Found this one on Thingiverse and gave it a print. Got the idea to shrink to 55% and use bb's (4.5MM) from a comment. Works pretty good once I used a lighter to clean up filament strands due to the use of silk. Also used a sandpaper and pencil lead to help smooth/lubricate some of the runs where things were catching. Printed on K1C, sliced via OrcaSlicer @ .16 with no supports. Did notice one of the little tracks supports failed during print but didn't affect the final product. Likely prints are better full-size or even enlarged. Model: https://www.thingiverse.com/thing:6537539 Other models’ creator has for purchase: https://www.etsy.com/shop/elegantmachines/?etsrc=sdt Hope you have a great day AND that your next print is a success!