I just checked mine, and if you death grip it, it does the same thing... But that means you'd have to be holding the device tight during the fall, not the brake end of the rope. If you grab the brake strand of the rope instead of death gripping the device itself, it will arrest a fall EVERY time. It appears as if the belayer was squeezing the device, not the brake end of the rope.
Way back when I was considering buying the SUM for a solo device. To use it in this manner the climber was to tie the device to the chest due to the heavy dependence on the directionality of the impulse at fall. I am understanding why when I see the video referenced by Spikeddem. BTW: I think it is awesome that you guys are hunting down this issue.
Meadows wrote: It appears as if the belayer was squeezing the device, not the brake end of the rope.
So this is not a device malfunction, but in large part a human error with the rope out of hand. I guess I am split on this issue. Does the device easily lend itself to misuse? _(yes)_ Could the hapless belayer have been me; could I have dropped a buddy with this device? _(yes)_
With an ATC all you have to mind is the brake end of the rope. These other devices bifurcate one's attention. Cell phone-related auto accidents and Grigri/ Sum/ Cinch grounders may all have common phenomenology.
I just checked mine, and if you death grip it, it does the same thing... But that means you'd have to be holding the device tight during the fall, not the brake end of the rope. If you grab the brake strand of the rope instead of death gripping the device itself, it will arrest a fall EVERY time. It appears as if the belayer was squeezing the device, not the brake end of the rope.
My Sum's cam functions smoothly with any grip strength. I'm beginning to think that the Sum in the accident was damaged or manufactured defectively.
I also hold mine much differently than in the video. As the Sum is lifted up in a fall, the brake strand (you can see that I climb with a verrrry skinny line) is lifted fully into the brake hand's grip.
When I used to work in a gym we would practice catching a climber, who had a back up belay on another rope, with a grigri with a piece of tape over the caming device so it would fail. To show that a grigri will work the same as an ACT if the belayers hand was on the brake side of the rope.
Would this be possble to catch a falling climb with a SUM that had the camming device taped so it would stay open?
What if you didnt know the assisted camming was not gonna work would you be able to catch the falling climber?
I just checked mine, and if you death grip it, it does the same thing... But that means you'd have to be holding the device tight during the fall, not the brake end of the rope. If you grab the brake strand of the rope instead of death gripping the device itself, it will arrest a fall EVERY time. It appears as if the belayer was squeezing the device, not the brake end of the rope.
"To feed rope:
pull with one hand the part of the rope leading to the climber. With the other hand hold the device and the free part of the rope as shown in the illustration. Fingers should rest lightly against the device and the index finger should be positioned as shown so that is can immediately catch the free part of the rope in case of arresting a fall. Keep SUM perpendicular to the direction of the rope. Unlike other devices, the belayer does not need to block a cam in order to feed rope quickly. The belayer must, however, remain vigilant and release the device if the climber falls."
If you hold the device with a death grip perpendicular to the rope it is akin to holding the cam on a grigri.
Meadows wrote:Also, this is what we recorded yesterday on the SUM and this is for SUM users to check their device. This doesn't provide a 100% answer on what happen or why after 1.5 years, this device does this (new SUMs do have tighter cams), but does raise questions.
What I also know about the device is that 1. The belayer did have his brake hand on the rope as verified by someone else who saw it. 2. In the jerk tests, the device failed to engage the cam when held in hand. 3. Cam did engage with hand on rope. I've raised the possibility of the device being loaded backwards, but I'm not sure if that is possible with the SUM without it feeling considerably awkward.
steph I am clearly out of my league as I have never used the SUM but I am interested in what happened... in the vid it merely sounds like dirt or sand is stopping it from moving when Todd has his death grip on it...is that correct, ie it might need to be cleaned?
kurtnorv wrote:When I used to work in a gym we would practice catching a climber, who had a back up belay on another rope, with a grigri with a piece of tape over the caming device so it would fail. To show that a grigri will work the same as an ACT if the belayers hand was on the brake side of the rope.
Would this be possble to catch a falling climb with a SUM that had the camming device taped so it would stay open?
What if you didnt know the assisted camming was not gonna work would you be able to catch the falling climber?
Yes, when my first SUM wore out and quit working/camming... It caught a lead fall just fine, I simply caught the climber and lowered like you would with a munter, without having to engage the cam to make it slip. The device was shot, but still worked when used properly, with a brake hand on the rope not the device.
cliftongifford wrote: I simply caught the climber and lowered like you would with a munter
So the brake hand up?
Is that the natural position to catch someone when using the SUM. Based on the videos it looks like most people have their hand down or in front of the device when catching a fall. If the second or so it takes for the climber to fall to the ground could you realize that the device isnt working right and switch you hand position from down or in front of the device to above it? And have control of the rope (its not flying through the device) to hold tight once you get your hand above it to stop the climber?
caribe wrote: Does the device easily lend itself to misuse? _(yes)_ Could the hapless belayer have been me; could I have dropped a buddy with this device? _(yes)_
With an ATC all you have to mind is the brake end of the rope. These other devices bifurcate one's attention. Cell phone-related auto accidents and Grigri/ Sum/ Cinch grounders may all have common phenomenology.
You can insert any device into that statement and still get a yes. I've seen the ATC misused and I know of two instances where the belayer lost control on a fall. But this is the same ol' argument that has persisted through the years - and just like religious and political debates, the arguments become senseless. They're never trying to convert someone, rather they are making an attempt to prove they are right.
Belaying in general has a common phenomenology with cell phone related accidents ... you can talk all you want and still maneuver a car, but the moment a problem arises, the attention is split.
And "bifurcate"? Does anyone else here ever use that word?
