Steel on a FRC Robot
 

How many people have seen steel on a robot? I'm just wondering because our whole lift is pretty much made of Stainless Steel. I've wondered if people have thought of using this as a solution to making things more rigid and stronger. I'll see if I have a picture of our robot to show you.

Re: Steel on a FRC Robot
 

I have been told that back in the day, steel was mostly used. I have seen a couple of my High School's team's old robots made of steel. I find it interesting your team used stainless steel. It's not cheap or light stuff.

Re: Steel on a FRC Robot
 

At first our arm support across the top was made out of aluminum but after testing (picking up a chair) with our claw we noticed that we bent it by several inches. We replaced it with a steel bar and haven't had problems picking anything up that weighs less than 20 pounds.

Re: Steel on a FRC Robot
 

I can't imagine making anything out of steel on our robot (besides some drivetrain components)

On our elevator this year, we even replaced a steel axle with an aluminium one to save weight!

Re: Steel on a FRC Robot
 

I've been wondering if steel on the end of a robot arm would accidently attract a magnetic mini-bot this season. It would be humorous and unfortunate all at the same time to see a big robot try to shake off the little guy. :yikes:

Re: Steel on a FRC Robot
 

Id wager that we might see that happen at least once for every regional: one team accidentally get inside anothers frame perimeter, and takes their minibot away. Now that I think about it, it might be a semi-valid strategy for finals :eek:

Re: Steel on a FRC Robot
 

All of it was donated to us by Oliver Products (Our mentor works there). we also found it to be strong enough that we don't need much to make a strong lift and with the thin wall we are using it would weigh less than the equivalent of using aluminum. We are doing a scissors lift so we are using round tubes. I'll get the specs on the tubes tomorrow (Diameter and Wall)

Re: Steel on a FRC Robot
 

Our robot has an all-steel welded frame, and it's worked quite nicely so far. Although steel is indeed heavier than aluminum, we make up for it by using thinner-walled material and very few bolts.

The trick with using steel is to take advantage of its greater strength. We're able to save weight by using many fewer supports than we would have with aluminum. Our frame is basically a flat rectangle, solidified by some diagonal corner brackets. It comes out a bit heavier than the aluminum equivalent, but it works nicely as a counterbalance for the elevator. The whole robot weighs 119.2 lbs, and is able to complete every element of Logomotion.

There are still many aluminum parts on our robot. Things that really need to be lightweight, like our gripper and minibot deployer, and things that aren't in high-strain positions are vastly aluminum. Our in-house machined components are also primarily aluminum, due to ease of work and speed. It is simply a matter of weighing pros and cons.

Steel's good to use in FRC, as long as you have the proper tools and skills at your disposal, and plan carefully. I suppose that magnetic minibots could be an issue... ours uses a fairly powerful neodymium magnet, and we haven't gotten it stuck to the frame yet. Yet...

Re: Steel on a FRC Robot
 

Last time we weighed to robot it was around 112 but we still had parts to put on. then we realized we had the battery on :yikes: so we are still in a good position. still waiting on minibot deployment (less than 8 pounds) and we took off 22 pounds for our claw/lifting mechanism.

Re: Steel on a FRC Robot
 

I'm not a fan of ordinary structural steel for FRC robots. The strength to weight ratio is awful, and the available sections are generally inconvenient. You see it occasionally, and you always wonder what set of design tradeoffs made that worthwhile for the team. (To be completely blunt, it's probably more like a lack of design that precipitated it.)

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.

And of course, steel (of all kinds) is stiffer (in terms of elastic modulus) than aluminum, so when distortion is a major criterion, you may want to choose it.

But as for stainless steel, I've got to ask: why? (There are lots of grades of stainless, but in general, while it's probably a slightly better material than structural steel for an FRC structural application, it has a lot of other undesirable properties—for instance cost and machinability, under most circumstances—that make it a surprising choice.)

Re: Steel on a FRC Robot
 

We used a little bit of 1/8" thick flat steel on the end of our arm; originally we intended to tap its magnetic properties for a little extra holding force to keep our claw steady, but we decided to go with an active mechanism later down the road. Beyond that, it's pretty much fasteners.

