Frame Rail Thickness

[cheapta]

I'm in the beginning stages of my first full-frame build on a 65 Nova.I have everything pretty well designed in my head but,as I get closer to the actual chassis construction I have to make a decision on frame rail size.
I'll be using 2"x3" mild steel but what thickness should I use? I was originally going to go with .087" wall but now I'm thinking that may be too light. 3/16" seems like overkill,maybe something in between?
What have any of you guys used?

Peter

[Paul_J]

As a good starting point look at what the frame builders are using. Art Morrison uses .120. That's what I use but my opinion counts a lot less than the big guys!

[MrQuick]

.120 is a standard.

[CraigMorrison]

The frame rail height plays a big role in how strong the tube is as well. Are you going to run a full cage? If so you should be fine with 2X3, but if not, you definitely need to go 2x4 or you are going to get a lot of flex along the beam of the chassis.

[rocketman]

If doing a frame only build(no cage) you need to use 2x4, 2x3 you can't strengthen enough to not twist or flex. Now if building a cage with it I would go 2x3 with a .095 wall cage, but only use DOM tubing for the cage.

[CraigMorrison]

Another way you can do it is to run a tunnel the full length of the car. We did some experiments, and if you do a 10gauge sheetmetal tunnel from firewall to rear of car, it will to a lot to stiffen the car up! It should be about 10" high and10" wide. If you don't want to do that, then you should go with a cage. I have a 40 Ford coupe with a 2X3 chassis and 8 point cage. Cage is welded to the chassis and I can still hear the cage creak (flex) when I am going across steep driveways, twisting the car, etc. It's pretty amazing to hear.

The cage is NHRA legal, and is .134"!

Are you just looking to save weight with the 2x3?

[fiorano]

yeah 0.120 is standard cage material for all scca stuff about 3K lbs.
this is good

[Paul_J]

Thanks Graig for the tip on the tunnel.