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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Sun Feb 05, 2012 2:47 pm 
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What a brilliant piece mind boggling design.

I know it works in practice (like tomatkins i had to make one to confirm).
But I can't make it work on paper...

Can any body explain the force diagram.
Every time I think about it I arrive at the same nonsense.
It goes something like this:
One line with end A attached to ring. Passes round bottom pulley, then top pulley then ring and end B is effectively attached to the top pulley
Assuming it is all frictionless there is the same tension (f) in each section of the line.
There are 2 sections of line going to bottom pulley. Thus force on bottom pulley = 2*f
There are 3 sections of line going to top pulley. Thus force = 3*f !!!!!!
Doesn't balance.

Where is spork when you need him...


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Sun Feb 05, 2012 5:10 pm 
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Attachment:
Force diagram.jpg
Force diagram.jpg [ 73.61 KIB | Viewed 918 times ]


Here is a force diagram of the Zeeko depower arrangement. The tension in the powerline T is split equally between the two lines coming up from the chicken loop, so each of these lines has a tension of T/2. The steel ring in the middle sees a tension of T/2, so the two lines entering and leaving the steel ring will each have a tension of T/4. This means that the line between the top pulley and the top attachment point sees a tension of T - T/4 = 3T/4. And this is also equal to the sum of the tension in the two lines descending from the top pulley, i.e. T/2 (left line) + T/4 (right line) = 3T/4.

I too am very impressed by the ingenuity of this arrangement. I made a Zeeko depower loop using steel rings (no pulleys) and 10mm polypropylene line, no stopper, and used it to fly my kite on the beach this afternoon. Pulling on the right line depowers the kite, pulling on the left powers it up. The force required to depower the kite is more than the force required to power it up. So I wondered whether this arrangement would be stable during times of high tension, like jumps, or whether it would slip and power up unexpectedly.

It worked perfectly. It is completely stable. The reason for the differential tension is because in the one direction (depowering) , you are pulling against the tension in the kite, while when pulling on the left side to power up, the tension in the kite is helping you.

I would need a stopper if I had to spin the bar, but I hardly ever do that, so I will leave it without a stopper.


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Sun Feb 05, 2012 5:58 pm 
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zigzag.
Thanks for your post.

I had previously considered the force diagram you drew.

However, I still struggle to grasp how the line going over the top pulley can have a tension of T/2 on one side & T/4 on the other.

I am obviously missing something..


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Sun Feb 05, 2012 8:09 pm 
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I also do not understand the unequal tensions on the two sides of the pulley.

A quick way to verify that this is actually happening is to make a make a Zeeko depower using elastic cord or elastic ribbon, like you might find in your wife's sewing basket. You can then mark off equal lengths on the different segments, and measure the extension when the system is loaded. You should see the elastic stretching twice as much on the one side of the pulley than on the other.


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Sun Feb 05, 2012 10:55 pm 
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ZigZag.
Nice idea. I tried it but only using rings in all 3 locations.
It wasn't very accurate but was good enough to confuse me further.

You are correct in that the stretch in the two segments labelled T/4 was about the same and approx 1/2 of that of the left hand T/2 segment.
What was rather shocking was the stretch in the Right hand T/2 segment was much more than any of the other segments (approx twice that of the left hand T/2 segment !!!)
I even reversed the elastic as i thought maybe it was not uniform but that made no difference.

I'm stumped.


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Sun Feb 05, 2012 11:00 pm 
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Spork woul say: "It works in practice, but it will never work in theory"

I would still like to know where Zeeko got the idea. I would bet that he is a rock climber.

I have set up the system, which I mentioned earlier, and have taken it out 4 times, and made modifications, after each session. I will start a new thread in the near future, describing the features and the intended advantages of my set-up... but, just for fun, and since the interest in this new 'line adjustment system' seems to be growing, here are some pictures of my project, so far... including the rudimentary "below the bar" depower 'double ball', and the 'stopper leash' (internal parts).

This is just the beginning of something good, as you will find, if you start tinkering. More later.


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Mon Feb 06, 2012 12:36 am 
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tomatkins wrote:
To be sure that the comment in my previous post was correct, I made a little model from some rope and some pulleys. After doing so I found the answer to another person's question about whether or not the system would slide back into a "full power", if an extreme amount of force was placed on the chicken loop. It appears that this arrangement of pulleys, rope and ring resists an extreme force and is perfectly balanced in any of its infinitely adjustable length positions.

ZEEKO,

WOW! What a great concept for any number of uses, where a quick and stable length adjustment is required. I have never seen this length adjustment system used for any other application. Did you create this concept, yourself, or did you find such a system in use for another purpose, such as adjusting the line lengths of a piece of equipment used on a sailboat or the lines of a tent?

Have you applied for a patent for this "infinitely variable length adjustment device"?

I can think of a possible application of this type of device where the rope and pulley system would serve not only the use of a "powerline adjuster", but also as the "safety system" for the type of a kite which uses a mini-fifth line safety system.

As an example, the Cabrinha Crossbow, uses the IDS (mini-fifth line) system, and it seems that a kiter could substitute the ZEEKO style system for the IDS system... by using about 30 feet of powerline, which would allow the bar to slide a distance of 10 and one-half feet, up the power line, when released.

This is the distance needed to engage the mini-fifth line system to bring the kite down to the water, where it would land in a depowered (flagged) state. It would seem that this system could function WITHOUT the "stopper/Prussic knot" adjuster device, and that the kiter could just reach up and grab one of the two power lines, in order to make an adjustment to the trim length. The rope might be slippery, but I would think that the kiter could head downwind, in the same way a kiter with a 'below the bar' cleat system must do, at times, in order to decrease the tension on the power line, before making an adjustment.

