A 300W scooter motor with an 80:11 reduction and driven at 24V. I use a Victor 883 to control the axe so I return the weapon at a slower speed and also tap that weapon on the floor before the fight. The machette is pretty light but I also use a 2kg sledge hammer which is rather too heavy. I prefered my 1.5kg log splitter but I snapped the handle.
The motor, chain and sprokets came from here http://www.oatleyelectronics.com