Gears in Spheres (Octahedron)

Eight interconnected bevel gears in a sphere. Turn one and they all turn. Why not?

Design your own figures or objects to go in the holes. The holes are designed for a 5mm x 5mm peg or key stock.

Print eight gears, avoid using brim if possible to keep the teeth as clean as possible. Print one each of the “Sphere Top” and “Sphere Bottom”. The “Handle” and “Connector” are simple designs to help with construction and testing, not intended for long term use. (Put in eight handles if you want a totally weird and useless device!))

After printing, be sure to clean up the pieces as much as possible, especially on contact surfaces and at the base of the bevel gears. Aim to use minimal support for the sphere pieces, just enough to hold them in place when printing. There will be a bit of print fail bridging the holes, but in the end it is better to just clean up the small imperfections than use support for these.

Apply a thin coating of lubricant to the contact surfaces and gear teeth. Vaseline works well. Be sure to avoid getting lubricant on any surfaces that you will be gluing.

There is a trick to getting all the gears in place. Look closely at the base of one of the bevel gears. You will notice that there is a very small wedge removed from one side. It might be helpful to mark the location of the wedge with a marker as in the picture.

Start with “Sphere Base” and insert the bottom gear. The next three gears will only snap into place when their respective wedges are aligned. Align the wedges and snap in a second gear, then rotate the first gear so the wedge is facing the next hole and snap in the third gear. Do the same with the fourth. This is where the little handle can come in handy!

You don’t have to worry about aligning the wedges for the next three gears that sit in the semicircles around the rim, but do make sure that they snap in as far as they can.

Place the final gear in the “Sphere Top”, and dry fit everything in place. The gears should rotate freely and not bind. It is possible to misalign the teeth when inserting the gears. If you feel the gears binding, remove them and start again.

Once you are satisfied that the gears are properly placed, connect the hemispheres with CA glue, being sure not to get any glue seepage inside.

I am hoping that people can design some more interesting objects and handles to incorporate with this!