On 30/05/2021 19:48, NY wrote:
"John Rumm" wrote in message
...

the purpose of stranded cable has nothing whatever to do with being
wound on a drum.

Of course it does.

And everything to do with the failure of one strand nit propagating a
stress fracture throughout the whole cable

That is also true, and a benefit, but I would like to see you deploy a
"single strand cable" (or steel bar as we might otherwise call it!)
that can be strung up through the winding gear for a cable car.

Yes I would say that there are two benefits to multi-strand cable:

- gradual failure, where one failure does not cause the whole cable to
break

- increased flexibility for coiling on a drum and feeding around pulleys
on the linkage between the car and the cable

Which of those two factors is the more important is difficult to say:
they go hand-in-hand.



It's why electric cable for installation in conduits of a house can be
single-strand (ie solid) but the leads of appliances which are plugged
into that wiring have to use multi-strand wires: for increased
flexibility (and springing back to a "neutral" un-bent position) and
greater resilience against being repeatedly flexed during normal usage.

The other point that all of you have missed is that at least in the case
of a winding cable, failed strands are normally at the outside (whether
caused by wear, mechanical damage, or corrosion because of inadequate
lubrication), and so readily visible in the periodic insurance
inspections, not to mention to the operators themselves.

Suspension bridge cables are another matter because corrosion or stress
corrosion can cause inner strands to fail. IIRC there are clever NDT
methods, also some cables use continuous acoustic monitoring to detect
strands snapping.