I recently posted this thread asking about the floors of shooters this year.
This thread is to discuss what teams did on the wall opposite their shooter wheels. I have seen some people do HDPE, some rubber, some roughtop tread. What did your teams do to get the desirable spin/ speed on the frisbee?
Also, the total amount of compression you put on the frisbee would also be helpful.
Thank you!
We used the banebots wheels with pool noodles on the other side. We found a post on CD saying that pool noodles add a great amount of compression, and it really does. It saved us from having to completely re-design our shooter due to large amounts of vibration with the pneumatic wheels.
We used a pneumatic wheel with lexan side wall. We didn’t think much about the opposite wall, it was really more a matter of the motors and the wheel type.
We used this stuff from inventables. It worked quite well, but we didn’t have time to test much else. :]
We tried a few surfaces briefly during prototyping, and liked our results with shelf liner. We later heard from a couple sources that roughtop tread worked better, but we didn’t have any on hand to prototype with. By the time we acquired some (thanks 341!), we had already set the dimensions for our shooter. The additional compression on the disc caused by the difference in width between the shelf liner and roughtop tread significantly reduced our performance, so we ended up sticking with the shelf liner. If there was enough time to adjust our shooter dimensions, we may have had different results and gone with the roughtop tread.
Walter,
Throughout our prototyping process we tried numerous different sidewall materials including:
From this testing we determined that rough top was the best option available. The goal here is to make sure you impart the maximum amount of energy from your shooter wheel to the disc.
Basically it all boils down to Newtonian physics, “For every action there is an equal and opposite reaction.” The equal and opposite action we want is maximum rotational inertia of the disc as it exits the shooter, and minimal slip between the shooter wheel, the disc, and the opposite wall. By using a material with a higher coefficient of friction on the wall opposite your shooter wheel, you are minimizing the energy lost to slip when the disc is in contact with the wheel.
The reason we chose rough top tread over other high friction materials is the compliance it added to our system. This allowed us to maximize the disc contact patch on the wall, as well as giving some play in our wall to wheel distance.
We found that the material made little difference, but the shape of the wall was very important. In both our curved/straight shooter tests, putting v for the frisbee to rest in increased accuracy significantly. Our best results were with HDPE though.
We used a piece of tread riveted to a woodblock that could be adjusted to add more compression. This worked pretty well during the competition season but at Monty Madness the would block snapped in half (along with much of the rest of the robot)a couple minutes before our first elimination match because we added too much compression.
We just used lexan strips to shim our shooter until we got the right compression. We weren’t going for max distance or anything though, we just wanted the disc to end up in the goal.
This is definitely a part of the shooter that you can settle for “good enough” in instead of “perfect”.
For running cycles at the pyramid, you are probably right - this is something you can probably just get close enough and call it good. For trying to shoot full-field with high accuracy, these are the kinds of little things that make a difference between a 3’ shot distribution pattern and a 1’ pattern. Those kinds of marginal improvements are what separate the top shooters from the next tier.
Of course, this brings up an important point - always make sure you are designing to your own design’s requirements. Doing the little things right can make a big difference if your design relies on great precision. If you don’t need that level of precision, you probably can spend your effort elsewhere.
No disagreements here - for a full court shooter you definitely want as much consistency and accuracy as possible. For some reason I was under the impression that the OP was asking about pyramid shooters specifically instead of shooters in general. A back of pyramid shot fired straight at the goal has a fairly low entry angle and allows for a surprising amount of variation in shot height. As with every design decision ever made, it seems like the optimal amount of effort depends on your design requirements.
We used a flat piece of pool noodle about 3/8 inches thick. That was covered with a piece of 1/16 adhesive-backed rubber. This setup worked the best for our shooter after extensive testing.
We use what some people call the roll-on equivalent of the polyurethane roller material 254 and other teams use. It’s Scotch® Rubber Mastic Tape 2228, and it looks like this. It comes in a few widths. I believe we picked it up at OSH.
As for compression, we didn’t measure. Our wheels and the motor mounts were adjustable, so we started testing with just a little bit, adding compression until the distance stopped increasing or started decreasing.
We found through testing that in terms of maximizing distance and precision it depended on your rpm at wheel. At higher RPM’s (I don’t recall the exact numbers, I can dig up the data if your interested) we found a grippier material helped to impart spin to the disc (albeit this slowed the disc down due to higher friction). However, we noticed that gripper materials introduced more variability in the system. So we switched to a slower (medium ) RPM and a smooth polished aluminum surface which we put a little graphite powder on. This kept the spin at a high rate and still gave us the distance the higher speeds were giving us.
We used tape that has a surface similar to a corkboard opposite our two plaction shooter wheels. The compression was pretty massive, as well- I can measure it tomorrow, but the frisbee bends quite a bit. Compression wasn’t pre-determined, we built our shooter to adjust compression and tested until we got the best range. Due to these factors, we got some wicked spin on the frisbee, enough to make it near impossible to catch at outreach events where we were shooting to people.