With this arrangement, without the stopper, the kiter could just let go of the bar and the kite would flag out. The kiter would then just pull in about 10 feet of the doubled power line to retrieve the bar.

If there was a severe problem the kiter could release everything by triggering the ONE safety release.

Anyway, I must congratulate you on this interesting and unique concept for a line length adjustment system.

Where did you get the idea?

Here is a picture of the "Z-Drag" system of pulleys and lines and 2 Prussic Knots, that is very unique, also, but of course is very different from your "Zeeko system".


This is one of the haul systems we study for rescue when we go to Texas A&M. They have one of the nations top fire and rescue training programs. It is called a Z-Rig unlike a regular pulley system like 2-1, 3-1, or 4-1 which reduces your ropes hoisting length. The Z-Rig will give you most of your ropes length. It works well for change of direction haul systems. Say if some one was stuck in a ladder cage you could use one pulley on the ground to a pulley over the person who is stuck to lower them down. A diagram would explain things better but I'm tired and lazy lol.


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Mon Feb 06, 2012 1:40 am 
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ZigZag wrote:
Attachment:
Force diagram.jpg


Here is a force diagram of the Zeeko depower arrangement. The tension in the powerline T is split equally between the two lines coming up from the chicken loop, so each of these lines has a tension of T/2. The steel ring in the middle sees a tension of T/2, so the two lines entering and leaving the steel ring will each have a tension of T/4. This means that the line between the top pulley and the top attachment point sees a tension of T - T/4 = 3T/4. And this is also equal to the sum of the tension in the two lines descending from the top pulley, i.e. T/2 (left line) + T/4 (right line) = 3T/4.

I too am very impressed by the ingenuity of this arrangement. I made a Zeeko depower loop using steel rings (no pulleys) and 10mm polypropylene line, no stopper, and used it to fly my kite on the beach this afternoon. Pulling on the right line depowers the kite, pulling on the left powers it up. The force required to depower the kite is more than the force required to power it up. So I wondered whether this arrangement would be stable during times of high tension, like jumps, or whether it would slip and power up unexpectedly.

It worked perfectly. It is completely stable. The reason for the differential tension is because in the one direction (depowering) , you are pulling against the tension in the kite, while when pulling on the left side to power up, the tension in the kite is helping you.

I would need a stopper if I had to spin the bar, but I hardly ever do that, so I will leave it without a stopper.


Zigzag,

Thanks for that analysis...i worked from the bottom up and wrote down the forces on each of the line segments, but couldn't figure out the short anchor section on the top, that you labeled 3/4T. If you look at my picture of the rings, you can see that I omitted that 3/4T section, and tied the short T/4 line directly to the pulley.

I do believe that even under a load causing failure ( a breakage somewhere in the system), that the rope will not slip through the pulley or rings. I base this hypothesis on the fact that yesterday, I was hot launching my 13M, and the rope did not slip. I did some fully loaded up 10 foot jumps, and the rope did not slip. It also did not "giggle" or loosen up from jerking on the line, or from whipping it. That is good enough proof for me to trust the system. I would guess that when the system is loaded up enough to fail, that the rope would break at one of the bends, where it goes around a ring. The rope will be weaker at the bend. Can you predict, from the force diagram where the rope will break? The highest tension would be in the 3/4T section, but that section is well anchored to the top of the pulley, and therefore should be less likely to break, than a section which has less tension, but is weakened by the more severe bends in the rope. I don't think the rings would break first, but the one pulley at the top might be the point of failure, if it is not strong enough. I think that there is only one pulley in the whole system. I think that the top of the chicken loop frame only has an 'axle' in the housing, not a pulley.

Since I will be using one of these systems, I have been trying to figure out what is likely to happen to the kite, when one detail or another of this system breaks... so far, I have figured out that some of the time the kite will be cut loose, and some of the time the kite will go to extreme full power, or be completely suspended on its rear lines. I don't have a plan for each of these contingencies, but would like to have one for each case. I could always release the kite with the one and only release I have in my safety-less system. I throw the bar to its safety, by simply letting go and it travels 12 feet, just like a mini-fifth safety line, so I don't need a separate safety mini-fifth line...less clutter!

I am very interested in using a very wear resistant component, where the double powerline passes through the bar... if the powerline breaks from fraying, then, the kite would go to full suspension on its rear lines.

I am glad that so many forum participants are interested in this kind of analysis.

So, would you want to try to guess where the weakest point is in the rope, pulley, ring, and axle system?


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Mon Feb 06, 2012 2:52 am 
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From this link: http://www.eastcofire-rescue.org/Rope%20Rescue%20Manual.ppt

a diagram of the Z-rig system.

-joedy


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 Post subject: Re: Zeeko ultimate bar no clamcleat no depower straps?
PostPosted: Mon Feb 06, 2012 3:14 am 
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tomatkins wrote:
ZigZag wrote:
Attachment:
Force diagram.jpg

So, would you want to try to guess where the weakest point is in the rope, pulley, ring, and axle system?


At one of the knots or at a ring. As far as safety goes I personally only use one and thats the one on my leash. I'm sorry but if your truelly in trouble best thing to do is ditch the kite all together than to hope flagging works and you need to release a second time. You just might not have time for it.

The best safety is your brain. Choose the proper gear for the conditions and keep an eye out for possible changes in the weather. I do kite alone a lot because of my schedule and this is how I keep myself out of the E.R. Plus our shallow easy access spot helps.


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