My First R/C Robot

[modeon]

The subject is self-explanatory. I need to build a R/C robot for a robot sumo competition. I do not need to have a weapon attached; the robot is only needed. This is my first time, and I have borrowed some books and read through most of the forum topics and articles on this site. After much debate, I've decided to go with geared DC motors. Correct me if I'm wrong, but I need a radio transmitter that will send signals to a receiver inside the robot. The receiver will be connected to a speed controller which will direct how much current is given to the motors. Do you recommend using a drivetrain or simply using gearhead motors? Do you recommend proportional speed controllers or relay controllers? I'm confused on how all of this comes together. I know that I want a lot of torque because I'm going to be up against 50 lb robots. Is the motor the basis of determining the type of battery and wheels? Thanks you guys!

[VegaObscura]

If your robot is anywhere near 50 pounds, you should use a drivetrain.  Too much weight directly on a motor shaft can bend things inside the motor and cause it to seize.

[koolraj09]

Hi modeon.
You can use drivetrain...but see to it that it doesn't weigh far too much.
Yes,the motors are the way your battery rating is going to be determined...because it's the motors that suck the current during pushing. You can calculate the battery rating by:
Voltage at which the motor operates*Current sucked by your motor*time(in hrs)*no. of motors used = Amp-Hrs of the battery required.
Regarding wheels you have to "optimize".
If you have larger wheels then your speed will be high but the pushing force will decrease and vice-versa. I recommend you not to keep the wheels too big.
Also you can use a ramp type wedge or scoop type wedge to your advantage.
Good Luck.

[koolraj09]

EDIT:
Battery rating = Amperes the motors suck*no. of motors*time in hrs