Space frame chassis. What type of steel to use?


Can anyone tell me the best grade of steel to use in a space frame?

Could it be safely built from A36 utilizing .083 or a .125 wall thickness?

What is the SAE equivilent to A36 mild steel?

I've found the yield strength of A36 to be around 36000 psi, which would be i believe SAE 1005 - 1018?


I use the A-36 tube and it works fine. 1018 is also another designation but usually used for cold rolled spec, which has a nicer finish. Most tubing is hot rolled and can have a bit more carbon than desireable, and scale on the surface so the product I try to get is Hot Rolled P&O, this is acid dipped and oiled to preserve the finish, a bit messy when you buy it but a little cleaning with solvent and it has a nice finish.
As far as wall thickness it depends where the tube is used, thicker wall in the main sections and thinner elsewhere such as bracing and brackets usually works out OK.
I used the same tubing as Phil stated all in .065 wall depending on the car you are building it works just fine. I had a Mechanical Engineering Student redo the drawings I had in Solid Works with the stress package add on. We used ER70S2 rod for tig and R45 and R60 for gas rod in our tests. All worked out OK ,very strong. Mind you that my car is a 4 banger. These test were done without the panning and spot welded sections. Make sure you have a good welder thats up for the task. 200 Amps minimum.
Thanks for your advice fellas,

Glad i bought the right kind of tubing. The learning curve has been steep with the tig welding. I bought a syncrowave 200 and its been a really nice machine. Running about 120 amps on my .083 tubing and it seems to get good penetration, as I've ground a few welds out so far. Warpage is always fun to deal with! My space frame is almost complete from a design perspective and its fully triangulated and has no doors so it should be very torsionally stiff. Dont have the numbers to back it up but by looking at what others have designed i think it should do just fine. Shooting for 500hp and a gross weight of 2200 pounds. Has a 40/60 weight and balance calculated so far. Thanks again. Having trouble uploading a rendering but I'll post one as soon when I get home to a better internet connection.