So for some reason this suddenly struck me, what if you use belts to shoot instead of wheels. Has anyone tried this? What are the pros/cons of using belts vs wheels? Just curious. Thanks!
In 2017, 4613 used belt for their shooter. It was pretty cool as it made the intake the same as the shooter thereby removing a mechanism.
We’ve considered it on a couple of occasions. One of the issues with using a long belt run is that the tension/compression varies along the run unless you have idlers holding the “diameter” out. In seven years and eight distinctively different competition robots, we’ve never done this. In 2012, we had one double pair of shooter wheels contacting the basketball all at the same time; no second impulse. In 2013, our frisbee launcher had two 8" pneumatic wheels on CIMS, with the first spinning at 70% speed, and the second at 100%.
We then skipped rotary shooters for five competition seasons: 2014: kicker; 2016: spring catapult. No “launchers” in 2015, 2017, or 2018 competition season. Our 2017 gear hanger “pushed” gears, and our 2018 competition robot was designed to “drop” them onto the scale or into the switches. We could have pushed cubes into the exchange with our wheeled ground intakes running in reverse, but I don’t recall that we ever did.
Our 2018 post-season robot had a launcher consisting of two wheels and a belt coupling the wheels on each side of the cube. The wheels were close enough together that they both contacted the cube for several inches of travel. Why have the belt make contact when you can have two or more wheels making contact simultaneously?
Belts are great for conveying gamepieces, but they have the disadvantage of very high compression at the pulleys and possible slack in between the pulleys. When 1986 described the important aspects of their shooter in 2017 they emphasized a gradual transition to almost no compression as the ball left the shooter. Having a high compression (like at a pulley) just before the gamepiece exits the shooter leads to inconsistency.
My own team found this to be true with our belted ball elevator from 2017. Our shooter wasn’t too bad by itself, but when fed by the elevator, our shooting became very imprecise. Several teams, notably 2056 (belts just for loading) and 4613 (belts for shooting), figured out how to use belts very well, but I would say it is quite challenging to get a setup like either of those dialed in just right.
2485 2013 is my go to for belted shooters. Can’t believe they haven’t been mentioned yet. Probably the best belted shooter ever.
Our 2012 belted shooter worked great, super consistent.
It gave the ball time to get up to a repeatable release speed and wasn’t dependent on compression like other shooters. I have been told we had one of the highest shot in goal percentages on our field at Champs that year. The drawback was the speed of our drivetrain and the speed we could feed balls to the shooter due to poor gearing choices. The previously posted release video was sped up.
Cons were it took a tremendous amount of power to run it as the energy required to drive the belts was high. The two 775 motors got pretty warm during operation and were changed out constantly.
It added compression over its length to minimize the drag the ball put on it as the ball was introduced into it.
The final shooter had a sandpaper backboard on one side and belts on the other to increase backspin. Originally it had belts on both sides.
There was a teflon tape covered belt tray under the ball side of the belt to keep the belts from deflecting away from the ball.
For single object shooting or for slow release to release shots it works great.
The issue is that only one object can be in the belt at a time for consistency.
It was fun but a shrouded shooter with as much wrap on the wheel as possible would be lighter and less complicated to build.
In general, wheeled shooters can run at higher RPMs than Belt shooters, so depending on the game, it might be necessary to use wheels. That said, for games that you don’t have to shoot something very far, belts are certainly an option and can definitely aid in feeding game pieces.
Back in 2006, my team (703) built a sort of “hybrid” shooter that was basically a standard two-wheel shooter, except the bottom wheel was a belt roller and the belt fed the balls directly into the other shooter wheel and launched them. Granted, our shooter shot at almost point-blank range, but it worked well for what we needed it to do.