
The Machard Knot and its 16-year-old inventor - briandear
http://www.summitpost.org/the-machard-knot/936995
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sswaner
I learned this knot as the GRB - "Guide's Rappel Brake" and also as an
autoblock. There are several entries each year in "Accidents in North American
Mountaineering" that describe failure to properly use a mechanical belay
device. I recall no accidents as the result of a faulty autoblock knot. This
knot is aligned with the KISS principle from software engineering. It is
remarkably simple and effective.

Interesting to read this story of its origin.

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chrissnell
Interesting that you mention "Accidents in North American Mountaineering".
This is the climbing equivalent of the Startup Post-Mortems story that was
posted the other day. They publish them every year and they're a great read.
Like startup failures, they tend to cluster around a few common mistakes--
typically failure to anticipate weather conditions and overconfidence in one's
abilities. Definitely worth checking out if you enjoy climbing and
mountaineering.

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brianmwaters_hn
It's called an "autoblock" by climbers today in the US:
[https://en.wikipedia.org/wiki/Autoblock](https://en.wikipedia.org/wiki/Autoblock)

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glomph
That appears to be a slightly different knot. The final stage where the bottom
loop goes through the top isn't done for an autoblock.

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masklinn
> The final stage where the bottom loop goes through the top isn't done for an
> autoblock.

That'd be the french knot which only blocks in one direction. The Machard knot
which blocks in both directions does not loop through itself, the karabiner
goes through both loops to close the knot.

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markbnj
Sailors have known and used "jamming" hitches like this for centuries. It's
the basic principle behind a sheep shank for example. Marseilles is of course
a port city, so I wonder if he found some inspiration along the waterfront.

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snowwrestler
This was not the first jamming hitch used in climbing--that would be the
Prusik, which is still used today.

The Prusik is trickier and slower to tie than the autoblock, and tends to stay
tight once it is tensioned. The autoblock runs looser and is easier to loosen
up once it has been tensioned, which is why it's generally preferred over the
Prusik as a rappel backup.

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tangled
An alternative to this is the mechanical ascender / 'jammer'. I've used the
Petzl version when caving:
[http://www.petzl.com/en/Sport/Ascenders](http://www.petzl.com/en/Sport/Ascenders)

They're practically bullet proof, although they can take a little longer to
bite when coated in mud :)

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sliverstorm
As a third hand for your rappel, a toothed ascender seems like a bad idea.
Petzl makes another device called the Shunt which is more suitable to third
hand use. Although in the case of icy ropes, maybe teeth are a hard
requirement.

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bhickey
The Shunt is great, but there are some potentially dangerous gotchas in its
operation. Never use it with ropes of different diameter. As a rappel backup,
the shunt can fail if you place it above your belay device. The risk is that a
panicked operator will hold the device open. In the correct mode of operation,
you place the shunt below your belay device. If you're disabled, the shunt
will lock off. If you panic and hold it open, the force you apply to the
device will arrest your rappel.

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sliverstorm
Yes, it's applications are very specialized, this is true.

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Fiahil
Oh, I remember using the Braid variant even it's a little more difficult to
make with one hand.

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jinushaun
Cool. Never used it before. A prusik seems easier, especially since I learned
the one-handed technique. I wonder what the trade offs are of each.

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cpa
One difference between the two it that the Prussik is much easier to release
after it's been jammed.

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JoshTriplett
If a knot is the only thing between you and a very long fall, "easier to
release" might not be a feature.

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sswaner
Not true. It is called the autoblock for a reason. You tie it by wrapping it
around your rope. To descend, you simply apply a slight amount of downward
pressure to the top of the knot. This is the easy to release part. If you
remove that pressure, by just moving your hand off the knot, it instantly
grabs and stops all downward movement. A Prussik will retain most or all of
it's tension, making it difficult to use in ascending or descending. I only
use a Prussik in a situation where I want no movement at all for the duration,
such as a backup to an anchor.

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amelius
This knot seems to work by friction. Is there any knot with the same
application that works without friction?

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jacquesm
All knots work by friction. Try to imagine any knot working with friction-free
rope (which doesn't exist).

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amelius
> Try to imagine any knot working with friction-free rope

Yes that was my question :)

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jacquesm
Ok, well in that case the answer is 'no'.

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amelius
You mean: "I can't imagine it". That is something else :)

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jacquesm
I can imagine lots of stuff that doesn't exist (interstellar spaceships with
earth as their origin, pink elephants wearing tutus, time machines and so on).
But when I limit my imagination to those things that can be constructed using
the laws of physics as we currently know them knots without friction drop
right off the menu along with the items above.

So if your question was serious then I consider it answered, if you want to
seriously know whether something that can't exist can be imagined then the
answer is yes, you can imagine it (and so can I), but I can't imagine _making_
one because that would violate the laws of physics somewhere along the line.

You could tie a knot in frictionless rope easily enough, but it would come
apart without any work at all and it would not hold anything and you wouldn't
be able to grip the rope on either end to tie the knot in the first place.
Friction and knots go together unless you're living in a mathematical ideal
world, which we don't.

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toolslive
Can it be that I've seen fishermen use the same to tie a hook to a line?

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Wingman4l7
If they're tying it to the _end_ of the line, they're probably using the
improved clinch knot, which has visually similar wrapping:
[http://www.netknots.com/fishing_knots/improved-clinch-
knot/](http://www.netknots.com/fishing_knots/improved-clinch-knot/)

