The incredibly prolific, woodworking whiz Matthias Wandel demonstrates the inner workings of a combination lock with his wooden mechanical model.In terms of neat mechanical things to build out of wood, I figured a single dial sequential combination lock would be a neat thing to make. It would be relatively simple, involve movement, and also show people how a combination lock actually works.
image credit: Matthias Wandel
I spent some time thinking about it, and the design I came up with was the simplest that would also be visually appealing that I could come up with. Unlike a real lock, my priority was to show how it actually works.
image/text credit: woodgear
To open the lock, one turns the dial to the right until the notch on the rear most rotor is aligned with the bar. The first number of the combination corresponds to the position that the dial needs to be turned to accomplish this.
After the back rotor is lined up, rotation is reversed. By turning counterclockwise one turn, one will catch the middle rotor with the tab pushing it in the opposite direction. As long as one doesn’t turn too far, only the front and middle rotors now turn with the dial. The dial is turned far enough to align the middle rotor.
After that, the rotation is again reversed, now turning clockwise again until the notch in the front most rotor is lined up with the bar. The picture at left shows all three notches lined up. The lock is ready to open.