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More on Rescue and Gear Shenanigans |
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28-Oct-2011 10:55:26 AM
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I recently hauled two people (one at a time) ten meters in heavy rain/hail on 3:1 with pulley ,through a reverso. Both weighed considerably more than me. First victim was on my 9.6 rope and was o.k, then i dropped my pulley 50mtrs....and second climber was on a 10ml static.. 2 biners replacing pulley. Practically a 1:1 and a bicep lockoff to work it through the device! I wish i used a grigri and have since got a couple of those little plastic pulley sheaths although i imagine they would fail if you increased the mechanical advantage to much?
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28-Oct-2011 11:38:00 AM
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On 28/10/2011 dangermouth wrote:
>I recently hauled two people (one at a time) ten meters in heavy rain/hail
>on 3:1 with pulley ,through a reverso. Both weighed considerably more than
>me. First victim was on my 9.6 rope and was o.k, then i dropped my pulley
>50mtrs....and second climber was on a 10ml static.. 2 biners replacing
>pulley. Practically a 1:1 and a bicep lockoff to work it through the device!
>I wish i used a grigri and have since got a couple of those little plastic
>pulley sheaths although i imagine they would fail if you increased the
>mechanical advantage to much?
Why would increasing mechanical advantage cause the sheaths to fail? Almost by definition the greater the mechanical advantage, the lower the load on each point ...
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28-Oct-2011 5:02:55 PM
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I agree Stev_e, OD has got it wrong yet again, defo a 4:1
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28-Oct-2011 6:03:27 PM
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Does anyone know if its possible to rig a 5:1 with a downwards pull?
(without just redirecting the rope through the anchors)
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28-Oct-2011 10:49:36 PM
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Sorry. OD has it right. His diagram is of a 5:1 system. Don't confuse compound mechanical advantage systems with simple mechanical advantage systems.
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29-Oct-2011 2:57:46 PM
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Would you be able to explain that please?
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30-Oct-2011 1:01:02 AM
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It's all in the linking.
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30-Oct-2011 10:08:23 AM
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There are four sections of rope starting from the girls hand. Girl is pulling T.
1: T
2: T
3: 3T (additional 2T from prussik)
4: 5T (additional 2T from prussik)
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31-Oct-2011 1:11:41 PM
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oh yes, redoing my calculations now comes to 5:1 thanks
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31-Oct-2011 8:22:16 PM
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On 28/10/2011 stev_e wrote:
>Does anyone know if its possible to rig a 5:1 with a downwards pull?
>(without just redirecting the rope through the anchors)
yes it is possible
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31-Oct-2011 9:12:15 PM
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On 31/10/2011 stev_e wrote:
>oh yes, redoing my calculations now comes to 5:1 thanks
Easiest way to work out multiplys is to imagine the person goes up 1 metre ,then work out how much rope ends in the haulers hand , here one metre rise ,bottom pulley will go up one metre (2 metres of rope )and top pulley down one metre (2 metres of rope )
1+2+2=5 metres hence advantage is 5 to one
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