Have you ever wanted to understand how a CPU works but are unsure of how much time that might take? Kill two birds with the 'Mechanical CPU Clock.' Lior Elazary designed the clock to teach his children how a central processing unit works as well as "justifying the cost of a new laser-cutter." His clock represents all the pieces of a working CPU complete with ALU (arithmetic logic unit), Buses, ram, registers and control unit, all of which functions mechanically.
Time is displayed by a series of registers that are 'switched' over by a ball bearing when time progresses. Shown in binary form, register 'A' represents what hour it currently is while the outer-edge of HEX numerals represents the clocks minutes. The ball-bearing moves from the bottom of the inner track (presumably by some magnetic-conveyor system) and then drops through register A to progress the hour. Once the hour reaches a count greater than 11, the ball travels through register B which works in conjunction with register C to display the correct time. This, of course, means there is no 'second-hand' displayed so only the hour and minutes are shown at any given time. It's an interesting concept at learning, but it's far more fun to watch the Mechanical CPU Clock change time. See more about the clock after this link.
Though, after hearing the ball drop enough times, I would have to destroy it or at least take it down.