[Wayne TenBrink]

1918 uses two aluminum drums, 4.5" long x 3.5" dia, weighing about 2.5 lb each. Each drum is directly driven by an RS775-18 via a BB 4:1 gearbox. Wheel speed is monitored, but control is open loop for now. Balls exit at around 65 degrees (fixed angle). Azimuth is controlled with the chassis - no turret. Camera assist for aiming. The bottom wheel runs wide open, and the top is throttled to maximize backspin and control distance. Drivers have preset speeds, but can scale and/or adjust the speed with the classmate if needed. The current drums have a smooth OD and are coated with belt dressing (which increased distance significantly, but wears over time). We compress the balls about 2". Balls enter the shooter head while travelling in a straight line through a feeder chute set at a 50 degree angle (moving belt below, parallel moving trigger "shoe" above, close fitting guides on either side). The system is very rigid. It worked well enough to achieve a Teleop OPR over 10.5 (and win at Gull Lake with the help of 85, 1677, and 4327) despite an early string of 4 or 5 matches where we didn't score any.

We plan to replace the smooth OD drums with "toothed" OD profile shortly in an attempt to minimize the effects of unpredictable surface friction coefficients and ball compression modulus. Reducing variation (or being able to score despite it) was and remains a high priority.