Can anyone help me identify the motor/mechanism used in this? I've been trying to recreate the Useless Machine found here:
http://www.youtube.com/watch?v=QdKtgfmfA7s&amp;feature=c4-overview&amp;playnext=1&amp;list=TLp4R5S7LPESk

In the description, there's a link to a brickshelf gallery that has detailed pictures of the insides of the machine: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=416984

I think I've figured out most of the mechanism, but can't for the life of me figure out what motor is being used, and how the motor stops running once the arm is sufficiently retracted. There doesn't seem to be another switch hiding at the bottom... Those two things have just been bugging me for a while.

First post here, I'm only just getting into LEGO, thanks for the help!
The motor appears to be a very standard 9V motor, presumably using a conversion cable as the switch is a PF one.

As for how it stops, it's not that complicated: when activated,the mechanism pushes the switch back to its "off" position, which is what makes the motor stop. You'll probably think the motor direction is reversed and that's what makes the arm go back in the box, but that's not the case: the motor is actually off and what makes the arm go back is simply its own weight.