# Dual Flywheel Help

We have a dual flywheel in a 1:15 gear ratio with 6 motors in high speed at the moment. We noticed that some ball would overshoot and some would undershoot. How could i fix this problem? What factors could affect my accuracy? Also, what could i do to reduce the coolup time between each shot, to shoot all the balls faster?

When my team had a flywheel design, we ran into the same kind of problems. The difference in shooting depends on the ball’s density, and that’s a problem you cannot really avoid. To work around this, our team would feel each ball in the preload pile and separated them into a soft pile and a hard pile. We shot hard balls at a different speed than soft balls. This might work for you, but otherwise nothing we did could solve this problem.

Yeah i figured it was that but I still dont understand why other teams achieve this. Some teams at at least at 90% accuracy but i dont know what they did to make that work

This problem is avoidable, look at our you tube channel for that. Especially this video, the missed balls were due to human error, otherwise we got past the density problem with some engineering. I think the varying ball densisites add an interesting challenge to the game. Use it to your advantage! Come up with a cool solution. DM if you have more questions.

I found that reducing compression on the ball to a minimum would help with having the balls all travel the same distance.
Also, having any kind of spinning on the ball will greatly increase the accuracy.

We tried this but the balls wouldn’t reach the goal. We right now how the minimal compression

my team had the exact same problem, we fixed it in two ways

1. you currently have 2 wheels, you need to add a second wheel to each shaft, this will cause the ball to automatically center between the wheels, also, increased wheel mass will decrease time between shots

2. use PID controls or the like to control your shooter velocity
if you just send it a motor power it will be terribly inconsistent, the PID loop will keep it at a constant speed, and this will also help reduce time between shots, because if the wheels slow down after a shot the PID loop will ramp up power to bring them back to speed

with these 2 changes our accuracy went from 25% to 85%

here is a tutorial on making PID loops

Thanks for the suggestions! I will definitely try them and report with the results in the future. My only problem right now is that I am not familiar with RobotC. In Puerto Rico everyone uses Easy C for some reason and im not sure if there is a way to make this robot C code into Easy C. Suggestions?

I like the gear ratio:roll eyes:. We here are some good tips:

1. Angel up the flywheels to around a 45 degree angle, you will then have a larger target area.

2. As has been said before, use a PID control. And if you don’t have RobotC, get it, it will boost your teams performance and is easy to learn.

Also, why do you have the piece of metal at the top like it is, have you tried without it?

I would greatly suggest this. It is worth getting. EasyC allows you to create variables and use them but it is a lot more annoying and the forum here has a lot of good ROBOTC PID and velocity PID examples.

Yeah, we have it at a 45 degree angle and we placed the metal on top to give it more stability. I haven’t tried removing it completely but i did try taking the shaft out of the bearing that was holding it (so it is almost the same thing) and it didn’t do much of a difference. Also, robotC does seem interesting but i fear it will take me too much time to get the hang of it and i would also have to get a copy of it since we haven’t bought it.

I also wanted to see if lowering the wheels a bit or adding a second wheel a little further down the shaft would work better but if I put it there it will be touching my intake (which is not good)

First i would change your gear ratio to 1:25 and make 4 motor running it on high torque… I have this for my robot and it works perfectly. Save your motors for something else.Good Luck

We used to have that gear ratio but i guess that we had too much friction and we couldn’t use 4 motors for some weird reason. But it would still have the same problem with the accuracy as i have now

Through some math, perpendicular entry into the net will require a 60-65 degree angle.

That is not to say 45 degrees isn’t a good angle, though, because it is the best angle for distance (meaning you can save some motor power there.

However, accuracy depends on goal entry area from the POV of the ball, so I would recommend a higher arc for closer to perpendicular net entry.

Using the lowest gear ratio possible is a key because that would allow for quicker acceleration up (remember that most teams don’t use full power, but somewhere around 60-80%).