Chromoly

[fastford]

nope, your wrong, im no metal urgist, but there is a lot of difference in a hardened leaf spring and moly tubing, but this whole conversation was hashed over on here several years back and im not going through it again. you keep welding yours with a tig and moly filler and ill keep welding mine with a mig and mild steel and we will see who gets the most stress cracks at the weld....

[let-r-eat]

http://www.lincolnelectric.com/en-us...ly-detail.aspx



Why am I wrong fastford. You think I'm talking out my ass?

[fastford]

I don't know what your talking out off, and don't care. that article has been out a while, ive seen it before and I think er80-02 is a form of low carbon mild steel filler, not sure. im not saying tig is no good, just saying that ive done both and have found less stress cracks with tig and mild steel wire. I suppose tig and proper filler like mentioned above , would be just as good, but no better and a lot slower. JMO, no offence.

[50j]

ER70S-2 works well on chassis and is flexible enough not to crack at the joints.

[MasterSbilt_Racer]

Not to pick on the guys above, but saying moly is more rigid is not really correct. All steel alloys have basically the same spring constant, or modulus of elasticity. The only advantage is simply a higher stress before yield occurs.

This comes in handy in areas such as the cage where strength is important. Otherwise, the rest of the chassis should be designed with rigidity in mind. If you replace mild steel with thinner wall moly, you may maintain or increase strength, but stiffness of the chassis was actually reduced.
Last edited by MasterSbilt_Racer; 08-13-2015 at 11:48 PM.


Like the modulus of elasticity of spring steel? That is a perfect example to explain the post I was making. Take a broken spring leaf and weld it together with mild steel. What happens?

I did use the word rigidity in the proper context. A mild steel filler on a moly tube is doing basically the same thing as it would on a leaf spring but on a much smaller scale.

Just clarifying my post.

A leaf is hardened to raise the yield point. Your repaired leaf would behave the same up to the point the mild steel starts to yield. A chassis isn't supposed to be a spring. It shouldn't see stresses that cause deflections that high.

[let-r-eat]

A leaf is hardened to raise the yield point. Your repaired leaf would behave the same up to the point the mild steel starts to yield. A chassis isn't supposed to be a spring. It shouldn't see stresses that cause deflections that high.


That is correct. But my point was that it is only as strong as the weakest link.................The mild steel...............which compromises the strength.

The chassis will be stronger with moly filler properly annealed.

[Bubstr]

Welding with softer material as a filler is not as big of thing as it seems. the softer filler mixes with the harder and strength is maintained by the thickness. All steel is rated by diameter and wall thickness, to compare one to another. If your weld is thicker than the wall, you gain a lot of strength in that place. This is why you see cracks, next to the weld, rather in the weld. No matter what some may think, these cracks are the result of two things on Molly. #1 molly transfers force better than milder steels. #2 you can loose the integrity of the heat treat where you heat for welding. It still comes to using just enough heat to get good penetration. Unless your very good with a MIG, a TIG is a better bet for heat control. Not saying you couldn't do it some other way. Just keep that blue heat line narrow.

When it all comes down, I'm not sure that something that bends rather than breaks isn't a better option for a lot of purposes. We can straighten or replace, with out loss of integrity. Just my opinion on the last part.

[fastford]

bubstr, I agree with your thoughts on bending is better than breaking, im old school, ive been welding long before the all mighty internet, but I have to admit, ive learned a lot from it. My youngest son is a senior in high school and has enrolled in welding. his teacher is an old friend of mine and considered to one of the best welders around, I told him maybe he can teach his old man a trick or two.......

[Windy]

chrome moly chassis vs. D.O.M. ...instead of starting a new thread id like everyones opinion on which chassis/material to buy for a new modified..my car owner just bought a new elite,car/d.o.m. ..built by the allison brothers..there are a lot of good chassis out there,beak built, huges, dw + to many to list....my preference is the rocket by ruhlman..its a rocket off thier jig,plymouth pro tube moly and brian puts the front clip on and it comes out to the black ft. end rocket settings..i know theres some other d.o.m. thats supposed to be better like db8 or somthing like that..????..i still would think the rocket by ruhlman would be the best..years ago i helped build some cars..one in particular we raced and at about 75 to 80 races it turned into a boat anchor especially the 2nd nite you raced it like fri., it was fair and sat., you couldnt hit the broad side of the barn with it..it was fairly stiff with underslung frame rails....most people i talked with that i thought knew more than me said the d.o.m. was flexed out..????..AND that brings me to the most important question with the day an age of the 5 thousand dollor an + bare mod chassis wouldnt the pro tube moly chassis be the best buy..ive worked with the ruhlman car and its awsome fast..also with a swartz mod and a bad fast and a grt..ive worked with rockets since the 90,s when francis started running them and i like them but its a cost vs., a lasting thing now with the cost of the chassis and parts being so high you will have close to 20 somthing in the roller with most everything ..looking for your experienced opinions,not wanting arguements or smart--- comments about modifieds please..just honest opinions and experiences..thank you all in advance..WINDY..~V~..

[SuperEight]

No more Moly for me, Ma.

Personally I'll never use a "Moly" chassis and I've included pictures to demonstrate. Moly breaks, usually next to the weld. Lots of people claim you can treat them and get them to be safe, but for me its a risk not worth taking.

[hammond motorsports]

On Chrome moly just make sure you use the correct gas and wire . Using a std gas and wire the chrome moly will crack .

[fastford]

On Chrome moly just make sure you use the correct gas and wire . Using a std gas and wire the chrome moly will crack .

would you please share what wire and gas you use? I still use 75/25 gas.

[Bubstr]

I believe nascar requires mild steel chassis yet. They hit things harder than most cars. Now NHRA requires CM tig welded only, but I suspect SEMA had something to do with that rule, to keep pro chassis builders in business.

[Bubstr]

would you please share what wire and gas you use? I still use 75/25 gas.

What I'd like to know is the annealing process. 4130 is heated to around 2000 deg then slowly cooled over a 24 hour period then finished in a oil bath, which is why CM is dark and oily, to mark that N on 4130N. Each number means something. the 4 means high carbon steel the others say how much nickle and molybdenum and the N means normalized.

[hammond motorsports]

tri mix gas Argon, Helium, Carbon Dioxide and I use a spoolarc 83 wire from ESAB . I have used this combo from the early 90s to today . Never had any cracks in my chrome moly welding