I designed a trick chess piece with hidden compartments

It's quite easy to model a traditional chess piece (apart from a knight) using CAD software. You basically just have to draw a sketch of the outline and revolve it around its centre. I modelled, and 3d printed, a Queen that includes some hidden compartments for storing small bits of paper, e.g. containing passwords or Bitcoin keys.

I'm calling it the "Queen's Gambit", because a gambit is both a cunning trick and a chess opening.

(Get it? Opening!)

If you like, you can watch a short video of me demonstrating it (but there's no talking, and it's not very close-up; the photographs in this post are better).

Here's a cross section of the final model:

It has 3 threaded connections, and another part that clips into the bottom, secured by a slight taper and the natural ridges from 3d printed layer lines. It is pushed out by sliding an allen key or similar down from the top, through the hole in the centre of the piece.

I started by creating the different pieces in FreeCAD, but with no threads as I'm not good enough at FreeCAD to model threads.

The white line is the shape of the body of the piece. The blue circles and green lines are control points for the Bezier curves.

I downloaded marcaxi's OpenSCAD screw thread library from Thingiverse and used it to generate all of the threads I needed, and joined them with the FreeCAD-modelled parts.

Here are some photographs of the piece in various stages of disassembly:

Thanks to the 3d printing layer lines, it is almost impossible to tell where the openings are. I'm very pleased with how it has turned out.

If you want to print one, you can download the STL files.

Please send me some photos if you make one.