[TowerTalk] blocks

[Malcolm Clark]

LEE ROGER WICAL wrote:
> 
> SWL=STATIC WORK LOAD??????
> DO YOU THINK ALL WILL KNOW THAT?

You're right.  It's Safe Working Load.

I should have also pointed out that a SWL of, say, 500 lbs, doesn't mean
you should use the block to lift a 500 lb object.  The possible shock
loading that might occur if the load is dropped should be taken into
account too.  One good way to "eyeball rate" a marine block is to look
it over carefully and decide if you would trust your life to it.  If you
would, the block should be safe to lift items at least as heavy as you.

(Before anyone says this is poor technique etc., I would like to say
that it is my experience that people just won't trust their lives to
marine blocks with SWL ratings of much under 1500 lbs simply because
they and their fittings look so tiny.) 

One more point, turning angle impacts the load on the block--and the
attachment point.  If the line turns 180 degrees you will DOUBLE the
load.  As an example, if a man standing at the bottom of a tower holds a
line that runs up to a block at the top of the tower, and then back down
to a dangling section weighing 40 lbs, the load at the block's
attachment point (and on the block itself) is 80 lbs.

The above example does not take into account friction which will
increase the load 5-10% more (for a single block).   

73
Malcolm KR4HP

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