Question 2
Luke 451
a rope using a pulley-like knot, specifically,
a trucker's hitch? Or would simply
pulling on the end of the rope result in
an equal force to such a contrivance?
Luke in Ca
roo
Any time you employ a mechanical advantage device (block & tackle,
lever, etc.), you can increase the load output while increasing the
distance traveled by the operator.
Conversely, you can manipulate such a system to create a mechanical
disadvantage as well which decreases the output load while decreasing
the distance traveled by the operator.
In both cases the energy input - losses (i.e. friction) = energy output
http://www.geocities.com/roo_two/Versatackle.html
You might try Googling "mechanical advantage" for more info.
-roo
--
See the Notable Knot Index for my real e-mail address
arja...@zonnet.nl
> Luke 451 wrote:
> > Can one exert greater pulling force on
> > a rope using a pulley-like knot,
>
> the energy input - losses (i.e. friction) = energy output
>
> -roo
so, when the friction consumes half the energy input, no mechanical
advantage is gained
this hypothesis might fit the truckers' hitch (and versatacle)
because the friction for this 'pulley' is large, it might not give any
extra force
but the advantage is: the friction prevents slipping back
(all distance that is gained is held in place)
some experimentation / tests might clear this
(and possibly reject this hypothesis)
knot with advantages,
Ben
Dan Lehman
> no mechanical advantage is gained
IFF the MA was 2-to-1, yes? But w/3-to-1 (the *theoretical* MA of the
Trucker's H.), you have some advantage.
It depends upon friction of your materials, but genearlly you should
get
some significant advantage using a Trucker's Hitch, for as Ben notes,
all the friction, if present, will hold your gains--and one can usually
impart a good burst of energy in a surge (more than one could do
in a sustained pull, i.e.).
It is informative to test these structures with weights, to see their
actual advantage (if any--the oft' heralded Poldo Tackle might not
show any).
As for the particular constuction of a Trucker's Hitch, the literature
mostly shows either some mid-line loopknot like a Sheepshank or
a slipknot (Overhand or Fig.8); but one might better use a dblEye
bowline (tie the Bwl using a bight as the end which, like the bunny,
comes out of the hole and runs around the tree & back down), or
a Portuguese Bwl, or Bollard Loop, or ... --many other ways. With
twin eyes in the loopknot, you get a slightly better sheave there,
and less wear on the rope at the eye(s).
One can also re-reeve the rope from the anchor through the eye
to get a Versatackle-like working, or reeve the end through each
eye separately to increase MA (though friction build-up is great).
--dl*
====
Luke 451
> One can also re-reeve the rope from the anchor through the eye
> to get a Versatackle-like working, or reeve the end through each
> eye separately to increase MA (though friction build-up is great).
That's a great idea! Loop the rope once more around the anchor and
though the loop of a trucker's hitch and you get the same locking
mechanism as with a versatackle. You also get whatever block-and-
tackle-like mech advantage there is, minus friction.
The problem w/a v.tackle is the more one pulls out the slack the
closer the two loops get to one another. Once the loops touch,
you're finished. One might suggest setting the loops of the
tackle further apart, but this is not always possible if you're
on a roof, or up a pole or a ladder.
However, I still like a slip loop better than a double. I'm putting a
big load on the loop (I'm pulling the slack out of a long, heavy
span of aerial drop wire) and I'm thinking most double loops
would jam up annoyingly after such a strain.
I tested this out today. With an icicle hitch on the drop and a
double truckers to the anchor I was able
to pull that sucker taut enough for tightrope walking. I felt like
I could have ripped out the anchor if I kept going. Best thing,
once the attachment was made with a permanent clamp I was
able to slowly transfer the load off the rope without losing
any tensioning whatsoever. Without the load, it's almost
amusing how the slip loop, truckers and icicle all crumble into
a limp pile as if exhausted.
As Ben noted, what's more important is holding on to whatever
gains one has attained. With this double truckers I think you get the
best of both worlds, a MA and a locking tackle.
