I have been wondering (because I have not seen much on the subject) on what people have been using as the “floor” of their shooter, aka “what the frisbee slides across.”
I have seen plywood, metal, and some plastic, but after testing did anyone find that one material worked better than another?
Thank you!
We’ve had frisbees slide on a lot of materials, both in prototyping and on the robot. We’ve had Frisbees sliding on aluminuim, powdercoated and unpowdercoated, polycarb, ABS and wood.
Probably the worst was the unfinished plywood we used in prototypes, but anything other than that worked fine. Of the materials we tested, the powdercoated aluminium in our final shooter was probably the “best” although ABS was pretty good and I’m sure HDPE would be even “better.” The reality is that frisbees slide really well on a lot of materials. They’re relatively hard plastic with not much contact area, so as long as the shooter surface isn’t bumpy or sticky, they should slide pretty well.
Aluminuim (powdercoated if you can) or ABS are probably your best bets. I don’t think there’s any need to spring for teflon coated aluminium or HDPE or anything like that. You should be fine with a lot of materials, just be sure you or someone else has tested it before using it.
We used smooth aluminum that was the inside of a c-channel (well, two c-channels), I don’t remember which type.
We didn’t do any tests, but I see no reason not to go with the smoothest material you can find, as long as you know it won’t break (which I doubt will happen with any but the flimsiest of materials).
Since the disc touches it all the way through its lip (or at least on the sides, but it’ll almost certainly be both sides), so the friction between the disc and the “floor” doesn’t change the spin, only slows the disc down, so you want as little of it as possible.
During the competition season, our frisbees slid across polished steel .5x.5x.0625 tubing beautifully. No catches, very little friction, and perfect support. While I don’t plan on using steel for an entire robot anytime soon, if we had another disc game, I’d definitely consider using polished welded steel tubing as a floor again.
We had a pretty accurate full court shooter that didn’t have anything for the frisbee to slide on. We had a V shaped curved rail made out of HDPE that the frisbee rested in. You must make the V in such a way that the frisbee does not wobble when being fired though.
Originally, we had the concern that we needed a smooth surface for our frisbees to slide on (despite a wooden prototype that could easily shoot the length of the field). We decided to put a piece of abs on top of our wooden shooter arm so that the frisbees would slide on that. However, when we realized we were overweight (which will happen if you build a wooden robot, even with a <30in tall robot and the smaller frame perimeter), we decided to remove the abs, and let the frisbee slide on painted wood. It only ended up shooting half as far (although there is a good chance that this happened because of another cause), but we aren’t a full court shooter so distance didn’t matter much. Precision is what matters more. At the Boston Regional on Friday, we made 27/27 shots in autonomous. On Saturday, our precision declined so that we would often only make about 2/3 shots in autonomous. At Beantown Blitz, our precision was down to about 1.5/3 shots. Could this deterioration be because we used wood? Maybe, I will let you be the judge of that.
Polycarb worked well for us, though we didn’t try other materials. anything smooth should work quite well
We used a shooter made completely from HDPE. This includes the deck (or floor), the rails to provide the semicircular shape, the hopper to hold the disks (that part also included a pickle bucked), and the wheel. This worked great as far as the sliding, shooting and manufacturing goes.
The main problem we ran into was the warping. Even with the aluminum angle support we added under the deck, it still warped throughout the season. This was partly our fault for not adding any of this support until we saw the problem midway though the season.
Did you apply friction tape to the rails to promote spinning?
We thought about friction tape, but in the end we made the shooter rails a little bit bigger and farther away than we knew we would need to add thin strips of Lexan as spacers. On top of those we put a black foam strip we got at Home Depot.
Very similar, if not the same to this:
My team used a simple peace of polycarbonate. We found ouy that the deck surface did not matter as much as the side rail surface. We applied a thin strip of sand paper and saw drastic results of faster shooting speeds as well as an exponential increase in range.
Teflon tape.
McMaster 6305A18
We used carbon-fiber on a plywood core. The Frisbee contacted the gel-coat surface.
We applied a strip of rubber to the outer arc for friction.
We used HDPE strips for the bottom of our shooter. as noted above, we noticed more improvement from changes to the backing over changes to the deck.
Our backing material is of choice is vertically ridged rubber conveyor belting material.
https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-ash4/1003357_10151816953810225_797321350_n.jpg
https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn2/1146584_10151816953595225_977656134_n.jpg
You can see the 7 HDPE curved sections, and the green rubber backing inside the shooter.
The 7 segments are all cut from one 3/8 thick piece of HDPE we got from a local plastics supplier. The segments nest inside each other. It was reasonably cheap. we could adjust the height using polycarb spacers, moving the slides up/down to suit.
Also, we turtle waxed the other surfaces the frisbee was in contact with. the hopper, intake polycarb and the feeder slot slide were all liberally waxed up after every few matches or so. Ask code orange how much of a difference it makes. We introduced them to it at IRI.
Our shooter surface was a piece of 1/8" thick plastic material called Starboard. It’s designed for marine applications and has a nice grainy surface that reduced the surface area in contact with the disk. In our testing, disks slid across the Starboard much more easily than polycarbonate. For rigidity (at a low weight penalty) we laminated the Starboard to a 1/4" piece of Coroplast and had the sandwich waterjet cut by a sponsor.
We just had some HDPE on our floor surface. But we also weren’t built to shoot more than a short distance. Our prototype had a wooden surface for the floor, and it shot ever further than our competition bot, but that’s more likely due to the additional compression on the prototype.
I think the wheel surface and the surface of the opposite edge it’s contacting are far more important in determining accuracy and distance.
If you were to follow any of these people’s advice, though, I’d recommend 2468’s. Have you seen their shooter? It’s deadly accurate from absolutely everywhere on the field. Their’s has to be the most consistent shooter I’ve seen in FRC this year. (Even more consistent than 67, I’d say).
The base of the shooter was lexan. There was some roughtop tread on the opposite side from the shooter wheels. We used Pledge (it’s a spray) that made the surface very slippery.
We initially used powdercoated aluminium on both sides of the frisbee, and it worked fine. Later we constrained the frisbee better using two HDPE blocks / strips on the ‘top’ and powdercoated aluminium on the bottom. If we did it again, we would probably have a pair of HDPE strips on both the top and the bottom. The important thing is to constrain the frisbee so that it cannot flex or tilt significantly.
Our setup is similar to 1310’s, with a few minor differences. The bottom of our shooter path is entirely HDPE instead of having strips. The back of the arc is also made of layered HDPE - so it’s slippery instead of grippy.
We ended up using Glasliner FRP, better know as the regolith used in 2009. We added a car wax spray to it once or twice a tournament and found it worked quite well.