texascavers Digest 12 Feb 2011 23:40:24 -0000 Issue 1245
Topics (messages 17124 through 17144):
East Texas Caver Cookout - update
17124 by: David
Re: Bear Grylls related
17125 by: Sheryl Rieck
OT-fly story
17126 by: Rick Corbell
17135 by: Rod Goke
17140 by: J. LaRue Thomas
17141 by: Rod Goke
17142 by: wa5pok
Re: Sanctum
17127 by: Gill Edigar
17128 by: tbsamsel.verizon.net
splitting gear
17129 by: Andy Gluesenkamp
Fake Petzl products
17130 by: Fofo
17131 by: Ed Goff
Great prices on Petzl Gear!
17132 by: Frank Binney
17133 by: Allan B. Cobb
Government Canyon Karst Project
17134 by: Marvin & Lisa
Re: Fake Petzl products and splitting gear
17136 by: Rod Goke
fake Petzl gear
17137 by: Mixon Bill
17138 by: Gill Edigar
17144 by: Rod Goke
Truck for Sale
17139 by: vivbone.att.net
Re: fake Petzl gear and strength ratings
17143 by: Rod Goke
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--- Begin Message ---
I am here in Brenham and just met the camp manager at Camp Happy Hollow,
and we discussed the Cookout.
If anybody wants to know the details, e-mail me privately.
As far as I can tell, he has no problem with cavers doing the same thing
we did last year.
He is the kind of old-timer that still does business on a hand-shake,
and he didn't let me down last year, so I have no reason to doubt him this
year.
The event is the weekend before Memorial Day weekend. Location is a
few miles EAST of the town of Burton, Texas in Washington County.
The key elements to the event are a fun, inexpensive family-friendly camping
for cavers and their families at a nice remote campground.
This will be an opportunity for all lovers of caves in east Texas to
gather that for whatever
reason do not make it to events in the Hill Country. ( I have
invited cave divers,
geology students, naturalist, non-active NSS members, etc. that I could find in
southeast Texas to this event, via e-mail and Facebook. )
I am optimistic that those who come will be glad they did, as that was the
reaction last year.
If you live within a 4 hour drive of this event, it should
be worth attending. But there are plenty of cavers that live less than
2 hours away, and I would like to see as many of them come as possible,
even if it for just a few minutes at dinner time on Saturday evening.
David Locklear
co-host of the Cookout
( still looking for another co-host ?? )
--- End Message ---
--- Begin Message ---
It is dissertations such as this that keep me on this list! Thanks for the
entertainment.
Sheryl
On Thu, Feb 10, 2011 at 2:59 PM, Rod Goke <rod.g...@earthlink.net> wrote:
> I don't know about those Red Ryder BB guns, but my old single shot, hand
> pump style pellet gun used to work great for shooting flies inside the
> house. It worked much better than a fly swatter. Fly swatters have two
> drawbacks. One is that flies quickly learn to avoid them. In many cases,
> it's hard to sneak up on a fly with a swatter in your hand. Get anywhere
> close and it'll fly out of range. The pellet gun, however, didn't seem to
> scare the flies. I usually could put the gun's muzzle within an inch or two
> of the fly without scaring the fly away. At that range its hard to miss!
>
> The other big advantage of the pellet gun over a fly swatter was that there
> was less mess to clean up afterwards. Swat a fly on the wall with a fly
> swatter, and you'd have a wet blob of gooey fly guts to clean off the wall.
> The pellet gun, however, would instantly dismember the fly into separate
> wings, legs, and some relatively solid body parts that would drift through
> the air and land on the floor, where they could be picked up easily with a
> vacuum cleaner, leaving no gooey mess.
