Jump to content

Load Limiters--Does anyone use these?


scrambler

Recommended Posts

So, I recently bought two Yates Screamers for trad climbing. I've never seen these in action though, in theory, these serve to lessen the impact force on pieces of pro. Bought these to use with small stoppers (BD #4 down to microstopper #3) or questionable gear placements with larger pieces. The smaller pieces of gear are rated at 5 or 6 kN. The stitching on the Screamer blows out at forces greater than 2 kN. Do any of you use load limiters (Yates Screamers, Zippers, Ice Screams, etc)? What's your experience? Do you use these for the first pieces of placement as described by Twight in ice climbing, on belays, or whenever you feel sketched?

 

BTW, I know the cardinal rule is: "Don't fall." I learned that the hard way. That's why I'm posting here, otherwise, I'd be climbing.

Link to comment
Share on other sites

  • Replies 33
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Hmmm...might just be better to back it up with another piece of gear but assuming you couldn't back it up then it seems the pro plus load limiter is better than nothing at all.

 

Just did a search for any threads on the 'dogbone draw effect' but no luck. The typical solution would be to use an alpine sling?

Link to comment
Share on other sites

the dogbone thisn is like when you use a short sport climbing quick draw. it is really stiff (compared with the length especially) therefore more suceptable to not only rope drag but also having the rope tug and possibly tug the piece out. but yes it is likely a longer runner would alleviate this.

Link to comment
Share on other sites

I don't know either, I've only used them under the same theory. I've put them on rusty pitons I've come across and a couple of times on a picket or screw. I think Craig Lueben used them as part of his testing of screws and such for that Falcon Press "How to Ice Climb" book. It's all theory I guess. Hearing about that Goran accident at Vantage isn't too reassuring for the trust in gear, I think. That he was "a big guy" means nothing for those of us tipping over 200 pounds as well.

If I actually did ice climb, I'd use those screamers for sure.

Link to comment
Share on other sites

Yeah, I read the accident report written up in R&I but I'm still unclear what happened at Vantage. Was the zipper effect a big factor? As for theory, with regard to this example, the fall factor should have been relatively small considering that a great length of rope was played out since he was near the top.

 

A load limiter should absorb some of the force on a piece by blowing its stitches thus reducing the force by several kilonewtons. I also saw an article that mentioned that the late Dan Osman used these when he did some of his climbing rope jumps.

Link to comment
Share on other sites

I have used them quite a bit and was just thinking how I needed to buy new ones. Only once has one I used actually been activated. The early models used a series of bar tacks that would be pulled apart. (Actually Forrest developed an expensive limiter before the bar tack scheme was developed but it was not extensively used) These had a reputation of causing a vibration that caused the gate to flutter open and shut. While open the 'biner is dramatically weaker. The Yates limiter uses vertical seems which are pulled apart. This method reduces or eliminates the gate flutter.

 

Do they work? Yes. I once witnessed a 75' fall being caught on a #2 RP. The limiter was one of the old bar tack models and it sounded like a burst of machine gun fire as the bar tacks flew apart. Had the RP pulled the guy would have smashed into a ledge. After seeing that I became convinced of their practical utility.

 

If you worry about gate flutter use a locking carabiner.

 

PP bigdrink.gif

Link to comment
Share on other sites

I am new to ice climbing but being 200+ lbs I bought 3 of the Yates screamers. Hope I never need to use them. As for using on rock, well I probably won' t use them in that application due to being like a draw and not dissapating the rope vibration enough not to pop pro...

Link to comment
Share on other sites

they did used to sound more like a machine gun than a zipper back in the early days of the Yates screamer, I thought so..

 

I believe mammut has some on the market now, I also believe pieces themselves could have resettable load limiters built in, but is wholly conceptual..

 

 

and yates has about 5 different kinds, depending on your use, from aid screamers, ice screamers, even adjustable daisys with built in screamers, its a broad variety out there now...

Link to comment
Share on other sites

I've activated two of them ice climbing. I used to use them on all screws I placed, but now just put them on sketchy pieces. For pro that is in good rock and ice - I wouldn't worry about using them, but if it's a dubious placement or in rotten ice it could be the difference between the piece holding or you going for a ride. hellno3d.gif

Link to comment
Share on other sites

whilst climbing at the Moaning Tree my friend Cam C. had a double dinner plate occur and pitched backwards and down 20' onto a 17cm screw in very soft wet ice. the On sight screamer not only held, but only about the first 5cm of the stitching unwove.

