PDA

View Full Version : thickness of tubing for frame



Schroeder
10-07-2015, 01:53 AM
I am going to be making my own rear frame clip to replace the stamped frame rails on my 77 trans am. I want to use 3x2 rectangular tubing with .120" wall thickness. That's 11 ga. I want it to be able to withstand anything I throw at it. Is this thing enough or do u guys recommend something else?

19,69camaro
10-07-2015, 10:55 AM
Thats what I used. you can get away with even less if you use a cage

raustinss
10-07-2015, 03:38 PM
I'd agree ,that's more then enough for a uni-body car . I would recommend that you tie your home made rear section to the front sub-frame to act as sub-frame connectors. For extra support make them similar to those made by DSE,going thru the floor and welded for extra strength and handling lateral loads. Good luck and post some pictures for us

Schroeder
10-08-2015, 02:53 AM
Thanks guys. I planned on doing that with the subframe connectors. It will have s full frame under it now.

Do u guys move ur shock mounts inboard then or do u fab them into the tubing to keep stock location. I planned on fabbing them in stock location but others move them in.

raustinss
10-08-2015, 07:18 AM
i would say its a six here half dozen there kind of a thing what would be more important would be making sure that the angle is kept the same if, it were to be changed that then changes the necessary spring rates which is easily figured out with some math. that same math is well beyond my abilities to tell you how to calculate it but im sure someone on here can chime in and guide you thru that

19,69camaro
10-08-2015, 07:43 AM
You will get the best response time from the shocks if they are mounted as far out as possible, but still have a reasonable angle like Ryan said.

Schroeder
10-08-2015, 11:35 AM
This is exactly what I was wondering. ..the springs are affected when you move inboard. It's a simple lever/moment calculation (forcexdistance). I didn't know if anyone else considered this. I'll cut pockets out of the tubing and fab my own brackets in their stock location.

When u guys but weld pieces of tubing together to follow a bend or whatever do u put internal or external gussets? I planned on drilling holes near my cuts, putting a small piece of 1/4" thick stock in the tub, plug welding thru the hole, and then doing the same when I bring the other piece of tubing in to but weld it.

I am also concerned with bracing for the time when the frame rails will be out of the car. What is the best method. I am planning on tacking a couple of long pieces of angle iron from the tail panel to rear seat sheet metal piece. I thought of using some long pieces and going from the tail panel all the way to the firewall, but I don't think much will be gained. Maybe a "gusset" piece of angle iron should be welded from these braces up to the package tray at a 45° angle. Would these 4 pieces be enough in accordance with a couple bottle jacks? What do u guys do? Maybe I have to upload a drawing to illustrate what I'm talking about.

raustinss
10-08-2015, 02:19 PM
yeah toss a drawing up here ...you lost me ,not that thats hard to do

Schroeder
10-08-2015, 05:43 PM
The bracing is shown in the pic. Is it enough? I'd like to think bottle jacks are enough. Problem is that they settle

Schroeder
10-08-2015, 05:50 PM
I forgot to add a picture of what I meant about adding the internal gussets at tubing butt welds for added strength. I was wondering if u guys did anything like this or if u just butt welded the pieces together and called it good enough.

raustinss
10-08-2015, 06:22 PM
Yes those gusset plates will work another way of doing it is a diamond shaped piece on the outside of the steel tubing. The diamond shape would be mounted in a way that a "point or corner " is towards the sky and another to the ground, like a compass if you can imagine. This would be placed directly overtook of the welds which have been ground flush. This is sometimes referred to as fish mouthing or fish mouth plates. Common in transport trucks when guys stretch the wheelbase. Now as to the angle iron drawings yes they will help keep things flat and true when you cut out the factory "frame rails "

Schroeder
10-09-2015, 01:15 AM
Thanks for the reply. The thought behind the internal gussets is purely cosmetic, but the diamonds wouldn't look bad on the outside either. People won't see that anyway. Would u do even MORE for bracing when cutting out the rails, or will this suffice?

raustinss
10-09-2015, 04:37 AM
Ultimately you can never have too much, now you must keep in mind not to put any braces that could be in the way of what your end goal is. Otherwise that's a waste of time. Placing braces on angles and from one side of the car to the other is what you want to keep things square. As for the bracing material 1"square tubing is cheap and strong enough. Google some videos of guys replacing their floors or quarters you should see them bracing the bodies, this would be similar to what you want to do. You could also just do one side of the new frame rail maker sure it's exactly what you want, copy it so you have the second made then put the first one back into the car,cut out the one for the second side and toss the new one you already made in.then its a matter of adding the cross members and such.

Schroeder
10-10-2015, 05:35 AM
That bracing is just for keeping things square when o cut the rails our. It isn't permanent. Sorry if I confused u

raustinss
10-10-2015, 05:50 AM
No I knew that but,you will want some going from side to side as well.eg a "X" In the truck

Schroeder
10-10-2015, 10:31 AM
Oh, ok. My bad. I see what u mean.. I will do that too. Thanks. Do u do many measurements before u cut stuff to verify after u have the rails back in? I'm trying to think of a good spot to measure and how to do it. Maybe this part will become obvious as I get under the car and cut???

raustinss
10-10-2015, 12:34 PM
The more measuring the better...again do one rail at the time, either use the laser level to project a line or a piece of tape. Then take some measurements from that. Place one new rail in and again measure from that same mark. Once the measurements are you same you know that they're in the same spot as the old ones

ford396
10-10-2015, 04:00 PM
118247

Here is my frame that I made out of 2x3 tubing w/.120 wall. You can see the diamond plate that I installed over the joint. I thought this may give you a good visual of what was being discussed.

raustinss
10-10-2015, 06:07 PM
118247

Here is my frame that I made out of 2x3 tubing w/.120 wall. You can see the diamond plate that I installed over the joint. I thought this may give you a good visual of what was being discussed.

That's awesome of you to do that thanks ....was trying to see if i had any pictures from years ago in school, yes thats exactly what i was reffering to . those gusset plates will now distribute any stresses along the frame .therefore increasing the strength of the welded joint underneath