This is a way of taking power from two Lego 9 Volt Motors througha differential
,reducing 9:1, and outputting through another differential assemblyto two wheels. It works well to reduce the power such that a Legovehicle (With the Largest Lego [Set 8880, 
]Tires) will move at a decent speed, while still having enoughtorque to move - two motors are essential for this.
Notice that there are universal joints (
)in between the motors and the gear-reducer, and also between thegear-reducer and the wheels. This allows all the elements to movewithout being hindered. If a straight connector (
)is used, the parts rub against one another and cause power loss.
(3D Views coming soon)
