[TowerTalk] Gin Pole Strength

[Hans K0HB]

On Friday, April 02, 1999 7:37 PM, Stan Griffiths 
[SMTP:w7ni@teleport.com] wrote:

>  Here is what you are missing:  The gin pole has to support
>  TWICE the weight of  the load since the load pulls down on
> one side of the gin pole and the rope you are pulling on to
> raise the load is pulling down on the  other side of the gin
>  pole.  The gin pole sees both of these down pulls and has to
>  hold them BOTH, or  twice the weight of the load.

>
>  By using a block and tackle, you can reduce the pull on the
> rope you are using  to lift the load.  If you use a 3 to 1
> block and tackle, you reduce the pulling force to 1/3 of the
> weight and reduce the total load carried  by the gin pole.

> Here is an example:
>
>  Supposing your big mast weights 200 pounds.  Pulling it up
>  with a normal gin  pole with nothing but a pully at the top
> means it must support 400 pounds.  If  you use a block and
> tackle, you can cut the pulling force
> down to 67 pounds and the gin pole now has to support only
> 267 pounds instead of  400 pounds.

Wrong.  Just plain wrong.  While the block and tackle gives
you a mechanical advantage, the gin pole is carrying
*only* the weight of the antenna (200 pounds), either with
a single pulley at the top, or with the multiple pulley
arrangement of the block and tackle.  In fact, the added
weight of the extra pulleys and rope places a greater
strain on the gin pole than just a single pulley at the
top.

73, Hans, K0HB


--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm