They're nominally 50kv motors (though we measured them as closer to 70kv), running on 10s. Originally it was going to be two of Deadlock's 5s 5Ah packs, but with the weigh issue I'm going to drop down to a more sensible 2.2Ah but still at 10s. I'm using two of these vescs: http://www.ebay.co.uk/itm/VESC-New-4.../182714259982?, which is basically what we have in Deadlock at the moment.
At 50A it should be able to wheel spin with an opponent on top and have a top speed of ~25mph, but I think the arena's probably a little too small to reach that.
Does anyone know what size the Robochallenge arena is?