I think I mention their names earlier, but they're from Dewalt drills supposedly 300w each. The gearboxes are from the same drills.

Yes using chain, we originally wanted to use V-Belt drive so that it would slip on impact and not stall the motor but we had spare chains and sprockets from an old bike, plus you can easily make a chain to the length you require.

In our case this was very short, and even the shortest fan belts are too long (from Mini's for instance). We considered using the drive belt (or 2) from an upright vacuum cleaner.

Once we fitted to the one way bearing and remembered were using a 6S Li-Po on a 12v fan motor we decided that pulsing the motor and turning it off on impacts would be better than just leaving it spinning the whole time.

Sam with NST I believe just had the spin switch on Ch5 and just flicked it on at the start of the battle (also used chain drive, I believe it's one of the more efficient forms) but he ran into also sorts of issues like contacts welding on Relays...