Cable Knots

[gafftapegreenia]

Originally Posted by Grog12

GTG...he's talking about using tie-line not the cable itself.

OH, well, then that makes sense.

[mrb]

Originally Posted by gafftapegreenia

OH, well, then that makes sense.

I took it as tying the cable itself around the batten as well

[sk8rsdad]

I am of the opinion that you should never ever put a knot in an electrical cable. These things have a minimum bend radius that should not be exceeded. Any knot that is tight enough to hold the cable is damaging to the conductor, the insulation, or both. These things are carrying electricity so any tight loops result in inductance and that translates into heat, which can become fire given the right (wrong?) conditions.

A technique I use for putting a strain relief on a cable is a piece of sash cord attached to the electrical cord with a Prusik knot. It won't slip under tension and it distributes the stress on the cable over a wider surface area. In this picture the electrical cable would be represented by the white rope, and the red cord is the sash cord.

[Dionysus]

In a more permanent-ish install you can tie a Kellems Grip to the batten with the Kellems Grip installed on the cable. Only problem is installing the Kellems Grip on the cable itself. You have to remove an end.
Other than that I'd totally go for sk8tersdad's suggestion of a prusik from tie-line.

Do not tie knots in the cable itself, or half-hitch it around the batten. It's not good for the cable.

Edit: Decided to show what a Kellems Grip or 'wiremesh grip' is:

[GreyWyvern]

When I suggested the clove hitch, I was talking about the cable itself. It is more than enough the keep it from slipping. A clove hitch tightens itself as it gets pulled on from one side. You could hang on the cable if you do it right, although that would be stupid and potentially damaging to the cable. And I would have to beat you...

Dave

[derekleffew]

The only ones who should be allowed to tie knots in cable are the Foy people.

--Bill Sapsis

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Spanset and shackle for strain relief. Each has his own intricate method, but all are mere variations on sk8rsdad's prusik.

[Grog12]

Originally Posted by GreyWyvern

When I suggested the clove hitch, I was talking about the cable itself. It is more than enough the keep it from slipping. A clove hitch tightens itself as it gets pulled on from one side. You could hang on the cable if you do it right, although that would be stupid and potentially damaging to the cable. And I would have to beat you...

Dave

Wow...really?

Don't do that.

Seriously.

Don't do that

GTG's right its really damaging to the cable to put that many kinks in it.

Go out right now and invest in tie-line.

Knots create kinds in cable and eventually breaks in the S/O. The most you should ever do is put a "loop" in the cable for a little strain relief (think the bow portion of your shoe lace not) and then tie that off with tie line to be safe.

[porkchop]

Derek, as usual, has a great point. Although tie-line is commonly used to keep cables up and tidy in the air, this is a hanging situation where there is stress (potentially significant stress if it's heavy cable) on one specific point, that being whatever is holding the cable to the batten right where it drops down. Now you have a load, overhead, with stress. Spansets and Shackles are rated, tie-line is not. Also the Kellems is a good idea too but I always cut myself on those d**m things.

Side Point: Derek why would Foy people be tieing knots in cables?

[Dionysus]

Flying by Foy uses a special Knot on their wonderful skinny wire rope. Since any other method doesn't hold very well on such small cable. Thus they use their "secret knot".

I defiantly have to agree on using shackles,etc because of rating over tie-line.
I use the Kellems often enough for various things (mainly permanent install), you get a hang of them. After a while they are easy to use. Plus they hold really well, and the electrical inspector certainly likes them more than tie-line, lol.

[GreyWyvern]

If you read the OP, he asked how to keep the cable from slipping down. A clove hitch does exactly that with out any chance of smashing, kinking, flattening, twisting, etc., the cable. The only way that would happen is if the cable itself was holding weight and causing the knot to tighten. Then there are other issues to worry about. I highly doubt that the weight of 20 feet of cable is enough to do any damage. The clove hitch works well because it puts no bends in the cable, the contact is distributed around the larger batten rather than one small point of tie line, and it is extremely easy to adjust to the exact height that you need. I just don't see how it is damaging to the cable.

Dave