[CRUSH-build] driving the collector drum with a belt

[Bill Bennett]

Wes, you're right, I shouldn't be suggesting you tweak the shooter design at 
this point. A rule I preach better than I practice I guess.

In the case of the roller, we're only switching from chain to belt, and the 
chain had not been really spec'd out anyway, so it's not much of a 
diversion.

About the speed calculation, I think we've got it right:
target ball speed is 3 m/s, about 120 in/sec
edge speed of the roller to achieve that is 2x, so 240 in/sec
the roller is 4 inches diameter, 12 inches circumference, so we need 20 
rev/sec, 1200 rpm on the roller
the motor should run about 2400 rpm, so we need 1/2 gear down
the motor pulley is 16 teeth, so we need 32 teeth on the drum end

Bill