5 to 1 fiddleblock set

Re: fiddleblock set

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Anybody know any good tricks for removing the fiddle blocks off of the load line and port-a-wrap when it is loaded?

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Not trying to be sarcastic... maybe I just don't understand what you're asking but... secure the load line with the porty and loosen the fiddle block.
Even with a big load you should still be able to pull the rope out of the cleat or slide the prusik on the heave line as long as the load line doesn't pull and re-tighten it. The heave line is only holding a fifth of the load. The kind with a cleat is easy to unload.
 
Re: fiddleblock set

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Anybody know any good tricks for removing the fiddle blocks off of the load line and port-a-wrap when it is loaded?

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If we can't get the primary MA system off, we install another 1 to it, 1 end just above the traveling block and the other on the anchor (usually a Porty), to create enough slack to release the prusik or camming device. NOTE: The forces involved may cause the rope to part and have a 'slingshot' effect on anything in line with the load. So, it's extremely important to know the approximate forces involved and the ropes history. Will adding that extra force be enough to 'snap' the rope.
That's why we have 10% to 20% SWL's for rigging.
When it comes time to release the tension, go very slow and controlled.
 
Re: 10 to 1 fiddleblock set

Sorry guys, about not being specific enough...

Scenario is pretty typical for lifting a limb before lowering, port-a-wrap included. My snag was from only being able to draw the fiddle block line half-way before needing to tie-off, release the tension via the cam, etc. With the blocks only half drawn the prusik attached to the lowering line was still 9' over the ground. No problem, I thought, just hook it with a pole saw hook, but the prusik was cinched too tight to pull down. Just as I told the guys, "you won't believe how cool this tool is", there I am hauling myself up the line like an ape to retrieve the top block. Not very cool. Any ideas?
 
Re: 10 to 1 fiddleblock set

Now I see what you mean. Yep, I've done the ape trick before too... impossible to do gracefully, not exactly safe either.

The only thing I can of off-hand would be some kind ring or something you could attach midline above the prussik and haul down with some cord to compress it.

Surely somebody out there has an elegant solution.
 
Re: 10 to 1 fiddleblock set

i've dragged it down with a small pulley mounted over; also jsut plot it to be in reach when done. Otherwise, you can also mount a pulley to Porty eye; to then mount the compression jig and prussik horizontally, rather than vertically. This will pull the Porty off course some, that places some slack in the line on release; so must over pull to compensate or tie off Porty high too, to fight the sidewards pull. Another way we've done it, that also helps place more dynamic absorbing line int he equation(and safer worker distance); is to replace the Porty with another Block, then run horizontal to another anchored that Porty is anchored on;and run the compression jig to there too. This takes some extra gear and distance; but gives more dampening and safe clearance; and sweating ability to the system.
 
Re: 10 to 1 fiddleblock set

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i've dragged it down with a small pulley mounted over;

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Ditto!
Had to take the tension off 1st. Lossened the hitch up from the braids on up to the coils (backwards). Then slid the pulley down with a polesaw hooked on a biner captured to a micro pulley tending the rope from above.
 
Re: 10 to 1 fiddleblock set

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My snag was from only being able to draw the fiddle block line half-way before needing to tie-off, release the tension via the cam, etc. With the blocks only half drawn the prusik attached to the lowering line was still 9' over the ground.

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Set the system up so that the MA is horizontal rather than vertical.

Easy to do--instead of putting the P-A-W at the base of the tree install a block at the base of the tree as a re-direct and place the P-A-W at the base of an adjacent tree. Thread the rigging line down the tree, through the redirect, and onto the P-A-W, then place the MA system on the rigging line.

The attachment is a 2:1 used to tension the rigging line.
 

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Re: 10 to 1 fiddleblock set

Another. This is a 5:1 used to tension a speed line.

The line that is slack is the rigging (speed) line. Tension is applied with the 5:1 and the slack in the rigging line is pulled tight on the P-A-W. With a set of fiddle blocks (as here) the MA is released with a flip of the wrist. If the tension created by the MA system is captured with a friciton hitch then tension has to be applied to the input line of the MA system so that the friction hitch can be released.
 

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Re: 10 to 1 fiddleblock set

Ya, they are not working for me.

Get to it, I want to see your pics!
grin.gif
 
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Then figure how much your input force is and multiply times the MA.

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How do you make this calculation?

Also, pulley's gat a *:* rating by the size difference between rope diameter and sheave size? Does this ratio have any effect on the MA ratio?
 
The MA is the amount of rope legs of pull on the load(output) divided by the amount of rope legs of pull connected to the input. So if you pull 1 leg of pull; that in turn pulls 5 legs of pull on load, that is 5:1. This also means that, you must shorten each of the 5 legs 1' to move the load 1'; so you have to pull 5' to move the load 1'; so this is a tradeoff. It also then means that the load moves at 1/5th the speed of your input pull.

Ummmmmmm rope diameter to sheave size?? Not sure; but axle diameter to sheave size gives the leverage of the sheave over the friction of the bearings or bushings on the axle; this is to measure the efficiency of the pulley; or how much of the 5:1 potential you really get etc.
 
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Then figure how much your input force is and multiply times the MA.

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How do you make this calculation?

Also, pulley's gat a *:* rating by the size difference between rope diameter and sheave size? Does this ratio have any effect on the MA ratio?

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As fhfr36 said earlier in this thread, you get the MA by simply counting the lines between blocks. This assumes you do not have a compound arrangement where one block and tackle is used to pull on another block and tackle.

The quoted MA normally does not include any inefficiencies of the pulleys. The topic of bushing bearings has already been covered. Even if you have perfect roller bearings there would still be some energy or force loss in the rope at the pulleys. When a rope does a 180 degree turn around a sheave, the outer fibers of the rope travel farther by a distance of pi*d/2, where d is the diameter of the rope. To do this, the rope fibers have to rub against each other. The larger the sheave, the less perpendicular force there will be between fibers and the less friction there will be.

I did a derivation about internal friction on Cavers Digest in 1998. To get it, go to http://www.caversdigest.com and get messages 5523 and 5524 from the archives. My derivation makes some simplifying assumptions and uses simple calculus.
 
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