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Questiong About Impact Force Difference Between Single and Half Ropes

Original Post
Eric LaRoche · · West Swanzey, NH · Joined Aug 2011 · Points: 25

So looking at say a Beal Joker Unicore the single rope impact for is 7.9-8.2KN. For half rope it's listed as 5.6-5.8KN. Is this because they doing the testing for all half ropes with a 55kg weight and singles with 80kg? I'm assuming that also means even if using this rope in a half rope configuration the impact force for an 80kg climbing is still 7.9-8.2kn. Is that correct since only one line is taking the impact still?

If that is correct how would you figure out that actual impact force of an 80kg climber for say the Cobra Unicore where there's no single force listed only a half of 5.1KN.

bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065

youve got it ...

the 80 kg impact force on a half rope is very roughly around 20-30%+ vs the 55 kg rating

What will the impact force be on half rope if it is tested with 80kg on one strand?
It will be around 25% more than the test result at 55-kg.

What happens if you clip both ropes together ?
The impact force increases by 20 to 25% on the clipped point.


bealplanet.com/sport/anglai…

its a myth that half rope have lower impact forces than singles because of the rope .... however other factors may lead have ropes to have less force on the runner such as slippage and reduced drag, but it aint because of the rope itself

read this ...

Here’s the total picture.

Rope A. 80kg-7.35kN, 55kg-5.39kN, published with 55kg-4.85kN

Rope B. 80kg-8.15kN, 55kg-6.23kN, published with 55kg-6.3kN

Rope C. 80kg-8.23kN, 55kg-6.25kN, published with 55kg-6.5kN

Rope D. 80kg-9.22kN, 55kg-5.88kN, published with 55kg-6.1kN

These drops were conducted without the regulation conditioning but complied with all other requirements and procedures. Relative humidity was 42%, temperature was 20ºC for 48 hours.


willgadd.com/single-and-hal…

;)

Eric LaRoche · · West Swanzey, NH · Joined Aug 2011 · Points: 25

Cool. For some reason I keep getting sent to a foreign language site for Beal so I can't really read what anything says. Your link works though. Thanks.

Just for thought. If you had two piece of marginal gear right next to each other and clip one rope to each would the impact force on the climber be 25% more but the impact on each piece of gear be half of the single rope impact since they'd be sharing the load?

bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065
Eric LaRoche wrote:Cool. For some reason I keep getting sent to a foreign language site for Beal so I can't really read what anything says. Your link works though. Thanks. Just for thought. If you had two piece of marginal gear right next to each other and clip one rope to each would the impact force on the climber be 25% more but the impact on each piece of gear be half of the single rope impact since they'd be sharing the load?
assuming everything is absolutely symmetrical the entire way up ... the impact force would be the same as for twin ropes overall ... which is roughly 25% higher than the single rope (80 kg) force which itself is roughly 25% higher than a half rope (55 kg) ...

now if you had 2 pieces of gear to split up the force ... then the load on each piece should be half the total on the runner adding in for the pulley effect ... remember that the UIAA number is for the force on the climber, not the last runner



DAV forces on belayer, climber, top runner, and rope path/drag

however in real life things are almost never perfectly symmetrical

;)
Eric LaRoche · · West Swanzey, NH · Joined Aug 2011 · Points: 25

Yeah sorry, I was throwing in forces at two different points in the system. I understand that the rating for ropes is on the climber and the gear is going to have a different load amount.

Thanks for the images. The second image definitely illustrates why to keep rope drag to a minimum.

Guideline #1: Don't be a jerk.

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