Scharfenbergkupplung (fidget toy)

This is a functional model of a Scharfenberg train coupler in the style of a fidget toy.

https://en.wikipedia.org/wiki/Scharfenberg_coupler

This is optimised to be printed with no supports, 0.2mm layers, a standard 0.4mm nozzle, no brim and needs no additional hardware.

WARNING:

If you print it and the axle has a bit of a “dogbone” shape like the photo to the right there is a chance you have bigger troubles in assembling the parts. This happened on a Bambu Labs with default profiles, on my Prusa machines the standard profiles were no problem, though the extrusion multiplier must be dialed in for the filament used.

If needed, print the files at 150% as 0.8mm walls then have 3 instead of 2 perimeters and tolerances aren't as critical.

Assembly instructions:

I suggest printing two identical sets of the coupling in different colors and then switch out the following parts from each other:

The assembly of the main axle is as follows: thread the small hook part and the main “disk” part on the shorter end of the axle. For orientation: the bottom layer is always the downward pointing layer.

The spring retaining knob must be pointing as shown in the next photo:

Getting the spring to sit flush against the "disk" part might require some force, an easy way is to use the tweezers as helpers to push on the narrow inner part of the spring that can accept this force:

The linkage part can now be threaded into the disk/hook part

The spring should fit snugly in the retaining geometry in the bottom part, after inserting the spring you might need to lift everything up a little to rotate the assembly over the stop

Add in the keylug as well as the lever and pressfit all together:

The mechanisms should work quite freely once they are used a bit. The couplings should be quite jumpy once released quickly :)

While the two halves of the cassis should fit quite snug, some glue may be advised if one actually wants to use it on a keychain.

Photo source of the ICE coupler:

https://commons.wikimedia.org/wiki/File:ICE_3-Scharfenberg_coupler_PNr%C2%B00236.jpg