Hi NeonMatt.

On the pillar drill. Even when you're not building a robot, it's a dandy tool to have.
But, don't buy too small. The £75 versions from Ebay or the DIY are capable enough for basic feathers or smaller machines. But the small motor will struggle with the better materials or bigger holes in metal. Especialy when using cheap and/or blunt drills. Better to safe up for a bigger one with a 500W or better motor.

On the TZ85's. For a basic drill drive, the BotBitz 30 A speedo is more than good enough.
Also, I myself buy TZ85's from BotBitz. Not worth my time to reprogram those myself.


KV stands for rpm per volt input. A 1000 KV motor will run 5000 rpm on 5V.

Kinetic energy aka KE. The faster a weight is moving, the more force will be in that object. A slow light disk will contain less force than a fast heavy disk.
Keep the same speed and double the weight, and the force contained in the disk will be doubled.
Kep the weight and double the speed, and the force contained in the disk will quadruple.

Wheel placement and such. In a vertical spinner the wider the wheels from each other, the less the gyro effect. The closer to the axle of the disk, the more weight on the wheels, so more control/torque availabe.