The functional crane model I’m working on requires a slip ring to rotate superstructure. Currently this is implemented as a 3D-printed casing for bronze rings (cut from a bronze pipe) and bronze wires bent to touch the rings. 2 bearings at the ends make sure that the model can take some load and retain coaxiality.

The design works fine, but I don’t know how durable the bronze pipes and wires will be in terms of electrical contacts. Also, it is rather bulky, which is fine for the crane, but might not be optimal for other projects.

Inner part of the slip ring

However, I’ve recently accidentally found another potential source for a slip ring, which is a USB cable with magnetic connector at one USB end. Such connectors are very handy to keep phone’s USB socket in good condition. Also some of them offer free rotation along 1 axis (and some even have limited rotation of another axis).

They are very cheap, compared to proper slip rings (6+ USD, depending on number of contacts). Here is what I had, paid 1.88EUR for it on a sale. Non-discounted price is around 5 USD, but there seems to be always some AliExpress sale going on. AliExpress search terms are "rotating magnetic USB cable". "540" means it has 2 moving axis, one freely rotating (360 deg) and one 180 deg. Beware that they differ in number of contacts they provide. Cheapest only do 2 contacts (GND and VCC for charging), more expensive ones also contain data lines and have 4 contacts in total.

Disassembly is rather easy, however, I damaged one contact disk (luckily there are 2). Removing soldered components will need to be done with a heat gun.

Anyway, disassembly shows that the pieces have potential to be incorporated into a miniature slip ring. Some casing will need to be designed, and load-carrying bearings will probably also be needed.

Stay tuned for further updates!

Teardown process