Re: Curly Cord

["Bob La Londe" <none@xxxxxxxxxx>]

"Robert Macy" <robert.a.macy@xxxxxxxxx> wrote in message
news:55107f6e-de4f-4ca4-8eca-ad55376c6526@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> On Aug 30, 10:36 am, "Bob La Londe" <n...@xxxxxxxxxx> wrote:
>> I am looking for a decent length multi conductor curly cord.  So far the
>> most I have found is 10 conductors.  Its for a custom built remote for a
>> CNC
>> machine, but if anybody knows wire its this group.
>>
>> I can get by with 10, but 12 would be better allowing my to run a
>> separate
>> common for critical items like an emergency stop circuit.  I'ld like
>> conductors large enough to tin and put in a screw terminal, and a fair
>> amount of straight jacket at each end.  If the curly part easily
>> stretches
>> to about 4 feet with a max of 5 or so it would be perfect.
>
> If you can't find it, I believe it's possible to construct your own
> using highly flexible wires and curly plastic tubing. Assuming you
> have room for that.  At least that way, you shouldn't run out of
> conductors.  As I recall, something like 4 inch diameter plastic
> coils.
>
> One project we used fibred flex cable all rolled up. take a look
> inside an old printer for an example. Interestingly, the strain relief
> had to extend several inches because even the longitudinal flexing of
> the cabling tended to break it.  Another polyimide PCB [I think, may
> have been polyamide, which works in a vacuum, too]
>
> From memory, the high quality curly cords we used were copper foil
> wrapped over silk thread. They were rather resistive, but never broke,
> and IMPOSSIBLE to kluge to to make a temporary connection.  The cheap
> ones out of Asia were simply tiny fibres of copper, like 15-22 strands
> per conductor, but they were one tenth the resistance and EASY to
> kluge connections to with a soldering iron, which is guarranteed to
> make a spot for the cable to break.

Typically with a curly cord there is a fixed cable pass through were
movement ends if setup properly.  There should be a strain relief installed
at that point also.  All splices, connections, etc should be made beyond
that point so that no movement can dislodge them or create high strain at a
"hard point" like the tinned end of a conductor.  Even something as simple
as the plug on the end of a telephone cord employs this principal to some
degree.  There is a plastic tab that compresses down and holds the cable in
place.  The individual conductors are then penetrated (for stranded) or
skinned (for solid) beyond that point to make the electrical connection.