Rappel Racks

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Rappel Racks

Postby David Grimes » Dec 2, 2007 8:58 pm

Is there a strength difference between a rack with a coiled eye vs a welded one?
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Postby fuzzy-hair-man » Dec 2, 2007 9:57 pm

I had read somewhere reports of coiled eye racks having the eye unwind under some rescue loads (~200kg -250kg) the solution as I understand it is welded eye racks. I'd imagine this is no longer a problem though and any rack with a bent eye would be suitably strong, if it was a problem in the first place. If you are after stronger racks than this for whatever reason try a U frame rack according to Gary Storrick's website http://storrick.cnchost.com/VerticalDevicesPage/Rappel/URacks.html these are generally stronger although you lose the ability to swivel out bars.

Here it is: (Quote from bill Storage's website http://www.bstorage.com/speleo/OnTech/ontech.htm ) Note: he was making a point about something else...
For example, a recent issue suggested that stainless rappel racks with coiled eyes should be welded at the eye to increase strength. These racks can uncoil under loads as small as 800 pounds. The author showed details of the weld procedure.

A good engineer might want to debate the likelihood of such welding, if done under less than ideal circumstances, resulting in an embrittled and corrosion-prone area about an inch from the weld. Or an engineer might make a point that while a 150 pound human hanging from a rack might survive a deceleration of 5.3 g (needed to begin uncoiling the eye) if its duration were short, it is inconceivable that a human would survive a load high enough to uncoil the rack for the length of time needed to uncoil the ten inch long coiled region. A practical caver might note that anyone subject to an 800 pound load on a rack has both locked off his rack and done some extremely poor rigging. Yeah sure, the rack article was concerned with rescue situations as opposed to standard caving; but if I were a victim I'd feel much better if my rescuers used wimpy racks and good rigging rather than the other way around.

All these intellectual arguments aside, let's say we agree that welded racks are essential. They cost twenty five dollars. Where on earth could you find a quality welder, one capable of doing a good job with austenitic stainless, for $25? Get serious. Revised advice: support your local equipment vendor. Buy a new rack. Learn proper rigging-for-rescue. Get a life.
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Postby Carl Amundson » Dec 3, 2007 9:49 am

The other issue with a U frame rack is that you can't put it on a loaded rope.
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Postby Ralph E. Powers » Dec 3, 2007 10:38 am

Before someone else thought that they needed my rack (and new harness) more than I did and permanently *ahem* borrowed it, I was using a coiled eye SMC stainless rack for years until just before it got *ahem* borrowed I had a friend who was a professional, weld the eye together.
I've had rescue loads on that particular rack before (pre-weld) and didn't experience or notice any change with the eye; in as far as distortion or warping or anything like that.

It was a good rack, put well over 30K feet of vertical on it over the years. I miss my old friend. :sad:
Without the possibility of death, adventure is not possible. ~ Reinhold Messner


http://ralph.rigidtech.com/albums.php
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Postby Tim White » Dec 3, 2007 11:06 am

You can download Nylon Highway Issue #34 that has Butch Felhaus’ article A SAFETY ENHANCEMENT OF CURLED EYE RACKS.

One should never experience loads that would cause a curled eye rack frame to fail in personal use. If you do, you have a lot more to worry about before the rack fails. Now for a rescue load…:eyecrazy: maybe, but let's hope we don't ever see those type of load / forces there either.


Ralph E. Powers wrote:...I was using a coiled eye SMC stainless rack...


To my knowledge SMC never produced a coiled eye rack frame. I could be wrong, maybe their first were coiled eye, but I don't think so. They are the leading manufacturers of the welded frame, kind of what sets them apart from their largest compactor.
Be safe,
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Editor, Nylon Highway
Senior Technical Manager - Over the Edge, Inc.
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Postby Ralph E. Powers » Dec 3, 2007 12:40 pm

Tim White wrote:
Ralph E. Powers wrote:...I was using a coiled eye SMC stainless rack...


To my knowledge SMC never produced a coiled eye rack frame. I could be wrong, maybe their first were coiled eye, but I don't think so. They are the leading manufacturers of the welded frame, kind of what sets them apart from their largest compactor.

It was probably one of their first as I've had it for well over 12-14 years before someone *ahem* "borrowed" it. I am positive that it was an SMC because I bought it with the bars and the bars were stamped with the SMC logo. Paid something like $75.00 for it. Now granted that the bars might've been SMC and the rack frame was something else but another memory of mine remembers seeing the SMC logo stamped on the frame near the eye as well.

Either way when I get the replacement it will be the same rack (only welded not coiled). I can't see myself using any other kind (though I have). It's like an old pair of jeans, you're just awfully comfortable and familiar with it. :caver:
Without the possibility of death, adventure is not possible. ~ Reinhold Messner


http://ralph.rigidtech.com/albums.php
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