What you need to get going
It’s not hard to create a remote controlled robot. About all you need are a motor, wheels, battery, speed controller and radio. Just make sure they’ve been tested and used successfully in competition.
Motors
Shop for MotorsDo:
Your motor should be your first priority. Motors are generally a 24-volt permanent magnet. Wheelchair motors seem to work best. If they don't come with a gearbox, you must reduce the RPMs by way of chain and sprocket, belt and pulley, or gears.
Don't:
Weak motors are the #1 reason 'bots fail. Start the whole building process with a proven motor. Stay away from window, windshield and starter motors. Industrial off-the-shelf motors are too heavy.
Tires
Shop for TiresDo:
You would do well by finding wheels that come with lightweight foam inside for flat proofing. House hazards and opponent weapons can end your day real fast. Rubber treads with a durometer rating between 55 and 70 work best.
Don't:
Leave the foam filling to the pros. There is no off-the-shelf stuff that works. Don't use hard wagon-type wheels, you need all the traction you can get. Beware; large tires (over 12") require LOTS of torque.
ESCs
Do:
There are only a handful of electronic speed controllers (ESC) that can hold up to the current demand of a battling robot. Make sure the one you choose has been recommended by an experienced builder.
Don't:
DO NOT presume you (or your uncle) can build your own ESC. 99 times out of 100, you will see your creation give up the dreaded white smoke.
Batteries
Shop for BatteriesDo:
12-volt sealed-lead-acid (SLA) batteries have a lot of power, are not very expensive, but can be heavy. "D" or "C" size rechargeable NiCad's are lighter, but expensive. Only buy batteries that claim to deliver a "high amp discharge".
Don't:
Any battery you choose MUST NOT be able to spill its contents if pierced. SLA's must be absorbed glass mat or gel cell. Don't choose a battery that is underpowered for your need.
Radio
Do:
The radio is really the only essential component that you can buy at a hobby store. Contact the competition you are building for, and see what their rules are for acceptable radios. It can vary from place to place.
Don't:
Don't skimp on your time to research the various competitions' radio transmitter requirements. You may end up fighting more than once and travel to other venues.