Okay, that uploaded quicker than expected!

Right, so my proposed design would feature as its weapon, a small bar-tooth drum. It would be hooked up to a Speed 900 running on 19.2V with a ratio of 4:1. This would give a theoretical top speed of 2600rpm, but take something off for friction losses. The drum is an aluminium/steel composite weighing 2kg. Everything else would be MDF.

In the video below, the two Speed 900s are running the above voltage and ratio. A couple of things to bear in mind are that the drum in the video is longer and of a larger diameter, so the drum I propose to use won't store as much energy. Also, the chassis getting tossed about weighs 2.5kg, five times lighter than the weight of most opponents. So I reckon it would be more of a tosser (if you'll excuse the term) than a rip-the-arse-outta-them spinner.