Author Topic: chassis welding question  (Read 10169 times)

Offline janjon

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chassis welding question
« on: January 21, 2014, 02:09:56 PM »
Hello Roo and everyone:
 I have seen pictures on build threads that suggest that maybe some folks don't fully weld every chassis joint in place and on the jig.
I am in the learning process of TIG welding, I have been welding up angled and notched joints, but "cheating" by repositioning the weldment to the easiest orientation to avoid awkward out of position welding. At least to this point. Obviously I would like to (and eventually will) become proficient to the extent I can weld anything, anywhere. Ha.
 My question is, would it work to tack everything really well, weld the accessible joints as fully as possible, avoid overhead welding and joint sections that would be really awkward to get at, and remove the structure from the jig and position it to make any uncompleted welds as easy as possible to complete? I would think in that case one would want to pay attention to symmetry of progress, maybe working side to side, and one end to the other, for example, to avoid distorting the structure overall.
 Or would you say don't even attempt a chassis build till you're fully competent to weld it fully on the jig?
Just keep the same amount of stuff on the right
as there is on the left. Seeing straight ahead is highly overrated....

dreracecar

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Re: chassis welding question
« Reply #1 on: January 21, 2014, 03:18:14 PM »
Tack on jig fixture--- weld off, get some books on welding airplane frame stuctures to learn about welding sequence.

Offline rooman

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Re: chassis welding question
« Reply #2 on: January 21, 2014, 05:26:00 PM »
Bruce is correct. It is virtually impossible to get to all the junctions while the car is on the jig, let along do a quality job of welding them. As noted welding sequence is important and the aircraft guys (old school tube frame stuff) have it sussed out.  Don Long told me that when he started out he welded one entire side of a car and then realized that the chassis had a big bow in it due to the concentrated heat input.

Roo
Yeah, I am from the south--any further south and I would have been a bloody penguin.

Offline janjon

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Re: chassis welding question
« Reply #3 on: January 21, 2014, 05:40:54 PM »
Thanks for the input!
Just keep the same amount of stuff on the right
as there is on the left. Seeing straight ahead is highly overrated....

Offline wideopen231

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Re: chassis welding question
« Reply #4 on: January 23, 2014, 08:25:54 AM »
I am in process of finish welding my car. I try to only go 1/4 to 1/2 way around  joint then move to next area.I think 1/4 maybe better but when a weld is going great and its so pretty its hard to stop.   I also alternate front to rear.   When a joint is finished I hit it with spray primer to help avoid missing any.   I have been told  1 amp per thousandths of material and  told er80s is tronger weld then the 70 I tacked with.Hoping mixing the two will not cause issue.    Maybe Roo can give advice here. I also try to get chassis upto 60 degrees for little while before welding on it.   Not sure how important but have heard few comments on that also and figure it can not hurt..
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline KeithDyer

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Re: chassis welding question
« Reply #5 on: January 23, 2014, 10:26:27 AM »
I am in process of finish welding my car. I try to only go 1/4 to 1/2 way around  joint then move to next area.I think 1/4 maybe better but when a weld is going great and its so pretty its hard to stop.   I also alternate front to rear.   When a joint is finished I hit it with spray primer to help avoid missing any.   I have been told  1 amp per thousandths of material and  told er80s is tronger weld then the 70 I tacked with.Hoping mixing the two will not cause issue.    Maybe Roo can give advice here. I also try to get chassis upto 60 degrees for little while before welding on it.   Not sure how important but have heard few comments on that also and figure it can not hurt..

FWIW - Knew a guy that used a high alloy rod (1 1/4 cr) to weld his CM car together. 

When he crashed, came apart pretty easily. 

Think there is something to be said for using mild steel rod on your CM chassis, the weld puddle will be a bit more ductile. 

Also knew a guy who would torch his completed welds dull red, wrap them, and let them cool slow.  You would know his name if I mentioned it . . . . .

Take care, K

dreracecar

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Re: chassis welding question
« Reply #6 on: January 23, 2014, 10:30:52 AM »
The only problem with post weld heat treatment is that if done incorrectly is worse than not doing it at all and you wont find out till its too late.

Offline wideopen231

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Re: chassis welding question
« Reply #7 on: January 29, 2014, 11:55:26 AM »
Roo Man,

 What filler rod do you use on CM? How about temp of materail while we are asking questions.
« Last Edit: January 29, 2014, 01:01:47 PM by wideopen231 »
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

dreracecar

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Re: chassis welding question
« Reply #8 on: January 29, 2014, 12:09:40 PM »
I use ER70s2
keep it sealed in tubes till I need it

Offline rooman

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Re: chassis welding question
« Reply #9 on: January 29, 2014, 01:27:19 PM »
I am using ER80 but have used 70 in the past.

Roo
Yeah, I am from the south--any further south and I would have been a bloody penguin.