Is it worth adding additional cores when buying SWA?

[robinbanks]

Ran the wifi down the armored with a tplink main plug worked a treat

Mmm, that wasn't wifi but you'll get mixed opinions on power line Ethernet adapters; perhaps best not to poke that bear

 

[flameport]

If there is any possibility of additional cables being required in the future, install multiple ducts.

Ducting is cheap. Digging up gardens and driveways is not.

 

[d000hg]

If there is any possibility of additional cables being required in the future, install multiple ducts.

Ducting is cheap. Digging up gardens and driveways is not.

The duct was laid 3 years ago because I thought I might want it one day.. I’m just pleased I have it at all

 

[Murdochcat]

It’s worth considering that it’s steel wired armour that does rust, so using 3 core is best in the long term

 

[SUNRAY]

I've not had a problem either, but it does help to keep them separated on the input. It's also possible to blow or suck draw cords through after, starting with a light weight one that you use to pull a heavier cord through, driven by a blockage such as a carrier bag. Depending. The size of the duct you may get away with even a domestic hoover or compressor

Only tool I've ever used to rod a duct pneumatically, 100+m of 150mm took a few minutes though

 

[JohnW2]

Maybe you and I have different things in mind when we each say SWA, but the armoured cable I'm thinking of would be impossible to twist to any meaningful degree if unrolled. If pulled sideways off the coil and straightened out it would have to twist to remove the loop because there is no way it would rearrange itself internally to absorb the rotation brought about by straightening of the loop

We're talking about the same SWA- which, as you say, to-all-intents-and-purposes cannot be 'twisted'.

I'm not talking about twisting of the cable but, rather, of axial rotation of it. In practice (particularly given that access is often less than ideal) prevention of any such rotation is very difficult, particularly if one is handling a long length of ('stiff') SWA. When that happens, it's very likely that rotation of the cable will be 'out-of-synch' with rotation of the pull cord attached to its lading end - so that the cord gets 'wound around' the SWA (one way or the other).

The only way I can think of that would prevent differential rotation of cable and cord would b to tape them to together at fairly frequent intervals - which would, of course, render the cord useless for its intended purpose

 

[robinbanks]

Sorry John, still doesn't make sense to me. As a thought experiment, take 2 metres of SWA, 2 metres of rope, tape them together at one end and hang it from the ceiling. Ensuring they are not already wrapped round each other fix the other ends to a board 4 inches apart and fix the board to the floor. Now we accept that the SWA cannot twist, nor can it rotate.. grasp the middle of the rope and wind it around the SWA. Half the coiling goes clockwise, half of it goes anticlockwise. This won't stay

The only way to get the rope round the SWA is to rotate the SWA like a drill bit would. SWA that is unrolled doesn't rotate. I'm sure whatever has caused your rope to twist up in the past must be related to some suboptimal uncoiling of the SWA. I've 20mm of SWA that runs my table saw and I un/roll it regularly, it doesn't rotate. If my father in law gathers it up it's all over the place and I usually have to pull it out straight again before I roll it up..

 

[d000hg]

Half the coiling goes clockwise, half of it goes anticlockwise. This won't stay

Not in your scenario. In the confines of a duct, under load, the friction might be sufficient that you can't 'pop' it. In fact I reckon if you roll a few turns of rope on a 1m section of SWA in one direction then a few in the other, and pull the end , it may well grip because you are pulling along the SWA. In the same way you have have a tangled cable which is actually not tangled at all, but pulling both ends won't help.

That said to get multiple wraps around your SWA - I assume this was verified by pulling it back out to look(?) - does suggest some sort of user error. Inattention on the person feeding it in perhaps, letting the rope go slack?

 

[JohnW2]

Sorry John, still doesn't make sense to me.

Fair enough.

As a thought experiment, take 2 metres of SWA, 2 metres of rope, tape them together at one end and hang it from the ceiling. Ensuring they are not already wrapped round each other fix the other ends to a board 4 inches apart and fix the board to the floor. Now we accept that the SWA cannot twist, nor can it rotate.. grasp the middle of the rope and wind it around the SWA. Half the coiling goes clockwise, half of it goes anticlockwise. This won't stay

Yes, if one has a cable(like SWA) which will not 'twist',then if one can maintain a fixed relationship between the positions of the cable and cord at the 'upstream'end (e.g. with your 'board fixed to the floor',then the problem go away. However,thought experiments and realty diverge when one is down a hole trying to manipulate, say, 30- 40metres of fairly large SWA!

I have to wonder whether you have ever done this, in realty rather than 'in theory'?

With a cable which can twist (particularly T+E) the problemist far worse,since the cable and cord can then 'twist together', the stiffness of the cable (again particularly if it's T+E) maintaining that twisting.

 

[robinbanks]

Most recently put 3 no 25m lengths of SWA through a 20m duct using a draw cord (three times pulling one cable each time, thanks to changing ideas). Had to do it on my own too, and it was a fair old chunk at 10mm per core * 4 but I don't recall the follow on cord presenting any issue.. Agree that it seems more likely thinner cable could be more problematic but the balloon-ribbon "pilot" didn't seem to suffer either, even when it drew through the meatier cord