Gear Ratio for flywheel

Hi, Everyone. I hope you are having as much fun with your new V5 system as I am.

What is the best gear ratio for a flywheel using the 18:1 V5 motor?

That really depends on the way your flywheel is structured. What matters most is the “muzzle velocity” you need for the shot and the way the flywheel(s) transfer the rotation to a ball.
In general, bigger flywheel diameter means higher surface speed (rpm/60 * circumference) for the same RPM, so with bigger flywheel, you need lower RPM. Then, double-flywheel shoots at about the wheel surface speed, while for single-flywheel, the relation is much more complex (depends on the ratios of the wheel and ball diameters)
The next question is the motor working point on the motor torque/power curve. The motor delivers highest power at about 50%(*) of the max RPM, but you don’t want to exercise it at that point. Either way, you can’t expect to reach more than 80% of the max RPM, so you need to design your gearbox accordingly.

(*) V5 motors are different in this regard, since they are managed and their natural power curves are clipped. Because of that, the real “max RPM” to work with in these calculations is higher than its nominal speed.

if not probably use high speed motors

Yes, about the double flywheel. For the single flywheel, with the same assumption about the surfaces gripping the ball, the speed is half that of the surface of the flywheel regardless of the diameters. It’s only different if the ball slips.

And a note for clarity: In both cases, this is the speed of the surface as the ball shoots out, not the speed of the surface prior to the ball contacting the wheel(s).

Thanks a lot nenik. In you math aquation where do you get the first rpm?

Thanks again,

A way to get the linear speed of the surface of the wheel is to multiply the distance/revolution by the revolutions/time. So multiplying the circumference by the angular speed (typically measured in rpm) will give you the linear speed. You probably don’t want it in ft/min or in/min or cm/min or similar, though. That /60 is to turn the revolutions/minute into revolutions/second. That way you’ll get a speed in ft/s or in/s or cm/s or similar.

You can query the motors to figure out how fast they’re spinning, which will give you that number of rpm scaled based on the gear ratio. So read how fast the motor is spinning and multiply by whatever factor you have from gearing. What you should do is look at the lowest speed the motor gets to when it shoots the ball, assuming you’re trying to keep the motors going at the same rate for the shot. The speed to be used could be slightly higher than the lowest you read, it should be roughly the lowest you read, because the ball slows the wheel down as the wheel speeds the ball up.