That was really cheap for the chromemoly. Why was it so cheap? Could I buy from them that cheap? I don't think there would be any problem mig welding chromemoly. My boss man has a Jery Hass Pro Stock car and he has miged a lot o stuff on the chassis, and it is a chromemoly chassis. Never had any problem with anything he has welded. He's been fabricating and welding for probably close ta 20 yrs now. Let me know something on the place you got the chromemoly from, very interested.

 

jpm, Yes you can weld mild to chromemolly but you use a different filler rod than mild or chrome. I would like to know why your teacher says you can mig chromemolly and do no heat treatment and what wire is he using. You can mig weld just about anything but how long will it last. mg98. Did Jerry Haas mig weld the chassis or your boss. You can mig small stuff on. edit We were talking and decided to post link but dont know how. So here is a site to look at as it is simple and explains some questions here. Tigdepot.com in faq. chrome. answers i wont go into process for liabilaty reasons but they do.

 

I got it that cheap because the school was puting their order in for tubing for the baja team and they added my order to it. The steel company they got it through is a one of the main sponsors of their baja and F1 teams so they take care of them real well. I doubt you could order through them since it was kinda of a inside thing plus they only order once a year before the season begins. ill try to post some pics they build some neat ****.


Motor monkey..

the way it was explained to me was they use regular mild steel wire (SD702) or something like that i think on the moly and there fore it requires no heat treating if chromoly wire was used then it would need to be treated. I dont understand how it all works so im jus going off memory.

 

The Pro Stock chassis did not come from Haas MIG welded. It would not NHRA certify if it were MIG'd. Haas is probably the most famous PS chassis builder in the country. A good friend more or less ran the Haas shop for a couple years . My friend had his own chassis shop in Tyler Tx. for years. A few years ago Victor Cagnazzi ( Jessica Enders old car owner) bought Todd's shop so Todd could head up his Chassis Engineering dept. I once asked where his MIG machine was. He said he didn't have one for fear someone MIGHT THINK he used it on chassis.

 

Im not really worried about passing tech otherwise i would make sure it was tigged im just playing the hand im dealt with. Will the car see the track sure.. will it be mostly street miles probably. im just concerned with the safety and longevity of it.



-john

 

The Hass chassis is tig welded. My boss bought the car as a rolling chassis. I just meant that he has had ta add some brackets and different little things for his application. He has tigged and migged on the chassis. You can weld mild steel to chromemoly, but i'm not sure what filler rod you would use. I have migged some chromemoly before just playin around and it welds just like mild steel. The strength i'm not sure about.

 

Can it be done… yes, should it be done… well...
- for that size tubing in CM to be legal you _have_ to TIG it and go at least 8/10pt
- I wouldn’t on something like the thin wall tube/cage setup. I would heat the area that you’re going to weld to at least a couple hundred degrees (normally you wouldn’t with a TIG but since a MIG is soo much faster you need to get some heat into the metal to guarantee the thin walled stuff doesn’t crack and to prevent hydrogen embrittlement) first and then run the bead, and I would even consider keeping it warm for a little while afterwards with a torch. What you’re looking for is a wider HAZ then you’ll get with the mig, something more like a TIG or even a gas torch weld.

Yep, no problem. Same filler and everything.

Depends on who you ask… If you read Formier’s chapter on roll cages in his metal fabricator’s handbook or the similar info in Carrol Smith’s books they flat out say that it is never safe to use CM in the safety structure around the driver.

It’s outlawed for roll cage structures in Cup type roundy roundy type cars.

Though if you control how long it stays hot and how fast it cools (largely dependent on how hot the base metal gets), it will be as safe as the NHRA/IHRA mandated TIG welded CM cage… well, assuming quality MIG welds.

