"I had a Hunter's block and
tackle I've elevated 25 elk on."
25 at one time? That's some block & tackle....
K3MGT
----- Original Message -----
From: <K7GCO@aol.com>
To: <towertalk@contesting.com>; <alwilliams@olywa.net>;
<w7jwj@contesting.com>; <k4vx@arrl.net>; <K6myc@aol.com>
Sent: Wednesday, September 05, 2001 3:06 AM
Subject: Re: [TowerTalk] ratings on wire rope
>
> In a message dated 9/4/01 7:49:51 AM Pacific Daylight Time,
> alwilliams@olywa.net writes:
>
> <<
> > Picture a pulley up on your tower and you want to pull a 1,000 load
> with
> > a rope that goes through and down to the ground where you're going to
> pull.
> > The load on the pulley is 2,000 pounds - 1,000# on the load side and
> 1,000#
> > on the pull side.
> > >
>
> A questions for the physics experts -- Is it true that in order to pull
up
> the 1000#
> load that the pull will have to be 1000# plus the amount to overcome the
> loss
> due to the pulley efficiency? What is the efficiency for a typical 3 to
5"
> pulley
> of various bearing designs?
>
> k7puc
> >>
> All question are worthy of some kind of an answer. I have to ask why the
> efficiency of 3 to 5" pulleys of various bearing designs is a question?
> Bearing drag percentage wise has got to be very small. I obtained some
> pulleys from Boeing Surplus and made a series of block and tackles with up
to
> 5" wheels. Many tried to buy them off me. I said "they were just for
show
> and tell."
>
> Here is a case where wheel drag was important. I had a Hunter's block and
> tackle I've elevated 25 elk on. I started using it on lifting the 20'
mast
> with a beam on top to get access to my PP motor or other heavy loads. It
got
> so that the pull on the rope with a 4/3 pulley was more than the weight of
> the load--or seemed like it? I took it apart to find out why it had so
much
> drag. Over 40 years dirt had accumulated between the no bearing wheel and
> the side plates so bad it was like a brake shoe with a fair friction. I
> cleaned it all out and installed 3/4" bearings in each wheel. What a
> difference! I could literally pull on the rope with 1 finger and lift a
> heavy load. Here was a "worst case of wheel drag totally reversed."
>
> I have an application for block and tackles outside permanently. I'm
looking
> for sealed bearings that will resist wind blown rain. Does anyone know if
> that oil impregnated bearing bronze is available in tubes say for a 1/4"
> bolt? It would make a great outside bearing for block and tackles. k7gco
>
> List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
> Trylon Titan towers, coax, hardline and more. Also check out our self
> supporting towers up to 96 feet for under $1500!!
http://www.anwireless.com
>
> -----
> FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
>
>
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|