Lego Combination Lock

A long, long time ago I got an itch to make a combination lock out of Legos. I made a little demonstration model, and it's been sitting in a bin for 5 years or so. This weekend I finally got around to documenting it so that I can take it apart and reuse the parts.

The design was inspired by How Stuff Works.



To make the notches in the wheels I used Lego tread, with one link of chain instead of tread. This creates a gap. The tread was wrapped around a large gear.



Here's a shot of the lock with the three notches lined up. The fence is currently resting in the notches.



Because of the limits of Legos, I had to use gears in pairs to make the disks. In the image above you can see the drive pin and the wheel fly of the first stage on the left, and the drive pin of the second stage to the right. Counting from the left, there are breaks in the axles between the first and second gears, and the third and fourth gears.



Finally, here's a goofy little video of the lock in action. It sticks a bit at the end and I have to jiggle it.