Hi Folks:
Interesting, productive discussions on Gin Pole loads...
On the net there are several sites that may serve as useful reference
points, as they have useful diagrams of pulleys, and different loads on
different parts of blocks and tackle. A picture is certainly worth
kilo-words here.
Use as search terms in Alta Vista:
"Block and Tackle", and
"Rope Specifications", and
"Mechanical Advantage", and
"TotalRescue" (Quotes required)
for a wealth of related hits...
I found a really useful pictures and explanations at the following two
sites:
http://howstuffworks.com/pulley.htm,
http://ourworld.compuserve.com/homepages/TotalRescue/ropersec.htm
Also, note the the rope working load is usually 20% or less than the
breaking strength of rope, so expressions such as "needs to be only as
half as strong," etc, should be chosen carefully...remember the breaking
strength will usually be 4 to 5 times the working load....to stay safe,
and this is for like-new rope....
73, DX, de
Pat, AA6EG/N6IJ;
aa6eg@hh.tmx.com
599 DX Drive, Marina CA 93933
"The Contest Station from the Government"
On Sat, 3 Apr 1999, George Cutsogeorge wrote:
>
> >, but it
> >needs to be only half as strong as the rope without the second
> >pulley.
> >
> The mechanical handbooks say that the rope needs to rated for the
> full load. Under static conditions there is no problem, but
> dynamically the full load could be applied to the rope. Also,
> it's the safe way. A pulley could stick, or the load could slip
> and drop a ways, etc.
>
> The pull rope can come from the top, as all the previous
> discussion has indicated, or the bottom pulley. The tower man
> can do the pulling from the top. This is possible with the
> mechanical advantage lowering the pull required. The load on the
> gin pole in this case is the load weight minus the pull rope
> tension.
>
> All this is interesting, but I think the best way is with a
> motorized winch or a tractor which can hold the load in place.
>
> George
> W2VJN
>
>
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