[FTC]: Shooter Wheel Safety

[Rick TYler]

I'm a veteran of Aim High in 2006, where we built a robot shooting the 7" foam balls with 8-inch wheels running on a direct-drive CIM motor. What is that, 3,600 rpm? It worked well.

Our FTC team has built a shooter mechanism for this year's game with a pair of 4-inch wheels spinning at an estimated 5,000 rpm using multiple motors and a three-stage gear train. This scares the whee out of me. The wheels go so fast that the rubber tread is visibly lifting off the plastic wheel as it spins.

I would like some thoughts from VERY experienced robot folks here. I am concerned about the safety of this mechanism, especially since these are axles running in bronze bushings -- not bearings -- using wheels that I am concerned were not designed for these forces. Since these are shooter wheels, there is no way to fully enclose the mechanism, either. Are the axle shafts designed for this? The wheels? Are the gears going to survive the heat build up without spectacular failure?

These aren't being used on a big FRC field with the drivers behind Lexan shields, either. Drivers are standing a couple of feet from these robots with no protection except for their eyes.

Am I right to be concerned here, or were these parts engineered with these forces in mind? I don't know if this has really been thought through and I would appreciate some discussion of this.