>
> Sure, you say, but what about all those bullet holes in the walls? Aren't
> they worse than squashed fly guts! The trick is that YOU DON'T PUT ANY
> PELLET IN THE PELLET GUN. That way you don't shoot holes in anything. When
> you pump it up and pull the trigger, all that comes out the muzzle is a puff
> of compressed air. If the muzzle is only an inch or two from the fly, the
> air blast is sufficient to disintegrate the fly without damaging anything
> else. Normally, it's not a good idea to fire the gun directly towards the
> wall, since that would splatter fly guts on the wall almost as bad as a fly
> swatter. Instead, I'd usually position the gun at an angle nearly parallel
> to the wall, such that fly parts would fly through the air and drift to the
> floor instead of splattering on the wall. The same technique also worked
> well for mosquitoes and small spiders. With small, fragile bugs, the
> technique often worked best with the gun pumped to only moderate pressure
> (like maybe 4 pump strokes using a pellet gun designed for a maximum of 6 to
> 8 strokes). That way the air blast would be sufficient to instantly kill the
> bug without turning it into a gooey mess that would be harder to clean up.
> Tougher bugs, such as wasps, were hard to kill with an air blast, even with
> the gun pumped to its maximum pressure. I killed a few indoor wasps this
> way, but I don't recommend it, since sometimes the air blast was just enough
> to put them into a bad mood.
>
> For safety, I'd always double check that the gun contained no pellet before
> using it for indoor bug blasting. First I'd open the action to see visually
> that it was empty. Then I'd close the action, pump the gun to minimal firing
> pressure (one or two strokes on that pellet gun), and fire it in a safe
> direction to be sure there was nothing in it. (At that low pressure, even if
> a pellet had been left in the gun accidentally, it would have been blown out
> the barrel at a low enough velocity to cause negligible damage or safety
> risk when fired in a safe direction.) Finally, when actually firing an air
> blast at a bug, I'd fire in a safe direction that would not have endangered
> anyone even if a pellet had been left in the gun.
>
> That old pellet gun, which I had had since I was a kid, eventually wore
> out, but it sure was a useful bug blaster while it lasted.
>
> As they say on TV, don't try this at home, kids (at least not while anyone
> is watching). ;-)
>
> Rod
>
> -----Original Message-----
> >From: Andy Gluesenkamp <andrew_gluesenk...@yahoo.com>
> >Sent: Feb 10, 2011 11:35 AM
> >To: Bill Bentley <ca...@caver.net>, Fritz Holt <
> fh...@townandcountryins.com>, "tbsam...@verizon.net" <tbsam...@verizon.net>,
> "dlocklea...@gmail.com" <dlocklea...@gmail.com>
> >Cc: "texascavers@texascavers.com" <texascavers@texascavers.com>, Mandy
> Holt <mandy.h...@ers.state.tx.us>, Jenny Holt <jennyh...@anthonytravel.com
> >
> >Subject: Re: [Texascavers] Bear Grylls related
> >
> >Someone needs to.
> >
> >You'll shoot your eye out.
> >
> >Fritz Holt <fh...@townandcountryins.com> wrote:
> >
> >>WATCH OUT! My daughters and I own Red Ryder BB guns. We shoot holes in
> cans, not
> >>birds or other creatures.
> >>I am a Bee Gee fan. They make good music.
> >>
> >>Fritz
>
>
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>
--- End Message ---
--- Begin Message ---
Place:Scurry Old Fields around Snyder in west Texas
Time: '50's (1950's)
Long hours waiting in the "dog house" at tank batteries could get boring. My
dad made a game of catching flies in his hand. He would sweep his cupped hand
an inch or two above the subject and more often than not the fly would fly
right into his hand. A quick squeeze would capture it. Try it sometime. If
the fly doesn't get caught between your fingers or a fold in your palm, you can
feel the buzz when it tries to escape. Kind of tickles. A clap would most
often dispatch the fly. Sometimes they get away, sort of like catch and
release.
Rod, et. al. thanks for bringing back the memories.
This could be cave related if you think about breaking out your lunch while
ridge walking and drawing flies with that smashed sandwich. While waiting on
everyone to finish, you now have something to entertain yourself.
