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#1
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Attaching a pull rope
I was wondering how knot experts would suggest
attaching communication cables to a pull rope in a conduit. Criteria: The pull rope is usually very stiff 3-strand twisted 1/4" polypropylene. It does not hold knots well at all, in my opinion. The cable to be pulled is 6-pair gel-filled buried drop wire with a diameter of abt 1/2 ". This wire is somewhat rigid in that it has 12 conductors, a copper sheathing, and a weatherproof black outer sheath. . Note: the sheathing can be stripped back to expose the conductors, and the conductors themselves can be tied to the pull rope. The splice between rope and drop has to be as compact as possible, as the diameter of the conduit is often as small as one inch, with several "elbow" turns along the way. Strength of splice is very important, because this cable is heavy and when the pull is over 100' there's a great deal of strain on the joint. What's normally done is the drop is stripped back and the a bight of the conductors is formed at the end. The excess length of the conductors is wrapped around the sheathing of the drop and taped down w/electrical tape, so you end up w/a loop at the end of the drop. The pull rope is the knotted to the loop. What happens from time to time is the loop pulls out, the knot is too bulky for the elbows, the knot slips due to the gel and stiffness of the rope, etc. etc. Any ideas would be appreciated. Luke in Ca |
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#2
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wrote in message ... On Sun, 3 Jul 2005 18:58:02 -0700, "Luke 451" wrote: I was wondering how knot experts would suggest attaching communication cables to a pull rope in a conduit. Criteria: The pull rope is usually very stiff 3-strand twisted 1/4" polypropylene. It does not hold knots well at all, in my opinion. The cable to be pulled is 6-pair gel-filled buried drop wire with a diameter of abt 1/2 ". This wire is somewhat rigid in that it has 12 conductors, a copper sheathing, and a weatherproof black outer sheath. . Note: the sheathing can be stripped back to expose the conductors, and the conductors themselves can be tied to the pull rope. The splice between rope and drop has to be as compact as possible, as the diameter of the conduit is often as small as one inch, with several "elbow" turns along the way. Strength of splice is very important, because this cable is heavy and when the pull is over 100' there's a great deal of strain on the joint. What's normally done is the drop is stripped back and the a bight of the conductors is formed at the end. The excess length of the conductors is wrapped around the sheathing of the drop and taped down w/electrical tape, so you end up w/a loop at the end of the drop. The pull rope is the knotted to the loop. What happens from time to time is the loop pulls out, the knot is too bulky for the elbows, the knot slips due to the gel and stiffness of the rope, etc. etc. Any ideas would be appreciated. Tape up the end of your cable to reduce drag and facilitate making the elbow turns. Use 500# test parachute cord as your pulling line. Tie it to the cable with either an Icicle hitch, http://tinyurl.com/7hmr3 a rolling hitch, http://tinyurl.com/ab7vh or a, gripping sailor's hitch, http://tinyurl.com/88d5a If space permits put a layer of tape over the hitch. I like the icicle hitch idea, but unfortunately I'm stuck with the 1/4" polypropylene. Contractors leave this stuff in the conduit long b4 I show up. It's hard, provides little friction, and does not hold a knot well. The knot tends to expand a bit due to the stiffness and loses some of its effectiveness. You think this would work with the slick black sheathing of the cable and the stiff pull rope? This brings up another question: why is this polypropylene rope so popular? I realize it floats, but that doesn't explain its ubiquity. Out here in NoCal, USA, every other pickup truck has bleached out lengths of it tied to the cleats, with the ends unraveled and frayed up the last foot of its length. Am I missing something? Isn't this the worst stuff you can choose to tie anything down? Luke in Ca |
#3
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On Tue, 5 Jul 2005 06:39:54 -0700, "Luke 451"
wrote: I was wondering how knot experts would suggest attaching communication cables to a pull rope in a conduit. Luke in Ca hi Luke, the icicle hitch or gripped sailor hitch might work in polypropylene line (the rolling hitch will not) may be in combination with this suggestion: Use a heat gun or hair drier to fuse the knots. Hold the knot tight with fingers a couple or more inches from the knot and heat the knot area until you see an outside fiber pop up; the knot will be fused, soft, and remain tied and fused when it cools and hardens. found at: http://www.bamboofencer.com/s.nl/sc....d.105/KB.76/.f a pull tape can be used and that gives more room for a knot and more surface for grip http://www.neptco.com/website/neptco...6?OpenDocument with a few knot suggestions: http://www.arncocorp.com/pdfs/pulltapebro.pdf http://www.neptco.com/website/neptco...0Tips?OpenView (links found in an earlier thread "dandy-line" in this newsgroup) if it is three strand rope, I would go for a chain spice http://www.neropes.com/splice/sp72_3...d_to_chain.htm it is compact and strong and easy to learn and smooth and looks good but it takes some time to do knot a knot suggestion, Ben |
