Best steel thickness for frame?

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srgould41

srgould41

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Question for you experienced fabbers!

Rather than hack up my FJ40 frame and try to make it work I decided it might be best to fab my own frame. I am thinking 2x4 steel and attaching the 1 3/4" tube cage to it using plates and bolting through the body so it's removable. I found a pro build that did this, but I can't find the link now :(

Does that sound OK?

The 2x4 I have seen is .120, 3/16, and 1/4. I don't want to add weight for no reason, but I want it strong enough. So which thickness would be best?

Steve
 
how much HP & torque is your engine putting out? what size tires? for the most part i would just run 3/16 wall if you can find it. 1/4 would be overkill (IMHO) 90% of the time unless your running a built diesel on 40" of rubber....thats just my thoughts on it though
 
I plan to run a stock Chevy 350 and 37" or 39" tires. The roll cage will tie into the frame.

I was thinking that 3/16" would work well.

Think the frame would hold air? I know some people use their cages as a storage bottle for on-board air, but could the rectangular steel hold a bit of air? Would that stress it too much?
 
I vote 3/16" if you build good crossmembers and tie them in well. Try to spread the loads over a bit. I recomend welding the 2 halves of the frame together as you build it to make sure they are exactly like the other and then seperate them after everything is tacked. Once you start building the crossmembers check for square after every couple welds.

Round tube will always be better at holding pressure than square but at 150 psi it shouldn't be a problem. If you can weld an airtight seam then go for it. Only problem I see is moisture from the compressor building up and rotting it from the inside. Even if you added a drain.......... it' be just something to get ripped off.
 
i dont think i would use the frame as an air tank...yes, it would work if you can make air tight welds (if you cant then i wouldnt even consider welding up your own frame). however i wouldnt do it because of the moisture...enough problems with stock frames rusting out. would be a shame to put all that work into making a brand new frame just to have it rot out on you...
 
Very good points on the rusting issue with moisture inside the frame. Duh! What was I thinking?

Thanks for all the input!
 
srgould41 said:
Question for you experienced fabbers!

Rather than hack up my FJ40 frame and try to make it work I decided it might be best to fab my own frame. I am thinking 2x4 steel and attaching the 1 3/4" tube cage to it using plates and bolting through the body so it's removable. I found a pro build that did this, but I can't find the link now :(

Does that sound OK?

The 2x4 I have seen is .120, 3/16, and 1/4. I don't want to add weight for no reason, but I want it strong enough. So which thickness would be best?

Steve
Click to expand...

Hack the stock frame.
 
ah....cut the serial number out and just welder 'er onto/into the new frame! they never check the #'s where im at but...could be a problem there i guess.
 
.250 is overkill but will never give up the ghost

.188 is great matches thickness of most off the shelf brackets and tabs.

.125 is ok but you will need to spend a little more time in prep and you will need to know how to weld to make it strong and not rip. it is easy for a novice welder to burn to hot and under cut 1/8th inch.

My vote would be the .188 or 3/16th's

Cam
 
2x4 design so much stronger to begin with then the C, so thickness does not relate at all really.

2x4 .083 wall edit seen mention now of sandwich cage might do .120

gusset any through holes, sleeve if compressing against it. same with breaks or butts.

I do prefer full cross support both lower and upper of the rails. ie 4 inch thck, do not do a trans cross hangin on only 2" of the rail.

full tie in cage anyway, tie through to front hoops, engine/rad tube.

matkins, Formed BENT frames made for production running with or without cage.
regular frame .125 formed walls down to .083
xtra HD frame .188 formed walls down to .130 to slightly less
Do have over the 2x4 just to give some strength back.

Just for another reference i have never seen a production box frame even hydro formed thicker then about .120, granted they have strength in bent walls, but we have full strength in the tied in cage throughout. also older production frames : mini toy, wrangler, etc...

sandwich, 3-4 bolt, and run shear pegs.

Running cage to protect and support or tie into most of the stress points anyway, weld in more ideal and can have more points.
 
Stock Frame Thicknesses

Hoping this is the right place for this. What are acceptable frame thicknesses in 60 series cruisers? By this I mean, if I find one with rust, if I caliper it what would be a good number for the thickness?
"Just for reference, the stock frame is 3/16" outer & 1/8" inner. I also vote for 2 X 4 X 3/16"."
 
Here is what I want to do

I really liked this frame done by Campbell Enterprises. It's what gave me the idea in the first place.
 
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