49:1 gear ratio going slower than 25:1

Hi! We have two single flywheels. The first is geared to a 49:1 ratio, with 2 layers each consisting of an 84-tooth gear connected to a 12-tooth gear. The second flywheel has a 25:1 ratio and it also has two layers, with each layer having a 60-tooth gear connected to a 12-tooth gear. Theoretically, the 49:1 should be spinning faster but this is not the case. Does anybody have an idea of why this is happening? Thank you in advance.

The load. The motors spinning at 49:1 are having to work incredibly hard to spin with that much torque. Being closer to their stall torque will make the speed the motor spins to be closer to 0.

The gear ratio will be faster if you have a constant input speed but motors are far from constant speed.

Edit: most people talk about motor stall like the motor is spinning perfectly happy up until they stall. Stall torque is at 0 rpm and close to stall torque is going to be close to 0 rpm.

The higher the ratio the more speed and less torque. Because the higher speed ratio has less torque, any small amount of friction will be too much for the motors to overcome. I would guess that is what is happening in your situation. Just because the theoretical ratio is 49:1 doesn’t mean that the motors have enough torque at that ratio to reach full speed.\

In fact I would guess that if you left the motors on full power (127) on the flywheel with a 49:1 ratio you will most likely trip the PTC quite quickly.

Edit: Tabor beat me by one minute and said it much more eloquently.

Thanks for the reply and that was very eloquent! On another note, you seem to be very knowledgeable and may have an answer to this. Do you know why lower gear ratios are needed for double flywheels than single flywheels? I guess I am curious as to the mechanism behind it. Thanks for taking the time to reply.

Two wheels need less RPM because you have two wheels to transfer the kinetic energy to the ball.

Two wheels also take less because if you place them opposite each other, you are not inducing (much) spin to the ball. On the one wheel launcher, that induced spin robs you of some energy transfer to the linear motion you desire in the shooting of the ball.

But the spin can be beneficial in other ways if you wanted the ball to do that.

https://vexforum.com/showpost.php?p=298327&postcount=1
To fully understand this you need to learn about electric motor curves.

Is there a formula for the flight path of a spinning ball and how the wheel makes the ball spin?

All I can say is you probably have too much friction. :slight_smile:

To fully understand this you need to learn about electric motor curves.

Please use the revised version, the original post is still relevant but the numbers for the 393 motor were wrong (long story …)

Motor torque-speed curves - REV2 post #2

along with what all of theses people are saying you really have to take into consideration of all of the gears that your motors are turning. we have a flywheel with 5 sets of gears and before we fixed our friction problem it would not shoot full court and would stall. but once loosening some screws and checking motor mounts we now make a hole in our ceiling!

How many motors are you using on your flywheel? Because if you reduce any major issues with friction you may have, you should be able to get the 49:1 ratio to work much better if you increase the number of motors on it. This would reduce the load on each motor by spreading it out allowing them to spin better.