OTOH, what are you building it for? Seems like you’re going to end up with a structure in the car that is not going to be even vaguely legal on any sanctioned track anywhere for any type of racing unless they don’t require a roll bar or cage at all. It will be in the way on the street, will technically need harnesses installed to be safe which are not DOT certified so they’re technically illegal on the street, and for that matter on some level or another the cage is illegal on the street in most states (for example, in MD they’re legal as long as you don’t have any bars intruding on your door opening, which means that your main hoop needs to be behind the B-pillar, you can’t have a door bar and your front bars have to come down inside you’re A-pillar, can’t go in front/around your dash)

Actually, recommended rods are (in order of preference as per most textbooks):
ER80S-D2
ER70S-2
ER70S-6
Which are all just normal, mild steel filler metals. You probably have some ER70S-(something) loaded in your MIG by default. Personal preference wise, I prefer the ER70S-2 over the 80… and I’m actually most likely to have S-6 around so I rarely end up using the ER80S-D2 unless someone supplies some for the project or I promise to use it for some reason.

 

Silverback,

thanks for the reply thats some good info... Il post up some pics of what were going to do here in a lil bit when i get back home to my computer.


I went with the .083 stuff since thats what all the other guys were running, using the torch to heat is a pretty good idea.

As for the car were going to build a 4link in to it so figure the standard 10pt type cage and then add in whatever additional bracing is necessary with any back halfed car. The car below is basically the jist of what were gonna do im gona run some of the bracing bars a lil bit different and narrow the rear frame down to around 24 inch or so. the car below is at 29 inch.

9sec93s car



-john

 

possibly something along these lines since i really like how the bars are set up.



-john

 

I havent been able to get on for a while.

Silverback, it looks like you changed your tune on tiging chrome. and especialey migging chrome. What did you learn about normalizing any chrome. welding.

Chrome. is where less weight is desirable and money is no object. I dont know if i would run out and use chrome. in a street car as painting it would hide the welds when you want to inspect them often.

 

In what way, I’m not following?

JPMuscle, I still don’t think I get it… why go to all that trouble for a setup that wouldn’t be legal anywhere?

 

basically it jus came down to I got a smoking deal on the moly so i figured why not...

As for not being legal at certain tracks, how do they go about testing your cages? I mean whats there to prevent me from saying my cage is mild and not moly, not saying that I would do it but how many tracks are going to inspect that closely?


-john

 

To be a cage, it has to be certified, and then they give it a sticker for what speed it’s legal to. Usually they’ll check the way and where the tubes are attached, the welds and in a lot of cases they’ll have you drill a couple of holes in key locations to check thickness or sonic check it. _I believe_ that the initial certification of any of the faster cages requiring CM the cage has to be bare, not painted so that the markings on the tubes can still be seen.

In your case it will be blindingly obvious that if nothing else you’ll either have too thin a wall thickness or the wrong type of welds.

If the car isn’t going to run 9.99 or 135 or faster then I guess it doesn’t matter since the 6pt bar doesn’t have to be certified, and I haven’t seen a tech inspector thorough enough to catch something like this in that case, as long as it’s the right diameter and has at least 6pts running to the proper locations you’ll be fine.

Where this can become a real hassle is say for fun you enter some event and win… well then if someone bitches “his cage isn’t right” and then if they check and find that it isn’t you’re usually automatically disqualified.

 

i'm taking a metallurgy class at our training center this week and the guy teaching it is a "forensic" metallurgist, meaning he's qualified as an expert witness in court cases involving all things metal...he's got some pretty good "c.s.i." type stories involving metal failings and how they found the culprit

i asked him what he thought about mig welding cm versus tigging it, and he emphasized that the post weld heat treat was the most important thing when welding cm

i'm taking another class next week that's taught by a guy who is much more into the welding side of metallurgy, the last time i talked to him he was getting ready to build an aircraft frame from cm.....he's also talked about some guys from the proving grounds coming over and doing different types of post weld treatment to cm roll cages to see what would be the "strongest" without becoming too brittle....i'll ask him what he thinks about it

 

jdustu, I would like to hear what you learn about that. I know what it takes allready but like to see what other people do. Im not a fan of migging cm but thats the way i was taught .
All the migged cm that i know of had failed and the type of weld a mig does, isnt benificial to cm.
I dont like the idea of laying a bead without control of heat and filler and another nice thing that tigging allows is a super small 100% weld.
I know i shoudnt have generalized heat treating as people get the wrong idea about procceces.
When i said peaple should learn about cm before anybody got hurt was proven in the confusion of this conversation. I dont know of any chassis builder who migs cm because it shure would save time. You could add brackets and small stuff but have to be carefule around existing welds.

