Zip Line Fun

I have wanted to build a zip line across the backyard for some time.  I have spent way too much time researching different gear, and different set-ups to make it the way I dreamt up.  You see, our backyard is perfect for a relatively safe zip line because it is mostly flat with a small hill on one side.  Because of this you can (in theory) ride across the whole yard while staying pretty close to the ground; safe and fun.  I had one major problem though; I didn't have a decent tree on both sides of the yard.  This meant I had to put a post into the ground to connect the line to on one side.  It seemed that this would be straight forward because the majority of the force should be trying to pull the post over, so I buried a 12 foot-4x4 2 feet into the ground with 240 lbs of concrete and connected a 8 foot-4x4 to it about half way up, also in the ground with 240 lbs of concrete.  Amazingly as I tightened the line, the main 4x4 just started to bend from where it was connection point and up.  I let it bend a bit though because I wanted to test the rest of the design anyway.  Here are a few pictures from our set up.

Some of the supplies.

I used 1/4 inch cable for the line and bought a massive 12 inch turnbuckle to make sure I could tighten the line enough to not have much sag in the middle.  The cable is 200 feet long, and the run is about 175 feet, so 1% sag would be almost 1.5 feet. 

Here are the first 2 holes, not very impressive.

Here is the only picture we took of the first set up finished.  This is my mom helping Jack get on the line.  Originally I attached a swing to it, so you just sit and ride. 

And Jack having fun while riding!

Here are a few video's of the kids riding.  In this first one you can see the problem we faced.  Because the pole was bending, slack developed in the line and you lost valuable altitude, which is needed since I was trying to keep kids close to the ground in the first place.  This video is actually after several runs, and as I tried to test it with more weight it got worse, actually pulling the concrete out of ground.  It was pivoting around the connection point of my brace, which wasn't supposed to happen...


Jonah on the Zip Line Ver. 1 from Julie Tull on Vimeo.

This video is one of the last runs on version 1 of the zip line.  The kids were still having fun even though it was sagging quite a bit because of the post pulling out, and then it really started to rain...


Zip Line vs. Heavy Rain from Julie Tull on Vimeo.

So the following weekend I took the line down and started digging out the original post.  It is really difficult to pull 240# of concrete out of a 2 foot hole.  What I didn't know is that this was actually the easy part.  Once I got it out and moved it to its new hole where it would act a brace to the new support pole, I had to dig the hole an additional 2 feet down to make it a 4 foot hole.  Of course I wanted to do this without making it too wide, and after about 3 feet it was impossible to pull dirt out with a shovel.  First of all you couldn't get a good angle to lift the dirt out, but more importantly 75% of the shovel was down in the hole!  So the last foot of dirt came out 1 scoop at a time with me lying on the ground dropping a small right angle shovel down and pulling it out.  It was crazy. Here are the kids in the hole when it was finished.

After I finished the holes, I put a 16 foot-6x6 post in and filled it with 1000 pounds of concrete.  I really figured this would be the end, no chance of anything pulling out, ever.  I let it dry the following week and then the next weekend hooked the line back up, tightened it, and the fun began!

Finally, here a a couple more videos.  I know this is a very video heavy post, but it is a zip line and pictures are not nearly as good as video!


Paige on the Zip Line from Julie Tull on Vimeo.


Julie on the Zip Line from Julie Tull on Vimeo.

More zip line posting to come as I need to make a couple more modifications (version 3) to make sure I can ride with a minimal droop in the line.  Right now it is creaking a little while I go, and bending a little when Julie goes.  Really unbelievable that the top 4 feet of a 6x6 post could bend like that.  Leverage is a great thing, but sure makes zip line installations without trees a lot tougher.