Luke in Ca
Dan Lehman
Luke 451 wrote:
> However, I still like a slip loop better than a double. I'm putting a
> big load on the loop (I'm pulling the slack out of a long, heavy
> span of aerial drop wire) and I'm thinking most double loops
> would jam up annoyingly after such a strain.
I don't know how you can believe this: the double-loopknot I
suggested (tying a bowline with a bight-end) is NON-jamming,
UNlike the slipknot, which is jamming (there is a dbe-eye version
of it, though: start as though for Butterfly, and then ...). And
the dble-eye will share the friction wear.
Sounds like you're dressing the slipknot well, for loosening,
though.
And, again, w/a dble-eye, you can make one pass in one eye,
the 2nd in the other eye, like reeving a 2-sheave block, which
of course increases you MA, subject to friction (esp. at anchor
point).
(-;
Luke 451
> > However, I still like a slip loop better than a double. I'm putting a
> > big load on the loop (I'm pulling the slack out of a long, heavy
> > span of aerial drop wire) and I'm thinking most double loops
> > would jam up annoyingly after such a strain.
>
> I don't know how you can believe this: the double-loopknot I
> suggested (tying a bowline with a bight-end) is NON-jamming,
> UNlike the slipknot, which is jamming (there is a dbe-eye version
> of it, though: start as though for Butterfly, and then ...).
I did test out the double loop in this scenario and you're right,
it did not jam up at all.
However, I experienced no jamming with the slip, in fact,
quite the opposite.
"The Book of Knots" (Budworth-Dalton) rates knots for ease
of untying on a scale of 1 to 5, with 5 being the easiest (least
likely to jam.)
A bowline on a bight was rated a 3,
and an overhand slip was rated a 5.
Isn't the whole idea of using a slip knot is that in a temporary
situation you can undo the knot quickly and easily?
My point was, I liked your idea of re-reaving around the anchor
to create a locking mechanism. That worked great with both
the single and double loops (altho the double required a 3rd
re-reaving to achieve the locking mechanism.)
Dan Lehman
> of untying on a scale of 1 to 5, with 5 being the easiest (least
> likely to jam.)
>
> A bowline on a bight was rated a 3,
> and an overhand slip was rated a 5.
1) One might wonder how these ratings came to be--in the
book, they are numbers (whose meaning is surprisingly (!)
hard to find); but how were the numbers determined?
(I wouldn't put much faith in these ratings, which are in
some cases obviously wrong; in general, such things
are material dependent, often.) The rating of "5" for ease
of untying overestimates the benefit of a slip-tuck--a too
common misreckoning, to my mind. And that of "3" for
the Bwl-on-a-Bight??? Perhaps the numbers come
from a roll of a die! (One should think that such a rating
system deserves a good explanation!?)
2) Neither of these knots is what I denoted: my Bwl is
in the bight, yes, but not "the" Bwl on the Bight of that book,
and your Slip-Knot is rather different in loading than the
stopper presented there--tensioning the loop gives much
greater chance of the Overhand being drawn tight.
> Isn't the whole idea of using a slip knot is that in a temporary
> situation you can undo the knot quickly and easily?
Well, that and it is quickly tied, in the bight. But as noted
above, a slip-tuck is hardly an easy thing to draw free, in
strongly loaded rope, of many common constructions:
if the knot is tight, getting movement of the end to even
begin drawing it out can be hard; and then, even with
some movement, managing to get the full eye of the
slip-tuck out is often impractical, as the sort of bulk it
forms when contracted at the nip defeats efforts to free it
(esp. if some torsion has worked into it, as often happens).
The Versatackle locking is nice, provided you have room
to effect the unlocking; it also has that *hold-the-gain*
aspect (i.e., after a good hard pull, one doesn't loose
some tension back through slippage after relaxing one's
haul on the line. With the double-sheave reeving, one
doesn't loose much overall tension on a little slippage,
as that length lost is allocated over the two reevings.
Cheers,
--dl*
====
Luke 451
"Dan Lehman" <dan_l...@hotmail.com> wrote in message
news:1125463670....@g44g2000cwa.googlegroups.com...
> > "The Book of Knots" (Budworth-Dalton) rates knots for ease
> > of untying on a scale of 1 to 5, with 5 being the easiest (least
> > likely to jam.)
