YouTuber Robert Murray-Smith has presented an interesting concept for an epicyclic gearbox that is manufactured entirely using 3D printing. The special feature: instead of classic gears, he uses ball bearings as friction elements, which enables a compact design and backlash-free operation.
Specifically, it is an epicyclic gearbox whose function is based purely on friction. Murray-Smith uses a commercially available thrust bearing with a diameter of 42 mm as the central component. Around it are several cylindrical rollers that are printed from flexible plastic using the FDM process. The flexibility improves frictional contact and thus ensures reliable power transmission.
The special feature of the design is that it does not require traditional gear wheels. Instead, rotational movements are transmitted via the friction between the printed rollers and the surface of the axial bearing. This results in no mechanical tolerances or noticeable play (“backlash”), as would be the case with conventional gearwheels. Such friction-based drives are therefore often used in precision applications, for example to adjust mirrors in laser systems.
The developer explains that the current version of the gearbox achieves a transmission ratio of around 2.5:1. This means that one full revolution at the input corresponds to two and a half revolutions at the output. The design of the gearbox is similar to classic “sun-and-planet” systems, whereby balls or rollers are used instead of gears. The contact surfaces of the rollers ensure higher friction and therefore allow efficient power transmission.
The entire CAD model is available on Thingiverse and can be downloaded free of charge.
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