Lambone Posted October 25, 2002 Share Posted October 25, 2002 quote: Originally posted by Beck: Lambone's comments about mm ropes/lower impact forces generally holds true, doesn't it? Thinner ropes less impact force, twins an even lower impact if clipped into one piece? This is just one small contributing factor to this whole topic, still it that might mean Ehmmic's rope choice is an OK one for her? Yes, although freeclimb9's point about the variablity in rope types is also true. 90% of the time thicker ropes have a higher impact force than thinner ropes. Yet sometimes the opposite is true. Take Sterling Marathon ropes for exmple. their 9.5 Marathon has a higher impact force then their 10.5 standard. Sterlings #'s are quite odd, if you have ever looked at them. Different types of rope construction have different types of elasticity, but geneneraly speaking, thicker ones are typicaly less elsatic. Regardless, I think putting good peices in is the most important thing, and doubling up on gear if one is questionable. You can get ropes with low impact forces, and biners with high open gate srength, but that won't make up for crappy gear. The falls I have seen taken on screamers have never generated enough force to strip any of the stitching out. Quote Link to comment Share on other sites More sharing options...
neversummer Posted October 25, 2002 Share Posted October 25, 2002 Let's see if I can make this make sense on paper... screamers dont make much sense to me, if you fall and pull out a screamer, the piece holding the screamer to the wall still has to be strong enough to hold the impact and tear the screamer right? I understand that the strength of a screamer is less than that of a well place piece but how much less? So really the screamer doesnt increase the chance of the piece staying in the wall, It just lessens the force experianced by the leader as he/she comes to a stop right? (which is important in its own right) So to me whether you put it on the questionable piece or the bomber piece doesnt matter so long as its the piece that catches the fall and holds. Somthing tells me I am completely wrong here, but maybe somebody here can explain it to me. Quote Link to comment Share on other sites More sharing options...
freeclimb9 Posted October 25, 2002 Share Posted October 25, 2002 neversummer, a screamer limits the force on both the climber and the piece being fallen upon. The limit on the piece is why they're used. BTW, nice snowboards. Quote Link to comment Share on other sites More sharing options...
neversummer Posted October 25, 2002 Share Posted October 25, 2002 quote: Originally posted by freeclimb9: neversummer, a screamer limits the force on both the climber and the piece being fallen upon. The limit on the piece is why they're used. BTW, nice snowboards. I figured that they did or no one would use them and I think I understand how, but I was hoping for a clear explaination. Yeah, I love their boards I own a few to say the least. Quote Link to comment Share on other sites More sharing options...
snoboy Posted October 25, 2002 Share Posted October 25, 2002 quote: Originally posted by neversummer: screamers dont make much sense to me, if you fall and pull out a screamer, the piece holding the screamer to the wall still has to be strong enough to hold the impact and tear the screamer right? I understand that the strength of a screamer is less than that of a well place piece but how much less? As I understand things: -Screamers are generally activated at 2.2KN as far as I know. -The main function of them is to spread the force out over time. This reduces the _peak_ load on the piece in question. -"Screamers not only absorb energy directly, because of the stitch ripping effect, they also allow your rope to absorb more energy from the fall by increasing the time interval of the fall."[from bentgate.net] There is some good, although verbose stuff on this topic here at the Yates website. I can't find the full explanation of how they work right now, but if I do I will post it here too. [ 10-25-2002, 02:44 PM: Message edited by: snoboy ] Quote Link to comment Share on other sites More sharing options...
DavidW Posted October 25, 2002 Share Posted October 25, 2002 the first and only time i ever took a leader fall ice climbing I was 15' above a screw I thought was as good as they get...... ie: excellent ice, proper placement, correct angle, etc etc...... the result of the fall was that the screamer was totally extended..... the screw bent at something more than a 45-degree angle and the ice all around the screw shattered and gone....... when I saw it I was totally surprised that it had, in fact held me. My second later removed it with a couple of wiggles...... so if thats what happens to a well placed screw in good ice...... well, it boggles the mind doesnt it? Also should point out that I was using twin rope technique with a pair of mammut 8.5mm dry ropes...... much softer catch than in the old days with big fat 11mm's Quote Link to comment Share on other sites More sharing options...