 

F1 cars are actually pretty much all carbon fibre/honey comb type deal, im sure they do have some Chrome Moly parts on them though. However the suspension links, cockpit, and other structures on the car is all CF/HC.

I'm sure you guys covered it quite well, but as to the fact of people saying MIG is so much easier and faster, that's why the MIG stuff fails, because people get carried away and think it's such a breeze. If you put just as much effort and prep work into a MIG weld as a TIG weld it will be just as strong, providing a confident welder with experiance, etc.. Yes, it's still faster, but that's were trouble can start, especially for beginner's or someone in a rush. (if that makes any sense or w/e probably not im tired and i cant think of the words I wanted to put it in)

I don't personally own a TIG welder, but I would like to one day, Right now though attending college and being poor I will have to suffice with the MIG we have. I must say I am pretty confident about my welds, I have doubts on some things, sometimes, but I try to stay confident, as most the stuff I test I cannot destroy with out a torch, i know this isnt excatly the same test that they use to determine the strength and stuff but hey I dont have all that fancy stuff, I m just glad that I can't, cause that would be bad... eek!. ( The stuff I destroy is mostly things I make mistakes on or made to small or wrong sometimes I like to just see how strong or weak my welds are, for giggles, not really but yea.)

I also have never messed with Chrome Moly, not sure if I would want to or ever need to as it is so expensive and Mild works just as well, for the purposes I use it.

 

Ok, motor setup im putting together for my car should put me past 9.99 and 135 on the bottle, that being said it will be impossible for me to get my cage certified just becuase i did not tig my moly cage together correct? I know for fact that im good to go regarding the wall thickness since .083 is what all the other guys with 4130 are running. Even if i have all the bars in the proper place etc etc, I will fail due to the method of the welding? Thats pretty gay..

 

JPM before you do anything you should talk to a chassis builder who is currently building cars for your track and being cetified for your index.
Make sure you dont build to ihra specs and going to frequent nhra tracks. Talk to tech inspectors of your track and ask what they like to see.
I think if you check around first it will save you time and money plus all the headachs and bs going on here since none of us that i know of is building your chassis. You need to find someone local you trust and has the experiance of cm to do your work and back up your cert.

 

Actually, you might find CM parts in the suspension and possibly bits of the chassis, but you’ll only find parts that have been heat treated after welding/machining/fabricating.

If you’re really curious you can usually get a pretty good indication of the quality/strength of the weld by taking and welding 2 pieces together, grinding the whole thing down so it looks like one straight/flat piece, sawing through the middle (should be difficult if not impossible to tell where the weld is without acid etching, should be no pourousity), and then clamping it down in a vice and bending it over with a sledge hammer (or the same in a press). You should be able to make 90* with most metals, and the weld should fail the same time or after the base metal for most steels (welded aluminum is different, the welded area can be as much as 1/3 the strength of the original base metal…)

When it comes down to it I don’t think anyone here can show me an application that they would built that cold rolled mild steel wouldn’t be as or more durable then CM in…, at least not that they could demonstrate in practice.

 

Yep, that was exactly my point from the beginning.

If you built the whole thing out of >.118” 1018 (doesn’t even have to be DOM) and MIG welded it it would be legal, even though NHRA/IHRA rules imply that .120” mild steel is inferior to .083” CM, and what bothers me even worse is that if you built 2 identical cages, one out of TIG welded, .083” (and in some parts thinner is legal) and a second in .120” MS (tig or mig welded), even though the MS cage would be stronger, more rigid and safer, it would only be legal to 8.50 and the CM cage would be legal below that.

This is something that I’ve been trying to avoid for 2 reasons:
- talking to the tech inspector that certifies cages can usually lead you to some interesting conclusions, but the thing is that if you move and need to get it recertified you may not be able to because the new tech inspector might actually decide to follow all the rules in the book
- more than talking, but using a well known chassis shop is sort of the dirty pool way around the whole issue. I’ve seen tech inspectors look, see the name plate of a specific chassis shop welded onto the bar and then pass the cage without even looking any further.