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Chockstone Forum - Gear Lust / Lost & Found

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 Page 4 of 4. Messages 1 to 20 | 21 to 40 | 41 to 60 | 61 to 71
Author
More on Rescue and Gear Shenanigans

E. Wells
28/10/2011
10:55:26 AM
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?
pecheur
28/10/2011
11:38:00 AM
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 ...

gnaguts
28/10/2011
5:02:55 PM
I agree Stev_e, OD has got it wrong yet again, defo a 4:1
stev_e
28/10/2011
6:03:27 PM
Does anyone know if its possible to rig a 5:1 with a downwards pull?
(without just redirecting the rope through the anchors)
davew
28/10/2011
10:49:36 PM
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.
stev_e
29/10/2011
2:57:46 PM
Would you be able to explain that please?
rightarmbad
30/10/2011
1:01:02 AM
It's all in the linking.
patto
30/10/2011
10:08:23 AM
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)
stev_e
31/10/2011
1:11:41 PM
oh yes, redoing my calculations now comes to 5:1 thanks

shortman
31/10/2011
8:22:16 PM
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
lacto
31/10/2011
9:12:15 PM
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

 Page 4 of 4. Messages 1 to 20 | 21 to 40 | 41 to 60 | 61 to 71
There are 71 messages in this topic.

 

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