SRT descender - J lock

I have just come across a 'J Lock' descender and I cannot find it mentioned on the internet, so I wonder what anyone thinks of it.  It is a tad shorter than a Petzl Stop, but much more robust construction.  To open it you have to push a thingy in on the top so it opens at the top not the bottom like a Petzl.    It seems to have a lot more friction than a stop.  Unlike a stop you have to pull the handle out to descend - hands free the handle will tend to close - thus applying a lot of breaking - so  the handle is the oppositte of a stop.

What is the advantage?  With a Petzl stop you could open the stop by pressing too hard on the maillon clip, that is not possible on a J Lock, the maillon can only attach to the back plate.
There is noticably more friction on a J lock - period.
The J lock can take a wider range of rope diameters (tends to thicker side)
Heat disipation should be noticably better due to more robust construction.

I like this thing   but is it still available?  I just can't find any reference on the internet to it - which is disturbing.

Have you got a picture?

It sound like you may be talking about the Gemlock or Gemlok type of desender. No longer available. Jopo designed or made these and will no doubt be along to answer in full later.

Rhys

Indeed it is a Gemlock, there is a drawing of one in "The Complete Caving Manual". 

I'm supprised it is unavailable.  The mere fact you can't accidently open it is enougth to recommend it.  It is very comfortable to use.

You can't open a Stop when you've got your weight on it. I'm not entirely sure that's the case with the Gemlock.

Alkapton said:

The mere fact you can't accidently open it is enougth to recommend it.

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Surely any device which could be "accidentally opened" while in use would be recalled and/or have warnings issued? At the very least you would expect there to be widespread publicity and a cessation of its use.

With Petzl Stop the fact the maillon clip is exactly where I hold onto the descender has always made me think if I press too hard I could open it, so I'm always thinking about that when descending.  Hadn't realised having my weight on the descender makes this a false fear, although I could press the 'clip' in so its ready to open - not something I actually want to do.

The Gemlock opens at the other end and can only be opened if you push a spring loaded locking 'thing', it can only be closed by pressing it as well.

build yourself a rack.  Cheap and far Superior on big pitches

Alkapton said:

Indeed it is a Gemlock, there is a drawing of one in "The Complete Caving Manual". 

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Yes, indeed.  Included at the time because the Gemlock was becoming a very popular choice.  Within a couple of years it had all but vanished.  I have no idea why.

Alkapton said:

With Petzl Stop the fact the maillon clip is exactly where I hold onto the descender has always made me think if I press too hard I could open it

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Do you use a maillon to connect your Petzl Stop to your harness attachment point?

Because if you do, don't - it's hardly surprising there's a risk your Stop may "accidentally" open which is probably the reason Petzl's technical instructions on the use of the Stop specifically warn against connecting one in this way.

http://www.petzl.com/files/all/technical-notice/Sport/D09%20STOP%20D09800-H.pdf

{The first diagram on the correct use of the Stop shows how to attach the device (and what not to use..... e.g. a maillon or a snaplink karabiner), page 2 - the instruction sheet is included with your Stop at the point of purchase; I heartily recommend you read it}.

It's not a "maillon clip" (your words); it's a karabiner attachment hole. Use a karabiner, not a maillon.

I will endeavor to explain.

I designed the 'GemLock' in 1992 when in partnership. The first models were produced (pre PPE days) before I was 100% happy with the design.
The partnership ended and I did some mods and produced in 1994 the REACT J Lock. With the advent of a EN spec. I was not inclined to get embroiled with setting up a approved workshop and the cost involved and, because I had not patented swing cheek pulleys in 1973, decided to concentrate on stretcher systems. So hardware production ceased.

The descender was designed to counter the Petzl 'plummet' in as much as you held it in the go position and letting go or squeezing stopped descent. You could also choose 3 different 'wraps' to change the friction for thicker/thinner ropes or when you had a lot of rope below you - but still have autolock. It was also intended to be a 'one handed' device without the need for a braking crab. It's main claim to fame (for me at any rate)was that is could give a safe, autolock, descent on a 13mm waxed laid rope for a customer. Surprised me as well!

The biggest con was that you had to hold the handle in the go position to pull slack through as the lock worked in both directions.
Some also complained that holding the handle in the GO position was tiring - however bracing your thumb on the frame made this of little consequence -at least I never found it a problem. To pull through I hold the unit, in my right hand, around the body with the back of my hand keeping the handle in the Go position and pull through with the other.

I have recently seen a descender that looks quite similar and have decided (two weeks ago) to have the REACT J Lock put through the relevant EN standard. When we produced the original descenders we did drop test for our own satisfaction but the other PPE parameters were never tried.

Who knows? If it meets the standard, or needs little modification to do so, you may well be able to spend your pennies (?'s rather) on another device.

Jopo

Now I have used it I like the J Lock a lot.  My only tiny gripe is that because there is no spring keeping the handle closed, when not in use the handle opens when one is walking/crawling.  So unless you remove it when not actually descending there is danger of damaging it.  Answer - always remove it when not in use.   

