Need help buying a cable

[Harry Bloomfield]

It's highly unlikely I would have mistaken copper for steel. They don't have the same tensile strength.

I agree copper is much softer, but the conductivity of steel is very poor - you would need 10x the csa of copper, to match it in steel. Yes, I have come across mains powered items from China which have used steel cored flexible cables. They do try to minimise cost at the expense of safety and reliability.

The wires strands are silver in colour and stiff. To me, I would put copper in the same feel as tin.

 

[DiyNutJob]

Well, I think that is unlikely, stranded are frequently tinned.

I believe what I read. Even if it's wrong, I still want to buy it: tinned 4 core heat resistant cable. Is there a special name for this cable? I don't want to buy one and end up not having tinned conductors. The exact appliance doesn't really matter.

 

[DiyNutJob]

Thanks all. I think I have found my ticket: https://www.ebay.co.uk/itm/194424781525?hash=item2d449ebad5:g:V1gAAOSwWilhYD-n

 

[Harry Bloomfield]

Thanks all. I think I have found my ticket: https://www.ebay.co.uk/itm/194424781525?hash=item2d449ebad5:g:V1gAAOSwWilhYD-n

There you go..!

 

[DiyNutJob]

There you go..!

Not quite yet. How do I work out what cable size I have? I have a caliper I can use to measure the jacket diameter. Will I be able to work out the conductor mm^2 from that?

 

[EFLImpudence]

Not quite yet. How do I work out what cable size I have? I have a caliper I can use to measure the jacket diameter. Will I be able to work out the conductor mm^2 from that?

No.


For a 3A protected cable, virtually anything will do ≥0.5mm².

The flex you linked will carry 16A.

Oh, and incidentally, from the link:

 

[EFLImpudence]

See post #2.

 

[winston1]

How do I work out what cable size I have? I have a caliper I can use to measure the jacket diameter. Will I be able to work out the conductor mm^2 from that?

Measure one strand with your calliper. Calculate the csa of that strand using, pi times diameter squared divided by 4. Multiply by the number of strands.

Tell us what the appliance is. We are all itching to know.

 

[Taylortwocities]

If you still think the old cable is steel, get out your trusty magnet.

Hint**
Steel will attach to the magnet…

 

[DiyNutJob]

See post #2.

Copper and tinned copper are not the same. Tinned copper is stronger and has other useful qualities. The links show what look like untinned wires.

Measure one strand with your calliper. Calculate the csa of that strand using, pi times diameter squared divided by 4. Multiply by the number of strands.

Tell us what the appliance is. We are all itching to know.

Thanks. That could be quite fiddly. I think I will twist the strands and then measure the rough diameter, and go from there. Since the solution has been found, the appliance is no longer relevant.

If you still think the old cable is steel, get out your trusty magnet.

Hint**
Steel will attach to the magnet…

Good idea. But I have given up on the idea of steel since tinning strengthens copper and gives it that steel feel. I was wrong about the steel, but it did look and feel pretty steely. I am no expert, I am ok to make mistakes.

 

[flameport]

Copper is tinned to prevent the copper reacting with rubber insulation.
When all cables were rubber insulated, all of the copper inside was tinned.
Some early PVC cables were made with tinned cores, but that didn't last long as once manufacturers discovered PVC didn't cause any reaction the tinning was removed to reduce the manufacturing cost.

Today, rubber insulated cables and flexes have tinned cores, PVC insulated do not.
It makes no difference to the conductivity or mechanical strength.
Whether PVC or rubber insulation is required depends on the particular application, rubber being more suitable for harsh environments such as those that involve oil, grease or being used outside.

 

[plugwash]

Even rubber cables often seem to be untinned these days, I wonder if the modern synthetic rubbers are less of a problem than the older natural rubber cables.

 

[DiyNutJob]

It makes no difference to the ... strength.

Tinning adds heat resistance and corrosion resistance. It also adds greater mechanical stiffness (I can testify with first hand recent experience). These are strengths. Stiffness can be a strength if the flexibility if not required.

 

[DiyNutJob]

I wonder if the modern synthetic rubbers are less of a problem than the older natural rubber cables.

Even older rubbers are not necessarily a problem. I have two cables, supposedly of the same age and same manufacturer. One has all its core jackets crumpling into dust, the other cable is in perfect condition. The outer cable jacket for both are fine and probably PVC. I am of the belief that the failure is due to commercial entrapment rather than material failure. A deliberately heat-aged cable might have been installed. The crumbling cores were arranged in such a way to increase the chance of a short circuit. The appliance did suffer from triggering the the circuit breaker in the past. Years later, now, I have finally found the reason.

 

[Harry Bloomfield]

But I have given up on the idea of steel since tinning strengthens copper and gives it that steel feel.

It doesn't make it stronger, the tinning is and was to prevent reaction between the bare copper and the insulation, for no other reason. Tinning was mostly dropped, soon after PVC insulation came along.