Non-motoring > zip lines Miscellaneous
Thread Author: No FM2R Replies: 8
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New Sun 8 Feb 15 13:27 
 zip lines - No FM2R
Anybody know anything about building one?

I have a gap, about 150ft I should think but perhaps a bit more, with large trees either side. Quite a substantial drop in the middle so it needs to be safe But that is mostly a future consideration.

In particular, at this the "pondering over a drink while staring at it" stage I am mostly wondering what kind of drop in height from one side to the other is desirable.
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New Sun 8 Feb 15 14:03 
 zip lines - Old Navy
I would think very little drop, if you are going to use a free running sheaved block, speed will build up rapidly. The main concern should be how to stop the user and a soft landing area. Sods law someone will fall into ravine in the middle. :)
Last edited by: Old Navy on Sun 8 Feb 15 at 14:07
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New Sun 8 Feb 15 14:43 
 zip lines - CGNorwich
If there is one certainty in life it's that whatever the problem the answer is on the web.



www.buildazipline.com
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New Sun 8 Feb 15 15:06 
 zip lines - Cliff Pope
We have built one twice, having moved it.
There is a critical relationship between the drop and the tension. Too much drop and tension and you just go crashing into the end. Insufficient tension and someone ends up stuck in the middle. Nearly enough tension but not quite enough and you get to within a few feet of the end, and then slowly run backwards again.

Another factor is that it cannot be perfectly suited to all weights of people. A heavier person causes the wire to sag more, so you need more tension. But only enough to bring to at a gentle pace at the end. But if you set it up for a heavier child a lighter one won't cause enough incline at the end so will just crash into the buffers.

Idealy build a platform at each end, eg from old pallets. I imagine landing on an aircraft carrier must be a similar feeling.

Tip: trail a light cord from the handle so that you can easily pull it back to the start again.

We have a country lane running through the garden. My proposal to string the wire from two trees one each side was vetoed as being too scary.
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New Sun 8 Feb 15 17:09 
 zip lines - No FM2R
Cliff,

Does that mean that there is quite a lot of tolerance in how much the height drops and you can tune the speed/arrival with tension?
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New Mon 9 Feb 15 08:21 
 zip lines - Cliff Pope

>>
>> Does that mean that there is quite a lot of tolerance in how much the
>> height drops and you can tune the speed/arrival with tension?
>>

Ours dropped about 3 feet over perhaps 25 yards.

You can tune the tension to accommodate any drop. Reducing the tension increases the sag which slows the approach speed because the last bit becomes more uphill.
But the risk then is that it becomes more sensitive to the person's weight. A heavier person will get up more momentum, so make the final climb. But a small child might not get up the incline so run back down again and be left danging in the middle. (That's a good reason for having a re-wind cord)

Another variable is how much the person flaps around. An experioenced zipper can use the swing effect to get up more speed on the downhill, and start off with a bit of a run. But a cautious child who panics and flaps about wildly will increase friction and slow it down, so less chance of reaching the end.

In the end you need to experiment and make adjustments - a bit scary for the first volunteer, which usually will be you.
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New Sun 8 Feb 15 17:07 
 zip lines - No FM2R
Thanks CG, interesting and useful although I am still in doubt about the height drop required.

My drinking and peering leads to the following;

As near as I can estimate the gap, at the height I want to be is around 300ft. The drop in the middle is substantial; probably not survivable if you fell.

Both sides are quite steep but have loads of big-a*** trees so the two ends are quite variable insofar as height and position are concerned.

I'd like to have another zip coming back again, hence wondering about the drops required. Otherwise I guess its some kind of rope bridge back.

Appreciate your help.
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New Sun 8 Feb 15 17:15 
 zip lines - Runfer D'Hills
Cor ! Jealous or what ! Can't do that here, too flat. :-(

We did have a "fireman's pole" in the last house though. Three storey drop. Top tip, don't use a fireman's pole when you're a bit "tired and emotional" and only have your skiddies on. Chafes like hell by the time you get to the bottom and brings a tear to both eyes when mountain biking the next day.
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New Sun 8 Feb 15 18:36 
 zip lines - Fursty Ferret
My dad built one for us when we were kids. Started from a tree-house 20 feet up and descended a gentle slope to stop about 150 feet away. It was basically a circular wooden seat fastened to a pulley. Lessons we learned:

* The wire tension REALLY influences speed.
* Jumping onto the slide as you set off is great fun (think: a highly practical introduction to simple harmonic resonance)
* A row of old tyres on the line at the end "sort of" works but is quite exciting at high speed.
* Dogs find chasing people on it strangely fascinating.
* Be wary of long hair flapping around close to the pulley wheel.

You can now get proper arrestor devices to put on the cable at the end which will bring any rider to a controlled stop. This is the approach I would go for if it were my slide.

If you're planning to put other people (besides yourself / your kids) on it - well, I wouldn't bother. I imagine the hoops that places like Go Ape have to jump through to satisfy their public liability insurance make it far too much hassle to be worthwhile.
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