Funny you should say that...

[SUNRAY]

If possible use a braided cord rather than poly rope. Poly rope is twisted and when under tension it tends to untwist and this can twist the SWA. Braided cord does not untwist when under tension. Poly rope can be used if there is a swivel connector between rope and chinese finger

Twisting the SWA by itself is not a significant problem but if you are also pulling in a new draw cord along side the SWA then the new draw cord will be wrapped around the SWA and not be much use as a draw cord.

Today a simple question of adding a bit more brawn...
About 4-6 years ago contractors laid a 6" duct, 220m with a 300mm pit (drainage access chamber) roughly in the middle. We pulled in 3 SWA's: 1.5mm² 12c all the way, 35mm² 4c to the mid point building and 16mm² 2c from there to the far end and a blue draw rope everywhere:

Since then there are 2 more cables about 15mm diameter to the mid point.

The plan was to pull in one more today all the way and finding 2 blue ropes in the first run thought it would be OK, after an hour of huffing and puffing a cheap USB camera was put down the duct on lightweight cable rods to find each rope is wrapped around a newer cable every metre or so...

Out came the Henry's...

 

[JohnW2]

... The plan was to pull in one more today all the way and finding 2 blue ropes in the first run thought it would be OK, after an hour of huffing and puffing a cheap USB camera was put down the duct on lightweight cable rods to find each rope is wrapped around a newer cable every metre or so...

My experience has been limited, but it has always been the same, even with a single cable and single rope.

Putting a rope in a newly-laid duct, with which to pull through a cable, is fine. However, if (as one usually would do) when one pulls the first cable in, one also pulls through a 'new rope' (for subsequent use) my experience is that the 'new rope' invariably gets totally wrapped around the cable. That means that one cannot use that 'new rope' for subsequently pulling through another cable, unless one also pulls out the original cable!

Kind Regards, John

 

[SUNRAY]

My experience has been limited, but it has always been the same, even with a single cable and single rope.

Putting a rope in a newly-laid duct, with which to pull through a cable, is fine. However, if (as one usually would do) when one pulls the first cable in, one also pulls through a 'new rope' (for subsequent use) my experience is that the 'new rope' invariably gets totally wrapped around the cable. That means that one cannot use that 'new rope' for subsequently pulling through another cable, unless one also pulls out the original cable!

Kind Regards, John

Professionals don't have the twisting ploblem, they either use a swivel (a proper ballrace version) or proper cord. As a BT apprentice I did 2 months with a rodding and cabling gang, in that time we must have pulled in 10 miles of cable (4 miles in one day and that was only 3 pieces) and only found one twisted rope. From the way the end was spliced the guys knew exactly who was responsible and made a report.

 

[JohnW2]

Professionals don't have the twisting ploblem, they either use a swivel (a proper ballrace version) or proper cord.

Yes, I'm sure that must help a lot. Furthermore I presume that they will usually (perhaps always) be pulling in brand new cable straight off a drum, and that should also prevent the cable from 'rotating' (which is the thing one has to avoid).

Kind Regards, John

 

[SUNRAY]

Furthermore I presume that they will usually (perhaps always) be pulling in brand new cable straight off a drum,
Kind Regards, John

Within the entertainment/conference/broadcast environment nothing could be further from the truth.

 

[JohnW2]

Within the entertainment/conference/broadcast environment nothing could be further from the truth.

That I can believe, but I was really thinking about your experiences as a BT apprentice when I wrote that - I would imagine that when BT pull in "4 miles in 3 pieces", what they are 'pulling in' would be "brand new cable off a drum"!

In other circumstances, I would imagine that (per my non-professional personal experiences!) it remains very difficult to stop the cable rotating, even with a swivel - and it probably only takes one turn of rotation to cause a problem, since the moment one pulls on the rope it tightens around the cable.

I have to say that, on the few occasions I've attempted it, I've ended up having to pull out all of the existing cable(s)+rope(s) (together), at the same time using them to pull in a new set of cable(s)+rope(s) (again, all together).

Kind Regards, John

 

[bernardgreen]

pulling in brand new cable straight off a drum, and that should also prevent the cable from 'rotating'

The cable as it comes of the drum does not ( cannot ) twist but the leading end can and does twist if the hauling rope under tension is untwisting it'self and there is no swivel joint between rope and cable.

 

[JohnW2]

The cable as it comes of the drum does not ( cannot ) twist but the leading end can and does twist if the hauling rope under tension is untwisting it'self and there is no swivel joint between rope and cable.

OK, my "prevent" was a slight exaggeration, but it's much less likely to twist (and can't really 'rotate' at all) if it's new cable coming off a drum, with our without a swivel joint.

If the incoming cable is simply 'lose' (lying ion ground), it's extremely difficult to stop it rotating, and quite probably would still be even with an (inevitably 'imperfect') swivel joint. As I said, I've personally never succeeded (albeit I've never had/used a swivel), even with a single cable.

Kind Regards, John