Weld subframe connectors loaded or unloaded?

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Dantra

Dantra

69 Dart.. AKA Butters
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Fab'n connectors now.. Weld in place with suspension loaded or unloaded? My doors don't shut great either way... Need alignment
 
The car needs to be sitting at ride height, all weight on the suspension. I tacked mine in just enough to hold them and then raised the car to finish weld them.
 
I did mine on cribbing under the tires and left the /6 and trans in the car. I felt it was important to keep the car loaded like it is when rolling down the road and "fix" it in that state. But it's just my opinion and the only car I have done it to so take it with a grain of salt.

I know of one car that had a bunch of chassis stiffening done to it on a lift and they struggled to get the panel alignments done after that. I think they bowed the chassis while on the lift and then welded it solid in that shape. But again, just my opinion.

I suppose if you could figure out if the chassis is bowed due to hard use, maybe you could bring it back into shape and then add the connectors, but not really sure how to figure that out. Maybe get the doors aligned and then put it on jack stands with the suspension unloaded and see if the alignment goes out?
 
DionR said:
I did mine on cribbing under the tires and left the /6 and trans in the car. I felt it was important to keep the car loaded like it is when rolling down the road and "fix" it in that state. But it's just my opinion and the only car I have done it to so take it with a grain of salt.

I know of one car that had a bunch of chassis stiffening done to it on a lift and they struggled to get the panel alignments done after that. I think they bowed the chassis while on the lift and then welded it solid in that shape. But again, just my opinion.

I suppose if you could figure out if the chassis is bowed due to hard use, maybe you could bring it back into shape and then add the connectors, but not really sure how to figure that out. Maybe get the doors aligned and then put it on jack stands with the suspension unloaded and see if the alignment goes out?
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If your car is all together and you aren't planning on doing any further work to it, put them in with load on the wheels. This will maintain all your panel alignments without changing anything you are familiar with. The downside to doing this is any wedge, damage, or mis-alignment that is present in your car will be locked in.

If its apart, put it on 8-10 jackstands, level and align the subframes to blueprint specs as called out in the FSM Body manual and then lock in the sub-frame connectors. This would allow you to put everything into an ideal position to dial in everything else going back on during re-assembly.

Dedicated race vehicles from reputable builders are built on a surface plate that is flat so the chassis is flat and square to begin with so any future damage can be assessed and repaired back to spec.
 
Keep in mind if you ever put real power to the chassis, it's already a pretzel
 
As long as you don’t intentionally put a twist in the car by significantly loading one corner and not the others it won’t matter a lick.

There are plenty of places, and numerous build threads on this very site, where frame connectors have been welded in with the car upside down on a rotisserie. Some really high end builds have been done that way and I haven’t seen anyone say they welded their subframe connectors in on a rotisserie and haven’t been able to line up their body panels.
 
I always loaded suspension except when I did my Ragtop. My upper door gaps to quarters were always tight before resto so I carefully hung the rear and welded up. Cured my issue but do not recommend this to anyone. Trust me I was pretty nervous doing this. Luckily it worked as planned.
 
I'm planning to do mine with the frame on jackstands, but only because I found that the doors and windows worked better with it that way. I lifted it up on a set of QuickJack scissor jacks to do all 4 tires the other day and noted how much better everything worked. I also have cracks on my rockers at the back edge of the door, so pretty sure my car is sagging already and could use a boost before getting stiffened up again.
 
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Exactly, the whole unibody structure was welded together "unloaded" and so my thoughts are, by welding them in with weight on the chassis, you allready have flex in the structure, and your welding in bracing to tie into a allready "stressed" structure.
 
replicaracer43 said:
Exactly, the whole unibody structure was welded together "unloaded" and so my thoughts are, by welding them in with weight on the chassis, you allready have flex in the structure, and your welding in bracing to tie into a allready "stressed" structure.
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I think the only way to get back to that point is to completely gut the car before doing any stiffening. No argument that doing the work while sitting on the suspension loads it, but on jack stands with a drivetrain flexes it the other way. And finding the "middle point" of that flex would be a flat out guess.

For a backyard build, I guess no drivetrain, front sheet metal or front/rear bumpers would be a close approximation?

Really the only way to do it "right" would then be a surface plate and bare chassis.

But in the end, unless the chassis has some issues, I would guess it doesn't make that much difference like Blu said. Maybe if you were building it for something like the Optima USCA series and needed 11/10th it would be important.
 
Dantra said:
Tossed them together a month or two ago... Why did I not make these years ago?? They're wonderful lol. Worst part is, Im a machinery maintenance / fab manager in a industry that is literally full of wood construction material.. I mean seriously, so much wood!
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I really liked having the car on them and will be putting it back on them soon for the T56 swap. But I hate getting them under the car. I split mine so I could go up in 2 steps and had to come up with a block to put on my jack to get the front end high enough to get the last level under the tires. Very nerve racking, maybe just because it was a new way to do it.

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I did mine unloaded kinda. Firmed up the rear a bit and a screw jack under the K member. Had the doors on and let them drag the bottom of the strikers a hair. Wild *** guess? Probably not. Been doing this **** for 40 years. I have some pretty good gaps.
 
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