> >
> > A bowline on a bight was rated a 3,
> > and an overhand slip was rated a 5.
>
> 1) One might wonder how these ratings came to be--in the
> book, they are numbers (whose meaning is surprisingly (!)
> hard to find); but how were the numbers determined?
> (I wouldn't put much faith in these ratings, which are in
> some cases obviously wrong; in general, such things
> are material dependent, often.) The rating of "5" for ease
> of untying overestimates the benefit of a slip-tuck--a too
> common misreckoning, to my mind. And that of "3" for
> the Bwl-on-a-Bight??? Perhaps the numbers come
> from a roll of a die! (One should think that such a rating
> system deserves a good explanation!?)
I got this book because it was good for my beginner needs....
lots of clear step-by-step pictures. Maybe it's time I
upgraded my library. I looked at the famous Ashley tome
but put it back on the shelf. It was like looking for a Boy Scout
manual and finding an encyclopedia.
> 2) Neither of these knots is what I denoted: my Bwl is
> in the bight, yes, but not "the" Bwl on the Bight of that book,
Would you be so kind as to fwd a link? I only know of
the one double loop bowline on a bight.
> Well, that and it is quickly tied, in the bight. But as noted
> above, a slip-tuck is hardly an easy thing to draw free, in
> strongly loaded rope, of many common constructions:
> if the knot is tight, getting movement of the end to even
> begin drawing it out can be hard;
I've had that very thing happen to me using clothesline.
One thing I never mentioned was the "rope" I used:
it was 1/8" polyester cord! It sheds the slip much more
easily that a regular sized line.
Thanks for your insights.
Luke in Ca
Carl
> Luke 451 wrote:
>
>
>>However, I still like a slip loop better than a double. I'm putting a
>>big load on the loop (I'm pulling the slack out of a long, heavy
>>span of aerial drop wire) and I'm thinking most double loops
>>would jam up annoyingly after such a strain.
>
>
> I don't know how you can believe this: the double-loopknot I
> suggested (tying a bowline with a bight-end) is NON-jamming,
> UNlike the slipknot, which is jamming (there is a dbe-eye version
> of it, though: start as though for Butterfly, and then ...). And
> the dble-eye will share the friction wear.
> Sounds like you're dressing the slipknot well, for loosening,
> though.
Yup, if you make the slipknot using the working end for the loop, like
the first stitch of a crocheted chain...and treat it gently while
getting set up, it will not tighten at all in a versatackle.
--
Carl West carlD...@comcast.net http://carl.west.home.comcast.net
>>>>>>>> change the 'DOT' to '.' to email me <<<<<<<<<<<<
"Clutter"? This is an object-rich environment.
beaure...@gmail.com
Any suggestions to improve the process are welcome, as are corrections of my nomenclature. I'm no expert like you guys; I'm more of a knot user than a theorist. I'd just ask you make your comments here rather than on YouTube. I can edit the video if warranted.
Thanks,
Luke in Ca
http://youtu.be/5G41Tve2nPg
ase...@aol.com
http://notableknotindex.webs.com/Versatackle.html
to lock your come-along in place.
I am familiar with the icicle hitch but according to this site the sailors gripping hitch outperforms the icicle.
http://notableknotindex.webs.com/sailorhitches.html
You show the results of the come-along but the camera does not show the come-along in operation. Would it be possible to focus the camera between the slip knot and the fixed point to show how these 2 points come together (and don't slip back) as you pull on the working end.
Very useful video. Tony
beaure...@gmail.com
Thanks for your reply and the interesting links. The icicle and sailor hitches seem interchangeable. My "greatest lateral pulling hitch" hyperbole comes from a claim I vaguely remember reading years ago about its introduction before the International Guild.
I will change my description from "modified trucker's" to "modified versatackle."
As for not showing the actual operation in the video: I did show a bit of it, but keep in mind that I was filming with a cell phone in one hand and operating the come-along with the other while hanging midspan from a 28' ladder. I had to pause and go both hands for part of the operation.
Luke in Ca