Motorized Excavator with Independently Power Undercarriage & SBrick

The original tracks were powered by two motors in the upper parts of the excavator, through a series of gears.  With power losses through transmission, the tracks moved very slow and didn't want to move when the batteries were half drained.  

As I am using two SBricks, I place one SBrick in the carriage with two motors and battery case.  The tracks are now independently powered regardless, moving smoothly and a little bit faster than I expected.  By separating the upper part and undercarriage, I don't need to replace the batteries so often.

I also modified the SBrick control panel designed by Jurgen.  The original design was to use two sliders to control the forward and backward movement of the tracks.  Due to sensitivity of the control, it was difficult to synchronize the movement.   I replaced the sliders with a joystick in the middle, turning it by 45 degree.  By moving the spot up, both tracks are moving forward.  By moving the spot to left, the left track is moving backward while the right track moving forward making a left turn.  It is easier to control the travel of the excavator now and can have several movements at the same time.