Edelrid MegaJul Belay Device

reboot wrote: and never practice things like swinging the brake hand around the hip to increase braking power. Then when you do try catching a big fall, it requires brake force equivalent to a good plate device. That would be quite an expectation shock.

One thing I don't like about the megajul is I have found I keep my break hand thumb through the cable pivot release to give a clean rope feed which keeps my hand right next to the device ( shown as 5a in the instructions ). On a traditional tube device I can quickly get my break hand down past my hip if I think my climber is about to peel but the design of the MegaJul makes this impossible to do fast.

Diagram 13a/13b suggests you must use a rope tarp with this device :-)

Jim,

Your chart maybe suggests that they need to add some cleats to the brake side of the megajul like the BD and Reverso devices?

Joe Platko wrote:Jim, pardon my ignorance of your testing method, but I assume that these results are from a static measure of grip force vs the load on the climber end. Do you have any testing planned to show the grip strength requirements during a dymanic test (say a given falling mass, height and FF) by belay device and the associated slippage?

These are the results from the normal pull test which is dynamic but slower than a drop test. We know from drop testing and pull testing that the results are comparable for these types of plates so don´t do the even more complicated and laborious drop testing.

Rick Blair wrote:Jim, Your chart maybe suggests that they need to add some cleats to the brake side of the megajul like the BD and Reverso devices?

Hmm, add more depth to the plate and drop most of the assisted locking like a BRD would be my suggestion.

Rick Blair wrote: One thing I don't like about the megajul is I have found I keep my break hand thumb through the cable pivot release to give a clean rope feed which keeps my hand right next to the device ( shown as 5a in the instructions ). On a traditional tube device I can quickly get my break hand down past my hip if I think my climber is about to peel but the design of the MegaJul makes this impossible to do fast. Diagram 13a/13b suggests you must use a rope tarp with this device :-)

I have heard this about the MegaJul but I can feed rope out as easily as an ATC by just pulling up with the brake hand. I have my left hand on the feed end and my right hand on the brake end. I find it easy to feed rope this way. For me, much easier than a GriGri.

Jim Titt wrote:

Is the use of a single 9mm rope a realistic test? Who uses a single 9mm rope to climb? I know single ropes are getting thinner but that is extreme. How about testing with a single 10mm rope. That would be a lot more real-life.

Also are we talking about unusually big fall factors? I have held >200 lb climbers on 15 foot falls and the device locked up automatically with no supplemental braking required by my brake hand.

Brian wrote: Is the use of a single 9mm rope a realistic test? Who uses a single 9mm rope to climb? I know single ropes are getting thinner but that is extreme. How about testing with a single 10mm rope. That would be a lot more real-life.

I haven't used anything thicker than 9.4/9.5mm for quite a while & plenty of people use thinner ropes still. It's one thing if 9mm is outside the design spec of the devices, but safety equipment should be tested to the extreme ends the device is designed for. Climbing accidents are no less real life than a walk in the park even if the former is much less likely.

reboot wrote: I haven't used anything thicker than 9.4/9.5mm for quite a while & plenty of people use thinner ropes still. It's one thing if 9mm is outside the design spec of the devices, but safety equipment should be tested to the extreme ends the device is designed for. Climbing accidents are no less real life than a walk in the park even if the former is much less likely.

Okay but in the extreme, if using a single 9mm rope in a factor 2 fall, I wouldn't have to go far out on a limb, to surmise that all belay devices will fail, or the belayer will because they can't hold on to the rope.

So basically these assisted locking devices are no worse than a reverso, and generally better with lesser grip strength?

I will say that with my alpine smart the initial lock off on "normal whippers" is MUCH better than an atc guide (which i also use extensively) ... And on 10mm+ ropes locks pretty well

Ill take that and the butter smooth autoblock anyways

Ive always maintained that folks should be very proficient with a tube device before moving to any assisted locking device, including the grigri

The emphasis on brake hand control regardless of device is one of the most important things in climbing

;)

Brian wrote: Okay but in the extreme, if using a single 9mm rope in a factor 2 fall, I wouldn't have to go far out on a limb, to surmise that all belay devices will fail, or the belayer will because they can't hold on to the rope.

A Grigri has demonstrated repeatedly it can hold a factor 2 easily. Even on a thin rope (but not so thin it can bottom out the cam action), the brake hand only need to exert enough force to engage the cam (think about spring tension in cam, it doesn't factor into the actual holding power).

But let's sit back and read what OP actual wanted: a device for his gf that ostensibly has better better braking power than a plate device. And let's also read what a lot of people find attractive about it: it (presumably) has better braking power over an ATC-guide in multi-pitch environment. Say you are doing some long route but like to keep the weight minimum, you may decide to use a 9/9.2mm rope. Without Jim's analysis, you may assume the Mega Jul has better braking power & given the thin rope you decided to take, that the Mega Jul would be the better choice. What I've just described are pretty real life scenarios and it would really suck to find out when your buddy factor 2 onto the belay and your device doesn't perform as you have expected.

