US Friction Saver

That looks like an adjustable false crotch.
Can you post pictures of the unit in use?

How is the climbing rope rigged?

Can it be used with the climber's rope rigged only around the pulley? If so, can it be retrieved with only the climbing rope? How?

Is the bottom picture part of the setup?

Thanks!

Tom
 
The bottom picture is the setup. The top picture was just a friction hitch I posted a while back on variation distal and how I use it. As far as the friction saver goes I just started using it. You could use it as a retrievable redirect I guess if you wanted. It's just something a little different than the guy climbing next to you. The strap between the pulley and ring is just half inch New England T 900 with a rating of 17,000 pounds.
 
ive been working on a similiar set up and hope to have the final draft soon. Big Jon, where did you get the pulley sheave and shackle? My only hold up is finding the right combo. And is the shackle of a locking nature? Now all you need is a release tether so it is retrievable from the ground. Tim brings up a good point also, are each of the components rated at 5000lbs. or more. The strap(rope) yes , the round ring probably, but the shackle and pulley sheave?
 
The shackle/clevis is a stainless locking clevis with a SWL of 1795. The sheave is just sheave from a cmi micro pulley. For now I just have bushings to fit the pin on the clevis. I am hoping to get a small pair of bearings. I just haven't made the trip, waiting for a rain day. I am thinking of changeing the setup to just a U shape rather than the C. I think it may be more stable. I believe there is a way to work off just the single pulley and still retrieve it from the ground.
 
You ask about ratings. I left one thing out earlier. The only rating I REALLY worry about and I think more people should worry about are the ratings of the tree,limb, and crotch they are tying into. I believe I would break a crotch out before any of my equipment failed.
 
BigJon,

I worry about limb strength too, but it is a variable that we can't control. We can choose the best tie in point based on our knowledge of the species and our experience, but you don't really know how strong the limb is.

We do know what gear is rated, we are supposed to anyway. We do have a safety standard to follow (ANSI Z133.1, CE, etc. depending on where you climb.) I know that the Z was established as a direct result of a tree climbing fatality. The standards are written to prevent further accidents and fatalities. There are some things the Z isn't clear on, we are working to change that, but some others are crystal clear:


ANSI Z133.1 -2000 3.13 false crotch. A system used to support an arborist climbing line other than a natural crotch. A false crotch shall incorporate rings or a pulley, or some other device that will protect the system and/or arborist climbing line from damage or failure. Each component of the system shall have a minimum tensile strength of 5,000 pounds.

There is no shortage of equipment that meets the standard, so it makes sense, to me, to use only approved gear and techniques.

Thanks BigJon,

TMW

[ September 08, 2002: Message edited by: Tim Walsh ]
 
Hi there,

finally i made it to register here now, after i´ve been following the discussions since the beginning.
so greetings at first to all of you who know me.


i just saw your picture of the new false crotch, and now i was wondering, how it is working. like a normal false crotch, the rope running through the pulley and the ring?
and if, isn´t it a problem, as long as the pulley isn´t in a cage, that it is rubbing (?) when the rope is running, at the ring on the other side?
But if you´re using it the other way, by only running through the pulley, how can you retrieve it, and if, also with a throwline?

about the knot, we played around with several variations during the last years, and don´t you think that compared to the DISTEL knot it has more friction to push it up again(even when you´re using a prusiklift).
or, let´s say it different, what are the advantages? but if there are some, let me know.

but hey, keep on inventing!
 
Does any1 have an idea why according to the Z133.1 a false crotch needs only to be rated at 5000 lbs. tensile strength while an arborists climbing line needs to be rated for 5400 lbs. tensile strength when new? The 5400 lb tensile rating for arborists climbing lines was in effect in the Z before false crotches were being used. Why is there a lower rating for a false crotch but not arborists climbing lines?

BTW, in the Z133.1, there is a statement that a 1/2 inch diameter climbing line = 12.5 mm diameter climbing line. This isn't true, it's 12.7 mm. Even though it's an insignificant amount of distance between the 2 measures, the conversion is wrong and printed to suite the writers of the Z. Most climbing lines are supposedly greater than the 1/2" diameter climbing lines as labeled for climbing lines. (I can't cite my source for this info since it's against this sites rules. The author of the article for which I read about this didn't cite a source for this info either, he just stated this is the way it is for climbing lines. The author also used the 12.5 mm conversion in his article when citing the Z.). It would make sense to be more precise with insignificant measures.

Joe

[ September 08, 2002: Message edited by: joe ]
 
Joe, Good question. I'm not too sure as to the Z's answer, but I would think that they threw the false crotch in with "climbing gear" and connectors (5000#) rather than seeing it as an extension of the climbing line.
confused.gif
 
Maybe it has something to do with how knots reduce the strength of the rope. And until a few years ago everyone had at least one knot in their rope. But if every piece of my climbing system has a 5000lb rating or more, I doubt my lil 160 lb. butt is going to be in much danger.

Rope ratings are rather meaningless anymore, though. My lifeline has a rating of almost 8000 lbs. When my rigging lines get retired, I replace my lifeline and my old lifeline becomes a rigging line. This way I always have a relatively new lifeline, and my handlines don't have that 'new' stretch the first couple times they are used. My rigging line's condition determines when I get a new lifeline, because I never put enough stress on a lifeline to drastically reduce it's strength.
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Joe et al,

The MBS for climbing lines, 5400lbs (>24.02Kn)came about from the ASC Z133.1, the way I understand it, because at the time the line most commonly used had that rating. It has stuck ever since. As was stated, the number is low in comparison to the strengths of the current climbing lines.

The rating for other equipment/gear, 5000# (22.24Kn) comes from OSHA. A caveat here, the standards state that equipment should meet or exceed certain ratings. In the case of gear, carabiners for example, a 22Kn 'biner does not meet or exceed the standard (22kn-->22 x 224.8 = 4945.6#) this is why only 23Kn and great 'biners, snaps, etc. are acceptable.

In terms of the minimum diameter requirements, the 12.5mm conversion may just be a rounding error, (1 inch = 25.4 mm, ½ inch = 12.7mm). The Z133.1 isn’t perfect, one of the reasons why we revise it every 5 years.

Thanks,

TMW
 
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