Anybody here built a zip line?

[Dargo]

My wife has been on to me about getting a zip line built that I talked about building a few years ago. She pretty well wants 2 lines. One that goes across my lake and terminates on the island in my lake. People can either ride it to the island or drop off into the lake. The other would just be a longer one running a few hundred feet across a wooded part of my property.

If you've built one, where is a good place for me to buy the trolley that rides on the line and a harness? We did a lot of zip lining in Costa Rica last year. That renewed her requests for me to get going on ours. I was frankly shocked at how small some of the cables were in Costa Rica that spanned 600 or 700 feet over deep ravines. Just guessing, I'd say they are only 3/8". Does that sound right?

 

[DocHeb]

With the zip lines in Costa Rica - how do they get the trolley back to the start?

The strength of 3/8" cable is nothing to sneeze at - Galvanized Steel, 7x19 aircraft cable has a breaking strength of 14400 pounds, more than enough for even American tourists.

This Site sells tandem trolleys (breaking weight 14000 lbs) for Zip Lines with 3/8" to 1/2" cable.

 

[Willl]

Did one many, many years ago with an upside down bicycle forks and wheel sans the tube and tire.

We were brave souls back then, no way would I trust that same setup today.

I see some of todays setups run 2 cables with a trolly that has 2 wheels.

 

[Dargo]

Thanks for the info and link. The trolleys we used looked like the listed "heavy duty" models. As you mentioned, they too have a breaking weight of 14,000 pounds. I suppose even the biggest American tourist has a better chance of uprooting a tree than breaking the trolley or cable. I am sort of shocked at how expensive the cable is though. Even though 1/4" would most likely work, I'd feel better going with the 3/8" like I have been on.

Rather than using trees, I'll be using buried I beams for anchor points on each end. Well, I may use a huge oak tree for the top side on one zip line. That way I wouldn't have to build as much of a platform from scratch and I wouldn't need to use such a large I beam.

 

[MossRoad]

Thanks for the info and link. The trolleys we used looked like the listed "heavy duty" models. As you mentioned, they too have a breaking weight of 14,000 pounds. I suppose even the biggest American tourist has a better chance of uprooting a tree than breaking the trolley or cable. I am sort of shocked at how expensive the cable is though. Even though 1/4" would most likely work, I'd feel better going with the 3/8" like I have been on.

Rather than using trees, I'll be using buried I beams for anchor points on each end. Well, I may use a huge oak tree for the top side on one zip line. That way I wouldn't have to build as much of a platform from scratch and I wouldn't need to use such a large I beam.

Wow! Sounds like a neat project.

Just remember that large oaks are often hollow on the lower end.

 

[carpenter383]

My jeep winch is rated to pull 12,000lbs, and it has a 3/8 cable. Smaller winches in the 8,00lb range have 5/16 cable. I'm sure the braking strength of the cable is higher than the winch will pull. But this may give you more of an idea about cable strenth.
Also I'm sure there is good cable and cheap cable so the quality of the cable your using will be something to look at.
You could look on ebay and see how much replacment winch cables are going for. I bet a good 5/16 cable would be more than strong enough.

 

[MossRoad]

... the quality of the cable your using will be something to look at.
...

Why don't you check out the prices of cable at Harbor Freight?

Hmmm.... maybe not. You can put down a cheap tool and walk away from it. A cheap zip line, on the other hand....

 

[/pine]

I have been considering one for several years as a way to cross the river here...I have so many other "works in progress" I have not gotten to it yet...

I think I would want something like a bosun's chair and a secondary line to pull yourself across and back...keeping the cable level and use a landing platform on either side...

 

[kevindsingleton]

Why don't you check out the prices of cable at Harbor Freight?

Hmmm.... maybe not. You can put down a cheap tool and walk away from it. A cheap zip line, on the other hand....

Where do you suppose the Costa Ricans got their gear?

 

[BruceWard]

The tension on the cable can be calculated as Tension=(Weight of cable, trolley and passenger x Length of cable in feet) / (8 x Sag of cable in feet).

For example a 700' 3/8ths cable weighing 175 pounds with a 300 pound passenger and 25 pounds of trolley sagging 20 feet at the mid point would have 2187.5 pounds of tension on the 14,400 pound break strength cable.

But if the cable only had 3 feet of sag the cable would have 14,583.3 pounds of tension. With anything less than 10 feet of sag it is likely that cable would be damaged and eventually fail.

 

[chrisreedtn]

Did one many, many years ago with an upside down bicycle forks and wheel sans the tube and tire.

