Frame question

[JayJay]

Folks, got a question on frame straightening. Early 30 frame, A280XXXX.

Frame rails are flat, and there is a bit of twist which I can get out by jacking on opposite corners. But the long cross dimension is out by about 1/8”. I’ve tried pulling the corners together but it springs back when I release the tension, so it’s pretty well where it is. I know that the proper thing to do (and what I’m sure Brent would do!) is to drill out the rivets, set it up on a jig and re-rivet. But practically speaking, is 1/8” racking significant? I’ve heard that body shops consider 1/8” to be acceptable. It may be that this discrepancy will lessen when I get the twist out.

Also, to confirm, the frame horns’ outside edge continues straight from the rails behind, right?

Thanks a million.

[Thodge]

I personally wouldn’t worry about 1/8” difference in your criss-cross measurement. Even our modern 3D electronic measuring system will say that within 3mm on a given measuring point is within tolerance. 1/8” “diamond” wouldn’t really affect the suspension on an A because because the wishbones tie in to the center line of the car anyhow. The frame would need to be clamped down on a frame machine and pulled if you wanted it any closer and I don’t think it would be worth the trouble.

[BRENT in 10-uh-C]

Yes, for me 0.125" is excessive. If the assembly is mounted onto a fixture and the cross-measurement is equal, then properly heating and re-bucking the crossmember rivets will correct this. When I use the term "properly", the key to doing this process is to use a small concentrated flame that directs the heat into the shank of the rivet. When done correctly, you will find the rivet beginning to turn red on the underside of where the heat was applied. At this point when the rivet is bucked from opposing sides with a great enough force, the shank of the rivet will swell and the top & bottom will tighten as the rivet cools and contracts. Once completed, the frame should stay within the same cross-measurements with minimal twist.

[JayJay]

Originally Posted by BRENT in 10-uh-C

Yes, for me 0.125" is excessive. If the assembly is mounted onto a fixture and the cross-measurement is equal, then properly heating and re-bucking the crossmember rivets will correct this. When I use the term "properly", the key to doing this process is to use a small concentrated flame that directs the heat into the shank of the rivet. When done correctly, you will find the rivet beginning to turn red on the underside of where the heat was applied. At this point when the rivet is bucked from opposing sides with a great enough force, the shank of the rivet will swell and the top & bottom will tighten as the rivet cools and contracts. Once completed, the frame should stay within the same cross-measurements with minimal twist.

Thanks, Brent. Although I would feel comfortable using the procedure you outlined, a frame and a large enough riveting gun and bucking setup to do this are outside of my reach. I know we had a discussion a few weeks ago about doing half-assed restoration work, but my inquiry was intended to see just what the consensus was on, for lack of a better term, "wear tolerance". I am a firm advocate of the "if it's worth doing, it's worth doing correctly" school, but in this case it would be a huge (if not practically impossible) stretch for me to go that extra inch. Or 1/8". And I'd like to use this frame, it's the original to what is an unmolested car.

And as attractive as it seems, it's not really practical for me to bring this frame to you across the country... unless you know of anyone here on the left coast that does this work.

[rotorwrench]

You might call around to local body shops and see if one has a frame straightening set up. Those rigs have enough power to pull it back to specs as long as the operator knows how to use it.

I use a 5X pneumatic rivet gun for the big rivets. There are larger ones but I've hot riveted some pretty big rivets with the 5X and an oxy-acetylene torch.

[Thodge]

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Jay Jay - when you measured your cross measurement did you only go from the very ends of the rails or did you also check it between the center crossmember mounting points? If the diamond still shows up when you check only the center section of the rails, then one is in fact further back than the other. If the center section is square but the measurements at the ends of the rails are off, then you probably have a sway where both rails are off to one side at the ends. What really matters in frame alignment is not so much the width between the rails but the distance of each rail from the imaginary centerline. The old school way of checking that is with centerline gauges which only shops that have been around a long time would still have, now everything is computerized but it gets the same result. I say again though, within 3 mm of the spec for a given measuring point is considered acceptable for the frame measuring systems.

