So you would like to build your robot tank? The Heneng Robot Tank Platform is worth a look. It doesn’t require any assembly and works with Arduino, Raspberry Pi, and other popular microcontrollers. It has 2 x 12V DC motors with max speed of 93RPM on load.
This robot tank can achieve max speed of 12m/min. It has max load of 22lbs and can overcome 40-degree slopes. Its track is made of ferronickel.