YES! you got it, Chris.
There's a 100 lb vector due to the load, and another due to
the lift. With ginpoles we know, it doesn't matter how many
ropes and wheels you put in the system---there's still 200 lbs
load on the ginpole, and on the pulley axles connected to it.
The more wheels, the more friction gets added to the system...
but generally, the less the line-load is.
At the end of it, though, there's still 200 lbs imposed on the
ginpole & its pulley axle.
But wait...what Mike IS true, although not with ginpoles I know.
If you had a 2 block pulley at the top of the ginpole, and a 2 block
pulled attached to the load, and you pulled from the load side...you
would divide down the load on the pole.
If you were pulling from the pole side, you'd still have the 100 lb
LIFT component of the load there. But pulling from the LOAD..the
tower section....looks like it would work, with a 3:1 reduction ratio.
Maybe there's a 4:1 to be had, pulling from the top. But where you
tie off matters.
Shoot, guys, I'm cooking dinner, here. The reason I went into marketing
is that I really DO have to draw this stuff to see the details. Somebody
want to check on this?
My point was: GET THE TOP OFF. THINK ABOUT THE LOAD. YOU CAN'T
MUSCLE IT, SAFELY, IF AT ALL. I'm not backing off that position.
I haven't seen a ginpole that reduces the load, so this is an academic
discussion. ((and yes, this was the part of engineering physics I
And I STILL ask....what is the spec on the ginpole tube? It's
bearing the load.
From: Chris BONDE [mailto:email@example.com]
Sent: Thursday, July 11, 2002 6:20 PM
Subject: Re: [Towertalk] mast disaster avoidance
It has been awhile since I have done any mechanical stuff with pulleys. I
think that you are on the right road but not all the way.
If you are lifting a 100lb weight with one pulley at the top, you need 100+
lbs on the other side to lift it. I would then say that there is 200+lbs
of weight on the pulley.
If you are lifting a 100lb weight with 2 pulleys at the top and one on the
load, then you have a mechanical advantage and need only 1/3 of 100+ lbs to
lift the weight (I think that that is correct, but it is a lot
less) Therefore, the total weight on the pulley is 100lbs plus the reduced
amount hence less.
I think that this is correct.
Chris opr VE7HCB
At 02:00 PM 2002-07-11 -0400, jljarvis wrote:
>If you had a ginpole with a 2 wheel block on top (never seen
>one, myself. Do they exist?), you would reduce the load on each
>run of line, proportional to the number of lines.
>But the load on the axle is still the sum of the line-loads.
>The compressive load on the ginpole itself is thus still the
>same, and the out-of-column bending loads are the same.
>From: "Mike Gilmer"<firstname.lastname@example.org>
>Date: Thu, 11 Jul 2002 12:16:03 -0300
>Subject: [Towertalk] Re: mast disaster avoidance
>I agree with most of N2EA's post except:
> > Solutions using added pulleys still leave the same load on
> > the ginpole material itself
>This is not true. As has been oft-discussed on this reflector in the
>past (and still misunderstood), judicious use of "added pulleys" can
>reduce the total load on the ginpole.
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