Custom suspension arms and welding

[BBBrad]

Hi there, just got a couple of questions to do with custom made suspension arms. I'm building a McRae Porsche 550 that has had custom made double wishbone arms made for it instead of the original vw swingarm setup. The work looks of very high quality and was told years ago that it was done by a McRae workshop tech, who is now long dead. That's the reason the car has been sitting untouched for a long time. Trouble is according to the hobby car manual it says that the arms have to be tig welded. Mine are all mig'd. Maybe the rules had changed from all those years ago? I have no dought of the strength and quality of the work, but it's not to the rules. To throw a spanner in the works I see you can buy all kinds of custom suspension arms on the likes of trademe etc, I suppose a lot made in china, that are all mig'd. (Some of them look very questionable!) how do these arms get through a cert etc?
Any advice would be a great help. Cheers.

[Grrrrrrr!]

Best thing to do would be to talk to the guy you intend to have do the certification. Take the arms along and explain the situation and see what he says. If he accepts they were made by a McRae tech and they look like good quality he may just decide they are effectively OEM parts.

[wde_bdy]

As said, talk to your certifier. Crack testing is going to be the minimum you have to do, quite possibly a grind off and re-weld job.

Callum

[evil_si]

Weve had to grind up mig'd arms and re weld with tig in the past,
The mig'd ones were crack tested and all, but certifier wasnt going to pass them.

As said best to talk to your certifier, take them and show him perhaps, certifiers all seem to vary a bit,

[touge_ae101]

there is a small fee when getting a cert to have the arms xray'd. this is a good non-destructive way of testing the arms.. from memoryit is ~$120

as for mig vs tig; tig gets better penetration and leaves a tidier weld but with a lot of structural type stuff a mig will give a stronger weld as it adds more beef to the part and is really easy to get right. I'm sure your arms will be fine! might be worth replacing the rose joints though if it has been sitting. make sure to use the teflon lined (expensive) ones though not cheap ones for suspension arms.

[Burning Angel]

a mig will give a stronger weld as it adds more beef to the part and is really easy to get right.

while mig welding appears to be easy at face value i think you'll find its the hardest of all the welding processes to master.

that may sound like im talking crap but when you actually do testing on mig welds that "look good" most will fail.

for example we recently got most of our welders at work certed and all but one failed mig first time(even though the welds looked fine)

I think people think its easy because you just pull the trigger and weld happens lol.

[d1 mule]

If you have a proper good welding machine / rig,doing MIG is a piece of piss, but witha $2000 dollar rig from super cheap / repco, of course it aint gonna be amazing every time