We were brave souls back then, no way would I trust that same setup today.

Yea, No kidding, I broke both my wrists at the same time on a boyscout adventure using a similar setup. Atleast I broke my fall with my arms, and my neck and back didnt take the full force of my body falling a couple stories.

 

[2manyrocks]

Back about 1992 or so, I went to see a church camp in the Smoky Mtns. They had a zip line from the side of a mountain that terminated in a man made lake. I noticed that the kids wasted no time getting out of the water even though it was hot July.

The host told me that the man made lake was cold spring fed water.

 

[PILOON]

The tension on the cable can be calculated as Tension=(Weight of cable, trolley and passenger x Length of cable in feet) / (8 x Sag of cable in feet).

For example a 700' 3/8ths cable weighing 175 pounds with a 300 pound passenger and 25 pounds of trolley sagging 20 feet at the mid point would have 2187.5 pounds of tension on the 14,400 pound break strength cable.

But if the cable only had 3 feet of sag the cable would have 14,583.3 pounds of tension. With anything less than 10 feet of sag it is likely that cable would be damaged and eventually fail.

Above info well presented,
but may I add:

Seasonal temperature changes will add stress (tension) as metal shrinks with cold!
For that reason ski tows always used weights at one end to keep tension constant.
I believe the safe way would be dead weight via pullies hung at one end.
With pullies you can 1/2 or 1/4 the needed weight.

Even bridges have expansion joints!

(not calculated) but even a 45 gal drum filled with concrete might be all you need (with pullies as multipliers)

 

[caver]

I've been toying with the idea on my place.
Zip Line Supplies
Karst Sports sells the hardware. I've bought caving equipment from them and they are a reputable dealer in the cave exploration community.

I'm waiting for the foilage to fall so I can see through the tress and cut of the best path.

 

[schmism]

(not calculated) but even a 45 gal drum filled with concrete might be all you need (with pullies as multipliers)

the tension in the string (cable) is always the same. i dont care HOW many pullies you put on the end. its still only (say) 500 lbs hanging off the end of the cable.

 

[MossRoad]

the tension in the string (cable) is always the same. i dont care HOW many pullies you put on the end. its still only (say) 500 lbs hanging off the end of the cable.

I think he's saying if you put a cable between two post and pull it tight, then measure the tension on the cable. If it gets cold, the cable contracts, putting more tension on, as it tries to pull the posts together. Conversely, if it gets hot, the cable expands and the tension on each end diminishes.

Can you see that in a long cable run, that could cause the cable to sag in the middle quite a bit in hot weather and pull very tight in cold weather.

Now put a 500 lb trolley on that cable. In the winter, the trolley may get you over most objects very fine. In the summer, it may dip too low to get you over those objects. Lets hope the zip line doesn't run over a cactus patch!

By putting some weight on the cable past one end point, you can keep the cable at the same elevation all year.

 

[Dargo]

I may have a line on getting some used elevator cable. A friend of mine has been an elevator repairman for 25 years and he told me that, per code, every so many years or some designated time the cables have to be replaced, whether they are showing any wear or not. I wonder if that cable would work. It sounds like I may be able to get it free, which is always a good thing.

 

[MossRoad]

Here's a diagram. Enjoy!

 

[MossRoad]

I may have a line on getting some used elevator cable. A friend of mine has been an elevator repairman for 25 years and he told me that, per code, every so many years or some designated time the cables have to be replaced, whether they are showing any wear or not. I wonder if that cable would work. It sounds like I may be able to get it free, which is always a good thing.

Elevator cable is most likely going to be overkill, but would also most likely not have to worry about breaking it with a 300 pound person. I've looked at our elevator cables and it is pretty close to 3/4".

I got some used winch cable from a towing company pretty cheaply many years ago. It is 3/8 or maybe 7/16. I use it for pulling firewood and trees dragged behind my tractor or truck. It is not safe for winching any more, but is still suitable for something like a zip line. But it was only a hundred feet long.

I wonder how long you could get a length of elevator cable in one continuous piece from him? As you said... free is good.

 

[Dargo]

Here's a diagram. Enjoy!

LOL! My wife asked "What happens if you don't let go?". Well, um, just like in Costa Rica, you ram into a tree. Duh! Actually, for some of the rather dense people on the zip lines in Costa Rica they throw a length of rope out on the line at the end. When the pulley hits that rope it really slows things down rather quickly. I told my wife that I'd pass on putting some rope on the cable and just let people ram either a tree or an I beam.