One thing those numbers suggest is that you cannot count on the MegaJul as a locking rappel device for a single strand rappel on a 9mm rope, especially near the end of a rappel with little rope weight on it, because with zero or near zero grip strength (i.e. you've let go of the rope), the thing starts to slip at about 70 kgf = 154 lbf. The Smart would be even worse, with an untended slip threshold of about 40 kgf = 88 lbf.

Jim pointed out to me in another thread that the instructions for the Alpine Up warn not to use it in "autolocking mode" for single-strand rappels; I'm beginning to see why that is.

reboot wrote: A Grigri has demonstrated repeatedly it can hold a factor 2 easily. Even on a thin rope (but not so thin it can bottom out the cam action), the brake hand only need to exert enough force to engage the cam (think about spring tension in cam, it doesn't factor into the actual holding power). But let's sit back and read what OP actual wanted: a device for his gf that ostensibly has better better braking power than a plate device. And let's also read what a lot of people find attractive about it: it (presumably) has better braking power over an ATC-guide in multi-pitch environment. Say you are doing some long route but like to keep the weight minimum, you may decide to use a 9/9.2mm rope. Without Jim's analysis, you may assume the Mega Jul has better braking power & given the thin rope you decided to take, that the Mega Jul would be the better choice. What I've just described are pretty real life scenarios and it would really suck to find out when your buddy factor 2 onto the belay and your device doesn't perform as you have expected.

Okay, so what do you recommend, that everyone use a GriGri for trad?

rgold wrote:One thing those numbers suggest is that you cannot count on the MegaJul as a locking rappel device for a single strand rappel on a 9mm rope, especially near the end of a rappel with little rope weight on it, because with zero or near zero grip strength (i.e. you've let go of the rope), the thing starts to slip at about 70 kgf = 154 lbf. The Smart would be even worse, with an untended slip threshold of about 40 kgf = 88 lbf. Jim pointed out to me in another thread that the instructions for the Alpine Up warn not to use it in "autolocking mode" for single-strand rappels; I'm beginning to see why that is.

Okay, but if you just flip the MegaJul up with the thumb loop up it acts like a regular tuber rappel device. That's how I rap with it. (With an autoblock too). I would also be hesitant to rap with an ATC on a single strand 9mm rope. I would definitely make sure I had a big knot in the end of the rope. I will try rapping on a single 9mm with a MegaJul in assisted mode to see what happens. (With a big knot backup.) That's easier than testing a factor 2 fall. :-)

And again...this is taking it to extremes...who does single rope rappels on a 9mm rope? Will you ever have to do it in an emergency? Maybe, but if you do wrap a prusik a bunch of times around the rope in an autoblock.

rgold wrote:One thing those numbers suggest is that you cannot count on the MegaJul as a locking rappel device for a single strand rappel on a 9mm rope, especially near the end of a rappel with little rope weight on it, because with zero or near zero grip strength (i.e. you've let go of the rope), the thing starts to slip at about 70 kgf = 154 lbf. The Smart would be even worse, with an untended slip threshold of about 40 kgf = 88 lbf. Jim pointed out to me in another thread that the instructions for the Alpine Up warn not to use it in "autolocking mode" for single-strand rappels; I'm beginning to see why that is.

Ive said it over and over again ... On single strand raps the smart is NOT autolocking

Even on a 10mm rope today the smart would slowly slip in a single strand rap

On double strand raps on thinner slick ropes it will slip especially near the bottom

The advantage is that when it does slip it generally does so slowly and requires very little force to lock off on rap

The same applies to lowering

;)

I think I have learned a lot from this thread. However, not being a physicist and having had trouble with the few applied physics classes I took many years ago, I am not sure that I am understanding the real world ramifications of the data that Jim posted. With that in mind, can one of you smart guys (Rgold or Jim) answer a few questions for me?

The graph shows that a fall generating ~150KG of force on the belay will require ~22KG of had force to stop when using a Smart / Jul. If one tried to catch a fall that generated 170KG of force on the belay with ~22KG of had force, would the rope slip a little bit and then stop as the force dissipated, or would the rope continue to slip and the belayer be completely unable to stop the fall?

I don't use a GriGri for trad because of the higher impact forces it generates. Assuming that the Smart / Jul will only slip a limited amount before stopping, wouldn't the slip actually beneficial in certain circumstances where you are climbing above marginal gear and want a soft catch?

Thanks to all the posters that have contributed to this conversation. Cheers!

bearbreeder wrote: Ive said it over and over again ... On single strand raps the smart is NOT autolocking Even on a 10mm rope today the smart would slowly slip in a single strand rap On double strand raps on thinner slick ropes it will slip especially near the bottom The advantage is that when it does slip it generally does so slowly and requires very little force to lock off on rap The same applies to lowering ;)

True dat, single strand overhand on a 9.5 slides right through the Smart. A small amount of hand pressure is all it takes to stop it but it's not hand free. The MegaJul is the same way. Sure makes full length overhung raps fast!

