At first glance this puzzle looks completely impossible — a solid structure with a ring that appears permanently trapped inside,but the secret is surprisingly simple. Hidden inside the housing are two short pins riding in an internal groove. When the puzzle is spun, centrifugal force pushes these pins outward, temporarily freeing the center pin so the ring can slide out.

Shaking, tapping or rolling  won’t work — it must be spun correctly.

This puzzle is easy to print, easy to assemble, and makes a great desk toy.

Printing & Hardware

This model is almost fully 3D printed. The only required hardware is:

• Dowel pins:  1. 3× Ø5 × 50 mm

                         2. 1× Ø5 × 40 mm 

                         3. 2× Ø5 × 20 mm 

Dowel pin embedding step:

• The housing is designed for a pause-at-layer dowel pin insert

• When the print pauses, place the two 20mm dowel pins into their slot and resume the print

   

Assembly Instructions

1. Print all parts
2. (Optional but recommended) Lightly sand the ends of the three outer pins so glue adheres better
3. Apply glue to the pin holes in the base part 2 (base with the embedded pins)
4. Press the three outer pins into place
5. Insert the steel inner pin and the ring
6. Apply glue to the pin holes in base part 1
7. Align the pin holes in the base part 1 with the three pins and press the it into place