Here is a heavy duty all-terrain tracked robot with wheelchair motors that can move up to 200lbs of weight. The SuperDroid Robots All-Terrain Tracked Robot uses 4 x 80RPM wheelchair motors and two 12V 35Ah SLA battery. It also uses a Sabertooth dual 60A motor driver.
The robot has max speed of 2.25mph. It has a custom rugged black chassis. The above video shows it in action.