NC Rock Climber wrote:I think I have learned a lot from this thread. However, not being a physicist and having had trouble with the few applied physics classes I took many years ago, I am not sure that I am understanding the real world ramifications of the data that Jim posted. With that in mind, can one of you smart guys (Rgold or Jim) answer a few questions for me? The graph shows that a fall generating ~150KG of force on the belay will require ~22KG of had force to stop when using a Smart / Jul. If one tried to catch a fall that generated 170KG of force on the belay with ~22KG of had force, would the rope slip a little bit and then stop as the force dissipated, or would the rope continue to slip and the belayer be completely unable to stop the fall? I don't use a GriGri for trad because of the higher impact forces it generates. Assuming that the Smart / Jul will only slip a limited amount before stopping, wouldn't the slip actually beneficial in certain circumstances where you are climbing above marginal gear and want a soft catch? Thanks to all the posters that have contributed to this conversation. Cheers!

Excellent questions. There is a saying about engineers that if you ask them what time it is they tell you how to build a watch. That is why this thread has gone on so long. What does this all mean in real life climbing? Wouldn't an assisted locking device GENERALLY be better in catching falls than a tuber style device in MOST circumstances?

rgold wrote:One thing those numbers suggest is that you cannot count on the MegaJul as a locking rappel device for a single strand rappel on a 9mm rope, especially near the end of a rappel with little rope weight on it, because with zero or near zero grip strength (i.e. you've let go of the rope), the thing starts to slip at about 70 kgf = 154 lbf. The Smart would be even worse, with an untended slip threshold of about 40 kgf = 88 lbf. Jim pointed out to me in another thread that the instructions for the Alpine Up warn not to use it in "autolocking mode" for single-strand rappels; I'm beginning to see why that is.

This is certainly true but a small amount of brakehand pressure is all it takes to lock the device. Based on my experience, the slipping rope still feels more controlled using a A-Smart than an ATC-G rapping single strand.

Brian wrote: Wouldn't an assisted locking device GENERALLY be better in catching falls than a tuber style device in MOST circumstances?

Except this really is the WRONG question to ask for a safety device. The question should really be: would this device be better in catching falls than a tuber style device in circumstances that are likely to cause accidents (or an even more difficult question to answer, does it reduce accidents in general)? That, unfortunately, cannot easily be answered through direct experiences. That it requires less hand force in baby falls is mostly a matter of convenience, though it probably carries a certain improved margin of safety. Jim's analysis doesn't prove one way or another, but I think it raises enough doubts.

NC Rock Climber wrote:If one tried to catch a fall that generated 170KG of force on the belay with ~22KG of had force, would the rope slip a little bit and then stop as the force dissipated, or would the rope continue to slip and the belayer be completely unable to stop the fall? I don't use a GriGri for trad because of the higher impact forces it generates. Assuming that the Smart / Jul will only slip a limited amount before stopping, wouldn't the slip actually beneficial in certain circumstances where you are climbing above marginal gear and want a soft catch? Thanks to all the posters that have contributed to this conversation. Cheers!

The answer isn't entirely physics. But the physics part says that the rope will run through the device, doing work against hand pressure as multiplied by the device, until the fall energy is absorbed. While the rope is running, work is being done against all the frictional forces in the system, and all of these contribute to fall energy absorbtion, so yes, the fall will be, or I should say should be, arrested after either a little or a lot of rope slippage.

The amount of rope slippage is not determined by the fall factor but rather by the absolute magnitude of the fall, meaning bigger falls with the same fall factor as smaller falls will cause more slippage. It is fortunate that the most likely high fall-factor falls are close to the belay and so are relatively short.

The part that isn't physics has to do with the belayer, who can lose control of the belay for a host of reasons. Certainly one of them is not being gloved. There is a very powerful automatic human reaction to release something that is burning you. It can be overcome, but apparently not in all cases---leaders do get dropped. Other problems come from the effects of big impacts on the belayer and the belay stance; we could have a whole other fuss-up about them. And finally there is the problem that no devices other than the Grigri will work at all in a factor-2 fall unless the belayer does something special that many people do not do and may not even know about.

It is true that having some slippage in the device will reduce loads on the top piece, and this is a good thing if the belayer doesn't lose control and if the leader doesn't hit something.

Personally, I've had to catch a factor-2 fall and a factor 1.8 or so fall, both of them relatively short. The impact moved me considerably on both, but neither were too bad. Both had a little rope slippage, but I was wearing gloves. People think of rope slippage as the rope whizzing through the belay for a while, but if that happens you've probably lost control. A quarter-second of rope slippage is already about a meter or so of rope, and you really hope you aren't going to need more than that.