frame material? 2x3 1/4" or 2x4 3/16"

[boostedz31]

So Monday I'm going to buy the metal for my frame. Im building another fj40.. this one will be more hardcore then the current '74. I've done some looking around, and would like some input on the following.

My goal is maximum ground clearance, low vehicle hiegth, and light enough for air shocks.

2x3 1/4"

or

2x4 3/16"

which is lighter and which is stronger. Light is my main goal, but if its not strong enough, whats the point.

If there is a better option let me know. Thanks

couple specs on parts going into this.. 22re with tdo5 on propane, duals with 4.7 twin stick, ifs rear axle and fj40 front with longs and detroits.

 

[DWitcher]

2"x4"x3/16".

 

[JLHEEPETR]

Your steel provider should be able to give all of this information to you. If they can't I would find someone else to go to. That being said the weight part is fairly straight forward. Assuming that 1/4" mild steel has a weight of "1" per foot, (2+2+3+3)x12x1 yields a weight of "120" while (2+2+4+4)x12x.75 yields a weight of "108" so the 3/16 will be lighter by the foot.

 

[JLHEEPETR]

I did a little research for you today.
1/4" x 2 x 3 square tube is rated to hold 2900# evenly distributed over an 8' span (standing on end). 3/16" x 2 x 4 is rated to hold 3900# in the same way so it is both stronger and lighter standing on end.

 

[boostedz31]

awesome, thats the info i was lookin for. I called a drag car builder today, and he said he uses 2x3 .085 and recommends 2x3 .125 for offroad.. but i'm thinking 2x4 3/16 is the way to go..thanks again man, those were the numbers i was looking for.

 

[DWitcher]

The taller rail will displace side mounted body mounts better too. As in body mounts that are mounted to the side of the frame.

 

[BellyDoc]

2x3 3/16" wall is already ridiculously strong. I see no advantage to going up to 2x4 tube in the same thickness. I have a bunch of 2x3 3/16" in my build and it's totally overkill.

If you're going to cage the build, and tie the cage into the frame, then you're going to get a LOT of structural support out of the cage. You don't have to also build the frame as if the cage isn't there.

 

[boostedz31]

thanks for the info guys. i preciate it. BellyDoc.. its an honor to have you post a reply to a question of mine, your build is obnoxious and i have read it multiple times.

 

[bustanutley]

3/16 should be fine no question, 1/8s is fine from a structural standpoint, however, it will dent unless reinforced in exposed areas.

 

[BellyDoc]

I'm sorry... I've been totally obsessed with this KOH essay contest thing! I forgot that I was going to follow up... and thanks for noticing my build.

Are you planning to tie a cage directly to the frame?

 

[boostedz31]

yes, its basically a buggy with fj40 dash/cowl, hood and bib and bezel. When i went to pick up my metal, I asked some more questions about weight and strength. The 2x3 .125 is about 3 lbs a foot. 2x4 3/16 inch is over 8lbs for foot. I went ahead and ordered the 2x3. Local chassis builders say that it is plenty strong for my weight and purpose. I guess the use 2x3 .088 for the drag cars.


So now I have a bunch of 2x4 3/16 sitting in my shop. I'm not sure what i will do with it.

 

[BellyDoc]

Metal NEVER goes to waste. It may take a while before you figure it out, but it's ALWAYS going to get used. For example, 2" - 2(3/16") = 1 5/8". 4"-2(3/16") = 3 5/8". Those are the inside dimensions of the rectangular 2x4" tube. Remember that when you're making brackets and stuff. If you need to space 3/16" tabs that far apart, you can just cut parts out of this stock. My shock mounts are made of 2x material that's 3/8" thick.