Aspects of a single flywheel?

Hello, our team has decided to use a single flywheel for this year competition. The problem is that nobody in our school has experience from NBN, since the people who did have experience recently graduated and went off to college :frowning: So we have no clue how to make a flywheel. What are some crucial aspects of a flywheel to making it very effiective? We also plan to the V5 system with no pneumatic system and we only want to allow two motors for both the ball intake and flywheel. Just in case if that’ll help answer the question. thanks in advance!!

-Team 11142B

A PID controller to make sure the flywheel is at the exact velocity you want. Also have as low friction and shortest axles possible in the gearbox. Study 2587Z “Klay”.

would the axle lenght affect the performace of the flywheel? We were doing some testing with 393 motors, while waiting for the V5 systems to come in, and we came across with a stalling issue. We used multiple of compound gear ratio(using a torque motor) and we used 3 motors. Although the axles are pretty long but we had to space it out so we could learn how it works. We also noticed that when we moved the gear that’s connected to the wheels, it doesn’t stall anymore?

You ideally want your axles to be as short as possible to prevent twisting. Flywheel gearboxes go super fast leading to more opportunities for axle twisting.

so speaking of that, would high strenght shaft be recommended? even making the gear box compact as possible but also allowing little to no friction to be present.

@Rocket-Robotics Some teams suggest using a high strength shaft for the final shaft of the compound gear ratio (the one with the flywheel on it) because its more rigid and cannot get bent after multiple passes of a ball. Its important that the flywheel stays as stable as possible because at a high rpm’s the instability is amplified.

Also axles on a flywheel will not bend, there is simply not enough torque for that to happen – if it built poorly it will stall. As I said above, they can bend (or already be bent prior to use).

Some other crucial components to be aware of are compression and grip. These go hand and hand with each other. When you are building and testing your flywheel you will need to experiment with different amounts of compression. By compression I mean how much the flywheel and the “hood” or “backboard” “squishes” the ball. If the ball passes through too easily, then the flywheel will not impart enough energy into the ball, but the flywheel will experience a smaller drop in rpm. If there is too much compression and the ball needs some force to get past the flywheel then it will impart more energy into the ball, but the speed of the flywheel will drop more and will need more time to get back up to speed. You should be mindful of these properties when you are building and tuning your flywheel.

Now for grip. These are slippery hard plastic balls so you might a slightly different setup compared to NBN. Some methods of increasing traction are covering your flywheel with rubber bands, or using the vex adhesive foam to cover the surface of the flywheel. Its too early in the season to be sure what works the best, or if these are the only methods, but having good traction on the ball is another factor to consider when designing a flywheel.

I personally don’t see the need for a HS shaft. With well care your axles should not bend

alright, thank you very much you guys. My last question would be is there a recommended gear ratio we should target for? As I said, we tried different combinations of gear ratio and we couldn’t quite figure it out. We tried both using a engineering formual and just plugging random gears(with our best educational guess)

oh and would a rachet and pawl machine be necessary? i dont see very many teams using these yet.

Well the gear ratio you use depends on the speed of the motor you are using and the size of the wheel. In general, I’d say that having a theoretical maximum of 3,000 RPM with 4 inch wheels is ideal. This would mean a 1:30 gear ratio with 100 RPM motors (the standard setting for 393 motors).

Honestly, I don’t think they are that important. They definitely reduce the stress on the motors when slowing down and probably save a minuscule amount of power (it’s probably not even noticeable though), but they definitely make velocity control a pain. I say this from experience of having one on our robot back in NBN. If you plan to make an intense and quick velocity controller, I’d recommend against it, though others may have had a different experience.

@Rocket-Robotics In VEX all PID math is only basic multiplication, division, addition and subtraction. There is no need to know the calculus behind PID. Once you understand how it works, its fairly simple, and you can understand the conversations about PID that others are having. I would recommend that your team all take a look at it together. Start with P and move to the next terms and try to understand them. This was first place where I fully understood how PID worked as a concept and this is the code that I looked through to see PID applied to code. I printed out the code and annotated it, and that really help me understand how a PID controller works and how to take advantage of it.

If you have anymore questions about PID you can PM me (Don’t want to get off topic on this thread) or google search “PID VEX” and look for vex forum threads. There are lots of them with al sorts of code and questions.

Also the mass/moment of inertia of the flywheel should be important. The higher the mass/MOI the more energy the flywheel will be able to impart on the ball without slowing down as much, but the flywheel will take longer to spin up.