Modeling Ball Shooters

[RoboChair]

Originally Posted by BBray_T1296

Hard to understand your exact setup, but if you only have one wheel and a backplate you must account for spin.

The part of the ball touching the wheel can only have a linear speed equal to that of the wheel at best. Assuming zero slippage, the part of the ball contacting the wheel is at the wheel's speed, and the part of the ball touching the back/compression wall is zero, and thus the actual velocity of the center of mass is half the wheel speed.

Also your energy calculations need to include spin. If it has a large spin it has non-negligible rotational kinetic energy

^^^^^^^^^^^^^^^^^
This.

With a one wheeled shooter (wheel surface speed)=/=(maximum ball speed).
Expect something more like (maximum ball speed)=1/2(wheel surface speed) before frictional, angular, and other efficiency losses.
A two wheeled shooter will fire at MUCH closer to the actual surface speed of the wheels because it eliminates that pesky rotational loss issue.

Our shooter this year had a surface speed of around 100 fps, but our shots were probably only in the range of 30-40 fps; far over 60% losses compared to the wheel speed but only an efficiency loss of 20-40% if you compare it to half wheel speed.