Project By: ScottsdaleSteve

This is my entry in the Carbide 3D Community Challenge #14 "Gears". A machine whose only purpose is to circulate ball bearings in a fun and loud way. If you want the original c2d design files, please look in this link:


Type Length Width Thickness Origin
Name Type Tool Feedrate Plungerate Cut Depth

General Comments:

Conceived 2 days after the contest was announced, it’s been a crawl/walk/run/mad dash to get the project, glamour-shots and video done by the deadline. Having never done gears, I thought they would be the hardest part, but they turned out to be relatively straightforward using a free online gear generator (link below).
The hardest part was getting the marbles to load, not fall out on the ride to the top, and then dump out consistently at the top. Gravity keeps them in place for the ride, because the gear rack tilt back 4 degrees. Then through trial and error I machined “divots” on the inside edge so the marbles fall out at the top. [Note: The “better” way is to drill the marble holes on an angle with a Forstner bit in a drill press. But who wants to use a drill press for 30 holes when they have a CNC???]

I had no particular plan. After successfully getting the lifter mechanism working, I just made it up as I went, adding on stick-by-stick until all paths led back to the start.

Design Notes:

  • All parts cut on my Shapeoko XL (Gears, Tracks, “Vortex Bowls”, Spiral staircase steps, Zig-Zag, Left/Right gate, etc.), with the exception of the legs and feet holding up the features.
  • I later modified the small vortex bowls by plugging the single hole and cutting double holes to turn them into “randomizers”.
  • I arbitrarily decided to make it all fit inside a 16x16x16 inch cube.
  • Added a couple idler gears just because I could and I like the way it looks.
  • 100% baltic birch, with 2 coats of Shellac.
  • 12 VDC, 9 RPM motor from Amazon
  • Pulleys and stock Z belt stolen from my Shapeoko maintenance kit.
  • 3/8” steel ball bearings (a.k.a. “Marbles”)
  • Through trial and error, 4 degrees seems to be the magic number for the slope on everything. Less and they didn’t roll well. More and they roll too fast and jump the tracks.
  • Gears designed here: 3 and exported as DXF files, then imported into Carbide Create
  • Marble Transfer Rate: 90 per minute; 5,400 per hour.

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