 

i have 5 and use them all the time ice climbing; rarely alpine or trad climbing. i usually take along one, and only clip it to sketchy fixed pins of unknown age.

 

RPS themselves can act as load limiters. if you place 5 or 6 in a small distance (like 6 inches apart) in a thin crack and fall on them, the first 5 or so may rip out or break cables, but this will dissipate force and the 6th one will then catch you. i have only theoretical experience in this but it was well discussed in Mountain magazine c. 1978

Link to comment
Share on other sites

Dru

 

Can you fill me in on the physics explained in that article on how they work? I'm not an engineer but have always wondered how the screamer really dissipates the energy and lessens the force on the anchor.

 

The first law of thermodynamics basically says that the energy in a system is constant. Newton's second law states that force=mass times acceleration. So you fall on a screamer, the potential energy of the falling climber becomes kinetic energy that is spread between the anchor, rope, screamer, climber and other gear. I can see how the screamer changes the deceleration and thus the force on the anchor but how do the ripping threads really eat up the energy or just change it into a bunch of smaller impacts spread out in time on the anchor?

 

No I'm not a geek Geek_em8.gifGeek_em8.gif, just want to know how they work.

Link to comment
Share on other sites

i am not a geek either but essentially energy is dissipated breaking threads/stitching/RP cables which reduces the total energy of the system, as i understand it. also the screamer extends the duration over which the force is applied thus reducing the total impact on the piece of pro.

 

some physicist can spray on me now. the_finger.gif

Link to comment
Share on other sites

Ducknut said:

Dru

 

Can you fill me in on the physics explained in that article on how they work? I'm not an engineer but have always wondered how the screamer really dissipates the energy and lessens the force on the anchor.

 

The first law of thermodynamics basically says that the energy in a system is constant. Newton's second law states that force=mass times acceleration. So you fall on a screamer, the potential energy of the falling climber becomes kinetic energy that is spread between the anchor, rope, screamer, climber and other gear. I can see how the screamer changes the deceleration and thus the force on the anchor but how do the ripping threads really eat up the energy or just change it into a bunch of smaller impacts spread out in time on the anchor?

 

No I'm not a geek Geek_em8.gifGeek_em8.gif, just want to know how they work.

This is really basic. As the climber climbs, he gains potential energy. When he falls, that potential energy goes into kinetic energy. That kinetic energy is transferred to the rope (into heat), the belayer (kinetic), and in this case, the screamer. (kinetic). When the climber stops (hopefully), he has no kinetic energy and lower potential energy than when he started falling. So all energy is conserved. Duh. rolleyes.gif

Link to comment
Share on other sites

Dru

 

Can you fill me in on the physics explained in that article on how they work? I'm not an engineer but have always wondered how the screamer really dissipates the energy and lessens the force on the anchor.

 

The first law of thermodynamics basically says that the energy in a system is constant. Newton's second law states that force=mass times acceleration. So you fall on a screamer, -snip-

 

Yeah, I imagine we're talking aboot microseconds here. So, you're falling and accelerating under the force of gravity (F=MA). The force is a function of mass and freefall time (9.8 meters per second per second, sumthin like that). In that nanosecond that the weight on the rope against the pro reaches 2 kN then the stitching begins to blow. That's like performing work, i.e., it dissipates energy. When the stitching has blown, then the remaining force is applied to the pro, hopefully it's less than the strength of the pro or its placement. Yeah, I ain't a physicist either.

Link to comment
Share on other sites

Dru said:

i am not a geek either but essentially energy is dissipated breaking threads/stitching/RP cables which reduces the total energy of the system, as i understand it. also the screamer extends the duration over which the force is applied thus reducing the total impact on the piece of pro.

 

some physicist can spray on me now. the_finger.gif

 

Great quick and dirty Dru

The energy is transformed in the stitching getting blown out. Load limiters are made so that only one set of stitches blows and this takes energy (2kn usually). If there is still enough left the next set goes same as the old bar tack style screamers. This keeps going until there isn't enough energy or no more screamer. The same happens in the nut scenerio your talkin about. If you set a series of sketchy nuts close enough you will pull some. The trick is to set them so that they use energy faster than you are makin it in the fall.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...