# zip line structure



## rocketdoctor (Mar 18, 2009)

I want to install a zip line for my kids that will go about 50'. I have a sturdy tree to attach the start too but need something to anchor it to at the end. I want it to be sturdy to hold 200 or more pound rider.

The anchor point won't be any higher than 6' off the ground so was thinking of getting a 4X6 PT and sinking it in concete about 4 feet deep. Maybe putting some 4x4 bracing on the front. I would bolt a long eyebold for the cable attachment.

this sound like its going to work, am I crazy?


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## nap (Dec 4, 2007)

> am I crazy?


yes but sometimes crazy can be fun.


You need to consider the fact the load will be pulling sideways. Not sure the 4X6 would resist the lateral load well without some additional restraint.

I don't know if this would solve all your problems but I have a fence post that I did something quite unique with. The fence material is tensioned quite a lot.(I like a taught fence) Even with a angled brace inside of the post, it would simply pull the post from the ground as it pivoted on the angle brace so, what I did was purchase a screw in ground anchor in the other side of the post and use a cable from the anchor to the top of the post. It;s held great. 

you also need to think about what the kids are going to run into when they hang onto the trolley all the way to the end. You need to configure some sort of soft stop for them

and don't put a stop on the zipline to stop the trolley before the end. If they a zipping along and hit the stop, it will flip them forward, ir even upward, if the hang on right before their inertia caused them to lose their grip and go flying into whatever is in the way.


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## rocketdoctor (Mar 18, 2009)

anchoring the post with cables is a good idea, its eather and better than putting braces in front. Well I was thinking of putting a stop on the zip line the way you warned me, wasn't sure of other ways to keep from hitting anchor point. The Zip line is going to be on a downhill slop so I guess I could run it a bit steeper than the slope and have the anchor point much lower so they hit their feet way before the anchor? would that work, any other ideas for stopping zipline


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## nap (Dec 4, 2007)

a REALLY BIG pillow?

a stop itself is not wrong, it is just where you put it. You have to imagine somebody hanging on this thing zooming down and hitting the stop. Try to imagine where they would swing to or where they might fly as the trolley is ripped from their hands. Depending on how fast the thing goes, there can be HUGE amounts of force ripping the kids from the trolley.


when you first get this set up. run it a couple times with nobody on it even hang a weighted bag on it to see how things flow before you risk one of the kids.


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## joed (Mar 13, 2005)

A stop would be a bad thing. You need something too slow them down slowly, not STOP them. I would suggest the low end should be higher up and the cable have some slack in it so the end of the line is actually an uphill type run. here is a picture with the basic principle I was tihnking of.


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## kwikfishron (Mar 11, 2010)

joed said:


> A stop would be a bad thing. You need something too slow them down slowly, not STOP them. I would suggest the low end should be higher up and the cable have some slack in it so the end of the line is actually an uphill type run. here is a picture with the basic principle I was tihnking of.


Exactly what I was thinking. I wouldn’t consider it any other way.


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## Troglodyte (May 4, 2010)

I've done cable harvesting work in forestry and if you are planning on the anchor point being only 6' off the ground then you will likely have to put incredible tension to maintain deflection off the ground the whole way. It won't be 200 lbs acting vertically on the cable, it will also be a massive amount of horizontal force pulling the tree and the anchor towards each other. Unless of course you have very favourable terrain (something like a checkmark), in which case you wouldn't need that tension to maintain deflection. When I say massive tension, I'm talking enough to snap the post, not just pull it out of the ground. I've seen a 1,000lb log topple a 15,000 lb cat because of excessive tension to maintain deflection.

I'm no mathematician, but from my understanding, you would be much much better off finding a place to put the cable so the attachment points are close to the same height, and then giving the line enough slack (test run, change slack, test run change slack) until the person on the zip line maintains a reasonable height above ground.

And anchoring the post to the ground is an absolute necessity, the tension and weight of the line on the post will be a constant pressure on it, and with time and use that post would move fairly dramatically.


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## rocketdoctor (Mar 18, 2009)

Thanks realizing my idea of running it down a hillside won't work since I don't have a way to slow it down properly. I found the instructions of the Zipline I was thinking of buying online and they recommend a difference in height no more than 3 feet. Looks like if I want to do this I would have to build a structure for both anchor points. maybe two 6X6s with cable anchors.


