SMARS uses small 6v 150RPM motors to drive the robot around. These cannot be powered by the Arduino or Raspberry Pi directly and so need a driver board. These motors have a tiny gearbox to provide sufficient power to move the robot around. They are 3v-6volt DC, and are described as Short Shaft Torque Gear Box Motor. 200RPM & 300RPM motors are also available, which are much faster but have less torque.