Single Flywheel Problems

Two of my middle school teams are having problems with their single fly wheels shooting far enough. They are transitioning from a dual flywheel to a single shooter and the transition isn’t going as well as we expected it to. They have looked at photos on the internet and watched videos of other single flywheel robots, but they can’t get the robots to fire more than half way across the field. They have plenty of motor power (3 motors) on one and 5 motors on the other) and a gear ratio of 1 to 25. Any ideas what they (and I) might be missing. I’m not with robots at this time so I can’t upload a photo.

Most of the time the issue has to do with the compression between the flywheel and an opposing plate. The calibration is very precise. My students have the plate mounted on standoffs and what they found is that the distance the ball travels can be affected by the size of the plate (smaller is better) and distance between the plate and the flywheel. So much so that they used washers as spacers to make tiny incremental adjustments to the compression.

To test my team left some of the screws out of the top assembly so they could manually push and pull it in small amounts to see what compression distance worked best. By the way we are running a 5 inch wheel on a 25:1 gear ratio. Also note that the photo below is old and my team has since removed the flat steel in the photo and they rely solely on the remaining angle bracket.

Good luck.

To me, the gearing seems too low, but I have delt with a lot more dual flywheels than single. A single flywheel (theoretically) needs to be spinning at twice the speed of a dual flywheel. Is the PTC tripping? 5 inch wheels?

Does that shoot full court? To me this does not seem fast enough. Again though, I have not spent a lot of time with single flywheels.

It is very consistent and a full court shooter. It frequently scores 20 during the autonomous period.

To use baseball references, I equate single flywheels to throwing a fastball because it has lots of backspin and it flies straight. Dual wheel shooters throw a knuckleball (a baseball pitch thrown so as to minimize the spin of the ball in flight, causing an erratic, unpredictable motion).

@Powerbelly - Once you have the distance down then the skill lies in increasing the fire rate.

This gives us some good things to focus on. Any suggestions for increasing fire rate?

Friction reduction, programming, and optimum gear ratio are the main things that will effect that. Also things like weight of wheels and compression have a big influence. It can take a lot of time to get all of these attributes to closely integrate well.

My teams experimented with a single flywheel early on but it was difficult to power properly, I can tell you what we learned. First of all the design was inspired by BLANK which based on the pic in this thread you guys were probably watching the same videos. They are using a 5" flywheel which will create a much greater rotational velocity than a 4" standard VEX wheel. Second they were using a 12/84 = 1/7 gear ratio with turbo motors. The final thing is the amount of compression at the final output. BLANK has a great thread in these forums where they discuss the details.

What worked for us was to just take some plate and bend it into a U shape with the U facing towards the output of the shooter(see attached pic). Attach this right above the fly wheel where the belt delivers the balls. With this simple device you can easily bend it to change the distance, therefore allowing you to quickly iterate through test to determine the optimal compression distance. Another option would be to use a slotted right angle gusset with a piece of plate or channel on the bottom facing the flywheel. This way you can easily adjust it up or down for testing. Once you figure it out you can then build the engineered, final part.