Rick Corbell
--- End Message ---
--- Begin Message ---
Yes, I've seen that fly catching technique. My father, who is now 98, used to
be good at doing it in his younger days. He used to catch flies in the manner
you described, but his method of dispatching them was different. Instead of
clapping, he would throw the fly as hard as he could onto the floor, which
might not kill the fly, but it usually would stun the fly just long enough for
him to step on it. I never mastered this fly catching technique myself, but I
always thought it was impressive to watch. Sometimes it was even more
entertaining to watch expressions on the faces of bystanders who happened to
witness the maneuver.
Rod
-----Original Message-----
>From: Rick Corbell <rlcorb...@hotmail.com>
>Sent: Feb 10, 2011 8:53 PM
>To: texascavers@texascavers.com
>Subject: [Texascavers] OT-fly story
>
>
>Place:Scurry Old Fields around Snyder in west Texas
>Time: '50's (1950's)
>Long hours waiting in the "dog house" at tank batteries could get boring. My
>dad made a game of catching flies in his hand. He would sweep his cupped hand
>an inch or two above the subject and more often than not the fly would fly
>right into his hand. A quick squeeze would capture it. Try it sometime. If
>the fly doesn't get caught between your fingers or a fold in your palm, you
>can feel the buzz when it tries to escape. Kind of tickles. A clap would
>most often dispatch the fly. Sometimes they get away, sort of like catch and
>release.
>
>Rod, et. al. thanks for bringing back the memories.
>
>This could be cave related if you think about breaking out your lunch while
>ridge walking and drawing flies with that smashed sandwich. While waiting on
>everyone to finish, you now have something to entertain yourself.
>
>Rick Corbell
>
>
>
>
>
--- End Message ---
--- Begin Message ---
My first husband also used to do the fly-catching and throwing-to-the-ground
thing. For the grandkids he had an interesting sleight-of-hand where he
could make it look like he ate the fly. I never could figure out how he did
that and he took the secret with him into the next life. Jacqui
----- Original Message -----
From: "Rod Goke" <rod.g...@earthlink.net>
To: "TexasCavers" <texascavers@texascavers.com>
Sent: Friday, February 11, 2011 5:58 PM
Subject: Re: [Texascavers] OT-fly story
--- End Message ---
--- Begin Message ---
Are you sure he didn't actually eat it? Certain cavers have been known to eat
larger insects than that. Right, Gill?
Rod
-----Original Message-----
>From: "J. LaRue Thomas" <jlrbi...@sonoratx.net>
>Sent: Feb 12, 2011 10:20 AM
>To: TexasCavers <texascavers@texascavers.com>
>Subject: Re: [Texascavers] OT-fly story
>
>My first husband also used to do the fly-catching and throwing-to-the-ground
>thing. For the grandkids he had an interesting sleight-of-hand where he
>could make it look like he ate the fly. I never could figure out how he did
>that and he took the secret with him into the next life. Jacqui
>
>----- Original Message -----
>From: "Rod Goke" <rod.g...@earthlink.net>
>To: "TexasCavers" <texascavers@texascavers.com>
>Sent: Friday, February 11, 2011 5:58 PM
>Subject: Re: [Texascavers] OT-fly story
>
>
>>
>
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--- End Message ---
--- Begin Message ---
... and/or arachnids ...
--------------------------------------------------
From: "Rod Goke" <rod.g...@earthlink.net>
Sent: Saturday, February 12, 2011 11:21 AM
To: "TexasCavers" <texascavers@texascavers.com>
Subject: Re: [Texascavers] OT-fly story
Are you sure he didn't actually eat it? Certain cavers have been known to
eat larger insects than that. Right, Gill?
Rod
-----Original Message-----
From: "J. LaRue Thomas" <jlrbi...@sonoratx.net>
Sent: Feb 12, 2011 10:20 AM
To: TexasCavers <texascavers@texascavers.com>
Subject: Re: [Texascavers] OT-fly story
My first husband also used to do the fly-catching and
throwing-to-the-ground
thing. For the grandkids he had an interesting sleight-of-hand where he
could make it look like he ate the fly. I never could figure out how he
did
that and he took the secret with him into the next life. Jacqui
----- Original Message -----
From: "Rod Goke" <rod.g...@earthlink.net>
To: "TexasCavers" <texascavers@texascavers.com>
Sent: Friday, February 11, 2011 5:58 PM
Subject: Re: [Texascavers] OT-fly story
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--- Begin Message ---
On Thu, Feb 10, 2011 at 9:52 AM, <tbsam...@verizon.net> wrote:
> Mercy killings? Did they split up his gear?