Re: Steel on a FRC Robot
 

That it was, but now I can't see using steel, maybe to reinforce something like some one else was talking about, but I can't see someone taking and making a robot entirely from steel, that's just nuts.

Just my two cents.

Re: Steel on a FRC Robot
 

in 2009 my former team, 1747, used a steel shaft for their shooter. i remember the aluminum one having too many holes/vibrations and having to machine a a steel one to replace it. luckily, steel fixed it.

Re: Steel on a FRC Robot
 

We have a small amount of 304 stainless on our robot because of the strength and package requirements for part of our arm. We also use steel shaft for the driveshaft of the arm.

Re: Steel on a FRC Robot
 

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.

Re: Steel on a FRC Robot
 

Maria -- our 2011 Logomotion Robot -- has a 1/2" stainless steel rod as the main support for her arm, and 3/8" steel rod elsewhere (in bronze bushings) for structural pivot points.

In previous years we have always used 3/8" steel rod for our axles.

Re: Steel on a FRC Robot
 

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

Re: Steel on a FRC Robot
 

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

Re: Steel on a FRC Robot
 

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.

Re: Steel on a FRC Robot
 

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.

Re: Steel on a FRC Robot
 

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.

Re: Steel on a FRC Robot
 

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.

Re: Steel on a FRC Robot
 

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

Re: Steel on a FRC Robot
 

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.

Re: Steel on a FRC Robot
 

We rely on the strength of our cross sections rather than the strength of the material itself. If you do this correctly you can produce very light mechanisms made from very thin material that are extremely strong.

In my mind, the only reason to go a different route would be lack of resources.

-John

Re: Steel on a FRC Robot
 

Has there ever been an FRC robot that didn't have ANY steel? (other than whatever is contained in the required electrical components, ex. the cRIO chassis)

I suppose you could build a bot with all aluminum fasteners, all aluminum gears, all aluminum shafts, no chain, etc., but has it ever been done?

Re: Steel on a FRC Robot
 

Which is one of the factors that drives most teams to make their robots differently than team 148 does.... :o

Re: Steel on a FRC Robot
 

I think that the only steel parts that we have this year, fasteners and gearboxes aside, are our axles. We used 1/2" steel hex shaft in 2008, and we are using them again this year. We tried switching out the steel axles for aluminum ones in Pittsburgh in 2008 for weight (even though we were slightly underweight already), but quickly switched back after one of the aluminum ones sheared during a match and we had to pound half of it out of the wheel with a mallet.

Re: Steel on a FRC Robot
 

I built a whole robot out of steel once, in 2002. The frame and manipulators were all steel. Granted, the whole robot was 12" tall, with a pair of 30" extending arms, and that was it, but for what we were doing it did the job and made the robot a veritable tank. It was mostly because we had steel welding capability, but not aluminum welding that year.

Since then, I've never used steel for anything outside of shafts, fasteners, or ballast.

Re: Steel on a FRC Robot
 

Welding aluminum is just as easy as welding steel for our team (metal shop down the street) so aluminum makes a lot of sense for our robot. It's hard to add support vertically to a scissors lift so we need the stronger material.

Re: Steel on a FRC Robot
 

The cRIO housing is not made of steel. Even better, occasionally the material is presumed to be cast-iron. It is actually a cast magnesium alloy, considerably lighter than aluminum. The clips that hold in the modules, the screws, and possibly the decorative placards are indeed steel. You'll also find it in the inner components like the backplane connectors.

Greg McKaskle

Re: Steel on a FRC Robot
 

Last year as rookies we decided to build our two kickers out of steel. The combined weight of the two kickers when we finally assembled every thing put our bot at about 160 lbs. It was a nightmare trying to cut our weight down to a manageable level, and it was not something that we as rookies were ready to go through. Steel is a perfect material for some applications, for instance this year all of the shafts on our robot are 1/2" steel, but typically it will make a bot too heavy too quickly.

Re: Steel on a FRC Robot
 

Actually, we used steel pieces at the end of our kicker last year to give it extra power (we had a spinny kicker).

So I guess the answer is that there is a place for steel, on FRC robots, but not everywhere.

Re: Steel on a FRC Robot
 

If you decide to use steel, you definitely want to spend some time designing the parts to be as light as necessary. The neat thing about steel is that you can make strong parts from thin metal. Look at car bodies...