BILLY THE PENGUIN - by Alex and Sahana
This is Billy the Waddling Penguin. Billy has two motors directly underneath his brain (the brick). The motors are connected from the back of the brick and to secure it, there are also connections on the side. Each motor controls a gear train, and each gear train is attached to one of Billy's legs. Each motor is run at the same time and at the same power, with the two legs in different starting positions, such that one leg takes a step forward while the other leg prepares itself to do the same, and so on. Unfortunately, Billy has had 1 too many fish, and has some difficulty getting his feet fully off the ground due to his weight. However, the motion of the motors and the legs still generate enough momentum so that Billy is able to waddle forward.
The gear train uses four gears -- the largest gear available in the LEGO kit is the driver. This gear train is designed such that the other gears in the train move at a higher speed than the motor. Two 24 tooth gears are used to move the legs, with an 8 tooth gear between them to make sure that each part of the leg moves in the same direction.
Something to note is that one of the motors inherently moved slower than the other--something that was not discovered until much later. Hence, since one motor moves more slowly than the other, in some of the videos, Billy's path may be skewed to one direction (like when billy moves backwards).
The motion when Billy went slower vs. when Billy went faster was a lot smoother. When Billy went fast, he jostled around a little bit but the slow motion was closer to the intended design.
Connection of Brick to Motors
Side view: gear train structure, legs, some connections of brick to motor
Back View of Billy (left)
Back view of Billy (right)
Billy moving forward at motor speed = -10
Billy moving forward at motor speed = -1000
Billy moving backwards