rated steel in both HREW and DOM. It's the steel not the process.

Yup, that is the emphasis of this experiment. We do have USA DOM steel here, but I need to check on the type of steel to see if it is the same as the USA HREW I tested. I will see about testing these also in the upcoming weeks.

I am going to post this over on Pirates. Wish me luck!

I started reading about this over on pirate and tried to finish reading it a little later and it was gone. Did the mods delete it or what? If they did that is such B.S. Finally some real world testing and the thread disapears.

thatīs exacly why I canīt stand pirate.... dissing this and that, but why is all the ass kissing with trail gear...

Yup, the thread I posted on Pirates was moved to a hidden forum, and I received an email from CAMO to call him to discuss it.

According to Camo, I was "spamming" and it was not a tech article. He said he would give it an "F" grade for a tech article. I even edited the closing paragraph before I posted it by removing the references to buy our product.

He offered to move the thread to the vendors section but said that he thinks what I am doing is a very bad idea because I am, quote "fighting a public perception"  -- WELL PRECISELY!! THE TRUTH MUST BE KNOW THAT THERE IS A COMPANY SELLING SOFTER BUMPER MATERIAL MASQUERADING IT AS MORE DENT RESISTANT THAN OUR OWN!

He told me, quote "I think you are trying to swim upstream without a paddle", and he said "the war was getting started".
Yeah, the war I am looking for is to educate people!
We get COUNTLESS emails and phone calls asking why our Body Armor is not as strong as a competitor's DOM. Who knows this to be true? Has anyone ever bothered to test this claim until now?? It is a massive widespread misconception that when the competitor uses the term "DOM", it is some golden platter of instant dent resistance! And until now no tech article has proven this to be true or not!

So my article was moved to the Vendor section and is located here: http://pirate4x4.com/forum/showthread.php?t=803975 You can see how I downplayed the closing paragraph:

If you care about your truck and it's occupants, make sure the body armor is made out of high quality steel. As proven here, just because it's DOM doesn't mean it's more dent resistant than HREW.

I would have to say this is perhaps the most unbiased article with the most substantiated claims I've ever written. I have been learning a lot in terms of how to post articles of this magnitude and I think it shows. It is well structured and organized, starts with a motivation and an abstract, and has a conclusion that supports the assumptions made.

I am going to cut this short to say alas, we really need to build a working relationship with Pirates as they are the largest forum for advertising, so I am not going to get into conspiracy over why this happened.

Camo said the discussion may be moved back to the Toyota - Truck and 4Runner tech forum but he wants someone other than me to create a new topic about it.

Kind Regards,
BigMike

I'm not sure that I think there's a direct comparison to hardness and dent resistance, but the crush test is spot on.  I'll admit that my material knowledge isn't significant, even though I hold an engineering degree, but I think that there are far more significant factors.

I'd like to see the crush test examined to include a long section of tube.  If you used a piece long enough to eliminate any end constraints and loaded it at the center it would be the closest approximation of a dent.

Also, some impact testing vs. controlled applied loads might be in order.  I realize that it's difficult to calibrate a hammer, but you could simply drop a specified weight from a specified distance.

Also, does bending have any effect on the dent resistance.  How about the same tests on a bend?

I think your on the right track and am only offering a few other ways to get additional results.

I'm not sure that I think there's a direct comparison to hardness and dent resistance, but the crush test is spot on.  I'll admit that my material knowledge isn't significant, even though I hold an engineering degree, but I think that there are far more significant factors.

I'd like to see the crush test examined to include a long section of tube.  If you used a piece long enough to eliminate any end constraints and loaded it at the center it would be the closest approximation of a dent.

Also, some impact testing vs. controlled applied loads might be in order.  I realize that it's difficult to calibrate a hammer, but you could simply drop a specified weight from a specified distance.

Also, does bending have any effect on the dent resistance.  How about the same tests on a bend?

I think your on the right track and am only offering a few other ways to get additional results.

blackdiamond-

These are excellent test ideas! It has been requested to run the crush test using longer samples and I plan on doing this soon.

Your testing of bends idea is excellent but I must come up with a way to cradle the samples without allowing any movement at the support to get consistent results. I probably don't have matching bend angles to play with (remember we currently have a limited amount of competitor's material to play with) but we could match bends for this.

Another test I can very easily do is a tensile test with a strain gauge. This will tell us how much deformation each material can withstand before deforming, and will give us elongation, necking, and yield stress numbers to compare. It takes more time than I was allotted so we'll have to see if I can run some other tests at the same time to make my time worthwhile.

All I know is that you guys are teaching me a whole lotta stuff that I did NOT know before. This thread is entertaining as well as informational. Keep up the good work(battle). 

Thanks man! This is the first time I've ever done testing of this kind and I think it is beginning to pay off. I have already pissed off a lot of people which means I am doing something right!!

BigMike

Mike,

Like we talked about today, I think you are on the right track. I'm interested to see what your USA DOM numbers come out as. I have no doubt it will be much better than that "other" DOM. I sure wish we knew what the true grade of the steel was, but it is extremely difficult, with out very expensive processes, to determine that precisely.

how about some bend tests on a longer piece of tube..... reading all this makes me wonder why we use DOM on links??

Please remember, Mike is testing DOM of "an unknown source". If you do your research and buy from an AMERICAN manufacture using American materials you will see a difference between HREW and DOM. For one thing HREW and DOM tubing are rarely the same grade steel. DOM is normally manufactured from a slightly higher carbon steel which will give the material more resistance to crushing.

so basicly what you are trying to prove is that your steel isnīt weaker than the competetors,  not that usa hrew is stronger than usa dom.

Good luck, but my   I would weld a 1 meter bar of each tube to something solid, then I would attach  something other end and give them both a equal force or pull and see wich one bends first.