Chassis Tube Size

[wellis77]

Building a full chassis for my project and had a discussion yesterday with a member about my build. As we were talking through some clearance issues, it was mentioned to run 2" x 3" front frame rails while using 2" x 4" tube for the rest (perimeter and rear rails). The 2" x 3" would give me an extra 1" of clearance and make packaging a bit easier. I have read posts by a couple well respected engineering minds that if you are not running a cage, use 2" x 4". I'm not planning a cage but can I get away with 2" x 3" front rails while the rest is 2" x 4", or would I be asking for trouble? Thanks.

[Bryce]

Calculations would be needed but 2x4 is a safer bet.

Is there any way to run down bars from the firewall to the front of the frame rails. This would help triangulate the frame. Also a brace across the engine to tie both sides of the suspension together.

[wellis77]

I can definitely run down bars and if I were to run 2x3 I would definitely run them. I have also thought already about running a brace across the engine to each shock mount. Is that what you are referring to or is there a better place to tie the suspension together? Thanks Bryce.

[Bryce]

A 2x4 from is roughly %140 stiffer than 2x3 frame.

From the shock or uca attach points would be helpful

[wellis77]

Hmm. I may have to stick with 2x4 anyhow. Thanks Bryce.

[wellis77]

Any thoughts on using 2"x3"x3/16" front rails into the 2"x4"x1/8" perimeter rather than 2"x4"x1/8" front rails? Not trying to be cheap, just trying to gain as much clearance as possible keeping it safe at the same time.

[Bryce]

Any thoughts on using 2"x3"x3/16" front rails into the 2"x4"x1/8" perimeter rather than 2"x4"x1/8" front rails? Not trying to be cheap, just trying to gain as much clearance as possible keeping it safe at the same time.

2"x4"x1/8" is 50% stiffer than 2"x3"x3/16". And 2"x4"x1/8" is still 15% stiffer than 2"x3"x1/4"

[67zo6Camaro]

Wow...good numbers Bryce. What reference can I find this stuff. This type of info can be invaluble during fabrication.

Thanks
Brett

[Bryce]

I use my engineering books to reference equations. I am sure there is stuff on the web.

I got these numbers from using beam bending equations and forces in the vertical direction.

[67zo6Camaro]

I have used the "I" beam charts in the past for construction projects but I was not aware of similar charts for smaller (stuff we use in autos) round and square tubing in the .065 to .25 range. I'll have to look again on the web.

thanks

[racedaddy]

I have used the "I" beam charts in the past for construction projects but I was not aware of similar charts for smaller (stuff we use in autos) round and square tubing in the .065 to .25 range. I'll have to look again on the web.

thanks

I had a strengths and measurements class in college so you might go to your local college bookstore and find one. It's been awhile but I remember strength charts in the book that listed things like this out.

[Bryce]

I was not referencing charts, but equations and plugging in the variables.

But there might be charts on the web??