My Educational Mechanical Examples Series

This model is one of my educational mechanical mechanism examples on 80mm x 80mm base plates.
You can find all models of the series in this collection => [Mechanical Mechanism Examples]

This model

This model shows three single-tooth involute gears meshing in two different ways. Note that the two gears on the both ends rotate in opposite direction.

Brief description

All three gears in this model are made of three heart-shaped plates stacked together with 120-degree phase differences. Each heart shape represents a single-tooth involute gear. A single plate alone cannot maintain continuous meshing, so by stacking three plates with shifted angles, we keep at least one plate always in contact with the mating gear.

If you look closely, the lower-left and upper-right gears have different stacking orders. The upper-right gear has the same order as the center gear, while the lower-left gear has the reverse order. The center and lower-left gears mesh like ordinary involute gears, so they rotate in opposite directions. In contrast, the center and upper-right gears rotate in the same direction. This behavior is unique to single-tooth involute gears and does not occur in normal multi-tooth gears.

Because the meshing relationships are different, the center-to-center distances between the center gear and the two side gears are also different. Please keep this in mind when assembling the model.

Reference

• https://karakurist.jp/?p=1250 

Related Model

Educational model of single-tooth invoute gear meshing with an eleven-teeth gear is also provided.

Case

This model is compatible with the case included in my first set.

Printing

• Use the models named ???-printable.stl for printing.
  The models named ???-assembled.stl are provided just to show how they should be assembled.
   
• Use well-dried PETG to have better dimensional accuracy.
• Use 0.1 mm or 0.08 mm layer height to have smoother surfaces.
• Use slow printing speed for overhangs.
• Select “Random” seam position to have smoother rotation.
  Randomly distributed seam should be easily worn out after some wearing.

Sanding and Filing

Sometimes, the gears suffer from the stringing effect and/or elephant foot effect, resulting in a too tight fit to the shafts (they are designed with a 0.15 mm radial clearance). 

If you see rough surface on the shafts due to stringing, sand off the roughness with a small piece of sand paper.

If you feel the gears do not rotate smoothly due to an elephant effect, widen the hole slightly by using a thin round bar file.

Without those issues, the parts should rotate very smoothly with minimal friction.

Assembly

Stack the heart-shaped plates in the right-order with right-angle. Then, install on the shafts and secure them with the retaining rings. The fitting should be tight enough without gluing.

As described above, the two distances between the three shafts are different. So, make sure that the gears on the center and the upper-right shafts have the same stacking order and the other on the lower-right shaft has the reversed stacking order.

Other educational models

You may also be interested in the models in my educational mechanical mechanism examples.

Find them in this collection:
https://makerworld.com/collections/15048577-my-educational-mechanism-models

Acknowledgement

I got into gears thanks to K.$uzuki's amazing articles and YouTube videos. Many of the mechanisms shown in this series came from the introductions on his website. He also makes excellent gear models himself. This series wouldn’t have existed without his inspiration.

I learned a lot about technical detail of designing gear tooth profiles from Haguruma-No-Hanashi website. I’m truly grateful for that.