SMIDSY technical FAQ
You need to have sufficient battery power to run your robot around for 5 minutes of combat. This equates to around 10-15 minutes worth of mucking around outside of combat. The batteries need to use gel rather than liquid because if they get broken or turned upside down they musn't leak all over the arena (and the inside of the robot) so there's no point stealing the battery out of the family car.
Most robots are designed around the batteries as they are generally the biggest thing that goes inside. They are also heavy, so don't buy more power than you need. Between 16aH and 25aH worth of battery should do fine. For this capacity at 24 volts you should expect to pay around 130 quid.
Using second hand batteries may seem like a good way to save money, but ask yourself why the battery isn't wanted anymore. If it's because it can't hold a charge and deliver the sort of power it was designed for, then it's not going to be of any use to you either. Yes, we've been there :-)
The most common choice for motors is Bosch. Ellis Components do deals for Robot Wars teams (80 quid each IIRC). The motors need to be around 750 - 800 watts to be any use and you'll need two unless you're being amazingly clever. They need to be able to run equally well in both directions and handle the high currents produced when stalled (pushing) very well.
Iskra motors are starting to be used, also from Ellis. We use one for the disk but aren't convinced they are the best option for drive.4QD speed controllers are made in the UK, but you need to work our how to interface them with your radio receiver. We use Team Delta boards from the States (Team Delta make lots of dope kit for Robots).
The boards from 4QD aren't designed for robots but seem to work alright and are around 100 quid per board. If you've money to burn, Vantec boards from the States are designed specifically for robots and are meant to be the best around but you'll pay around 500 quid for a pair.
There are other people making speed controllers, or you could make your own if you're clever enough. Oh, if you're wondering, speed controllers control the speed and direction of the motors which allow you to drive the robot around!
If you use simple spade connectors then the impacts in the arena will easily be enough to knock something free. We use push-push connectors because they cannot be knocked apart.