>
Yeah, Ted, that's the kick in the ass: They didn't split up the dudes
gear--or even their lamps and batteries or Clif Bars.
--Ediger
--- End Message ---
--- Begin Message ---
A passel of Hollywood wussies.
Feb 10, 2011 11:05:47 PM, gi...@att.net wrote:
On Thu, Feb 10, 2011 at 9:52 AM,
<tbsam...@verizon.net> wrote:
Mercy killings? Did they split up his gear?
Yeah, Ted, that's the kick in the ass: They didn't split up the dudes gear--or even their lamps and batteries or Clif Bars.
--Ediger
--- End Message ---
--- Begin Message ---
Some of us were gnoshing on Joe Ivy's IronMan bars long after his demise.
Since
they were never really edible in the first place, they didn't seem any worse a
year or so past their expiration date.
AGG
Andrew G. Gluesenkamp, Ph.D.
700 Billie Brooks Drive
Driftwood, Texas 78619
(512) 799-1095
a...@gluesenkamp.com
________________________________
From: Gill Edigar <gi...@att.net>
To: tbsam...@verizon.net
Cc: jpbrook...@sbcglobal.net; texascavers@texascavers.com
Sent: Thu, February 10, 2011 11:05:47 PM
Subject: Re: Re: [Texascavers] Sanctum
On Thu, Feb 10, 2011 at 9:52 AM, <tbsam...@verizon.net> wrote:
Mercy killings? Did they split up his gear?
Yeah, Ted, that's the kick in the ass: They didn't split up the dudes gear--or
even their lamps and batteries or Clif Bars.
--Ediger
--- End Message ---
--- Begin Message ---
�Hola!
Well, it had to happen at some point: Petzl has detected fake products
out there:
http://www.karstworlds.com/2011/02/attention-petzl-warns-for-fake-chinese.html
Let's be careful.
- Fofo
--- End Message ---
--- Begin Message ---
Awesome! Lead carabiners would be great for cave divers. What could you do with
a melamine headlamp? Feed it to your cat?
Ed
On Feb 11, 2011, at 9:27 AM, Fofo <gonza...@msu.edu> wrote:
> ¡Hola!
>
> Well, it had to happen at some point: Petzl has detected fake products out
> there:
>
> http://www.karstworlds.com/2011/02/attention-petzl-warns-for-fake-chinese.html
>
>
> Let's be careful.
>
> - Fofo
>
> ---------------------------------------------------------------------
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--- End Message ---
--- Begin Message ---
I was strolling through San Francisco's Chinatown yesterday and stopped at
the Sum Ting Wong Trading Company and stocked up on new Petzl carabiners and
ascenders at bargain basement prices. Anybody up for joining me for vertical
practice next week off one of the big walls in Yosemite?
Frank
PS--The store also has great prices of Rolex watches, designer handbags and
high-protein cat food!
--- End Message ---
--- Begin Message ---
Does your new Petzl gear have the Folgers Coffee label? You know, the one with
the motto "Good to the last drop".
Sent from my iPhone
On Feb 11, 2011, at 1:08 PM, Frank Binney <fr...@frankbinney.com> wrote:
> I was strolling through San Francisco's Chinatown yesterday and stopped at
> the Sum Ting Wong Trading Company and stocked up on new Petzl carabiners and
> ascenders at bargain basement prices. Anybody up for joining me for vertical
> practice next week off one of the big walls in Yosemite?
> Frank
> PS--The store also has great prices of Rolex watches, designer handbags and
> high-protein cat food!
>
>
>
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--- Begin Message ---
The 100th trip of the Government Canyon Karst Project will take place on the
5th and 6th of March. We will meet as usual at 9:00 on both days in the
parking area of the Volunteer/Research Station to organize teams and
objectives. On the evening of the 5th (Saturday) we will have a hog roast,
awards ceremony, and presentation in celebration of the 100th project trip.
