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Construction DIY Backyard ZIP-line strength question

  1. Dec 21, 2011 #1
    I am building a DIY backyard zip line - total length is 175 ft, starting anchor is a steel pole (6 inch diameter) - 21 ft long, I plan to bury in lots of cement about 4 ft deep - cable will be attached near the top, no guy wires planned, I will "board" the seat on a tree fort near the top of the cable, the lower anchor will be a solid tree - I will anchor it near ground level

    by various websites and my own research - every 100 ft you need 6 ft elevation change, and also 2 ft slag for every 100 ft of line, my starting height is about 9 ft platform/tree fort, but the cable will be around 15 ft high

    Dont worry, I wont be hitting the tree to stop - I have grass in front of the anchor tree, and can attach a bungey system to slow down and stop

    Questions::::: how deep to bury the pole?? how big diameter of pole?? what about 4 inch diameter?? do I need guy-wires to support anchor pole? how big of cable size?? I am about 200 lbs, children are lighter. Can it support me??
  2. jcsd
  3. Dec 21, 2011 #2


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    Gold Member

    I won't give you any advice on this subject for obvious injurious events that could occur if advice is misinterpreted or ill advised by not inspecting the site. Also, you mention solid tree as an anchor but you have no way of knowing how secure the tree actually is.
  4. Dec 22, 2011 #3
    Generally speaking the vertical load on the pole will not be your problem. You are creating a giant leaver arm. Based on your description you are applying a load to a 21 foot side which needs to be countered by the 4 foot side in the ground. You can easily see how any force you apply to the top will be greatly amplified at the bottom. This is why telephone poles which go more than 4 feet deep always have guide wires to prevent torquing the pole excessively. For something like this I think you should always over engineer it.
  5. Dec 22, 2011 #4


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    Staff: Mentor

    Sorry Jon, we don't give advice here for dangerous undertakings. Thread is closed.
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