Chassis/Cage Fabrication

[tomasharvey]

Andy,

I wanted to get some opinions on what process to use on car chassis fabrication. I know this really comes down to personal choice( car is carbon steel chassis) but I wanted some ideas. I have been GTAW welding for a few years and have passed ASME sec IX certs for tubing and plate. I have been SMAW for about 10 years and have passed the same ASME tests.

The question is, if I have never MIG welded before should I even consider buying a MIG to put a car together? I don't know if I should change gears so to speak and learn a new process. I have been meaning to try MIG but I just have not had the chance.

I do not have a welder and home. I am looking at the Millermatic 251 or one of the Maxistar GTAW machines. Any input would be appreciated.

Tom

[dyn88]

there are a few posts that are fairly current about this subject. Myself if I were to do this work on my own car I would tig weld it(the look is much cleaner). Be aware that some sanctioning bodys wont allow your vehicle to pass inspection if you have painted over the welds. Im not sure if you can paint after inspection of said chassis.

[wrench3047]

Harvey

where are you from. I knew a nathan harvey that was in the army. related?

[Bendaman]

The mm251 is a great machine. I have used mm251 and the mm210 for that
type of work. The mm251 would make a great addition to any at home shop.

[tomasharvey]

there are a few posts that are fairly current about this subject. Myself if I were to do this work on my own car I would tig weld it(the look is much cleaner). Be aware that some sanctioning bodys wont allow your vehicle to pass inspection if you have painted over the welds. Im not sure if you can paint after inspection of said chassis.

Dyn88,

Thanks for the reply. I have seen so pretty good pulse mig welds but I realize this option is not included in the base MM251. I would agree with the appearnace of a good TIG bead being superior to MIG.

You are right on the inspection. NHRA inspectors will not accept painted welds or any grinding of welds. They are very picky on wall thinkness of tubing and will normaly UT your cage to verify thickness...I think mild steel is 0.188" minimum. They use a visual inspection for the welds and verify that the bars near the head liner are 360 welds.

I am leaning towards TIG since that is what I am good at. It may take longer but at least I will know what I have got.
Tom

[tomasharvey]

where are you from. I knew a nathan harvey that was in the army. related?

SGT Joe,

I am from Maine. I am a Navy Reservest. My brother is a Capt. in the Army. I don't know a Nathan.

Tom

[Alex]

thomas,
Why would you want to spend the dough on a mig machine if you don't really have a use for it? Like has been posted already, most sanctioning bodies will require that at least the roll cage and suspension be tigged. Flip side, if you can tig and stick, you can mig. Question: why would they UT the tubing, but only perform a visual on the welds? If they have the capability to UT the tubing, wouldn't they have the capability to eddy current the welds? Or, at least fluorescent penetrant?

Be cool,
Alex

[Paul Seaman]

There are many types of car building and many different requirements. Most of the components on my 4x4 were built with mig. We can't assume that a build means NHRA and if I remember right that rule is for cars faster than 10's.
If your looking for a machine to build a car with and tig is what you want then buy a syncrowave or dynasty, the others wont have enough duty and amperage for you. The mm251 would be a bit of overkill, I would go for the mm210. If you plan to only build one car then buy a mm175 and your investment will be less and you should get about 80% back in 2 years resale.

All these migs are good models you have to balance amperage, duty cycle and dollars to come up with what is right for you. My bang for the buck award went to the mm210 which I own.

Hope this helps,

[tomasharvey]

thomas,
Why would you want to spend the dough on a mig machine if you don't really have a use for it? Like has been posted already, most sanctioning bodies will require that at least the roll cage and suspension be tigged. Flip side, if you can tig and stick, you can mig. Question: why would they UT the tubing, but only perform a visual on the welds? If they have the capability to UT the tubing, wouldn't they have the capability to eddy current the welds? Or, at least fluorescent penetrant?

Be cool,
Alex

Alex,

I don't have a machine at home. I was thinking mig for the speed over tig. NHRA only requires TIG for chromoly chassis and/or cages...which as far as I know can only be welded with TIG. I am only familiar with the 7.50 second certs. The 25.1 certs are different for Pro cars like John Force who is running 320 plus MPH! As far as the the UT, the chassis inspectors only use the small hand held machine that you would use to check say plate thickness. We use them a lot on ships to determine hull plate thickness.

The inspectors want to ensure your not using thin wall tube. Most guys I know at least dye pen check their work for their own safety. As to why the NHRA does not NDT sportsman class chassis welds, I don't know. I have seen some pretty bad looking beads that most NDT guys would fail soley on a visual check, but that have passed.

Thanks for the feedback. I think I will keep on TIG'n and forget buying a MIG.

Tom

[tomasharvey]

There are many types of car building and many different requirements. Most of the components on my 4x4 were built with mig. We can't assume that a build means NHRA and if I remember right that rule is for cars faster than 10's.
If your looking for a machine to build a car with and tig is what you want then buy a syncrowave or dynasty, the others wont have enough duty and amperage for you. The mm251 would be a bit of overkill, I would go for the mm210. If you plan to only build one car then buy a mm175 and your investment will be less and you should get about 80% back in 2 years resale.

All these migs are good models you have to balance amperage, duty cycle and dollars to come up with what is right for you. My bang for the buck award went to the mm210 which I own.

Hope this helps,

I sort of said the same thing to ALex but you can build an entire car to run 7.50 seconds with a MIG. I have a friend with two of them. NHRA is more interested in proper tube thickness and bar location for full frame VS. Uni-body vehicles than the welding process. I would bet a good stick welder could sneak by NHRA guys.

Thanks for the reply.

Tom

[tomasharvey]

Ok Guys,

I am going to stick to my guns and buy a TIG machine. I use the Syncrowave 180 and the Maxstars. just to open another can of works I am not overly impressed with the SD180's ability to weld Aluminum with AC.

Thanks for all the replies. Anybody want to sponsor my car...kidding.

Tom

[tomasharvey]

NHRA Cage welding

This is directly from the source...NHRA.

All 4130 chrome moly welding must be done by approved TIG Heliarc process; mild steel (or ST51) welding must be approved MIG wire feed or approved TIG heliarc process. Welding must be free of slag and porosity. Any grinding of welds prohibited.

[wrench3047]

Tomasharvey
Just Curious, The Guy I Meet Was From The Other End Of The Us. (oregon)