The event will take place at the Volunteer/Research Station. All are invited
to come. The hog will be provided courtesy of the Government Canyon Hog
Hunters (feral hog eradication). A vegetarian entre will also be provided.
Please bring a side dish and your own drinks. The meal will begin at 5:30.
Many participants will be camping at the volunteer campground nearby so
bring your tent and join in the fun. Then go caving, digging, or
ridgewalking on Sunday.
Directions to the Government Canyon Karst Project:
Find the intersection of U.S. 16 and Loop 1604 in northwest Bexar County
(clearly shown on any state highway map). Drive 2 miles north on U.S. 16 to
the third traffic light and turn left onto FM 1560 (there is a Shell station
on the corner). Follow 1560 for 3 miles till you see the sign for GCSNA.
Follow the arrow to the right and drive 2 more miles to the sharp left turn
in the road. The gate to GCSNA is straight ahead. Enter at the gate and then
take the first right. There is an unlocked gate that will need to be opened
and then closed behind you. Continue to the Volunteer/Research Station,
where we will meet.
Marvin Miller
(210) 415-5190
--- End Message ---
--- Begin Message ---
Notice how difficult Petzl claims it is to distinguish their real products from
the dangerous fakes, ... something to think about when you're splitting gear!
Rod
-----Original Message-----
>From: Fofo <gonza...@msu.edu>
>Sent: Feb 11, 2011 9:27 AM
>To: texascavers <texascavers@texascavers.com>
>Subject: [Texascavers] Fake Petzl products
>
>¡Hola!
>
>Well, it had to happen at some point: Petzl has detected fake products
>out there:
>
>http://www.karstworlds.com/2011/02/attention-petzl-warns-for-fake-chinese.html
>
>
>Let's be careful.
>
> - Fofo
>
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--- End Message ---
--- Begin Message ---
I suspect that the safety factor in the strength of real Petzl gear
over what is really needed for normal use is so great that the fake
gear is not really dangerous. For example, does it really matter
whether a Croll opens at 900 pounds or 1350 pounds? You should never
take a fall on an ascender anyway. Still, of course, if you think
you're getting Petzl gear, you should get the real thing. Just don't
get paranoid about relying on somebody's Petzl gear because it might
be fake. -- Mixon
----------------------------------------
A fearless man cannot be brave.
----------------------------------------
You may "reply" to the address this message
came from, but for long-term use, save:
Personal: bmi...@alumni.uchicago.edu
AMCS: edi...@amcs-pubs.org or sa...@amcs-pubs.org
--- End Message ---
--- Begin Message ---
They showed at least one photo of a Kroll (?) that was opened
up--whether that was from human weight or a testing machine wasn't
obvious.
--Ediger
On Fri, Feb 11, 2011 at 7:00 PM, Mixon Bill <bmixon...@austin.rr.com> wrote:
> I suspect that the safety factor in the strength of real Petzl gear over
> what is really needed for normal use is so great that the fake gear is not
> really dangerous. For example, does it really matter whether a Croll opens
> at 900 pounds or 1350 pounds? You should never take a fall on an ascender
> anyway. Still, of course, if you think you're getting Petzl gear, you should
> get the real thing. Just don't get paranoid about relying on somebody's
> Petzl gear because it might be fake. -- Mixon
> ----------------------------------------
> A fearless man cannot be brave.
> ----------------------------------------
> You may "reply" to the address this message
> came from, but for long-term use, save:
> Personal: bmi...@alumni.uchicago.edu
> AMCS: edi...@amcs-pubs.org or sa...@amcs-pubs.org
>
>
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--- End Message ---
--- Begin Message ---
Since they specified the force at which failure occurred, I presume that
testing was done on a machine capable of measuring this force.