Beck Posted October 25, 2002 Share Posted October 25, 2002 ...not an expert here, but the screamer takes a potential heinous yank on a piece into a series of successive, small, 350 (or whatever they're rated at) pound tugs on the anchor, as each stich line is ripped thru . From FALLING,Force factor placement failure, to, FALLING,rip,YANK,rip, YANK,rip,slightly less yank, until you stop ripping, or until the piece either fails, or it holds, rips all the stitches (does Yates still make two "sizes" of screamer?) and the screamer is now a near full-strength runner. Quote Link to comment Share on other sites More sharing options...
Gordonb Posted October 25, 2002 Share Posted October 25, 2002 From a physics standpoint Force = mass X acceleration (F = ma) One Newton (N) is the force to accelerate 1 kg by 1 m/s^s. So if we have a 100 kg climber and we slow his fall from 10m/s (about 1 second of free fall) to 0 in 1 second (assuming a smooth deceleration) it would generate (F = (100 kg) * (10 m/s)/(1 s)) 1000 N of force for the full 1 second of deceleration. If we add a screamer to the pro so that the deceleration time is increased to 2 seconds we would only generate 500 N of force. All this assumes a very perfect world where decelerations are smooth and even. Add a good static yank in there somewhere and forces go up very quickly. Quote Link to comment Share on other sites More sharing options...
snoboy Posted October 26, 2002 Share Posted October 26, 2002 quote: Originally posted by Beck: [QB(does Yates still make two "sizes" of screamer?) [/QB] Try 4. Screamers Quote Link to comment Share on other sites More sharing options...
snoboy Posted October 26, 2002 Share Posted October 26, 2002 quote: Originally posted by DavidW: correct angle, etc etc...... That's a whole 'nother can of worms isn't it? What is the "correct" angle for an ice screw? Quote Link to comment Share on other sites More sharing options...
DavidW Posted October 26, 2002 Share Posted October 26, 2002 I believe i bought the Yates "load limiter" variety....... instead of successive, individual bar tacks..... "yank-Rip, yank-Rip" etc... the stiching is arranged in the same direction as the force and in a continous line so there is not the staccato, force and release effect. The thing did indeed pull all the way out and become a regular length sling albiet with tons of purple "fur" from all the blown stitching! With regard to ice screws..... I think there has been some differing points of view on this but I thought that at least one time Chouinard published some diagrams showing screws inclined about 10-15 degrees uphill from perpendicular to the ice. That seems like it makes sense to me and hey.... i'm still here but am certainly not a physicist. Quote Link to comment Share on other sites More sharing options...
Beck Posted October 26, 2002 Share Posted October 26, 2002 ...my bad in not describing appropiately! Quote Link to comment Share on other sites More sharing options...
Lambone Posted October 26, 2002 Share Posted October 26, 2002 no. I don't think falling on one piece would stretch a rope to the point of being static. of course there are alot of vairables, like how much rope is out, how dynamic the belay is etc..., but as was stated in the accident thread, it takes alot to strtch a rope to its maximum capacity. Quote Link to comment Share on other sites More sharing options...
mattp Posted October 26, 2002 Share Posted October 26, 2002 quote: Originally posted by chucK: So you guys don't buy the argument/fear that the stretched out rope will blow away the bomber piece (as apparently happened to Goran) since the rope is now static? In a word: no. And even so, I'd still put the screamer on the questionnable piece because if I thought it was totally worthless I would skip it entirely, but if I only think it is questionnable I want to give it as much chance of holding me as possible. Again - I do not remember ever pulling what I thought was a bomber piece but I have worried about (and even occasionally pulled) sketchy pro lots of times. Quote Link to comment Share on other sites More sharing options...
mattp Posted October 26, 2002 Share Posted October 26, 2002 Goran's accident is startling, yes, but it has not caused me to suddenly doubt the dynamic capability of my ropes or my judgment as to the bomberness of a piece of pro. Because of the nature of the rock, I always doubted the quality of gear placed in those cracks over at Vantage anyway, and the actual number of instances in which I've heard of someone breaking gear is still extremely low (though I noted already that I have broken a biner before). [ 10-25-2002, 01:30 PM: Message edited by: mattp ] Quote Link to comment Share on other sites More sharing options...
