I am trying to make this one safe Geoff
I need to look at space within the robot (thus why Im not using a bigger motor) This is why I am using a drill motor. A drill motors high RPM is am advantage when it comes to discs, but Ill have to get the spinning mass perfectly balanced. I have decided on a 14mm steel axle, mounted on 10mm aliminium blocks on both sides. 14mm bearings are to be mounted within each block. The disc is to be an 8mm thick steel disc, about 6.5cm diameter, still allowong the robot to be invertable. Im having the centre of the disc milled out to 4mm, aiding the kinetic energy within the disc. I have decided to mount the drill motor (not overvolted) in the blocks Dominic is using in his UK robotics drill mod kit.
I am using a small belt to the weapon axle (from the drill motor) that will have a total reduction of 1:1.5

This setup will all be within the 8cm height of the robot. This is going to be a disc mounted under the wedge (youll know what I mean if your saw my bot at the FWS) designed to nibble at the undersides of an opponent as he goes up the scoop...

Any more suggestions gladly recieved