What kind of conduit do I need for buried armoured cable?

[d000hg]

What ever duct you use put a rope through it prior to burying, flexi duct comes with a draw wire, but i still prefer using that to pull a more sturdy blue nylon rope in

I'm a bit paranoid about it, I'd probably put at least two in if I was doing the work personally

 

[JohnW2]

I'm a bit paranoid about it, I'd probably put at least two in if I was doing the work personally

In my experience, one problem with having two or more ropes/strings/whatever, and using just one to pull a cable though (and, similarly, using one rope/whatever to pull through cable plus a 'new rope', for future use) is that the remaining/new rope(s) always seems to get twisted around the cable and hence usually/often are unusable in the future for pulling anything new through.

However, others may have had different experiences!

Kind Regards, John

 

[bernardgreen]

If you use braided drawcord then there is no twist created when the cord is stretched.

 

[JohnW2]

If you use braided drawcord then there is no twist created when the cord is stretched.

That may well be true but, in terms of what I said, my personal experience is that attempts to pull a 'replacement cord' through with a cable almost always result in that cord ending up wound around the cable, and hence effectively unusable.

Kind Regards, John

 

[bernardgreen]

my personal experience is that attempts to pull a 'replacement cord'

Were you using braided cord to pull cable and replacement cord into the duct. ?

 

[JohnW2]

Were you using braided cord to pull cable and replacement cord into the duct. ?

I think I've probably tried most things over the years.

However, I'm not sure that the nature of the cord has much bearing on the issue I was describing. The problem arise because the cable rotates as it is being pulled through - so that, if another ('replacement') cord is being pulled through with it, that cord ends up wound around the cable - and I'm not sure that braiding would significantly reduce that, would it?

Kind Regards, John

 

[bernardgreen]

If you must use twisted lay drawcord then use a smaller one of THESE between drawcord and the cable

 

[Taylortwocities]

That’s something for the Xmas list!

 

[d000hg]

I think I've probably tried most things over the years.

However, I'm not sure that the nature of the cord has much bearing on the issue I was describing. The problem arise because the cable rotates as it is being pulled through - so that, if another ('replacement') cord is being pulled through with it, that cord ends up wound around the cable - and I'm not sure that braiding would significantly reduce that, would it?

Kind Regards, John

Depending on the cable I'd be dubious it can rotate all on its own as you pull it through. That would be building up a lot of rotation which you'd surely notice at the end the cable is being pulled in. If I think about even quite thin lighting cable, it really doesn't like to be twisted on its axis.

On the other hand I can see friction building up really quickly when cables are rubbing past things for the same reason that they don't limply snake along the conduit but try to retain their shape - with a cable already in there this is only going to get much worse so it might just be that?

If you ever have some clear pipe handy, do an experiment

 

[Notch7]

If you must use twisted lay drawcord then use a smaller one of THESE between drawcord and the cable

£235

 

[JohnW2]

Depending on the cable I'd be dubious it can rotate all on its own as you pull it through.

I can assure you that it can, and does

That would be building up a lot of rotation which you'd surely notice at the end the cable is being pulled in.

When one is pulling on 'a piece of string', maybe dozens of feet from the end of the cable one is pulling, there is no way that one will notice the rotation, particularly given that one will repeatedly release, and then get hold of again, that 'piece of string' as one pulls.

If you ever have some clear pipe handy, do an experiment

I've already 'done the experiment' on a good few occasions, when I have ultimately pulled out an entire cable with a cord/whatever comprehensively wrapped around it!

Kind Regards, John

 

[JohnW2]

If you must use twisted lay drawcord then use a smaller one of THESE between drawcord and the cable

If I understand that product correctly, quite apart from its ridiculous price, I don't really see why it 'swivels' - since that would seem to exacerbate the problem I've been describing.

A non-swivelling version, which I imagine one could fabricate oneself 'for a few pence', might well reduce, or even eliminate, the issue I mentioned!

Kind Regards, John

 

[bernardgreen]

The swivel allows the stretched drawcord to un-twist without the torque generated by the un-twisting affecting the cable being pulled.

 

[JohnW2]

The swivel allows the stretched drawcord to un-twist without the torque generated by the un-twisting affecting the cable being pulled.

Hmmm. It's the rotation of the cable, not the twisting of the cord, which results in the phenomenon I've described.

I perhaps should have added that, particularly with long ducts, the 'cable rotation' issue usually arises only during the early phases of the 'pulling though', since the cable is much less inclined to rate one an appreciable amount of it is in the duct. The 'winding of a cord around the cable' therefore generally only affects the initial part of the cable. However, just a turn or three around the cable (towards one end) can be enough to render it useless (for pulling other things through) - and, although one might think that it would be fairly easy to 'unwind' that turn or three, in practice it can be difficult/impossible.

Kind Regards, John

 

[d000hg]

Do you actually mean the cable is rotating, or that the cable is 'orbiting' the first cable and wrapping it up? Difference between me twisting my finger 360 degrees (ow) Vs stirring my cup of tea with my finger, if you catch my drift.