"Elevator" system?

[RogerM]

\"Elevator\" system?

Could someone please explain how to set up an elevator
system. An example would be for something like switching
techs out during a TCC or for a first time recreational climber(with experienced climbers present).

 

[Kevin]

Re: \"Elevator\" system?

It's just a block with two climbers on each leg of the rope.
As one comes down it forces the other up.
Weight is a factor and some assistance may be required if there's much of a weight difference between the two climbers.

 

[Tom Dunlap]

Re: \"Elevator\" system?

Getting an elevator balanced can be a challenge. If there is a weight difference between the climbers some sort of friction device should be used. The simplest setup is to use a small bollard instead of a pulley at the top. Then the two climbers add a bit of push or pull to move along the rope.

There's another way to rig this but it's a little more complex. The heavier climber is in the tree and attached to the end of the rope. The lighter climber on the ground attaches to the rope in mid-line. Enough rope is needed in the system to equal three times the height of the climb. The heavier climber attaches a friction hitch to the side of the rope that the lighter climber is attached. This will look like a normal climbing setup. Half way down is where the two will meet. Then, the friction hitch needs to pass the lighter climber. If the two climbers meet on a branch, this is easy. If they meet in mid-air it requires some tricky work.

Another option is to have a belay at the base of the tree to control the elevator.

"Ground floor...Climbing tools, boots and lunch counter!"

 

[TheTreeSpyder]

Re: \"Elevator\" system?

That is a nice deal Tom.

Of course if the climber that needs to come up + Friction is less than climber coming down; system is self working.

But, if the climber that needs to come up + Friction is heavier, a pull line for ground help can be attatched to lighter climber. This gives 1/1 of the ground pull. But if the heavier climber pulls on the line, it is 2/1; for the heavier climber now pulls down (for example with a 50# pull)to do 2 things: lighten themselves by 50#, as they also exert 50# pulling the other man down. Likewise, efforts by the upper man also work in 2/1; for as they pull up 50#, then they as equal and opposite are making themselves 50# heavier. So, as a relative example of "2 handing" are using their directed force, anid it's equal and opposite to target!

Of course, tag line is only good for 1/2 way up for the 2/1 by lighter climber + friction lowering; but good for the 1/1 by groundy the whole way(pulling lighter climber down); as is the 2/1 by heavier climber + friction going up(good for the whole tour).

See also: Flash animation of 2Handing Principal

Orrrrrrrr something like that!
/forum/images/graemlins/crazy.gif

 

[RogerM]

Re: \"Elevator\" system?

I assumed that it was fairly a simple process, THe friction for the decent with heavier at top was good. Also i thought that a static line might be set if the heavier climber was at the bottom, allowing bottom to pull with counter weight(other climber). Maybe additional safety on lighter climber at top in case heavier bottom climber gets tired. Setting up so bottom climber(heavier) can't lose ground if s/he let's go. /forum/images/graemlins/santa.gif

 

[TheTreeSpyder]

Re: \"Elevator\" system?

Seeing as the upper climber has 2 lines; i think they should connect a prussik to their 'other' line. At midway, this would switch off. Descending climber riding original prusik first, but also having 2nd ready on their own line. As original prusik is headed for ascenidng climber's lap. This would give double prussik secuity at changeover too/ no total disconnection. Back up/ less safe alternate; would be to shake hands at midway, and upper climber always keeps legs laced through 'other' line; applying or ready to apply friction.

With pulley support, you only have to work to make up the differances in weight. If climbers kept within 60# of each other; and use 2/1 strategies; that gives 30# effort. Upper climber doing work, swithching off at mid way. Tag line on descending, allows them to share work to half way point, and allows ground help to. Should be able to get work load down near everyone's effortless powerband.