This is a combination lock I made for a toy safe I'm designing. My goal was to make a lock that was compact, easy to integrate into various designs and allowed for (relatively) easy change of the combination.
Operation is similar to a common group 2 safe lock, with a few differences. To open the lock you start by turning the dial four full rotations counter-clockwise to the first number followed by two rotations clockwise to the second, then one or two rotations CCW to the third (depending on the code, see below). Finally turn the dial CW to zero to unlock. To lock it again turn the dial CCW at least one rotation.
Due to the design of the lock and how the wheel pegs are attached there are a few quirks to take note of:
- Wheel 1 and 2 can be set to any number from 0 to 9.
- If wheel 3 is set to zero the lock will get stuck open. Therefore this position is blocked.
- If wheel 3 is set to a lower number than wheel 2 you have to turn the dial two rotations, otherwise one, to align wheel 3.
- If wheel 3 is set to one below wheel 2 they will both align when wheel 2 is dialled in, therefore this is not recommended.
- Since the locking pin only fall into the slots by gravity it's important that it can move freely.
Things to think about when printing and assembling:
- Wheel pegs should protrude equally on both sides of wheel 2 and 3. On wheel 3 it should only protrude on the marked side.
- It's important that the wheel pegs don't come loose during operation. If they sit too loose or too tight you can play around with PrusaSlicer's XY size compensation (Horizontal expansion in Cura) to find a sweet spot.
- The wheels have to rotate freely but if they're too loose they can easily get knocked out of alignment. Applying a bit of grease at the centre will help a lot.
Roffe
