This year we constructed most of our robot using 1"x1" aluminum tubing. It worked, but we had numerous problems: warping from over tightened bolts, extra holes needed to help guide and tighten bolts, etc. I know every year can be different, but what types of metals (and in what shapes and forms) do you mainly use and for what reason? We know the basics: aluminum being lightweight, steel being strong; heavy; and prone to rusting, etc.
Thank you for taking time to help!
We used a lot of 2x1 and 1x1 Versaframe. We also made use of some aluminum flat stock, steel flat stock, and pieces of old KOP chassisâŚ
We used the Versaframe mostly because of the pre drilled holes and how easy it is to buy. The 1x1 was really just used for extra support and for mounting bumpers. The 2x1 formed the majority of the shooter structure.
The aluminum flat stock was bent and used to build the platform the boulder rests on. We would have probably used steel if we had the means to bend it.
The steel flat stock was used to mount a cylinder.
And, the pieces of old KOP chassis were used as a climber hook, battery mounts, and a little extra support for the underbelly.
Our team uses a lot of .75" x .75" aluminum tubing. Never had a problem with it.
If your team has access to a wood shop (table saw, planer, joiner, etc.) it is easy to make tight fitting wooden plugs, one to three inches long, to go inside rectangular or square aluminum tubes. This makes it easier to join tubes, using gussets, through-bolts, pivot bushings, etc., without crushing them when you tighten the fasteners.
As an engineer in the truck-industry, Iâve taken Panther Robotics 1108 in a different direction. We use steel.
It costs about half as much, its half-again stronger than aluminum and if it bends, we can just bend it back without losing strength.
We have a flux-core wire-feed welder in the shop, which is inexpensive to operate and the kids learn to make some great looking welds. Add a bracket? donât need to drill and boltâjust weld it on! Also note, weâve never had the money for aluminum welding.
Mostly we use 1/2" x 1/2" x 0.062 wall thickness square section tubing, but also on round parts we use EMT conduit. All available at the local farm store or Home Depot in the city. Also cheap at mcmaster.
Takes up less room too. Canât imagine building in 1/2" tubes in aluminum. Would fold like tinkertoys. Steel is super strong.
And oh-yeahâour robot weighs 105 this year. No lightening holes either. Yes, steel is heavier, but we just use less.
I remember aluminum robots put together with rivetsâthey were always rickety and wobble. These are solid.
We use 1x1 T-slotted extrusion. Never had a problem.
Thereâs different levels of frames depending on experience, machining capabilities, and CAD use.
Kit Frames.
Hand Built with Alluminum Cross Sections
Machined Alluminum Cross Sections
Machined and Welded Alluminum Cross Sections
Sheet Metal Waterjeted (Or CNC Milled) and bent/riveted
We use various materials based on its application.
2 x 1 Aluminum tubing:
1 x 1 Aluminum tubing:
Aluminum Sheet (1/8" and 1/4"):
Lexan:
In addition to KoP Chassis parts, we used Vex versaframe, 2x1x1/8" aluminum channel, and 1-1/4"x1-1/4"x1/8" channel this year.
You are less likely to crush tubes if you use blind rivets rather than bolts. You will need about twice as many, but theyâre much lighter than bolts and donât crush tubes.
The only place we usually use steel is where we do use bolts and nuts, a few shafts. chain, and internals of COTS items.
We made a few parts out of a rubbermaid garbage can this year. Not for structure, but it worked well keeping the cheval de frise out of our robot, and if weâd had a lot of trouble running over boulders, we had figured out a flap on the front made of rubbermaid to push boulders away but allowing us to use the wedge for climbing over obstacles.
1/16", 1/8", 3/16" and 1/4" 6061 Aluminum plate can be found on our robot. We lay a 4âx4â sheet down on the CNC router bed of whatever thickness we need and cut it from there. One day weâll learn how to CAD metal bends properly, and when we do⌠look out 
Our tubes are 2x1 VersaFrame and 1x1 regular thin wall 6061 Aluminum.
Our standoffs are made from AM Churro or VEX ThunderHex, for the most part. We also have 1" solid aluminum round turned down to make a complex (but sturdy) axle and orthogonal mount for our intake.
Connectors include #10-32 socket head bolts, 3/16" aluminum rivets and 1/4" aluminum rivets. Since ThunderHex and AM Churro are immediately tap-able for 1/4-20, we also use 1/4-20 x 1/2" length into the ends of those.
Ooh, ouch. Those are fightinâ words⌠Weâre 33 matches into our season with no wobble on our riveted drive train frame. Donât get me wrong - we would have loved to weld it this year, but couldnât find a sponsor who could turn it around in time. So rivets have worked really well. The trick: Cleco clamps, and rivets every half inch. If 2 of the holes were precision-drilled, then we were able to get away with hand punch/drill on the others. VersaFrame helps a lot, IMO.
We used very little metal on our robot this year, aside from the aluminum kit chassis. Most everything else is wood. We used a few pieces of aluminum strap, and a couple pieces of thick sheet aluminum for corner gussets. We also used polycarbonate sheet for the top and bottom, mostly to keep things such as the defenses, boulders, and other robots from getting into or snagged on the innards of our robot. And there are a few pieces of steel strap.
