Technical Are '35-'40 Frames Bowed?

While taking some measurements on the frame of my '40 Coupe, I noticed that the side rails have a downward bow in the section between the front & rear kick-ups. This area looks straight and parallel to the ground to the naked eye, but now I'm wondering if my frame is sagged. The doors fit fine, with even gaps before I began a body-off rebuild. Wescott's drawing "appears" straight in this area. What's your experience been?

 

They are definely "bowed". I just used some repair sections on my '41 truck frame and they were formed on a press and were not bowed. Therefor I had to add some slices in a couple of places to try keep the right side rail level with the left side. Also the cab sits on wood blocks and they are curved on the bottom. I sanded the bottoms to match the repaired frame so the cab floor remained level at least side to side. If your frame isn't rotted or otherwise damaged and the body fits , you're good to go.

 

Hi, I have experienced the same when trying to set a ‘40 frame level i my welding jig.
Regards Uffe


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Yes, they are bowed, or sway backed. The center of the radiator X is also lower than the rails.

 

Thanks, Joel. My side rails aren't corroded as bad as some that I've seen, especially the right-hand side. It seemed inconceivable that a 5-1/2" tall section could be bent so uniformly in its vertical plane while leaving the upper flanges remain perpendicular and unwrinkled.
I discovered that patch sections are available, but I've got to check with the suppliers, as I suspect they don't incorporate the curve. That might work okay on a coupe, which doesn't use wooden pieces between the body and frame, but I believe your method of making some cuts to allow incorporating the bow would be the better solution.
Also, thanks for posting the links. I spent a a couple of hours reading the stories that others shared.

 

Thanks

Thanks, Dr. for sharing your experience.

 

The curve in the rails is probably not as critical because the car bodies don’t sit on the main rails the whole way. The B pillar and the next one back sit on the “ outriggers” that are riveted to the main rails. The holes for those are pre-punched in the repair pieces. Also the bodies sit on rubber pads and usually some shims are necessary. BTW the only repair pieces I would use come from Joes Antique Auto.


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