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-   -   5" square tube frame rails (http://www.hotrodders.com/forum/5-square-tube-frame-rails-212422.html)

belchfire 01-13-2012 12:32 PM

5" square tube frame rails
 
My '53 Studebaker pick up has seen a lot of different drive trains and chassis over the last 40 years. I will now embark on the last and best chassis that I hope to build. I have a '97 T-bird IRS and will get a '03-'07 crown vic front susp. I'll be running a Ford 300" six with an AOD 4 speed auto. With 12" &10" discs, rack &pinion and all 4 wheels independent, the handling should be spectacular. The problem, of course, is that I will be using a ladder frame. I've seen a lot of frame articals and they look rather flimsy. 2x3 tube may be OK for a weekend roadster, but mine will be a daily driver and will compete with today's machines. I'm thinking of using 5" square tube .125 wall. Mainly because I already have some. With some well placed crossmembers it should have good torsional stiffness. Being only .125 wall, I calculate that it should weigh around 350#. I don't know how that compares in the frame world, but it didn't seem that heavy to me.
Just looking for some feedback and if there is some glaring no-no that I may be missing.

nine4gmc 01-13-2012 12:39 PM

i am body dropping a yukon and it is common to use 3"x5", 3/16" box for the rails, this is a large heavy suv though and requires the thicker wall. i would think your 3x5 1/8" could work but lets hear from some car experts.

matts37chev 01-13-2012 12:41 PM

when you say 2x3 tube seems flimsy, think about what that stock ford parts donor frame is made from

matts37chev 01-13-2012 12:46 PM

Quote:

Originally Posted by nine4gmc
i am body dropping a yukon and it is common to use 3"x5", 3/16" box for the rails, this is a large heavy suv though and requires the thicker wall. i would think your 3x5 1/8" could work but lets hear from some car experts.

I think he is planning on using 5x5 1/8"
I think it will work ok, but I think what you are using( 3x5 3/16") would be better

belchfire 01-13-2012 10:25 PM

frame
 
I was comparing a '76 1/2 ton ford frame which is under it now and it is 5x3x.187 channel. There was a possibility of a > '97 dakota frame and that is 6x3 rect (I think). Didn't the 427 cobra use 4" dia x .090 tube? I don't plan to do any heavy hauling with it and I think that's why the truck frames are over built. If I were to buy new steel, I was leaning towards 5x3x .187.
5x3x.187 comes in @ 9.68 lbs/ft and 5x5x.125 is 8.27 lbs/ft. Seems that I could have a larger cross section and greater torsional rigidity and lighter weight. Since the sub frames are complete units, I don't think that there will be a lot of concentrated dynamic stress points where the wall thickness will be an issue.
Point is that steel ain't cheap and I already have it.


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