Rod
-----Original Message-----
>From: Gill Edigar <gi...@att.net>
>Sent: Feb 12, 2011 7:32 AM
>To: Mixon Bill <bmixon...@austin.rr.com>
>Cc: Cavers Texas <texascavers@texascavers.com>
>Subject: Re: [Texascavers] fake Petzl gear
>
>They showed at least one photo of a Kroll (?) that was opened
>up--whether that was from human weight or a testing machine wasn't
>obvious.
>--Ediger
>
>On Fri, Feb 11, 2011 at 7:00 PM, Mixon Bill <bmixon...@austin.rr.com> wrote:
>> I suspect that the safety factor in the strength of real Petzl gear over
>> what is really needed for normal use is so great that the fake gear is not
>> really dangerous. For example, does it really matter whether a Croll opens
>> at 900 pounds or 1350 pounds? You should never take a fall on an ascender
>> anyway. Still, of course, if you think you're getting Petzl gear, you should
>> get the real thing. Just don't get paranoid about relying on somebody's
>> Petzl gear because it might be fake. -- Mixon
>> ----------------------------------------
>> A fearless man cannot be brave.
>> ----------------------------------------
>> You may "reply" to the address this message
>> came from, but for long-term use, save:
>> Personal: bmi...@alumni.uchicago.edu
>> AMCS: edi...@amcs-pubs.org or sa...@amcs-pubs.org
>>
>>
>> ---------------------------------------------------------------------
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>>
>>
>
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--- Begin Message ---
Hey Ya'll,
My Amazing Truck is for sale. It's a 2003 3/4 ton Dodge 2500 quad-cab, long bed
w/ bed liner and roof rack. Runs great, fancy paint job. Single owner, well
maintained. I am religious about oil changes. My other car has 340,000 miles on
it, and is going strong, for instance.
More info here:
http://austin.craigslist.org/cto/2208647143.html
This is a great truck for moving a lot of heavy stuff with 6 people comfortably
in the cab. It is not a good off-road vehicle because of its super-long wheel
base. So it's not really a caving vehicle, but a great work horse. You can put
1.5 tons in the bed and pull 16 tons in a trailer and it doesn't even feel it.
This is caving related because I have to sell this truck by Next Wednesday or
call of my planned trip to New Zealand leaving Feb. 22nd for an amazing caving
expedition to the Fiordland. I'm letting her go cheap. I'm down to $7,000. Blue
Book is $8,325.
So help me spread the word!!
Vivian Loftin (512)659-9486
--- End Message ---
--- Begin Message ---
"...does it really matter whether a Croll opens at 900 pounds or 1350 pounds?"
Bill,
Those safety factors are not as over-engineered as many people might be tempted
to assume. As an old time caver with a strong background in physics, you
probably already know most of what I'm going to write here, but I think it's
worthwhile to point out a few things for the benefit of those who haven't
thought much about what equipment strength ratings actually mean.
Lots of cavers today don't pay much attention to equipment strength ratings,
because most of the time, they don't have to. They buy equipment designed for
caving by Petzl and other reputable manufacturers, and they quite reasonably
assume that these manufacturers design their equipment with adequate strength
for its intended uses. As long as cavers use the equipment as intended (and
sometimes even when they don't), they assume that it's safe without paying much
attention to the actual numbers. After all, why would individual cavers worry
about how much safety margin is adequate when expert equipment designers
already have done that for them?
Acquiring safe caving equipment wasn't always this easy. When many of us old
timers started caving (1968 in my case), there was almost no commercially
manufactured equipment designed for caving. We could buy a few items, such as
carabiners, brake bars, and Jumar ascenders, that were deigned for rock
climbing, but, mostly, we built and improvised our own vertical gear using
parts and materials manufactured for different applications. There were no
static climbing ropes made for caving, so, for long drops, we used braided rope
made for marine and industrial uses (remember Samson rope). For rappelling, we
used multiple carabiners with brake bars, and we linked the 'biners together
using ordinary chain links purchased at local hardware stores. We made our own
climbing harnesses from various types of nylon webbing, buckles, and threads.
