how to choose the right motor for robot?

[marteenjwiil]

Hi all,

Now I was build a tank base robot, my robot dimension is 30x30x27 cm (lenght, weight, and height) and the weight was 4 kg and using 2 (two) motor DC EMG30 (http://www.active-robots.co.uk/emg30-gear-motor-encoder-p-384.html) to drive the robot.

But after several experiment i feel the motor not work as my expected and I'm planning to change the motor.
Can you tell me how to choose the best motor for my robot? and what kind motor (brushless or brush) should i use?

Sorry if my english was bad. 

Thanks
 

[Webbot]

Presume you found http://www.societyofrobots.com/RMF_calculator.shtml