This is fundamentally a re-design for 3D printing of this mechanism posted on GrabCad here: https://grabcad.com/library/reuleaux-triangle-intermittent-mechanism-1
According to a (modified) Reuleaux triangle (see: https://en.wikipedia.org/wiki/Reuleaux_triangle#Rotation_within_a_square) the mechanism transforms continues rotary movement to intermittent rotary motion. The Reuleaux triangle providing movement to and from the gear-to-be-rotated and the gear's rotation. Very neat, I guess.
Produced in Moment of Inspiration (Moi), simulated in SimLab Composer Mechanical and published in Diamond Age PLA within an Ultimaker original.
Note that contained in the stl files is an optional part Reuleaux rotor spacer. If you're able to print everything 14, you may not need to use this. I found that all 'keeper' could completely tighten screws, but not the screws retaining the handle lever. From the photos and video I've spaced the handle lever outside but they are fiddly to fit so that I designed the aforementioned spacer.
Note also that the posted stl files differ slightly from the model that I printed. I've changed the hub keeper added 3 more holes in the base to accommodate a wider range of rubber bands, and setup to one twist from 3 screws.
Equipment required:
1 longish rubber band
3mm x 10mm long button head cap screws. At least 11 with a maximum of 16.
A video of this model 'in action' is here: https://youtu.be/_lvGsT3ATXw
A simulation is here: https://youtu.be/HkxusRPVYAA
A 3D pdf document in which you can rotate the model to some attitude and then run it is contained in the files.

Print Settings

Printer Brand: Ultimaker

Printer: Ultimaker Original

Rafts: No

Supports: No

Resolution: generally 0.2mm see Misc. Notes

Infill: 30%


Material: Diamond Age PLA was used by me. If you will need the Reuleaux rotor spacer, which is only 0.5mm thick as designed, 0.1mm resolution is appropriate otherwise 0.2mm is, I think, fine. Generally for models of mechanics, such as this, I use 1.2mm wall section everywhere. To warping I suggest a good brim for the parts that are bigger. NOTE. I have NOT oriented the parts for printing. Most do NOT, although some will have a suitable orientation.


Firstly the normal cleaning up.
I use a tapered reamer to clear excess.
For holes in which parts rotate I bring the holes to size with the hand reamer.
Notice that the hole in the handle lever that accepts the handle stem should NOT be reamed out. The handle stem should be a tap fit into the handle lever.
All parts should rotate freely.
Finally, the rubber band. You should aim to have the rubber ring barely stretched when the pawl is engaged in the gear. Use as long a rubber band as possible and twist a 3mm x 10mm (or a bit longer) screw into the proper hole.

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