Herewith, some more shameless regurgitation of fantastic Lego creations I found on the excellent TechnicBricks.
Hybrid pneumatic/electric robotic arm:
Another feature-packed car (unfortunately, Lego do not make little rubber cones that'd make the suspension authentic):
Combination-lock safe:
And my favourite - a brick-sorter, which can only detect four sizes of brick, but which does it entirely mechanically, using a single motor!
16 February 2012 at 9:34 pm
Love that last one. The gripping action must store the value of how far to turn before releasing the brick. But the brief view of the innards wasn't enough for me to see how it does it.
17 February 2012 at 7:09 pm
That really is a very clever mechanism.
If you look closely, you can see that the input power is fed into a differential, which splits it between the beak and the mechanism which rotates the entire bird. When the beak clamps down on a lego piece, the beak mechanism's resistance is suddenly greater than that of the rotating mechanism, and so the power shifts to turning the body. And since the power reverses direction at a set interval, the bird will rotate a different distance depending on how long it took the beak to close on a piece (Which of course is determined by how long the piece is,) before it comes to a halt and drops the piece. I would guess that the mechanism with the tires is controlling the reversing of the power, and also seems to add room for a little slip to the mechanism so that the beak can hit a stop when it's over the infeed without grinding any gears apart.