mattp Posted October 26, 2002 Share Posted October 26, 2002 sorry about the double post. [ 10-25-2002, 01:31 PM: Message edited by: mattp ] Quote Link to comment Share on other sites More sharing options...
haireball Posted October 28, 2002 Share Posted October 28, 2002 I was wondering when someone would bring up the subject of ice protection. (sorry, guys, I've been away for a couple of days, and this is a damn good thread!) A few years back, Chouinard, March, Lowe, & Freedom of the Hills all agreed that ice screws were best placed a few degrees upslope of perpendicular to the ice surface. This seemed intuitive. More recent TESTING (within the last five years), yields the "counterintuitive" recommendation that we place screws a few degrees DOWNSLOPE from perpendicular. Apparently, the pullout strength tends to be greater, in most ice conditions, than the fracture strength of the ice. (this is a particularly troubling datum, for me, as I recall the numerous screws I've had ripped out by rope-drag on mushy Washington waterfalls...!) The gurus are also saying not to tie off long screws (I always did this rather than buy short ones) because when the screw bends, as the ones tested inevitably did, the tie-off slips down to the eye of the screw and the leverage destroys the placement. the bad news is that even the very best numbers I've come across are pretty scary for ice pro. the good news is that, placed correctly, short screws yielded failure values about as high as long ones (again, counterintuitive). No worries about rope failure, but I'll stay with my leashes and count my tools as the primary belay for now... -Curt Quote Link to comment Share on other sites More sharing options...
SEF Posted October 28, 2002 Share Posted October 28, 2002 Regarding ice screw placement, Black Diamond has done some research: http://www.hi.is/~haraldg/isskrufu_paelingar.html Tilting the screw placement down from perpendicular is the current advice for placing BD threaded screws in “ideal ice conditions.” While such ice remains somewhat intuitive, the paper above does describe what that means. An excerpt about test results: quote: What we observed is that the direction of loading is significantly stronger. In fact, at 15 degrees from perpendicular the screws are over two times stronger when placed in the direction of load. [ 10-28-2002, 03:09 AM: Message edited by: SEF ] Quote Link to comment Share on other sites More sharing options...
daler Posted October 28, 2002 Share Posted October 28, 2002 DavidW Were you on twin ropes(clip both ropes into every piece) or half ropes(alternate ropes into pieces)because twin ropes actually have a very high impact force, even compared to a single 10.5 or some 11 mm ropes. Twins are not a good idea for ice climbing. They were designed for the Euro style straight up alpine routes where two ropes are needed for the descent, but a trail line is not desired. Ice is almost impossible to read but if you had perfect ice the srew placement should be placed down so the threads are what catch a fall. Think of a wood srew sticking out of the wood a couple of inches. If you pulled straight out with pliers it would be impossible to pull it out. but you could bend it over with your fingers. Dale Ps The ice in Colorado is coming in, with the high stuff ready to go. Quote Link to comment Share on other sites More sharing options...
JayB Posted October 28, 2002 Share Posted October 28, 2002 quote: Originally posted by daler: Ps The ice in Colorado is coming in, with the high stuff ready to go.[/QB] Yup Probably looks something like this right about now... (on 10.24.2002) Current Conditions Comment: Mt. Lincoln conditions on 10/24/2: Main flow is in, wet, thin in spots on the lower bit. The upper bit is wide & fat. Rocky stretch between the 2. Scottish-type gully on L is good, fun. Lower R curtain is fat, vertical, chopped out. R side of lower R curtain is in, less steep, chandeliered a bit. Upper curtain is not touching down. 2 sets of bolts on top of main flow. 1 set of bolts on far R side of lower R curtain. Busy, 12+ people, 7+ cars today. Also, I-70 sickle, Idaho Springs falls are dripping, not in. -------------------------------------------------------------------------------- [ 10-28-2002, 07:59 AM: Message edited by: JayB ] Quote Link to comment Share on other sites More sharing options...
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