fixing a Model A frame

[phat46]

I have a Model a frame on my frame table, well at least the rails from a Model A frame. One rail is bent up about 7/8" at the front. I can see where the bend is and using a straightedge confirms my eye. Now I have to figure out how to bend this rail back down so it matches the other one better. I have no torches and I'm not sure heating it would be the best way to go anyway. The top of the offending rail has a dip in it at the start of the bend; I'm thinking that if I apply a BFH in the back of the dip, with the front of the dip supported, that it might help the rail move back to where it belongs. I'm open to suggestions and i can get torches if that's the best or only way. I added a pic to show the difference in the rails.

[wayne petty]

before.. you bring out the BFH.... have you measured it.. perhaps.. this frame horn is not up... the other is bent down...

what year model A ...   perhaps there are frame dimension charts available...


here is one i got off google images..

http://i89.photobucket.com/albums/k202/flatred53/AFrame-B.jpg


looks like the top if flat...

flip it over... see if it lays flat...


here is another...

http://www.showcars-bodyparts.com/ford206.gif


one last thing....  that frame jig looks new..     do you have one of those fancy laser levels.. that shoots a wide level beam...    

you already know this.. but just incase somebody else reads this...

make sure your table is level in all 4 corners.

 use some  masking tape tabs... with a precision line drawn an inch up from the top surface..    line up the level with the closest tab.. then see where the others are...   just to be sure...

[phat46]

Wayne, I'm pretty sure the rail is bent up, the o
ther rail is nice and flat on top. I have a six foot straight edge that lays flat on the top of the good rail and has a big gap under it on the bent rail. The one I think is bent also has the dip in it where it appears to start to bend, it's enough to see by eye.
The frame table has been used by me before and it's flat, straight and I spent an hour to make sure I had it level; it has adjusters on all six legs.

[GPster]

Model "A" frames are straight on the top. Turn it over and look at it that way. I would be afraid of using a BFH because it would concentrate the force on one small are and the bend is probably in a longer span. The way I would do it is with a long section of chain and a jack but because an "A" frame is channel it would require some thought to keep from twisting while trying to take a bend out of it.I've got in my favorites dimensions of an "A" frame but I'll need my computor wizzard to transfer it to post it here. Of course there are only three crossmembers in a "A" frame so it might be helpful to know how much of the frame you have to help with suggestions. GPster

[chris spokes]

here is a link to the tech section   by enjenjo

http://www.roddingroundtable.com/forums/viewtopic.php?t=4644

[GPster]

Here it is. GPster
http://olskoolrodz.com/forum/showthread.php?t=40401
[/url]

[phat46]

Thanks for the link to Franks tutorial, that gives me a few ideas.
Thanks Joe too, for the info, I see  that the top rail is indeed flat, my bent one isn't. I am only using the rails on this project, and maybe the rear crossmember, the rails are separated  now and I will soon cut the horns off the front.
Looks like the easiest way would be with a torch!

[unklian]

Frames are pretty thin, try a Propane torch.

[enjenjo]

You can probably fix that cold. It depends on where the bend is. I'm guessing it is near the firewall.

What I would do, is get a piece of heavy tubing, 2 by 5 or 2 by 6, and lay the frame on it with the outside face against the tubing on one of the wide faces of the tubing, with the bottom edge of the frame lined up with one of the narrow faces of the tubing. Then align  another piece of tubing to the bottom edge, so it laps onto the first tube, and can be clamped together. Then shim  the bottom edge at the bend, I would start with 1/8", and clamp the bottom of the rail tight to the tube about 2 ft away in either direction. You might want to put a spacer in the frame to keep it from distorting where it's clamped. Then, insert a block of steel, or tubing shimed to fit tight inside the bend.

Then use a fair size hammer working back and forth on the top flange, against the block inside the frame.What you are doing is stretching the top of the frame back into the correct shape. Lots of moderate hits is better than a few hard ones. What you are doing is unlocking the stresses that are holding it bent.

Then remove the block, and work the ouside face of the frame against the heavy tubing supporting it, while you still have tension on it.

The aim is to stretch the metal back into place. You may have to go back and forth several times.  You may also have to add more shim, depending on how bad it's bent, but from your discription it's not too bad.

If it won't straighten cold, then you can use some heat, but that usually complicates things. Hiiting it causes vibration, which is heat, but much more controllable. Heating with a torch does the same thing, just much more active.

As long as you work it cold, the metal tries to go back where it belongs. As soon as you heat it, it becomes happy where it is, and you have to force it back into place.

[chimp koose]

good advice again enjenjo. I once had to straighten a 30' x4'x 2" sheet of steel for a machining job. All the hammering was done on the concave side as was suggested with the peening side of the hammer to stretch the compressed side of the metal.