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Well, it's the end of my graveyard shift at work this morning, and I had an idea for a project.
In short, I want to make a cable-cam for time-lapses. To do that, I need a horizontal line with a good amount of tension in it.
I have some old frayed 11mm static line laying around that I'm thinking about using for the main line. Now, all I need to do is get it really tight.
One example I saw used a Petzl Protraxion, but that's a little out of my price range.
I hope this question isn't completely irrelevant to this forum, but do any of you have any ideas on a cost-effective Tensioning system for my line? I'm stumped.
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Who better to ask than folks who like to play with rope? 
If you go to this link http://www.cavedig...tical/4RIG_BAS.pdf and look at the diagram at the bottom of page 68 you will find a drawing of a simple tensioning setup that doesn't require any additional hardware. You can research haul systems on the internet if you need a more complex system. A pulleys will make it easier to tension up the line.
If you plan to suspend yourself off of this rope, you should REALLY get some additional expertise in rigging. The loads on tensioned horizontal lines is tremendous.
Abby Normal
[last edit 12/4/2012 7:20 PM by Abby Normal - edited 1 times]
"Government is not a solution to our problem, government is the problem." Ronald Reagan | |
You should NEVER do this with a life support system, but:
For this you might be able to use a vehicle to tension the rope. Just tie onto the car's towbar. Using a few prusik knots and some creativity, you could even set it up so that you can tension the rope across two anchors using the car, and then take the car off the rope and leave it.
But if you do this, you should never again use that rope for life support. It's too easy to damage the integrity of the rope using the force of a vehicle.
"You have brains in your head. You have feet in your shoes. You can steer yourself any direction you choose. You're on your own. And you know what you know. And YOU are the one who'll decide where to go..." -Dr. Suess | |
How much tension do you need? my gut says steel cable is what your looking for - far less stretch than static rope.
either way - steel or nylon the easiest way (i can think of at the moment) to tension it in the field would be a turnbuckle.
http://en.wikipedia.org/wiki/Turnbuckle
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why not just make a 3:1 pulley with a progress capture device (could be as simple as 2 prussiks)?? Probably the easiest way I can think of...
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Talk to some slackliners, this is their favorite subject. What we usually do is run the rope (webbing) across, hitch a biner on it, go around a biner on an anchor, back through the first biner, another biner on the anchor, and then back through the first biner again- beneath the original pass. Works really well with webbing.
To get longer stretches more taught we repeat the system off the tail from the above, abusing the f-ck out of mechanical advantage.
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just how frayed is your "old frayed" rope? heh
small diameter steel cable is pretty cheap, you wouldn't need much to run a camera across; could get away with some super thin diameter stuff.
I've actually used the Petzl Minitraxion for tensioning rope. It's internal progress capture works splendidly. The mini is cheaper than the pro, as well as smaller and more lightweight.
Some advice: to unhook the capture spring, you need to pull the rope TIGHTER than what it's currently set at, to release the device.
(this is true of most progress capture systems. Once it's jammed up tight, you have to unweight that part to release it)
So if you pull it mutherhellafricking tight, and then capture with something mechanical that grabs it RIGHT THERE... hehehehe.... well you see the problem. =)
Again, with just the weight of a camera you could probably achieve enough tautness with a simple pulley and prussik. Don't forget that the force at your anchors is largely magnified when you're tensioning a line, and once you weight it laterally, the force at the anchors jumps up by, what is it, a factor of 5?
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