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## Gary in WA (Mar 11, 2009)

And an Insurance Rider on your Homeowner's Policy to cover anyone riding because you are liable for building it............ 

That alone may wet blanket it in CA. Let's see some picture when done!

Be safe, Gary


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## Jim F (Mar 4, 2010)

I didn't know they were called zip lines. My one and only experience on such a thing was in the Army. We had to let go and land in the water before hitting the lower anchoring point. A year before, a guy in Ranger training drowned on the thing so they mandated life vests for the course. After hitting the water and flipping end over end I could see where someone could drown. I was glad to have the life vest pull me back up to the surface because it was very disorienting.


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## stadry (Jun 20, 2009)

that's a nice sag to the cable in the drawing but it'll only be there when not in use,,, when weight applied, it'll look more like a ' V ' & that V will move across the cable,,, weight + speed = more force in my book.

roger that on the army ' slide for life ',,, oh the things we did when we were younger, huh ? :thumbup:


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## Jim F (Mar 4, 2010)

Oh yeah that's what they called it. Slide for life. Wasn't a Ranger myself but we got a taste of their training one day at Ft. Lewis. Wa.


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## Willie T (Jan 29, 2009)

Yeah, Benning had one wild course!


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## JohnFRWhipple (Jun 3, 2010)

*Building a zip line for the kids*

I have a killer Zip Line at my house.

Plan your testing for 800 - 1000 lbs not just 200.

Many fasteners will only have ratings for 600 lbs. Design a safer system and check it each time the kids use it. A bag of concrete (50 lbs) and a baby swing are a good rig to do your test with.

Take it from someone who has spend over 50 hours building my rig. This is a lot of fun. The neighbors kids will freak out. 

Lots of fun. Good clean (could kill you) fun.

My kids have 5 point harness from MEC and I have used an 1/2" steel cable.

I have built in 2 layers of backup and we have been enjoying the zip line for 3 years now.

How do you work out the ratings of these "Dangerous Tools".

Anyone building a structure like this must understand that you are playing with people lives here. Good clean fun but dangerous. When I was a kid we had cement under the monkey bars and tried daily it seams to make some one throw up on the merry go round. These rides are fun.

Build in safety and multi layers of back up.

My zip line is down for the renovation but will go back up this summer. I'll post some pictures of my braking system, roller system and fail safe extras I designed (under my wife's orders).

Don't take any advice from use and blindly build away. Source your fittings - test them - these are your kids! Your neighbors kids.


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## forresth (Feb 19, 2010)

as mentioned earlier, you are talking huge amounts of tesion. you will probably want a couple guy wires on the tree too, even if it droops.

remember, a cables only works with tension

do the geometry

if the cables are at 15 degrees and the load is 500 lbs vertical load each half of the cable must suport 1000 lbs tensoin

if its only 5 degrees, it jumps up to close to 3000 lbs of tension

speaking of the stupidity of youth, I stood on a tensioned winch cable (the jeep's 8,000 lbs winch wasn't strong enough to get it out), and the vehicle moved. wrap you mid around those numbers when building your Zip line.

If you think 500 lbs is high, think a gain. kids bounce around.


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## rocketdoctor (Mar 18, 2009)

well all good information , unfortunately I don't think I can make this work in my Yard within my Budget. In order to make a fairly level zip line run I would have to build two structures to anchor the line to since I don't have two trees to work with. its starting to look like I would have to sink a steel beam deep in concrete and then have a couple concrete piered anchor points for the guide wires.


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## Scuba_Dave (Jan 16, 2009)

Now you have me thinking about a zip line over my pool to the deep end 

But I'd guess I need some strong support
Disney has the zip line to one side of the support


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## rocketdoctor (Mar 18, 2009)

> But I'd guess I need some strong support
> Disney has the zip line to one side of the support


thats what I was thinking of doing but all the discussions above were how the kids would go flying when they hit the stop on the zip line. However its no big deal when you go flying into a pool


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## nap (Dec 4, 2007)

here is a method to stop the trolley:

http://www.youtube.com/watch?v=5a64ZTj-nYQ&feature=related


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## nap (Dec 4, 2007)

I know this is kind of old but when I saw this video, I just had to post it.

http://www.liveleak.com/view?i=65f_1279762493


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