Material for Chassis

[m.glisson003]

I want to build my own chassis. Yes I mean start with some metal, or other material, and cut and weld it into a chassis. ANY advice or helpful sources would be greatly appreciated.

What Im really looking for is what material would be best to use for lightweight and strength. Ive noticed many sports cars use aluminum and carbon fiber such as the lotus models and mclaren. Unfortunately Im doing this project on a budget so I cant do something that is too expensive. But Id still like to know what is the best of the best no matter what the cost.

[curtis73]

Unless you have mad CAD skills, skip the aluminum. Its much more expensive, very difficult to weld, and unless you do it just right, you have to use so much more material to get the strength you need that it won't end up being much lighter.

Hands down IMO, Chromemoly steel. Its a little finnicky to weld and has special proceedures, but if you're already good with a welder it should be no worry. Get your self a good joint jig, buy a whole bunch of CM tubing, and plan it out.

Just FYI, pound for pound, round tubing provides the most strength for the weight

I'm personally not good at it, but I know a racer in PA who builds his own. He makes two different ones: a full safety stock race version which weighs 800 lbs, and a superlight mini version that weighs 470 lbs.

[MagicRat]

Excellent advice.
A good joint jig is also used for cutting the tubing. One would use something that looks like a hole saw on a drill. It will cut the tubing at whatever angle you want so tubing ends will mate perfectly with other round pieces.

I think one can get tubing sections pre-bent to angles, 90 deg, 45 deg. etc. The alternative is to take any tubing that you want bent to a muffler shop that has a tube bending machine.
You can use miter cuts to make angles fro the tubing, but it's not as strong.

Finally, withing reason, given the same weight, a larger diameter, thinner wall tube is stronger than a smaller, thicker wall tube.

[m.glisson003]

Originally Posted by curtis73

Unless you have mad CAD skills, skip the aluminum. Its much more expensive, very difficult to weld, and unless you do it just right, you have to use so much more material to get the strength you need that it won't end up being much lighter.

Hands down IMO, Chromemoly steel. Its a little finnicky to weld and has special proceedures, but if you're already good with a welder it should be no worry. Get your self a good joint jig, buy a whole bunch of CM tubing, and plan it out.

Just FYI, pound for pound, round tubing provides the most strength for the weight

I'm personally not good at it, but I know a racer in PA who builds his own. He makes two different ones: a full safety stock race version which weighs 800 lbs, and a superlight mini version that weighs 470 lbs.

Thanks for your feedback.

What is CAD? I did a google search but came up with many results. I guess its a popular acronym.

So is Chromoly steel better than 1020 steel? I read somewhere that its best to use 1020 but Im not really sure. I wish I could find a source where they compare all of the different steels by weight and strength. That would be amazing lol.

[m.glisson003]

Originally Posted by MagicRat

Excellent advice.
A good joint jig is also used for cutting the tubing. One would use something that looks like a hole saw on a drill. It will cut the tubing at whatever angle you want so tubing ends will mate perfectly with other round pieces.

I think one can get tubing sections pre-bent to angles, 90 deg, 45 deg. etc. The alternative is to take any tubing that you want bent to a muffler shop that has a tube bending machine.
You can use miter cuts to make angles fro the tubing, but it's not as strong.

Finally, withing reason, given the same weight, a larger diameter, thinner wall tube is stronger than a smaller, thicker wall tube.

Hmm...that doesnt really make sense to me lol. I believe you but its just kind of hard to believe that a larger thiiner tube is stronger than a smaller thicker one. Seems to defy logic sort of.

[MagicRat]

Originally Posted by m.glisson003

Hmm...that doesnt really make sense to me lol. I believe you but its just kind of hard to believe that a larger thiiner tube is stronger than a smaller thicker one. Seems to defy logic sort of.

As I said, given the same weight. This means that if you have 2 tubes that weigh the same, and have the same amount of metal, the larger, thinner-wall tube is stronger because the metal is arranged more efficiently.

For an extreme example, take 2 empty soda pop cans. Pick up one and try to bend or twist it.
It has some rigidity, right? Take the other cans and squash it flat. Now, it is much more easily bent and twisted, right?

For tubing, this works up to a certain point. Tubing can be so large and thin that it is no longer practical to use, because it cannot be easily welded, is too bulky and easily dented.

[m.glisson003]

Originally Posted by MagicRat

As I said, given the same weight. This means that if you have 2 tubes that weigh the same, and have the same amount of metal, the larger, thinner-wall tube is stronger because the metal is arranged more efficiently.

For an extreme example, take 2 empty soda pop cans. Pick up one and try to bend or twist it.
It has some rigidity, right? Take the other cans and squash it flat. Now, it is much more easily bent and twisted, right?

For tubing, this works up to a certain point. Tubing can be so large and thin that it is no longer practical to use, because it cannot be easily welded, is too bulky and easily dented.

Oh ok. The soda pop example helped.

[curtis73]

Originally Posted by m.glisson003

Thanks for your feedback.

What is CAD? I did a google search but came up with many results. I guess its a popular acronym.

Computer aided drafting.

So is Chromoly steel better than 1020 steel? I read somewhere that its best to use 1020 but Im not really sure. I wish I could find a source where they compare all of the different steels by weight and strength. That would be amazing lol.

Chromemoly seems to be getting replaced by 1020 in a lot of applications. I think 1020 is a bit more expensive, but its not as difficult to weld.

as far as metallurgy, here is a very basic primer for you:
http://home.sprynet.com/~monel/metallurgy_faq_v11.htm
http://en.wikipedia.org/wiki/Tensile_strength

That second link discusses tensile strength, but under the "see also" there are links for the other physical properties of materials.

[KiwiBacon]

Originally Posted by curtis73

Computer aided drafting.



Chromemoly seems to be getting replaced by 1020 in a lot of applications. I think 1020 is a bit more expensive, but its not as difficult to weld.

as far as metallurgy, here is a very basic primer for you:
http://home.sprynet.com/~monel/metallurgy_faq_v11.htm
http://en.wikipedia.org/wiki/Tensile_strength

That second link discusses tensile strength, but under the "see also" there are links for the other physical properties of materials.

1020 is plain carbon steel with 0.2% carbon content. It's just plain old steel.
Chromoly is a fairly generic term, but if you chose something like 4130 (what most people mean by chromoly) it's tougher than plain carbon steel, especially when heat-treated. But the ultimate tensile strength isn't much different.

My advice, if you want to build a tubular steel chassis or space-frame then build the first one from mild steel exhaust tubing. It's cheap and will bend a long way before it breaks.
Once you've got the layout and function right, then buy some of whatever you'd like it to be built from.