Don Terrill’s Speed-Talk

New to the forum……I find a wealth of information here….and I’m really enjoying it.

I think I have a unique question…but if this has been covered by some other thread I have not seen just let me know….

I am wanting to build a full tube chassis….a Fiat bodied altered to be exact. I have found a set of Blue Prints with Mark Williams. The plans call for 4130 moly tubing and I would like to use Mild Steel in the place of. I can MIG weld but have never used TIG and don’t have access to that equipment. I would use DOM mild steel on all cage materials. So my question is if there is good method for converting the various tubing sizes (outside diameters) called for in the plan?? I know that specs require that the wall thickness be a minimum of .118 for MS and .083 for 4130. I initially thought I might be able to keep all of the “outside diameters” measures the same and take the thickness requirements to .134 (for safety) for mild steel. But I wanted to ask the experts before I made that assumption.

Any recommendations?

Thanks!

Neal

maydayneal wrote:New to the forum……I find a wealth of information here….and I’m really enjoying it.

I think I have a unique question…but if this has been covered by some other thread I have not seen just let me know….

I am wanting to build a full tube chassis….a Fiat bodied altered to be exact. I have found a set of Blue Prints with Mark Williams. The plans call for 4130 moly tubing and I would like to use Mild Steel in the place of. I can MIG weld but have never used TIG and don’t have access to that equipment. I would use DOM mild steel on all cage materials. So my question is if there is good method for converting the various tubing sizes (outside diameters) called for in the plan?? I know that specs require that the wall thickness be a minimum of .118 for MS and .083 for 4130. I initially thought I might be able to keep all of the “outside diameters” measures the same and take the thickness requirements to .134 (for safety) for mild steel. But I wanted to ask the experts before I made that assumption.

Any recommendations?

Thanks!

Neal

Neal, the .134 is seamed M/S. DOM is .120 and is stronger and the same price as C/M in my neck of the woods. One point is that seamed M/S is butt welded at a certain length and DOM is not. I would worry if it was any where in my cage they butt welded the tube! DOM is mil spec as with C/M that is why they come in different foot lengths.

maydayneal wrote:New to the forum……I find a wealth of information here….and I’m really enjoying it.

I think I have a unique question…but if this has been covered by some other thread I have not seen just let me know….

I am wanting to build a full tube chassis….a Fiat bodied altered to be exact. I have found a set of Blue Prints with Mark Williams. The plans call for 4130 moly tubing and I would like to use Mild Steel in the place of. I can MIG weld but have never used TIG and don’t have access to that equipment. I would use DOM mild steel on all cage materials. So my question is if there is good method for converting the various tubing sizes (outside diameters) called for in the plan?? I know that specs require that the wall thickness be a minimum of .118 for MS and .083 for 4130. I initially thought I might be able to keep all of the “outside diameters” measures the same and take the thickness requirements to .134 (for safety) for mild steel. But I wanted to ask the experts before I made that assumption.

Any recommendations?

Thanks!

Neal

http://www.sfifoundation.com/

If you go to that site you can buy SFI specifications for building chassis. lots of good drawings and they show the way the roll cage should be made to pass tech.
I bought the 25.4 spec for my T-Bird and it has a chart in it showing the tubing sizes needed theu the roll cage for both chrome-mnoly and mild steel.
Only $35.00 and well worth the money.
If you call them and tell them what you are doing they will help you get the spec that best suits you.

You do realize that you limit the ET of the car and the resale value with the mild steel? Get a tig. You won't regret it.

Dave Koehler

Another question on this topic. Is it ok to weld 4130 tabs or other support brackets to a MS frame?

maydayneal wrote:Another question on this topic. Is it ok to weld 4130 tabs or other support brackets to a MS frame?

TIG only because of the 4340 and cool slow. MIG cools to fast for that and makes it brittle.

As af2 suggested, go with the seamless. Just one less variable to worry about. Be certain to check, double check, and then triple check the weight distribution before you start fabbing to avoid wheelstands (Page 9 below).

Also, make adjustment of left front "droop" as convenient as possible to provide equal rear tire loading on launch. Altereds are generally considered to be a handful to drive, but, with the right amount of droop in the chassis, your Aunt Rose could drive it (Pages 4, 5, and 6 below).

Billy,Do mind me PM you on another matter regaurding spring rates VS weight?

af2 wrote:Billy,Do mind me PM you on another matter regaurding spring rates VS weight?

Go right ahead, af2. Or, you could phone or fax me at the number on Page 1.