tubing questions

[hammerhead]

I am going to build a sand rail and need advice on tubing. Which type of tubing can i get by with and which is best and can these be welded together.

The types that I have in mind ar e.w., d.o.m, and 4130 I have very little knowledge in this area and any help would be greatly appreciated.

[matts427]

E.W. or electrically welded tube is the cheapest. DOM, or drawn over mandrell is more expensive, but is the most accurate as far as being within a few thousandths tollorance to it's advertised size, both ID and OD. 4130 is Chromemoly, and is by far the most expensive. It's much lighter than steel, is much stronger, and it takes a lot of practice to get your welds right. And as far as I'm concerned, the only way to weld 4130 is with a TIG. Also, if you do choose 4130, make absolutely sure that it is 4130N (normalized). Anything else will crack immediately when welded. Your filler rod must also be 4130N. You CAN weld 4130N with ER70S-2, but your welds will not be half as strong as they should be. It's suggested that if you're welding mild steel to 4130N, use the 70S-2 because the joint is only gonna be as strong as the weaker base metal anyway, and the 4130N filler will tend to crack the HAZ of the mild steel. (HAZ = heat affected zone, adjacent to the weld)

As far as sizes, I'd stick to NHRA guidlines.... 1 5/8" .134" wall mild steel tube. Or 1 1/2" .090" (I think) 4130N tube. Make sure your bend radius' are as large as possible so as not to stretch the metal on the outside of the bend too much, and I think you'll be just fine. Hope this helps!!
Matt

[ASKANDY]

Sounds like good advice Matt. I would use the DOM. Sand rails don't see the punishment that a stock car does. With the proper triangulation of tubes, the vehicle should easily be strong enough. Like Matt said, 4130 should be Tig welded and if you don't have a ton of experience, lets stay with MIG materials.

A-

[Engineer1]

tubing

Just wanted to make a correction to the post by Matts427. Matts427 stated that 4130N is much lighter and stronger than steel. 4130N actually weighs about the same per linear foot as mild steel but since it is so much stronger you can use a thinner wall tubing making for a lighter overall chassis weight. Also, 1-1/5" 4130N comes in an .095" wall thickness as well as .083" and .065". Though some sandrail manufacturers use .095" wall 4130N for their chassis many use .065" wall for lightweight 2 seat rails and .083" wall for lightweight 4-seat rails.