My Incredible Full Adder

It has been a long time quest of mine to build a mechanical Von Neumann machine. Lego is a particuarly interesting platform to try this on. Recently my sister reminded me of a game I used to play back in the day when the world was a lot bigger,.. The Incredible Machine (TIM). Classic game in it's time (in my opinion), and still fun to create the odd Rube Goldberg machine.

After finding the game and reacquanting myself with the devices and physics, I set out to create something usefull (this is relative..) I set off with designing some logical gates. The AND, OR, and NOT gates were a breeze, but the XOR gate was more of a challenge. Size is critical here.. It's not an option to build an XOR out of OR's and AND's.

Heres a picture of my AND gate.
The link between the gates was a red laser. Red laser on = 1, Red laser off = 0.

Here's the links to all my gates: AND, OR, XOR, and NOT.

Now the only logical thing (excuse the pun) to do when you've built these gates is construct a full adder. Here it is.

The fullsize image can be downloaded here.