Here is a powerful all-terrain tracked robot with wheelchair motors that can carry up to 200lbs of load. The Heavy Duty All-Terrain Tracked Robot from SuperDroid Robots has max speed of 2.25mph. It uses 4 x 80RPM wheelchair motors and a Sabertooth Dual 60A Motor Driver.
This robot has a custom tough black chassis. It runs on 2 12V 35Ah SLA battery. It weighs 154lbs. You can find out more about it here.