Tanzendes Skelett

My build notes, hope these are useful to someone.

I recommend getting a set of cheap needle files before attempting this build. Any print blobs in the wrong place will thoroughly gum up the works, and will need to be removed. Also, I find things go more smoothly when you print geared parts on a raft.

The assembly video has a lot of little quality control checks you should follow at every step, which are quite useful. But there are a few more I could suggest:

• Before assembly, check the fit of the cam shaft through the escape (Escape.stl) and the 4-hole gear (Gear 2.stl).

• Make sure the arm linkages (Arm Shaft.stl) move freely through the arms and shoulder joints, and cut away any blobs.

• Check the fit of the legs and leg pins through the body hip joints, and file down anything that does not move freely.

There is a very thin layer near the top of the leg model right in the middle of the hip joint. I used Blender to yoink vertices around to make each side about 0.5mm wider, with no ill effects, but that really ought to be fixed in the official model.

Unlike many geared mechanisms, this has gear faces directly in contact with other gear faces, which potentially introduces a great deal of sliding friction. It probably wouldn't hurt to sand them down and lubricate them.

There is also a lot of sliding friction in the Movement Structure, the oval frame that sits on the chest and transfers motion from the cam to the arms and legs. You should print this in the slickest, glossiest plastic at your disposal--I used natural PLA.

Finally, I don't know if this was an issue for anyone else, but I think the holes in the chest plate aren't correctly aligned with the winding shaft and the cam axle. It's fairly easy to move them around but since the chest alignment isn't super-precise I don't know if I'm the only one who thought this was odd.

The assembled toy works fine but the spring doesn't provide a lot of power. A few videos show skeletons dancing for 5 cycles but I never got more than 3. You should probably force the spring to unwind another quarter-turn before putting the toy away, because hysteresis will do terrible things to PLA springs.

All told, this is a really fun build and the design is super-cute. I only know of one other printable dancing robot model (GZumwalt's Fab Lab Tulsa Trophy), but that doesn't have a wind-up motor. Even in its current state, the wind-up version is worth building at least once for the comedy value alone.

Finally, I want to note that the body cavity is just about large enough to house one of those yellow TT geared motors used in cheap robot projects, which take 3-6VDC and at 3V will run at something in the neighborhood of 1 rev/sec. It would be fairly straightforward to remake this toy to run off a cheap motor.