Has anyone thought off using friction drive for disc weapons? I have used friction drive in 2 feather weight disc weapons. The first was in Hellbringers saw using a RS-540 (next size smaller then a drill motor) with a foam wheel giving a 2:1 ratio. It was only good at hitting coke bottles (6m up in the air) but the friction drive did make a good clutch.
My next robot, The Aggressor, used a RS-775 (next size up from a drill) with a 6:1 ratio onto a 12 inch bicycle wheel. The bike wheel made an awsome fly wheel and at the last event I bent the 5mm steel teeth 30 degrees back rather then the wheel deforming. It also hit our opponent 15cm into the air in the process too.
Anyway the motors are of the high speed kind and even with the light weight saw fixed between bearings and 2:1 ratio it wouldnt have hit 4000 rpm. Thats all I wanted to say.