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Unread 15-02-2012, 02:15
RRLedford RRLedford is offline
FTC 3507 Robo Theosis -- FRC 3135
AKA: Dick Ledford
FRC #3135 (Robotic Colonels)
Team Role: Mentor
 
Join Date: Jan 2010
Rookie Year: 2009
Location: Chicago, IL USA
Posts: 286
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Re: Gear ratios for launcher

Team 3135 has a prototype shooter with two 8" AM-FIrst (AM-0420) wheels from 2010 mounted side-by-side on a 5/8" shaft. and temporarily driven by a single CIM with 1:1 ratio using dual 30 slot pulleys and the KOP timing belt.
Opposite the wheel pair is a 1/4" plywood sheet that the balls squeeze against it with ~2" peak compression. The plywood is covered with high friction shelf liner mesh. So, we are near near 5000 rpm on the 8" wheel pair.
We had to sand a radius on the outer corners of the wheels, since they were too sharp and were making lines on the balls. The wheels are somewhat lightweight, and it seems that the RPM drops a lot during the brief interval of ball compression while in contact with the wheel, so we are considering adding a large 60-tooth aluminum sprocket that has an outer hole circle where we can add several screws with steel washers for a better flywheel effect. This should reduce wheel slowdown and raise the exit velocity of the balls.

This initial CIM driven setup has us making baskets on a real basketball court from half court into the 10" high basket.

We are replacing the CIM motor with either a pair of the Banebot CIM-U-Lator 775 (1-motor) gearboxes, each gearbox powering one end of the wheel shaft, or with a single Banebot CIM-U-lator 550-2 (dual-motor) gearbox. These gearboxes give a 2.7:1 reduction of these high RPM motors.

AN initial pair of CIM-U-lator=>775 gearboxes were ordered with a total of four 775 motors, because of the internal shorting problem. Expecting maybe one in four to test bad, our order arrived today with THREE SHORTED MOTORS out of four. We are bailing out on using the 775 motors for ANYTHING EVER AGAIN. I hope we can get a replacement pair of DUAL 550 CIM-U-lator gearboxes shipped ASAP.

-Dick Ledford