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Mechanics and Construction => Mechanics and Construction => Topic started by: Matt627 on May 03, 2012, 12:37:35 PM

Title: Strongest Material Endurance for Bending Wires (28 AWG)
Post by: Matt627 on May 03, 2012, 12:37:35 PM

Hi all,

I'm working on a design that runs a few servos.  I've run into an issue with the wire reliability.  After 15K cycles, the wire strands fracture due to the stress from bending back and forth.

Does anybody have any experience with different core fiber materials?  Which ones have the strongest bending endurance?

What are some other solutions for relieving bending stress on the wires?

Thanks.

Matt

Title: Re: Strongest Material Endurance for Bending Wires (28 AWG)
Post by: jkerns on May 03, 2012, 05:34:54 PM

I assume the wires are bending at one "sharp" corner where it comes out of the servo?

One solution is to make the bending happen over a length of wire so it is not so concentrated at one point (which results in work hardening) -  big U shaped loop of wire supported by some flexible plastic for example.

Title: Re: Strongest Material Endurance for Bending Wires (28 AWG)
Post by: Soeren on May 03, 2012, 07:22:17 PM

Hi,

Fine stranded multi core wire (i.e lots of very fine wires in a bunch, instead of fewer heavier wire) are the most flexible . Many R/C shops have this with silicone rubber outer isolation and it comes in many gauges - used extensively for probe wires in pro multimeters as well.

Another method, for sharing the load over a length of wire, besides the U-shape, is to make a single coil loop (just be careful that you don't get interference as a result).

The best solution, if at all possible, is to use slip rings (or a similar setup) where the wire would bend. They're not cheap, but they last and if you are just a bit handy, you can make them yourself.