How to build a sumo robot ?

How to build a sumo robot ?
Sumo wrestling is an interesting and thrilling event and it has a history and tradition behind it.Basically it may be held as an autonomous or wireless controlled event.So lets see the basics of building a SUMO robot.
CHOOSING A MOTOR
First deceide the motor you are going to use.Speed is inversely proportional to torque.So go for a slow speed motor that gives good torque.And then start building the chassis click here ---> > for more mechanical designs and ideas.
STEERING MECHANISM
Then build your chassis .And deceide the steering mechanism that you are going to use.Always go for differential steering than ackerman steering mechanism.Differential steering provides more manuverablity and easy control which is crucial.Incase you dont know what differential steering mechanism is I will explain you with the following diagram .



I'll explain you the steering mechanism

Both motors forward bot moves forward . If left motor is switched off or reversed bot and right motor is forwarded turns towards left ..and the other way for the right turn.This is very basic and most people know it.
INTERFACING RADIO CONTROL
Then you have to choose a radio control kit.it is always better to have two kits to avoid frequency interference.You can use RC kits stripped from old cars .Then you will have to use the signal from the receiver and drive your motors.If your are using big motors do not use the receicer to drive the motor directly .you might fry it.So you have to make a driver to drive the motor.A H bridge is usually used to drive the motor, relays can also be used.If you use relays you need not worry about voltage and current ratings of motor.
VERY VERSATILE H BRIDGE


Click on the image to see clearly .

This is a very versatile H bridge circuit.And D88O is a power transistor having a max current range of 3 A and voltage range more than 50 v and more amazing is is that it costs only 4 rupees in my backyard.So what happens is when D1 and D3 are switched on motor runs in forward direction and when D2 and D0 is switched on motor reverses its direction.
TIP
If you look at the RC kit you will find 4 controls forward ,reverse,left and right.So the easiest way to drive the robot is use the forward and reverse channel to control one and left and right to control another.Of course can make better controls by decoding the output but this is the easy way.
LOOKS CRAPPY BUT DAMN EASY!!!!


click on the image to see clearly .
RELAY BASIC IDEA
This is the circuit to drive the motors using relays.A relay has 5 pins 2 for the energising coil and 3 for contacts .There is one movable contact and two fixed contacts .And the movable contact is in contact with a default pin when the relay is not switched on .For more tutorials on how relay works> click here .
HOW THE ABOVE CIRCUIT WORKS
So here when when one transistor is switched on the movable contact moves and comes in contact with the +ve supply and since the other end is grounded the motor runs in one direction .And the viceversa happens when the direction is reversed .(Those protection diode is not needed this transistor can withstand much abuse)
AND AT LAST PS
PS:THIS CIRCUIT MAY LOOK COMPLICATED BUT ITS VERY EASY I'VE USED THIS CIRCUIT A LOT OF TIMES .YOU CAN USE 12 V OR 6 V SUPPLY.AND YOU CAN EVEN USE A 6 V RELAY IN CASE YOU ARE USING 12 V SUPPLY(its so versatile), AND NOTHING HAPPENS WHEN 6 V RELAY IS CONNECTED TO 12 V SUPPLY (thanks to back emf)...