Steel Frame

[Dick Linn]

Jim,

For this particular configuration, I don't blame you for using steel. The stiffness:weight ratios of steel and aluminum are pretty close. They you have to consider the section. Plus, it's a lot easier to weld steel axles on steel tube.

[Al Skierkiewicz]

Jim,
We have used steel in the past. One of the drawbacks was the ability to rework in the pits. It's tough to drill speed holes in the steel frame to loose weight and drilling takes more time when you need to mount something. If you have the weight, which this year's game seems to allow, then you should have a workable frame.

[Chris Fultz]

8020 can be a great frame material also.
The key is to make sure connections are tight and stay tight.
Some nylon insert screws, or the removeable locktite is a good solution.

Every material choice has pros and cons - the key is to determine your specific needs and capabilities, and make the best of your choice - whichever material that is.

[,4lex S.]

Rough estimates would say steel is about 3 times the weight of an equivalent piece of typical aluminum.

Not exactly. I believe (don't hold me 100% to this, I am only in 1st year material science), the most important characteristic for a FIRST robot framing material is the specific stiffness [Elastic Modulus (willingness of the material to bend)/ Density]. Steel and Aluminium are pretty much equivalent in this regard. Still, you can get a more durable frame out of aluminium, for equivalent weight.

If you have the weight to spare, it is a cheaper (and easier to fabricate) solution, and cost is a real world parameter that many teams have to deal with.

[Steve Kaneb]

Originally Posted by Dick Linn

Plus, it's a lot easier to weld steel axles on steel tube.

That's what brazing is for. 190 has parts from our '99 swerve drive that are brass->steel, and they've held up remarkably well. Brazing is also excellent with aluminum->steel.