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Edelrid MegaJul Belay Device
shoo wrote: You might know (or think) that, but how am I supposed to know that from what you've provided? Also, I am still failing to understand why you are using the average values in your regression lines, rather than just using all the data. Best case scenario is there is little/no difference, worst case is you've biased your results. Why not just use all three data points you've collected? You are wasting information. Partial list of "vaguely important" information that we don't see based on your results, which could easily be examined through better statistical methods: 1) Are the force curves between these devices statistically significant, and to what degree/confidence level? 2) How "random" are the forces? In other words, how much would you expect the catching forces to vary for each device? 3) Is there a difference in the "randomness" across devices? How big of a difference? 4) Is the "randomness" consistent* across the drop force curve? In other words, would we see bigger variation in drop test forces at higher/lower forces? Note: I am intentionally using layman (i.e. non-statistical) terms here. Yes, I am extremely aware that words like "consistent" have a very different technical statistical meaning than I am using them above, but I am not talking among statisticians.The graphs are a presentation of the relative power of various devices for the easy appreciation and understanding of those amongst the internet users who are neither engineers or statisticians. They are not part of a PHD thesis. They can accept them at face value as reliable guidance from an experienced engineer who has more experience in testing belay devices than almost certainly anyone one earth and who regularly tests other products and uses (simple) statistical methods in his daily work OR they can choose to believe in lizards in space. Either way it´s not a burning issue in my life. The spread in rope/friction testing is of the general order of 5 to 20%, with enough experience you can get to a confidence level of around 5%. Bill Stronge from Cambridge University also shows this level of variation with repeat tests. Depending on the rope itself you can obtain more or less confidence in the results, new ropes are fairly good consistancy-wise BUT a rope is only new once and the actual braking results tend to be all over the place due to the dry treatments so most testers go over to used ropes to give more a real-world experience. The forces a generally 20% higher but depending on the type of use and wear of the rope it´s a matter of judgement as to what is a good section of rope or not. Statistical analysis won´t tell you how consistent the devices are, they are by nature completely stable and would give consistent results except the rope is variable through it´s length. Another 8.5 rope will give different results to mine as well which is why it is always the same rope used in comparison tests (and why there is no belay device performance test for CE/UIAA since the test rope can´t be in two laboratories at the same time and would anyway change during the tests). The randomness does change with force but not to any great extent, nothing which would change the relative strengths of the devices to any appreciable amount compared with the variation in ropes and belayer grip strength. |
bearbreeder wrote: thats a VERY interesting claim ... so you are saying that levering it open you can fall on it and the rope wont run through??? if anyone in squamish has a mega jul and willing to take whippers ill catch you ... well tie a knot about 10 feet down as a backup of course thats a VERY important thing to test before making that claim ... as thats one of the most common ways folks get dropped with assisted locking devices ... smart and grigris included ;)Their product video doesn't say one way or another and I would be interested in finding out as well. Of course, I ordered one before stumbling upon this gem of a thread. :-) I was mainly interested in the autolocked rappel mode as sort of a backup on rappel. It seems like Elelrid doesn't recommend that as the primary mode so it kind of defeats a reason for buying one, for me at least. One thing I could see that might be bad with it is that it instills a habit of keeping the brake hand close to the device. I don't know if that will turn into a bad habit when going back to a traditional ATC. Mine is on route. Maybe I will just return it unopened. |
O.L.D.S.A.G. wrote: One thing I could see that might be bad with it is that it instills a habit of keeping the brake hand close to the device. I don't know if that will turn into a bad habit when going back to a traditional ATC.it does ... in fact thanks for reminding me that i need to practice catching good sized whippers on my ATC again, i havent done so for a few months now ... only on grigris and smarts i noticed that to transition back to ATCs from assisted lockers (smart, grigri) - one tends to keep the brake hand too close to the ATC as mentioned - one tends to pull to much on the climbers side rather than simply push/pull simultaneously when feeding out ... leading to the ATC sticking on some ropes for lead belay - one tends to get a bit lax with their brake hand control ... not so much in terms of letting go, but rather in holding it too lightly expecting the assisted locking to kick in - one tends to overcompensate for the above by gripping the rope too hard straight down rather than work the angles ... the sharper the angles the easier it is to hold assisted lockers IMO offer an additional margin of "safety" even if they arent truly "hands free" ... but that can easily be offset by a gradual loss and development of bad habits in terms of brake control technique remember everything is muscle memory when your climber falls ... ;) |
O.L.D.S.A.G. wrote: Mine is on route. Maybe I will just return it unopened.Don't believe everything you read on the Internet. Try it yourself. I use it with a variety of diameter ropes and with a Petzl Attache II biner and have none of the problems reported here. It belays as easily as an ATC (for me). |
O.L.D.S.A.G. wrote: I was mainly interested in the autolocked rappel mode as sort of a backup on rappel. It seems like Elelrid doesn't recommend that as the primary mode so it kind of defeats a reason for buying one, for me at least. One thing I could see that might be bad with it is that it instills a habit of keeping the brake hand close to the device. I don't know if that will turn into a bad habit when going back to a traditional ATC. Mine is on route. Maybe I will just return it unopened.I have rapped on this thing in autoblock mode and it sucks, very jerky, but if you need the back up, it works. My biggest problem with the device is training my brake hand to be next to the tube. This thread is very informative but you also have to consider what affect the device has on people. The gri-gri seems to have a horrible affect on people, both experienced and inexperienced users seem to drop their partners. I like this device and do not have many of the problems feeding rope refered to above. I will keep using my MegaJul until I see more real life data and thanks to this thread I will beware of its limitations. |