#4
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Luke 451 schreef: This brings up another question: why is this polypropylene rope so popular? Isn't this the worst stuff you can choose to tie anything down? Luke in Ca cheap polypropylene is popular, and with polyethylene, it is the worst stuff ... "Both PP and PE can be found in many forms, shapes and qualities. The quality of cheap, general available PP and PE is quite often poor. UV stabilizer (expensive component) is not added at all or only in very small quantities" http://www.lankhorst-touwfabrieken.n...20and%20PE.htm well, knot nessecarily, Ben |
#5
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On Sun, 3 Jul 2005 18:58:02 -0700, "Luke 451"
wrote: I was wondering how knot experts would suggest attaching communication cables to a pull rope in a conduit. Maybe you should ask conduit-pulling experts. I have just watched as over twenty miles of conduit in our new house was filled with everything from 500kCM (thumb-sized copper) down to 2 pair, 28 ga wire. The electricians here made a loop in the end of the pull cord (often just an overhand knot around the standing part, with the bitter end taped along the standing part with electrical tape. The wire was fed through the loop and twisted to itself and the whole joint was taped over starting at the wire and ending up on the pull rope so as to have the overlaps facing the right way. If the wire was large, the conductors were exposed and twisted to themselves; if the wire was small, the whole wire, including insulation was twisted to itself. The one thing that ALWAYS happened was greasing the line to be pulled. They used a white grease from Greenlee designed for lubricating pulled wire. The lead electrician (over 40 years in the trade) said this was essential, even though it made pulling into a pretty nasty job. On thing they NEVER did was pull wire unsuited for the purpose. You say you are pulling buriable drop wire through conduit? You may need to provide a much larger conduit or a much more flexible cable. -- --Pete "Peter W. Meek" http://www.msen.com/~pwmeek/ |
#6
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On Sun, 3 Jul 2005 18:58:02 -0700, "Luke 451" wrote: I was wondering how knot experts would suggest attaching communication cables to a pull rope in a conduit. I'd like to have the materials in hand in order to better respond to this. Knots behavior is material dependent. Criteria: Thanks for the details! The splice between rope and drop has to be as compact as possible, as the diameter of the conduit is often as small as one inch, with several "elbow" turns This is quite a tight fit--2/4 + 1/4 leaves a scant 1/4 from the tightest enclosure, and as for making right-angle elbow turns, whew, I don't really see that so well!! elbow turns. Use 500# test parachute cord as your pulling line. This isn't necessary: one coul use the parachute (or other strong, fine, compressible) cord at a connector between the (cheap & present) pulling line & cable. In fac, it might be that one would get something like the parachord but then remove the core so as to increase the cord's ablity to flatten; then one would fashion an attachment structure from it. But I think that the full cord should work pretty well. to the cable with either an Icicle hitch, http://tinyurl.com/7hmr3 a rolling hitch, http://tinyurl.com/ab7vh or a, gripping sailor's hitch, http://tinyurl.com/88d5a If space permits put a layer of tape over the hitch Another idea is to whip the PP rope about 18" or so from its working end, then unlay the rope to that point so as to yeild a trio of strands (each a third of the 1/4" rope dia.) to make your joint with. The strands could be half-hitched and wrapped to fashion a "stopper" akin to what Yale markets as YaleGrips: http://www.yalecordage.com/html/indu..._grip-old.html E.g, one might incorporate some sort of hitch series. Cf.: http://storrick.cnchost.com/Vertical...nderKnots.html This brings up another question: why is this polypropylene rope so popular? It's CHEAP, pretty strong, colorful, moderately tough. (And it comes in a variety of formulations.) Copolymer rope--blend of PP & polyethylene--has greater strength & abrasion resistance (or so it's claimed), and has made inroads in commercial marine use. But for cable pulling, what I see in the Washington D.C. area has been cited above by Ben, polyester tape (Neptco, i.p.). This is lubricated (slippery/slimy feel--comes off on fingers, e.g.), and usually 1800# test, white with foot markers on the tape, coming in a couple of widths. (There is some straw-colored Kevlar tape, too.) --dl* ==== |
#7
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Thanks to all for yr great ideas. I've decided the best way to deal with the problem is to use the lousy pull rope to pull in an appropriate one, like polyester tape as suggested. Then the tape shld be able to grip the drop with a good icicle hitch. I'll tape off the icicle so it doesn't loose its integrity in the elbows as it gets scraped against the inside of the turns. The lube idea is good too; messy, but it beats blowing in a new tape. Thanks again for all your insights. Luke in Ca |
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