Our practice bot was almost entirely made of .075 steel plate, and it was underweight. Our main bot had .090 aluminium side plates and was 5lbs lighter. We also had steel backed bumpers (19.6lbs per pair!)
We use mostly 3mm aluminium with some similar steel portions where extra reinforcements are needed. For main support structures we usually use 25x25mm SHS, although apart from the drivetrain not much of that was required this year for us.
Most of our parts are bent into shape as sheet metal, however some 90 degree joints (such as our shooting shroud) are riveted (or even welded) into place. Our rhino plates this year are 3mm with supporting churros and SHS to prevent bending and to hold them firmly in place.
Our robot last year was the stock base with a 3mm steel baseplate. Our âA frameâ lifting guiderails were 25x25, 3mm steel SHS, welded into a slanted A frame and bolted to the chassis.
Vast majority is 1x1 and 1x2 Versatubing. We do have some 3/4x3/4x1/16 tube this year.
For plate we mostly use 0.090" 6061, with the occasional 0.040" for light brackets as we can bend it in house. We do have 1/4", 1/2" and even 1" thick AL on the bot this year.
Most hex shafts are AL from VEX, though we do use some steel hex from McMaster. We tried the Thunderhex and Iâm not sure if it was just the oversized batch but it was a nightmare to work with and we wonât be going back.
We rivet most everything and get critical pieces welded by our local sponsors.
lets see, this year involved:
1/4x 4" flat bar for the intake pivot and motor mount. (6061)
1/16" 1x1" tubing to support and making up the intake frame (6061)
Piano hinge for anything operable in the robot that was not powered by a motor. (in this case it was to allow us easy access to electronics on the bottom of the robot.
3x3 aluminum angle stock (6061) for PG motor mounts
KOP chassis and bumper mounting kit. (50 series aluminum I believe)
where ever possible tubes were connected with gussets and rivets or rivnuts. This makes it much harder to crush the tubing.
and a metric but load of polycarbonate in 1/8" and 1/4" thicknesses. This makes up almost all gussets and the belly pan of the robot that was cut then thermoformed to fit the chassis so it wraps up the front and back in one continuous piece.
and some trace amounts of aluminum bar stock in rectangular and round flavors for spacers and mounting bosses for the tubing where it needed to T into a flat plate.
1/4" baltic birch plywood is most of our metal, whether for structures or gussets. Itâs exceptionally strong, lightweight, easy-to-machine (even without a laser cutter) and inexpensive. We also use some 1/8" plywood for small or non-structural stuff.
In terms of actual metal, we mostly use 1x1x1/16" square 6061 tube. Its profile gives good resistance to bending and twisting and its thin wall keeps weight low. Also, lots of Vex 1/2" tube axle (with the ends tapped for 5/16-18 bolts) for both axles and standoffs.
We also have some small parts that take high loads (axle mounts, winch ratchet and pulleys) laser cut from .125" 5052 aluminum by a sheet metal shop that sponsors us.
Weâll also make small parts out of HDPE or Delrin on our CNC router or from thin delrin sheet on our laser cutter. Lexan sheets are also occasionally used.
We occasionally use 1x1x1/8" or 2x2x1/8" 6061 angle and 1/8" or 1/16" 5052 sheet if it better suits the application.
For fasteners we use #8 Torx screws for wood-wood joints, 3/16" rivets where possible in metal (lighter, easier to work with than bolts), 10-32 and 1/4-20 bolts where rivets wonât fit or arenât strong enough and 5/16-18 bolts for attaching tube axle. Mostly socket-head cap screws from McMaster-Carr with nylock nuts.
Edit: glad to see a good mechanical design discussion thread going. Iâve been missing these.
Metal? Whatâs that?
In your original post you have the basic flat sheet aluminum. But if you go down that road you also need to understand the different types and how to use it. First off you need to have a dedicated CAD designer that understands how to design with sheet metal and the appropriate way to bend and rivet Aluminum. Also the two most common types of aluminum for FRC, and what I recommend for your first year designing with it, is 5052 and 6061.
5052 should be used in flanged(bent) pieces. Technically you can use it for just flat pieces to, but itâs not as strong as 6061.
6061 should never be used in a bent piece. The metal has a interesting habit of cracking and âexplodingâ when bent in a break.
Oh and by the way you will also need to find a company that can cut and bend your aluminum design for you. Depending where your team is located I may be able to help you with that.
1065 uses .125 thick C and L channel as well as versa tubing for our robot construction. We buy large amounts of it before the season starts and get it powder coated early in the build season so the end robot is always powder coated without taking time out of the build season to get it done.
4592 is an all sheet metal team. So the entire robot is built from .090 5052 made by our sheet metal sponsors. Occasionally .125 inch is used when thinner material is not strong enough. We also use quarter inch thick plate for gearboxes and wheel hubs.
Yeh, 1114âs robots are always soo rickety and wobbly /s