I like the way rope can be threaded in different ways - I was wondering about that - on the J Lock is one way of threading while in the book is a slightly different way - it makes sense.

cap 'n chris said:

Do you use a maillon to connect your Petzl Stop to your harness attachment point?

Because if you do, don't - it's hardly surprising there's a risk your Stop may "accidentally" open which is probably the reason Petzl's technical instructions on the use of the Stop specifically warn against connecting one in this way.

http://www.petzl.com/files/all/technical-notice/Sport/D09%20STOP%20D09800-H.pdf

{The first diagram on the correct use of the Stop shows how to attach the device (and what not to use..... e.g. a maillon or a snaplink karabiner), page 2 - the instruction sheet is included with your Stop at the point of purchase; I heartily recommend you read it}.

It's not a "maillon clip" (your words); it's a karabiner attachment hole. Use a karabiner, not a maillon.

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My mistake   But I seem to be missing something.  In the picture of the right way to connect the Stop an oval locking karabiner is used.    My oval maillon seems to me to be functionaly the same as long as it it is screwed up tight.  I realise the maillon is more likely to open accidently but don't see the difference when it comes to accidently opening the karabiner attachment hole.

In the same way Petzl seem to discourage using a 10mm D ring maillon as the main sit harness attachment point, instead they recommend 10mm D ring locking 'karabiners'.    Again the only reason I can think of for this is the possibility one forgets to screw up the maillon (they are so stiff I can't see how they could undo accidently) - and everyone I know still uses maillons.

Is the problem the maillon can open accidently of am I missing something more important.

Alkapton said:

I realise the maillon is more likely to open accidently but don't see the difference when it comes to accidently opening the karabiner attachment hole.

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Try it. The krab won't open it when you twist it, whereas a maillon will.

Is the problem the maillon can open accidently of am I missing something more important.

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I suspect that has more to do with Petzl wanting to sell their fancy and expensive gear

I suspect that has more to do with Petzl wanting to sell their fancy and expensive gear

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Quite so.

A maillon will deform hideously but stay together under weird loads whereas a Krab is more likely to come open.

An Omni is no less weak if you forget to do up the sleeve whereas a D-ring maillon is. Other benefits of the Omni are ease of opening for a "quick release" and a visible red alert that the sleeve remains unscrewed.

Admittedly it's significantly more expensive than the 20th century curio.

FWIW I can't think of (m)any manufacturers that don't try to sell stuff.

damian said:

Try it. The krab won't open it when you twist it, whereas a maillon will.

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Regarding a Stop being opened by a maillon attachment, in practical use, I think the word is 'could' rather than 'will', and even then, it seems highly unlikely to happen accidentally, at least with a 10mm long maillon.

While it is easy to demonstrate how 'dangerous' a Stop/10mm maillon combination is by holding one piece in each hand and doing the appropriate twisting/sliding motions, I'd suggest people try to do the same thing with the Stop's maillon actually attached to a harness, as it would be in Real Life, just by manipulating the Stop.
Even if you know exactly what sequence of pulling/twisting/pushing you need to do, I think it would be an underestimate to say that simulating accidental opening that way was rather harder.

The chances of the necessary sequence of actions happening accidentally seem to be sufficiently small that I suspect they'd pale in comparison to the chances of someone just forgetting to close the Stop's gate properly, and I'm sure that they'd be tiny compared to the chances of someone forgetting to to screw up the maillon properly, or having it unscrew itself while moving around the cave.

potholer said:

damian said:

Try it. The krab won't open it when you twist it, whereas a maillon will.

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Regarding a Stop being opened by a maillon attachment, in practical use, I think the word is 'could' rather than 'will', and even then, it seems highly unlikely to happen accidentally, at least with a 10mm long maillon.

While it is easy to demonstrate how 'dangerous' a Stop/10mm maillon combination is by holding one piece in each hand and doing the appropriate twisting/sliding motions, I'd suggest people try to do the same thing with the Stop's maillon actually attached to a harness, as it would be in Real Life, just by manipulating the Stop.
Even if you know exactly what sequence of pulling/twisting/pushing you need to do, I think it would be an underestimate to say that simulating accidental opening that way was rather harder.

The chances of the necessary sequence of actions happening accidentally seem to be sufficiently small that I suspect they'd pale in comparison to the chances of someone just forgetting to close the Stop's gate properly, and I'm sure that they'd be tiny compared to the chances of someone forgetting to to screw up the maillon properly, or having it unscrew itself while moving around the cave.

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All true of course (and this is resurrecting the same arguments from an old thread).

But since the oval carabiner option is less likely to result in accidentally opening a bobbin descender (Simple as well as Stop plus maybe others as well with similar closing mechanism), why not just use the carabiner?

It also means that you have a spare oval carabiner when not descending which is more useful than a spare maillon. Plus the carabiner makes some procedures easier: such as using the "Vertaco" method in tight pitches or when using a Stop in hauling setups for example.

I'm with you on this, Potholer (and I'm with Paul too  )

cap 'n chris said:

An Omni is no less weak if you forget to do up the sleeve whereas a D-ring maillon is. Other benefits of the Omni are ease of opening for a "quick release" and a visible red alert that the sleeve remains unscrewed.

Click to expand...

Light too