Chassis Stiffening
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Joined: Jan 2012
Posts: 84
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From: Columbus, OH
Chassis Stiffening
Hey guys,
I have an 83 chassis I'm putting a turbo engine in and plan to race in the future. I'm in central Ohio and would like to compete in NASA, PCA, and SCCA non-spec events.
The car is currently down to the bare frame. I have a good welder and was considering doing some seam welding to increase rigidity and strength. Does anyone have experience with this on a 944? If I'm going to do it, I'd like to while I've got it stripped down before paint.
Will this disqualify me for races such as GTS events? I've looked through the short info on the series but didn't see anything regarding seam welds.
Thanks guys!
www.designed4racing.com
I have an 83 chassis I'm putting a turbo engine in and plan to race in the future. I'm in central Ohio and would like to compete in NASA, PCA, and SCCA non-spec events.
The car is currently down to the bare frame. I have a good welder and was considering doing some seam welding to increase rigidity and strength. Does anyone have experience with this on a 944? If I'm going to do it, I'd like to while I've got it stripped down before paint.
Will this disqualify me for races such as GTS events? I've looked through the short info on the series but didn't see anything regarding seam welds.
Thanks guys!
www.designed4racing.com
Three Wheelin'
Joined: Jun 2003
Posts: 1,971
Likes: 134
From: New Zealand
the answers you got in your pelican thread were pretty good. also have a look at these
https://rennlist.com/forums/924-924s...eavy-pics.html
i'll try and find his 924board build thread.
Bass has been away from rennlist and 924board for some time so unsure if you ask him anything whether he'll respond.
https://rennlist.com/forums/924-924s...eavy-pics.html
i'll try and find his 924board build thread.
Bass has been away from rennlist and 924board for some time so unsure if you ask him anything whether he'll respond.
Three Wheelin'
Joined: Jun 2003
Posts: 1,971
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From: New Zealand
Burning Brakes
Joined: Jan 2007
Posts: 1,213
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From: Austin TX
Having an integral roll cage is probably required - and it will certainly stiffen things up a whole lot. Compared to most 80's hatchback sports cars - the 944 has a really nice frame. Its galvanized, its thick gauge metal, and they didn't chince on the number of spot welds. They are nice solid ones. Again - for the street - this car has a really stiff frame compared to most other factory cars I've driven - even modern ones.
Rennlist Member
Joined: Aug 2003
Posts: 4,779
Likes: 104
From: Midwest - US
Would all depend on what class you plan to run - but yes, seam welding can be illegal. Sometimes even reinforcement of suspension pickup points is not allowed. PCA just approved welded repair of pickup points within the past couple years for stock class cars. SCCA can be real strict on this type of thing, depending on class (although a 944 w/ a 951 engine will have to run in a regional ITE type class, which has pretty open rules).
Do you have the undercoating stripped off the tub? Acid dipped? Otherwise, the seam welding is a big pain. The undercoating and seam sealer are flammable.
Honestly, I think the seam welding done in the 924 build link is excessive. Mostly a waste of time. There may be some benefit around suspension pickup points, but very hard to prove that. Fatigue failures that I have seen on 944 tubs are always cracks near seams, I have never seen the spot welds pull apart. So re-welding the joint will not preclude the flexing of the sheet metal adjacent to the joint - so little increase in stiffness. Only improvement would be to add sheet steel patches to reinforce known/expected failure points; I dont think MIG stitch welds by themselves will help much at all.
Certainly the design and installation of a quality cage is dramatically more important to chassis stiffness than stitch welding over top of spot welded body seams.
Do you have the undercoating stripped off the tub? Acid dipped? Otherwise, the seam welding is a big pain. The undercoating and seam sealer are flammable.
Honestly, I think the seam welding done in the 924 build link is excessive. Mostly a waste of time. There may be some benefit around suspension pickup points, but very hard to prove that. Fatigue failures that I have seen on 944 tubs are always cracks near seams, I have never seen the spot welds pull apart. So re-welding the joint will not preclude the flexing of the sheet metal adjacent to the joint - so little increase in stiffness. Only improvement would be to add sheet steel patches to reinforce known/expected failure points; I dont think MIG stitch welds by themselves will help much at all.
Certainly the design and installation of a quality cage is dramatically more important to chassis stiffness than stitch welding over top of spot welded body seams.
Nordschleife Master
Joined: May 2004
Posts: 6,446
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From: Altered States of America (B'ham)
I would definitely check the rules for your class before going forward.
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Rennlist Member
Joined: Aug 2003
Posts: 4,779
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From: Midwest - US
In the end, I think it was a waste of time and would not recommend for others to do much of any seam welding, and I will not do it again on any future builds.
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Rainman
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Thread Starter
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Joined: Jan 2012
Posts: 84
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From: Columbus, OH
Thanks for the responses guys. Sounds like it's a no go on the seam welding. The car hasn't been acid dipped, and would be quite the process to remove all the undercoating. Seems like the general consensus is that it won't make much of a difference anyway. I'll put my efforts into a cage.
Thread Starter
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Joined: Jan 2012
Posts: 84
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From: Columbus, OH
Thanks for the info Chris!
Where were you before painting?? Lol based on the opinions i got here there isn't much for me to gain by doing the welding.
I hope to see you at an event this summer!
Where were you before painting?? Lol based on the opinions i got here there isn't much for me to gain by doing the welding.
I hope to see you at an event this summer!
Rennlist Member
Joined: Jan 2003
Posts: 15,225
Likes: 7
From: Burlington ky
good luck with the project! Even a rear rollbar stiffens the chassis enough that ive felt a difference, but a full cage is rock solid. Let me know if you need any advuise with the turbo motor swap, ive done a few of these before. BTW_ i showed Dale your website with pics of his old car and he was amazed.
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Joined: Aug 2003
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From: Naperville, IL
I really hope you can make it out. Lots of new faces in 2012 so it should be a great season!
