DIY Backyard ZIP-line strength question

[Jon Z]

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 won't 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??

 

[256bits]

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.

 

[Hologram0110]

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.

 

[berkeman]

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 won't 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??

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

 

[LudusRex]

I would first like to commend you on taking the time to do research and plan out your DIY backyard zip line project. Safety should always be a top priority when undertaking any project, especially one that involves physical activity.

In terms of the strength and stability of your zip line, there are a few factors to consider. The depth and diameter of the starting anchor pole will depend on the type of soil in your backyard and the weight it needs to support. The general rule of thumb is to bury the pole at least 1/3 of its length, so for a 21 ft pole, you would need to bury it at least 7 ft deep. However, if your soil is not very compact or sturdy, you may need to go deeper. It is also important to use a pole with a diameter that can support the weight of the cable and the tension it will experience.

In terms of the cable size, it is recommended to use a steel cable with a minimum diameter of 3/8 inch for a zip line of this length. This will ensure that it can support your weight and the weight of the children using it. It is also important to regularly inspect the cable for any signs of wear and tear, and to replace it if necessary.

As for the need for guy-wires, it will depend on the stability of your starting anchor pole and the weight it needs to support. If you are unsure, it is always better to err on the side of caution and use guy-wires to provide additional support.

Lastly, it is important to consider the weight limit of your zip line. As you mentioned, you weigh 200 lbs and the children using it will be lighter, but it is always better to have a safety margin. Make sure to check the weight limit of the cable and other components, and make adjustments if necessary.

In conclusion, I would recommend consulting with a professional or experienced builder to ensure the safety and strength of your DIY backyard zip line. It is always better to be safe than sorry, and to prioritize the well-being of yourself and others using the zip line. Good luck with your project!