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[TowerTalk] blocks

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Subject: [TowerTalk] blocks
From: (Malcolm Clark)
Date: Fri, 17 Apr 1998 10:11:16 +0000
Pat Barthelow wrote:
> HI Russ,
> We found a very small, deceptively strong block at a local marine supply
> store.  Stainless steel, and nylon body/wheels with ball bearings, the
> thing was not too
> expensive...about $12.00. The pulley wheel was only about 1-1/2" diameter,
> but
> the block was rated at 2000 lbs working load.  


WARNING!!!  Don't use that block for loads even approaching 2000 lbs. 
There is no way you can buy any ball bearing block with a SWL rating of
2000 lbs for $12.00--stainless strapped or otherwise.  If you paid
$12.00--and it is a BB block--the SWL is probably 200-300 lbs, possibly
500 or so lbs, and certainly no more than 900 lbs.

Ball bearing blocks have substantially lower load ratings than plain
bearing blocks and cost dearly when you reach the 2000 SWL level.  The
cheapest 2000 lb SWL BB block that I could find in a marine discount
catalog was over $80.00.

Block SWL ratings are typically 1/4 of the absolute maximum ratings
(read point it breaks) although it can vary by manufacturer.

E-mail me any names, numbers, and/lettering on the block and I can
probably find the true SWL spec for you.

If there are no markings send me a full description including
measurements and materials and I will probably be able to give you a
ball park estimate.  Again, there are no $12.00 2000 lb SWL
blocks--including plain bearing.  $120.00 2000 lb SWL BB blocks--yes.

Malcolm KR4HP

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