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If you want a rap backup, you might want to eye the Petzl Shunt. A little pricey and heavier than a prusik to be sure, but expressly designed to be a rap backup. Can double as an ascender, and also used by some people for TR soloing. |
Patrick Shyvers wrote:If you want a rap backup, you might want to eye the Petzl Shunt. A little pricey and heavier than a prusik to be sure, but expressly designed to be a rap backup. Can double as an ascender, and also used by some people for TR soloing. From their website SHUNT Back-up rope clamp Used below the rappel device, the SHUNT works as a rappel back-up and replaces self- jamming knots like the Prusik. Works on single and double ropes.I had one. Bought off of here actually. Was stolen. But I don't think I would get one again. It took some effort to do it smoothly and it weights a ton. A prussik cord weights nothing. I like the idea of a built-in rappel backup in the mega jul. |
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Thanks for the read guys and especially thanks to Rich and Jim for some real analysis that was educational. |
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Thanks for all the info, everyone. Jim, thanks for sharing your testing results. Forgive me if I have overlooked something while reading the thread but there seems to be something missing from the discussion here. Kilogram is not a unit of force. Are we all talking about Newtons? Not trying to be pedantic - I would really like to use the data for kinematic calculations that approximate real life situations. I also second shoo's request for the raw data - I doubt it is all still lying around but in the future it would be extremely helpful. I suspect climbing has more than its fair share of engineers and math nerds. |
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I use kgf often as the numbers are easier to understand for things like belay devices, if I say a belay hand force of 25kg then everyone can tie a 25kg weight onto a rope and see what it feels like to hold, writing 0.25kN force on the belayer side rope would mean nothing to most people. That it is force is defined in the caption. The raw data is utterly uninteresting, it either an endless stream of csv values which I tell my computer to do something with or me eyeballing a digital readout and making a judgement about when the value has settled down enough to be an accurate reflection of the forces I am seeing. Rather than re-analysing my data the engineers out there would be better employed actually running some tests themselves to get independent results. |
Adam Anderson wrote: Well, in climbing, lbf (pounds force) and kgf (kilograms force) are often used as an approximation of force. You could convert it to Newtons easily if you like. Since F=ma, force in Newtown, mass in kg, acceleration in meters/s^2. Simply multiply kg x 10 to get Newtons. (9.81 if you want to be more precise) |
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I only read a couple pages of this thread but haven't seen this mentioned yet; as someone who owns a megajul and has used it several days in single and multi-pitch terrain, I would not recommend buying one. The device tends to twists the rope(s) more than a guide ATC. As mentioned repeatedly, it's not in the same class as a gri-gri so it's hard to really compare. If you're looking for something comparable to a gri-gri maybe try an Alpine-up |
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Thanks for clarifying that Jim and Greg. I was unfamiliar with kgf and was unsure whether the gravitational constant was included in the force measurements or not. I am very curious now to try the MegaJul with a 10mm rope. With ~135 kgf provided hands free (assuming it engages), a 70 kg (155 lbs) climber at height d above his last piece of protection should come to a stop within about 2d below that piece if the protection holds and there is about 1 meter of slack. For the areas I climb the only place I would really be concerned about this is below the third bolt as their might not be 2d before ground. |
King Tut wrote:... 3. Assisted locking devices are useful for holding hanging climbers and for minimizing fatigue for belayers and may give some (false) confidence to leaders...but are no substitute for proper knowledge, experience or technique and will not stop severe falls. Only brake hands will. ... 5. Fools are able to defeat any "foolproof" device. ... Climbing friend, for obvious assisted locking devices they are nary a substitition for proper knowledge, experience, and technique, and it is agreed by all that fools are able to defeat any foolproof device, yet still, assisted locking devices are indeed less easy for a fool or unconscious person to defeat, and therefore would be safer than the deadly ATC. |
Aleks Zebastian wrote: Don't get me wrong, be-muscled climbing friend, I wholeheartedly endorse the Way of the Gri for most of my climbing (such as it is these days). But we must admit it is more complicated than that when people are injured by misuse of the Gri-Gri yet seemed to never to have been dropped by hip belays (though I have been, fortunately for me not far). There is an element of inattention that we humans fall into, complacency and neglect born of repetition etc...it is likely to be impossible to eradicate this unless we use a truly "automatic" belay robot. Maybe it was the threat of rope burns on the belayer that lead to such careful attention and safer results with hip belays? |
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Looking back to the device comparison: I have recently tried both Megajul and Sawela Ergo for lead belaying - for both I found unpredictable on paying out rope for clipping. Sometimes easy and then a lock up that prevented rope going to the leader. I realize these passive locking devices may have a learning curve, but do not want to put my partner at risk during my curve. The concept of a passive locking device makes sense, but the application seems to still have some bugs to work out. I wonder if the BD ATC Pilot, if it ever gets released, found the geometry for ease of paying out rope and reliable passive lock when needed. |
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I found the thumb hook on the BD Pilot to be too small and wouldn't stay put reliably when feeding out slack, I was not the only one with that experience |
Paul Deger wrote: Are you lifting up the thumb loop the whole time while paying out on the megaJul? If not you are going to lock it up, if you watched their video it clearly shows this way of lead belaying. |
David Ponak wrote: I used it just once in the gym and have watched a few videos now. I may give it a try again, but it struck me as a balance of force between pulling up on the thumb loop and the rope pulling it to lock down. |
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Just tried out the Mega Jul 2 - I found it easier to use than its forerunner. Only drawback is weight and need for rappel device, I always carry an F8 anyways. This is my new go-to. |
