Taking inspiration from epicyclic gearing and the Spirograph, this model houses an asymmetric planetary gear system. Magnets (5mm dia, 3mm thk) in each gear guide steel balls, creating roulette curves in the sand. Simply twist the upper portion of the housing to work the magic.
180mm in outer diameter, approximately 17mm in height.
NOTE: This model is completely unprinted/untested. Fusion 360 file is included for making any necessary adjustments.
The author marked this model as their own original creation.