Strength of aluminum and mild steel tubing?

Hi guys,[CENTER]I'm new to this forum and I'm trying to build a new training aide for use in the Emergency Medical field. What I'm looking for is some information on the use of aluminum or mild steel tubing. I have built at prototype with 3 1/2"x 1 1/2" x1/8" aluminum tubing and we are looking at changing it to mild steel. I'm trying to keep the weight down as this aide is basically a mock car and I want to be able to roll it on its side or top. The current model weighs 250lbs. Is their a mild steel tubing that would match this weight and be as strong?[/CENTER]
[LEFT]Thanks, Russ Sweet[/LEFT]

You never said why you are thinking of mild steel. What problem are you trying to solve? People that are looking to save weight rarely ever change from aluminum to steel. Its usually the other way around.

I'd guess Russ is looking to save money for his organization...?
If you want "same" strength in steel it'll be heavier. period. Cheaper yes... lighter no.
So you need to weigh out the trade and decide what is really that important to you? Or maybe what best suits what it is you're trying to simulate.

Stiffness of steel v aluminum is around about a weight-for-weight thing. A well designed, triangular braced steel tubing structure will be lighter and/or stronger than an aluminum one.

Not so many years back the aircraft industry realized this fact and reverted back to predominantly all steel landing gear.

You need some expert Engineering help with designing a "space frame" structure in steel tubing, probably with 4130 steel at that. It's what they build race cars and small planes from.

Aluminum is lighter and more expensive than steel. If your looking to have a light weight design stick with aluminum. If your looking to save some money then change to steel. I highly doubt you'll be able to save money and weight by changing to steel. You just have to decide what is more important... Now there are different aluminum alloys of different strengths. You might look at using a stronger aluminum alloy.