[JayJay]

Originally Posted by Thodge

Jay Jay - when you measured your cross measurement did you only go from the very ends of the rails or did you also check it between the center crossmember mounting points? If the diamond still shows up when you check only the center section of the rails, then one is in fact further back than the other. If the center section is square but the measurements at the ends of the rails are off, then you probably have a sway where both rails are off to one side at the ends. What really matters in frame alignment is not so much the width between the rails but the distance of each rail from the imaginary centerline. The old school way of checking that is with centerline gauges which only shops that have been around a long time would still have, now everything is computerized but it gets the same result. I say again though, within 3 mm of the spec for a given measuring point is considered acceptable for the frame measuring systems.

Thanks for the input, Thodge. I measured front cross to rear in using two holes front and rear (the farthest front holes (radiator) and rear holes are elongated), then also approx center body mounting bolts to front and rear. I made some conical centering fixtures by turning a taper on some 1/2" nuts then lock-tite them to allthread. I then chucked up the fixture in the lathe and put a hole dead center.

I also measured using some 1/4" holes at the front of the frame members, I think they may be the hood latch mounting holes. Everything was pretty consistent.

What I did not do is measure for a diamond using the centermost body mounting bolt holes, fore and aft of the center crossmember. I'll do that today.

I did the measurements both using a tape measure as well as trammel points.

BTW, I do have some evidence that the car may have been hit right front, presumably a collision - bent bumper bracket, the right steering arm had been welded to the spindle (never seen that before!), front fender bracket may be twisted aft. That's the frame side that seems to be pushed rearward. So all this is not inconsistent.

[Thodge]

People would be surprised to hear that most frames back in the day were literally straightened by eye using centerline gauges. Three or four of them are hung down the length of the frame and you sight down the center pins just like aiming a rifle with open sights. It’s actually more accurate than measuring with a tape. Less room for error. They’re also very good for showing if one rail is higher or lower than the other.

[JayJay]

There are body bolt holes approx. 20” in front of and behind the center cross member. I measured across them with my trammel and the discrepancy is still there. I’m convinced it’s real.

Here are the centering inserts I made out of 1/2” nuts and all thread.

[Thodge]

Okay so there’s no question it has a small diamond in it. Just keep in mind that 1/8” in a cross measurement is probably only 1/16 or maybe 3/32” that the rail is actually back. If anyone can tell that difference in the gap between the bumper and the body from side to side, they’re Superman.

[JayJay]

Follow-up: Through the judicious and delicate application of chains, jack stands, floor anchors, come-alongs and senior citizens bouncing on the corners, a club member and I got my frame to about 1/16" diamond, no twist and flat rails. I'm going to declare victory and move on. It was an interesting experience, not one I'd go out of my way to repeat.

[Chuck Dempsey]

Thanks for the update, JJ.

[Planojc]

I think it was the senior citizens that did it.

[Cape Codder]

I must say 1/16" is sure close

jay-jay - In your opening thread you stated "I’ve tried pulling the corners together but it springs back when I release the tension, so it’s pretty well where it is."

I am not an expert doing this procedure, but I have read many times when straightening the frame sometimes one needs to go beyond when bending so when you get spring back it will fall into where you "really" want to be!

Just wondering why you didn't do it that way?

[JayJay]

Originally Posted by Cape Codder

I must say 1/16" is sure close

jay-jay - In your opening thread you stated "I’ve tried pulling the corners together but it springs back when I release the tension, so it’s pretty well where it is."

I am not an expert doing this procedure, but I have read many times when straightening the frame sometimes one needs to go beyond when bending so when you get spring back it will fall into where you "really" want to be!

Just wondering why you didn't do it that way?

Codder - When I pulled it crosswise initially the frame taco-ed on me because I didn’t have the corners secured. The movement in the cross measurement was all in the folding of the opposite corners, not in actual movement of the joints. That’s why it disappeared when I released the tension. So I stopped until I could get it to a location where I had floor anchors. The second time I pulled it I had floor anchors on the corners so the frame didn’t taco but instead pulled the way I wanted. Yes. I had to go beyond to allow for spring back.

Excellent question, sorry I didn’t make that clear.

And if I didn’t have access to floor anchors, I was prepared to leave it as a 1/8” diamond.