My team has built a double flywheel launcher with two wheels on each side, and I was wondering what specific types of wheels other teams with flywheels are using. We have 5" traction wheels on ours. (The ones with loads of small green bumps, not the smooth surface. I don’t know what else to call these wheels.) We are currently in the process of making our flywheel more consistently able to shoot into the goal as well as increasing the firing rate without sacrificing accuracy, and it is therefore necessary to improve the flywheel in any way possible. My intuition tells me that that a wheel with a more regular surface would be better, as it would tend to contact balls in the same way, although we have attached rubber bands which seem to be helping, but I wanted to know what other teams have found to work best. Also, we would strongly prefer 5" diameter wheels because using any smaller than that would necessitate a major redesign of our flywheel. Just to reiterate, I am only seeking advice on what type of wheels to use, not other aspects of the flywheel, as I do not yet have any other specific questions. Thank you in advance!
Ya… I’d stay away from those 5" wheels but not for the reason you are describing. How many are you using? Are they stacked?
This image does not show the whole flywheel, but it does show the wheel type, number, etc. and the rubber bands.
Oh wait, I don’t think it attached properly. Give me a minute to figure this out.
Here it is. The gear ratio is 1:21, and also ignore the ultrasonic sensors. Those were planned for something later, but have since been removed.
We would prefer to stick with two wheels on each side. Although it requires more time to spin up to speed, the flywheel requires less time in between shots as a result. (Since flywheels operate based on the momentum of the wheels) The 5" wheels, regardless of type, have a higher mass than smaller ones and so the same argument about flywheel momentum can be applied as a well.
WAY too much weight, and that interconnected gearing is causing unnecessary friction. I speak from experience building about 10 different prototypes of these things. Also switch to two 4 inch wheels or something those 5 inches are way too heavy and don’t do the job any better.
Important things to consider on wheels:
- weight & moment of inertia
- wheel surface (consistency and friction)
- wheel size (smaller wheels make things easier to package)
- shaft diameter (thicker shaft will prevent bending)
Which wheel makes the most sense if you follow these steps?
We’re using Omni’s stacked on top of the 4 inch wheels. They seem to work very well…
One of our teams uses this flywheel setup and it tears up the balls quite a bit because of the omni wheels. Does your robot have this issue or how did you stop it from tearing up the balls?
We are currently using the 4 inch wheels and they seem to be working well.
One of my teammates had the idea for interconnecting the two sides bc that way, any differences in speed between the two sides would add more fiction to the gearbox rather than left/right spin on the balls. I have no idea if this is even necessary, but we have not been having issues with said excess friction. We have to slow the motors down to about 60% power anyway to avoid overshooting due to the angle at which the flywheel is positioned, so I don’t think finding ways to reduce friction is very high on our list, especially since there is lithium grease on everything. This angle cannot be changed without exceeding specs, by the way.
Anyway, the point about weight is valid but we previously had a much smaller gearbox made of aluminum, but it did not work very well. This design is much more reliable and just more well-built in general than the last one, and we are happy with it. Any suggestions as to how it make the gearbox smaller are welcome, however, if you have more constructive feedback than just saying what you don’t like.
Another question: Is there a way to make the 5" wheels have a more consistent surface? Also, why do omni wheel flywheels work so well? That seems counterintuitive to me, given all of the rollers on those wheels.
I was talking about the weight of the wheels themselves, the weight of the assembly has nothing to do with flywheel performance which is what your question is. Seems like there are a number of things that you don’t want to change…
I’ve built 10 different prototypes each time because the old design didn’t allow much room for change. I highly recommend you start fresh and really think about what you want to do with this version. PM for more help!
yeah we have that problem too. Is it illegal for that to happen?
Well it would technically be classified as damaging the field objects…
Depending on the severity and what the referee at the event considers “damaging”. I think eventually a more blanket ruling about damaging balls will come out 
Thru all of our summer testing, we choose the 5" wheel as the best wheel for our flywheel setup. Most of the other teams at our school are also using 5" wheels also.
This might sound stupid but did you try mecanum wheels?
https://vexforum.com/showpost.php?p=387930&postcount=17
I don’t think these would work very well because of the unevenness of the wheels, I would imagine that depending on the setup it might be inconsistent depending on which area of the wheel the ball touches.
This thread should have a poll.
Ok I was just wondering and we don’t have any that teams aren’t using so I can’t test it.