DOM vs. Moly

[Pook]

Actually I was asking because alot of the welds I see on stuff being built look less than beautiful and I don't see many TIG welds.

That being said I was curious why very few use moly but now I gather it is cost and that it has to be tig welded.

I am starting to overhaul my CJ and was thinking of moly as the stuff is lighter than mild or DOM and it just seems like a higher quality finished product when you use moly.

Lighter and stronger is always good.

You don't need to tig well moly...it can be mig welded.

Nowhere in ANY post have I said DOM is shitty so you should get some glasses. I was just curious as to why other than cost moly isn't used.

I see you are quick to speak without checking facts.

Those pics of the rolled truck and buggy show DOM's strength and thats great. I was just wondering why if you could get the same strength in a lighter material why it wouldn't be used more often and you fail to see that point.

The only answer I get is cost but with people spending $50K plus on a buggy then the extra cost for moly seems like pennies to me.....

And have fun building with lighter walled moly were its going to get beat by rocks...it will dent and be scrap in no time.

 

[Money Mark]

And have fun building with lighter walled moly were its going to get beat by rocks...it will dent and be scrap in no time.

DHR ain't building ****.....he's all talk.





And he's wrong. :awesomework:

 

[82toyomud]

You don't need to tig well moly...it can be mig welded.

To have a proper weld you should TIG weld it.

 

[Binder]

We have done weld tests using 1020 and 4130 tube on one of the MTS machines here on campus, and the 4130 came out much stronger than the 1020. None of the samples were post weld heat treated, and both samples were tig welded.

What kind of weld test?

 

[Corey Y]

:corn:

 

[Pook]

Here is a fun weld thread.

http://weldingweb.com/showthread.php?t=22818

 

[Bunk1]

Well i checked prices on chromo and holy crap, I can get it for a smokin price. (i priced 1 1/2 and 1 5/8ths .120 wall)

However treating it is a issue in wa state. There is no oven big enough around here to do a chassis, So i see no reason to use it on a rig thats gonna get beat on. Plus the tig issue(for me) makes a chromo chassis unreasonable.

 

[Corey Y]

Do you know what hardness the material you quoted is? Isn't there 3 different hardnesses available?

 

[Bunk1]

Do you know what hardness the material you quoted is? Isn't there 3 different hardnesses available?

I'll check tomorrow, I figure its normalized but im not too sure on this "thin walled" stuff. Im tempted to get some simple because of the price.

 

[Corey Y]

Can you check on the price for 20, 20' sticks of 1 3/4" .120 wall Titanium for me? Non medical grade.

 

[82toyomud]

What kind of weld test?

We took 1.000x.065 and 1.250x.058 in both 4130 and 1020, and tig welded them, with ER70 filler rod. We butt welded 10 samples of each material, cut them in half, then cut/ground them into the dog bone shape, and put them on the MTS tensile tester machine. All but two broke right at the outside edge of the heat effect zone, which is right where you want them to be. I can post up some pictures of us doing this tomorrow if you'd like, and we'll be doing another set here in a couple weeks for our baja competition.

 

[82toyomud]

I'll check tomorrow, I figure its normalized but im not too sure on this "thin walled" stuff. Im tempted to get some simple because of the price.

All of the really thin walled (.028, .035, .049, .065) stuff we get is normalized.

 

[nowires]

Correct me if I am wrong but DOM will bend and absorb the impact, Molly will crack
Molly is stronger but DOM is more forgiving
Dom chassis will flex and spring back to a point and molly once sprung will stay that way
A DOM chassis if sprung you can straighten, A molly one you start over

 

[CHOP SHOP]

I can post up some pictures of us doing this tomorrow if you'd like, and we'll be doing another set here in a couple weeks for our baja competition.

Please do, it would be appreciated:awesomework:

 

[Pat]

Correct me if I am wrong but DOM will bend and absorb the impact, Molly will crack
Molly is stronger but DOM is more forgiving
Dom chassis will flex and spring back to a point and molly once sprung will stay that way
A DOM chassis if sprung you can straighten, A molly one you start over

I read this as well (in a book, not on the internet).

"There are few applications that warrant the use of chrome molybdenum unless you're building and airplane, a Formula-1 car, or an Indy Car."

"Yes, it is stronger than mild steel. It is also less tough... under impact, as in a crash, a chrome moly steel part is much more likely to break rather than bend."

Absorbing impact by bending = GOOD :awesomework:

Roll cage breaking apart in a crash = BAD :eeek:

 

[nowires]

I

Absorbing impact by bending = GOOD :awesomework:

Roll cage breaking apart in a crash = BAD :eeek:

I don't think it will break, But I don't think "MOLLY" likes getting nailed and punished on a routeen base like on a rock buggie

 

[Binder]

I don't think it will break, But I don't think "MOLLY" likes getting nailed and punished on a routeen base like on a rock buggie

I think you guys are on crack! Cromo after heat treat gives it a "spring" property. The way I understand it all steel deflects the same. Same size and shape with the same load will deflect the same regardless of the material. The different material and treating tells if it will return to shape or stay bent or maybe just break.

 

[Hip]

The way I understand it all steel deflects the same. Same size and shape with the same load will deflect the same regardless of the material.

if you ever had to bend some 2" .120 wall dom vice 2" .120 wall HREW in a manual bender you would not say that. MAJOR difference.

DOM dimple strength is twice that of HREW of the same material and thickness.

Unless your talking just impact deflection vice sustained deflection?

And id be very interested in seeing testing pictures of the Chromo tubes.:awesomework:

 

[DHR Motorsports]

If anyone has ever bent moly in a bender they wouldn't say thet it doesn't have "spring back" as you have to bend it way farther to get your desired bend than HREW or DOM as it has lots of "spring back"

 

[Binder]

Here's a quote from the materials bible on pirate...

Stop! Read that again! Yes, that's right - the modulus of elasticity is the same for ALL steels. This means they are all comparably stiff, they will ALL resist bending or twisting about the same amount - from cheap pipe to expensive cr-mo tubing. The difference between them is what happens when they bend - in other words, the stress/strain curves are different. The better, more expensive steels, due to their much higher yield points and greater elastic ranges, will be able to easily shrug off the load, wheras the lesser material may yield (take a permanent set, or bend) or actually rupture. This is very important, and hugely misunderstood concept, so I'll repeat it. All steels will bend or twist the same amount under the same load - the difference is in how they handle this loading - good steel will "spring back", poorer steel will bend permanently or break.