Kombi

This CAD model was designed by Oskar van Deventer, copyright (c), 27 August 2025.

Kombi is a four-ring combination lock. Each ring has ten segments, numbered 0-9. The segments have different size. The goal of the puzzle is to take apart into 40 dovetailed pieces. When the two rings are properly aligned, using the secret code 1638, then the gaps between the numbered pieces align at two places, and one half can be slid from the other half. After that, everything can be taken apart easily.

The puzzle is based on the prime numbers 2x3x5x7, using a angular grid with 360/(2x3x5x7) degrees spacing. The gaps at the first ring are at multiples of 360/(2x3x5) degrees apart. The second 360/(2x3x7), the third 350/(2x5x7), and the fourth 360/(3x5x7). This assures that when four gaps align at one place, there can not be any aligned four gaps elsewhere. This rule is violated at one point with an aligned gap that is exactly midway between two grid angles. This assures a unique solution, as well as many near misses where two or three rings align.

Here are some links about this design.
https://www.youtube.com/watch?v=dkQQaXRzFNk
https://puzzleguy.store/products/kombi-four-ring-combination-lock
https://twistypuzzles.com/forum/viewtopic.php?t=40543

Feel free to 3D-print an extra sample to give to a friend, as long as you mention the designer and don't charge money.

If you are planning to sell some samples, then please contact me for a license agreement. The royalty fee is 10% of your selling price.

Please do not upload the design to a commercial service, or redistribute the design in any way other than linking to the YouTube video: https://www.youtube.com/watch?v=dkQQaXRzFNk

Enjoy!

Oskar
18 October 2025

Contact: 
https://oskarvandeventer.nl/index_contact.php?subject=Print%20It%20Yourself