Joined: Sun Feb 05 2006, 11:51PM
Location: Pa
Posts: 3064
It's usually 16 - 18 gauge sheetmetal in the structual areas. The thinner stuff ( 20-22 ) is used in the other places (most reproduction companys didn't have equipment capable of making stuff from the thicker gauges in the beginning, so they used 22 ga. which is like (IMO) using aluminum foil
BTW, I'm sure Scott will agree with me that when sectioning framerails you want some 3/16" or thicker plate plug-welded inside the rails to beef up the splice...... <span class='smallblacktext'>[ Edited Fri Mar 24 2006, 10:46AM ]</span>
Joined: Tue Oct 11 2005, 01:33AM
Location: Calgary, Alberta
Posts: 5893
stitcherbob wrote ... I'm sure Scott will agree with me that when sectioning framerails you want some 3/16" or thicker plate plug-welded inside the rails to beef up the splice......
Well, as an engineer, I'll disagree. Plug welding a plate inside doesn't make it stronger, it makes the joint weaker. The problem is welding changes the ductile strength of the frame rail and creates a very localized transition point at the weld. To add strength you must distribute the anomaly and the best way to do this is a tube within a tube approach. Do this with fish plates welded on the outside using an overlap of at least twice the internal span on the rail. In other words, if the rail is 3" wide, use 6" plates to externally overlap the joint. You have to be careful however that you don't make the joint too stiff because a frame must have some flex to absorb impact loads. It's a lot like fixing a broken fishing rod, too little and the joint fails, too much and it won't cast.
I am with ya both. I understand where Bill is coming from, but that would have left too much evidence of the repair. So we did plug weld in plates inside the frame rails.
I had contemplated pealing the trunk floor back to access the inside of the rails and do a more complete weld, but in the end we decided that might just open up another can of worms. And it was about that point we decided to add frame connectors. The connectors we added are probably the strongest part of the whole car, massive! We did peel back the torque boxes and overlap them directly around the rear rails.
And now in an effort to not totally hijack the thread- Dan, don't forget that B-Body pans and floors can be adapted for a C most of the time.
Joined: Mon Oct 10 2005, 10:45PM
Location: Lansing MI
Posts: 513
Thanks for the info.
I have seen what can be done with the B body parts, but quite honestly this is not that sort of project. The goal is maximum structural integrity for minimum cost.
When I got this car 3 and a half years ago, it had enough rust issues that it should probably be a parts car, however my intention has been to keep it as a driver, for as long as possible, so I am really not concerned with making the underside look nice, if it can be made solid for a lot less money.
AH! Then I would highly suggest the homemade frame connectors like my car has! Cheap, low tech, and strong!
They are fabbed out of square stock, and slip over the rear rails. One of the guys had a slick idea for fabbing a bracket to weld to the front subframe and then bolt and stitch the connector to that. But you could always weld directly to the subframe, it woud just make it more difficult to remove later.
Materials are probably $50, and could be done in a weekend if you knew what to do. They made a difference, really cut down on body flex, and I can now change both tires on one side with only one jack!
Joined: Sun Feb 05 2006, 11:51PM
Location: Pa
Posts: 3064
That's gotta make for one stiff, great handling convertible Scott. Does anyone know if SafeTCap/Auto Rust Technicians makes rear frame repair pieces? I know they came out with front rail and T-bar repair parts.
On the plug welds, in the resto biz originality and looks are very important. That is why all the repairs are done to the inside of the framerails. Plus, in the unit construction, all of the surrounding panels (wheelwells, inner quarters, rockers, shock crossmember, trunk floor, and package tray in sedans and coupes) spread the load so I wouldn't worry about flex or loss of flex with a properly done plug-welded box inside of a framerail repair. Just make the plug welds in holes that are about 1/2" in diameter and space them out to keep heat damage down. Then weld the cut lines to the box and each other.
Joined: Mon Oct 10 2005, 10:45PM
Location: Lansing MI
Posts: 513
Re: Frame connectors
I like the idea of the connectors. After looking at your pictures, and looking under the car, I think I see how they fit, but have a couple of questions.
There is a reinforcing rib across the floor pan where the rear seat foot area is, did you cut through that and place the frame connectors flush with the floor?
It looks like the bottom of the frame connector tube is slightly lower than the bottom of the rear frame rails, and the top of the connector is notched to fit under the frame, with plates on each side to hold the two together, is that correct?
I assume the width of the connector is the same as the original frame rails, do you know what the height of the tube is?
Dan, you got it! The rib was notched and the rails touch the pan. We didn't weld it to the pan. The shop didn't feel it was needed, and didn't want to risk warping the pans.
The top of the connectors were notched to slip over the frame rails. and the bottom was bent up to contour the rails at the torque box. So the rail slides into the connector. The connectors are one piece, except for the bracket on the subframe, whch is optional.
The connector stock has a 3/16" side wall! probbaly over kill, but no twist! The ID of the connector is the OD of the frame rail. 2 1/2" is sticking in my head. It is square stock. We had considered a 2.5"x3.5" stock and cutting them up into the floor pan for extreme strength, but finding the stock was difficult.
Probably the most difficult part of the whole thing is cleaning off all the undercoating crude to get clean metal to work with.