Mini Rzeppa constant velocity joint for fischertechnik

A working [Rzeppa](https://en.wikipedia.org/wiki/Alfred_H._Rzeppa) [constant velocity joint](https://en.wikipedia.org/wiki/Constant-velocity_joint#Rzeppa_joints) with only 15 mm diameter and connectors for fischertechnik 4 mm clip axles (Rastachsen). Needs six 3 mm steel balls, I got mine from aliexpress. For postprocessing you'll need a 3 mm drill, a 3 mm round file, a flat file, and a round headed Dremel file tool with ca. 5 mm. All parts must be printed very precisely and post processed to free them from any excess filament and make them as frictionless as possible. Print all parts as provided, with .12 layer height or less, 100% infill, use a brim if necessary. The outer race comes in two versions. The slotted one is nice as you can see the mechanism at work and it is easier for assembly and disassembly, but the closed one is more robust and might print better. The cage is the weakest part of the design, print it in PETG at high temperatures for maximum sturdiness. H