Steel on a FRC Robot

[kgzak]

Originally Posted by Tristan Lall

for instance cost and machinability, under most circumstances—that make it a surprising choice.)

as I said for cost, it was donated (I am assuming they use stainless for what they do and said we could use some) and we didn't machine it all so we didn't have issues with that. With the load on it we need something stronger than aluminum. Stainless steel was what we had available so we used it.

[tutkows1]

Last year my teams robot was made complete out of angle iron steel, and this year our part of our arm is stainless steel.

[Zholl]

One of the axles on our claw mechanism is currently made of steel, mostly because the aluminum rod that was in there before kept bending under load. Otherwise, it's aluminum and a wooden board

[MrForbes]

Last year we made our chassis of MIG welded thinwall mild square steel tubing. It's strong, a bit heavy but not too bad, and it's relatively easy to build. Also it's locally available and not very expensive.

We also make the Typewriter Repairmen underwater ROV frames from steel strap, for similar reasons. A coat of spray paint keeps it from rusting.

If you do a good job designing your manipulator to be light, then a bit more weight in the chassis really doesn't hurt anything.

[Hawiian Cadder]

last year the drawback for our kicker was a pair of wheels with a little pins to drive each other, this needed to be made out of steel because we did FEA on the part and aluminum was not strong enough, an aluminum part on a high torque part must be made larger to offset the torque. steel can be made smaller and thus easier.

[s_forbes]

2840 made an appearance at the Duel in the Desert and was sporting a steel chassis, so I know of at least one steel framed robot this year.

Steel is a great building material... cheap, easy to work with (if you have a mig welder and a chopsaw). It ranks up there with wood and fiberglass in terms of my favorite robot building material.

[JamesCH95]

Originally Posted by Tristan Lall

I'm not a fan of ordinary structural steel for FRC robots. The strength to weight ratio is awful[...]

Alloy steels, particularly chromium-molybdenum steels like AISI 4140, are very useful, however. In the annealed condition, the strength to weight ratio is around the same as AA 6061 wrought aluminum. The difference is that you can weld annealed AISI 4140 with negligible loss of strength, while AA 6061 will drop dramatically in strength when welded. That makes welding a viable construction method for high-stress, high-strength parts.

The trouble is, because the steel weighs more, you have to use thinner material. This can be difficult to work with. Also, since 4140 typically comes in solid and tube sections (and doesn't work very well as sheet metal), you'll see it used in space frames, rather than stressed skins.

4130 steel is available in many tube cross sections with very thin wall thicknesses, down to 0.035in. If one was going to make structures out of steel that's what I'd recommend. I'd then advocate the use a weld-in nuts to fasten everything to the frame.

[flippy147852]

I know in the past 1918 has used steel bars as ballast to get weight where we want it

[SGS]

Our whole forklift/arm is made of steel, completed the arm weighed about 30 lbs, and ultimately caused our robot to weigh about 124. We had to disassemble and cut holes in everything, but our robot is VERY robust.

Last year, our whole frame was made of 1' square steel tubing , it was the only tunnel robot near the weight limit, but in the finals at Lone Star, it was an indestructible defensive robot and still quite fast.

Granted steel may not be the best material, but it is often a practical option and it is possible to create a decent if not relatively good robot with it.