catbirdseat

I've noticed a handful of rock climbers use Yates Screamers. Screamers are mostly used by ice climbers to reduce the chance that ice screws would pull out in a fall. It seems to me that they might also be a good idea in rock climbing for those critical first one or two pieces of protection where fall factors are high. For those who don't care to read all the way through, the upshot is that testing shows that use of a screamer on a bolt (or piece of pro) would reduce the load on that piece from from 2000 lb (9 kN) to 1200 lb (5 kN) in a FF 0.5 fall. There are some types of pro, for example small nuts, that would fail at 9 kN but hold at 5 kN. The following is clipped from the above Techweenie link: Physics of Screamers by YATES Author: John Yates/ Pro Design USA Email: prodesig@snowcrest.net Date: 1998/12/08 Forums: rec.climbing (Snip) Screamers are a stitch ripping device that allows forces to be decelerated over a longer time interval than they would be if the Screamers were not in the system. Standard Screamers or ICE-Screams are configures from stitch patterns consisting of 6 rows of zigzag stitching sewn into each wing of the unit. This stitching is done by means of a computerized sewing machine. The machine can be configured to allow the Screamer to activate basically anywhere between 1 and 650 lbf. We chose to use an average activation of 550 lbf. because it seamed to be about the right force to use as a upper limit for marginal protection and ice screws. Not every thing is a real science. Some interesting things happen when you look at how much energy is "absorbed" in the system when a screamer is used. If the "True" absorption is measured in a completely static system, lets say doing a drop test with a steel cable and weight we will see that about 5-600 lbf was absorbed by the stitch ripper (Screamer). When a Screamer though is put in a system which uses dynamic climbing rope instead of static steel cable the amount of energy which is absorbed is increase by 25-40%. We see that the absorption of energy increases to 800-900 lbf. I can attribute this extra energy we see being absorbed to the fact that the "Dynamic" climbing rope in the system is allowed to elongate and remain dynamic for a longer time interval than it would be, if there was no screamer in the system. An example: A dynamometer or load cell is placed on a bolt hanger. A climber takes a fall which generates a fall with a factor of 0.5. This generates a force of 2000 lbf as seen on the dynamometer. When a Screamer is hooked in the system below the dyno. the same fall only shows a peak force of 1200 lbf. We know from extensive testing that the Screamer can only absorb 500 lbf. So how do we account for the extra 300 lbf seen in this example??? The increased time interval(duration) of the fall allowed the climbing rope to be more absorptive!! Thus Screamers limit loads and dissipate energy over a an increased time interval. This increase in the duration of the fall is most important in a "Dynamic" systems because it allows the rope to do its job even better than it was designed to do.

I agree. Take it back.

Bill, you carry six Tri-Cams, which is more than most folks carry. I carry the three smallest ones, but plan to get more. When you consider that tricams fill a size range as large as SLCDs at a fraction of the weight and cost, you would think that more people would use them. Dru says he likes them a lot. I think he said he uses them INSTEAD of SLCDs. They are also much cheaper than SLCDs. With practice they can be set fairly rapidly. So why is it more people don't use them?

The dude sounds like he knows what he is talking about.

The article is about perfluorooctanoic acid. Interestingly, there is a closely related compound Lithium perfluorooctane sulfonate which is used to poison wasps and yellow jackets in bait traps. These compounds are chemicially so stable that they will be around essentially forever.

Good one.

I have no idea who you met at Vantage. The scramblers use an area across the street from eightmile campground not normally used by climbers, mostly easy boulders and slabs. The Everett Branch Intermediate Climbing Course was on Mountaineer Dome. The students were learning to place pro on top rope. I dare say there were probably not any other climbers who would have willingly gone climbing in the rain. It sucked. I hope you had fun at Vantage.

So how does one distinguish the Mountaineer asshole from the non-Mountaineer asshole without a guide? Judge people based upon how they act and not on who you think they are or how they look. Calmly explain yourself when you know you are right.

April 26-27. TLG, if you have a rope up and someone is climbing on it, fine. The rules are the same for everyone. If the Mountaineers have a rope up and no one is climbing on it, tell them to take it down and let you have the route.

Hi, trask.

You could be asked by a ranger to show your permit. Possible, but unlikely, and then only on the two most popular routes.

Sorry for the confusion. We were at Icicle Canyon all weekend. All I know is that Vantage was mostly dry. I don't know about Tieton.

Trask, what is that expression? All publicity is good publicity.

This thread is sponsored by Immodium AD.

This design has been around for many years. People call 'em "tubers". Click here for information on the Trango Pyramid. The one I used seemed to give a herky jerky rappel, no matter which way I oriented it. I'll stick with my BD ATC for fat ropes and my Trango Jaws for skinny ropes.

That story was a gas.

Hey, vegetablebait, stick it where the sun don't shine.

PLAB = Professional and Linguistic Assessment Board There's your search results.

DFA is married. Woohoo! 1000 posts! I did it. Yippee.

I want to know too; that, and "WERD". Is it an acronym. My daughter was able to explain "bling bling".

I've come to the conclusion that hexes don't need the same kind of intimate contact with the rock that nuts do. They are large enough that combined with the camming effect, they can hold even if the placement isn't perfect.

Prophet, you must have had a great weekend. It always makes going back work that much hard.

No, trask is never one for subtlety. He doesn't beat around the bush. He goes right to the bush and puts his face in it.

I might be interested. The weather is probably more reliable at Tieton than at Leavenworth. We were there this weekend and it rained both days.

I have never spent that much money on all the cars I have owned my entire life, and probably never will. The 4-Runner used to be a nice little basic 4x4. Now it's a bloated monster.