Backyard class 2 pole zip lines

  1. Looking to build a zip line with 4% decline for the kids with:

    Class 2 50' CCA syp Class II telephone poles sunk 6.5ft.
    3/8" cable 7x19 Galzanized cable for guy wire and zip line.

    1st zip: 100ft Starting at 26ft on a 6' hill->Ending at 22ft
    2nd zip: 120ft Starting at 22ft -> Ending at 17.2 on a 6'hill
    3rd zip:100ft Starting at 17.2ft on a 6' hill -> Ending 19.2ft
    4th zip:150ft Starting at 19.2 -> Ending 13.2ft

    8ft. Ground anchors on Guy wire tension pull tested to 5000lbs. preferably at 45degrees to pole within 1 foot of zip line attachment location.

    I plan on buying a tension meter to check cable tension.
    A few questions:

    What should the Zip Line Tension be with 250lb person from center of zip line
    What should the guy wire tension be without 250lbs person on zip line?
    What should the guy wire tension be with 250lb person on zip line?
    Up to what angle am I ok installing the guy anchors to? 45 is recommended. but we may be short on space.

    Looking at the guy wires from a site plan view; What angles should I set the guy wires in relation to the zip lines? On the same plane for the second pole and third pole as the incoming zip lines? and on the 1st, 3rd and last poles at what degree?

    See attached files for more info that I have gathered and sketched up. I would like to learn as much as possible in this process. I am somewhat comfortable with math, but it has been a few years.

    Attached Files:

  2. jcsd
  3. PhanthomJay

    PhanthomJay 6,334
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    As I am sure you know, zip lines can be extremely dangerous if not properly installed for proper sags and tensions , hardware connections, support systems, etc. I would carefully follow installation instructions provided by a reputable zip line dealer. And properly guying the poles , setting the poles, installing the anchors, etc. , is an art in itself. I wouldn't fool with it myself. And that second pole is a tough one... You essentially double the loads on the guying and poles by reversing cable direction. And steeper guys lead to greater guy tensions and pulls on anchors, and if too steep , become ineffective in preventing pole leans. Sorry I can't be more helpful, but this is serious stuff requiring engineering and construction expertise.
  4. Thank you for your input, there will only be one rider at a time.
    Last edited: May 23, 2014
  5. PhanthomJay

    PhanthomJay 6,334
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    Yes, but the wire had to be pulled up rather tight for the zip to work properly, perhaps on the order of 1 percent sag which in a 100 ft span yields about 300 pounds tension under the wires self weight. Now add a person and the tension might be say 2000 pounds. With a 1 to 1 guy slope , say 3000 pounds in the guys, you have two, so not too bad , but throw in a safety factor of 4 and you have an ult load per guy of 6000 pounds. Steep the slope to 1 on 2 and you've got 9000 pounds in the guy and anchor. Now this is all doable, but what is the holding strength of the anchors? Soil conditions? Anchor type? Compacted backfill? Hardware connections? You've got to be sure there is no slippage, no anchor creep out, no bending in anchor , etc. actually tour guy arrangement looks pretty good, I'd separate the anchors at the double guys about 10 ft min. These are just rough numbers and not for design.
  6. nvn

    nvn 2,124
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    Goodluck: First, (1) what is "a conventional top-rope belay system"? (2) What is "a conventional traversing element operated using a self-belayed lanyard system"? (3) Which of these two systems are you using? (4) What does "static belay" mean? (5) What does "dynamic belay" mean?
  7. nvn

    nvn 2,124
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    Goodluck: Please cancel my questions in post 5. I now figured out items 4 and 5. And, I currently think you will be using item 2 in post 5, not item 1.
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