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Sliders and pulleys vs Rings - Safety Tip

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Hansen Design
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Sliders and pulleys vs Rings - Safety Tip

Postby Hansen Design » Mon Feb 13, 2012 10:34 am

In another thread there is some discussion about line wear in active bridles with pulleys or rings. The ring configuration shown in the attached pic is potentially dangerous because the bridle line must bend around a small radius on the order of (or even smaller than) the line diameter. The tight bending causes a high degree of flexing in the braid with significant movement, rubbing and kinking of the internal strands which will eventually degrade and weaken the line. Note: line damage due to tight bending is not the same as frictional wear on the outside of the line and may not be visible.

If your kite uses rings (or you have substituted them for pulleys,) you should consider replacing them with a pulley or slider (as shown) which has a larger radius. New lines would also be a good idea...
Cheers! :thumb:
Ring.jpg
Ring.jpg (6.84 KiB) Viewed 2851 times
Slider.jpg
Slider.jpg (35.88 KiB) Viewed 2851 times

ptraykovski
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Re: Sliders and pulleys vs Rings - Safety Tip

Postby ptraykovski » Mon Feb 13, 2012 3:33 pm

Thanks for that important tip. I hear lots of guys talking about replacing pulleys with rings for safety, and always tell them it is a bad idea!

What readily available line would you recommend for bridle replacement running through small pulleys or sliders.

Seems the black line in your picture is something different from amsteel that many use. I see some manufacturers use line with a tighter braid than amsteel, maybe so it doesn't flatten out so much?

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby tomatkins » Mon Feb 13, 2012 6:47 pm

I have been looking for some of those items. Where and how can I buy some? How much?

As far as the history of the use of these rings go, it seems to be of recent times. The first one I can recall is the one used by Naish on their chicken loop, and this one combined a screw pin anchor shackle with the large ring. Then, it seems that Cabrinha used them, starting 2 or 3 years ago. Now, they are used by others.

Here is a picture of a similar item, made by GIN kiteboarding.
Attachments
GIN ring.png

ronnie
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Re: Sliders and pulleys vs Rings - Safety Tip

Postby ronnie » Mon Feb 13, 2012 7:05 pm


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Re: Sliders and pulleys vs Rings - Safety Tip

Postby nobby raish » Mon Feb 13, 2012 7:15 pm

How about we loose the pulleys/rings all together?

Or,ALL kites should at least come with a pulley/ring-less bridle option.

Wainman,Slingshot rally,& Ozone are way ahead on this.

worn bridals are the first thing that needs replacing on kites.

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby Hansen Design » Mon Feb 13, 2012 8:14 pm

Hi Peter:
In testing, we found a braided-jacket line from a high-quality paraglider line-maker to be superior to loosely woven spectra lines like amsteel. The fibers in the jacket are aligned more in the hoop direction and the core is closer to the axis where there is less differential movement and internal wear. I have not checked at a West Marine or other marine chandlery store but I suspect there are similar over-the-counter lines available for small dinghy control lines.
Cheers! :thumb:
ptraykovski wrote:Thanks for that important tip. I hear lots of guys talking about replacing pulleys with rings for safety, and always tell them it is a bad idea!

What readily available line would you recommend for bridle replacement running through small pulleys or sliders.

Seems the black line in your picture is something different from amsteel that many use. I see some manufacturers use line with a tighter braid than amsteel, maybe so it doesn't flatten out so much?

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby ronnie » Mon Feb 13, 2012 8:51 pm

Marlow ropes charts for selecting ropes (unfortunately kiting is not listed directly but you can decide based on whether the rope is cleated or runs around a pulley [control lines] ).

http://www.marlowropes.com/index.php?op ... &Itemid=65

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby edt » Mon Feb 13, 2012 9:24 pm

ronnie wrote:I think those rings have been used in yachting for a while


low friction rings are as old as sailing itself, but you use it for a fairlead, that is it's a ring that guides a rope at a slight angle around objects.

antal low friction rings were never designed to be used as pulley replacement which is what kiters are doing. Are ronstan orbit blocks that expensive?

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby Hansen Design » Mon Feb 13, 2012 10:01 pm

Ronnie:
The Excel Racing 75 or Elite 78 is closest (in the Marlow catalog) to what we are using.
ronnie wrote:Marlow ropes charts for selecting ropes (unfortunately kiting is not listed directly but you can decide based on whether the rope is cleated or runs around a pulley [control lines] ).
http://www.marlowropes.com/index.php?op ... &Itemid=65


Edt:
Looks like they have progressed beyond fairleads and into vangs and other applications. The slider pictured previously is stainless steel rather than aluminum. I do not think it is totally a matter of cost. Pulleys have other inherent problems.
edt wrote:low friction rings are as old as sailing itself, but you use it for a fairlead, that is it's a ring that guides a rope at a slight angle around objects.
antal low friction rings were never designed to be used as pulley replacement which is what kiters are doing. Are ronstan orbit blocks that expensive?

Antal Rings.jpg

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby edt » Mon Feb 13, 2012 10:15 pm

Hansen Aerosports wrote:they have progressed beyond fairleads and into vangs and other applications


look at their ad!

"They can be used for lazy jacks, furling line leads, fair leads . . . "

Doesn't sound new to me unless you are using them out of spec.


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