When Gibbs ascenders became available, many of us began designing and building
our own chest pulley boxes for our own use, using whatever materials we thought
would work. When we heard about other cavers beginning to use rappel racks,
cavers in our grotto (the Florida Speleological Society in Gainesville) began
buying steel rods and bending them on a homemade jig to make racks for our own
use. In those days, we couldn't rely on commercial caving equipment
manufactures to determine safety margins for us, so we had to rely on our own
judgement to obtain information about product strengths and to decide for
ourselves what was suitable for vertical caving. Most of us actually survived.
>From those days, I recall looking up the strength ratings of various metal
>products, such as steel chain, and of certain nylon products, such as ropes,
>and finding that each product had two different kinds of strength ratings. One
>was "breaking strength", which specified the force required to break a product
>in new condition, and the other was "safe working load", which specified the
>maximum load that could be safely applied to the product in normal use. The
>ratio of breaking strength to safe working load was called the "safety
>factor", which typically was about 4 or 5 for metal products and might be as
>high as 10 for nylon rope. The safety factor was intended in part to
>compensate for manufacturing variations and for gradual weakening due to
>normal wear and tear. More importantly, if my understanding is correct, the
>safety factor was also intended to prevent the product form being weakened by
>repetitive application of excessive stress, such as by metal fatigue in metal
>products or by similar stress damage in nylon rope or webbing. Whenever a
>product was subjected to stress exceeding its safe working load, it might not
>break immediately, but the excessive stress could weaken the material,
>effectively lowering its breaking strength from then on. Repeated stresses of
>this type eventually could cause the product to fail with a load significantly
>lighter than the initial breaking strength. Thus, in normal use, it was the
>safe working load, not just breaking strength, that we should avoid exceeding.
I don't know what safety factor is considered adequate for a Croll ascender,
but my understanding is that 4 or 5 is common for metal products. Suppose, for
example, that it is 4. In this case, an ascender with a breaking strength of
1350 pounds would have a safe working load of 337.5 pounds, a load unlikely to
be exceeded by most cavers climbing with normal amounts of cargo. In contrast,
an ascender with a breaking strength of 900 pounds would have a safe working
load of only 225 pounds (assuming the same safety factor of 4), a load that
easily could be exceeded by the weight of a large caver with a heavy pack, or
merely by the weight of a caver is some cases. Hence, with these assumptions,
an ascender with a 900 pound initial breaking strength might be repeatedly
subjected to stresses greater than its safe working load during normal use,
causing it to gradually weaken and perhaps eventually to fail with a load much
less than 900 pounds.
This example considers only the typical case where one caver is climbing
normally with an ordinary amount of gear. Significantly higher loads can occur
in less typical situations, and I don't just mean dynamic falls. For example,
consider certain rescue situations where an ascender might be subjected to the
weight of more than one caver (e.g., rescuer + victim). Also, some rigging
arrangements, such as tyrolean traverses, can place exceptionally high stresses
on equipment. Whenever vertical equipment is used in these less typical
situations, it is especially important to consider the actual forces involved
to make sure the equipment is not overloaded.
Substandard equipment is not necessarily dangerous if you know its limitations
and avoid exceed them. The hazards occur when people mistakenly count on
equipment being stronger than it actually is.
Rod
-----Original Message-----
>From: Mixon Bill <bmixon...@austin.rr.com>
>Sent: Feb 11, 2011 7:00 PM
>To: Cavers Texas <texascavers@texascavers.com>
>Subject: [Texascavers] fake Petzl gear
>
>I suspect that the safety factor in the strength of real Petzl gear
>over what is really needed for normal use is so great that the fake
>gear is not really dangerous. For example, does it really matter
>whether a Croll opens at 900 pounds or 1350 pounds? You should never
>take a fall on an ascender anyway. Still, of course, if you think
>you're getting Petzl gear, you should get the real thing. Just don't
>get paranoid about relying on somebody's Petzl gear because it might
>be fake. -- Mixon
>----------------------------------------
>A fearless man cannot be brave.
>----------------------------------------
>You may "reply" to the address this message
>came from, but for long-term use, save:
>Personal: bmi...@alumni.uchicago.edu
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>
>
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