[TowerTalk] Rope

[Paul Beckmann]

Great response, Mickey. Thank you!

Pulley and little me knowledge in sailing is a solid reference, for sure!

73

Paul, wa0rse

On Wed, Mar 10, 2021 at 7:00 PM Mickey Baker <fishflorida at gmail.com> wrote:

> The strain is in the direction of the sheave. Typically, a shackle is used
> at the top of the pulley, away from the sheave. All surfaces exposed to the
> line are smooth, so even a "floating" line under sudden slack won't be
> pinched.
>
> In the referenced block, the faces of the sheave are completely covered by
> the frame. The space between the sheave and the frame is many times smaller
> than the cordage for which it is built. Without a cordage failure (where
> all bets are off anyway) there is no place to capture and crimp the cord.
>
> This block is rated at about 200 pounds working load, so, given that it is
> a quality product, the user can expect no deformation under normal antenna
> loads for 1/4" lines.
>
> The design should keep tension on the cord. This is why most wire antenna
> hoist systems are weighted.
>
> The typical hardware store pulley may deform under load, has a lot of space
> between the pulley wheel and the frame (slop) and can capture a small line.
>
> Mickey Baker, N4MB
> Palm Beach Gardens, FL
> *“The servant-leader is servant first… It begins with the natural feeling
> that one wants to serve, to serve first. Then conscious choice brings one
> to aspire to lead." Robert K. Greenleaf*
>
>
> On Wed, Mar 10, 2021 at 4:58 PM Richard (Rick) Karlquist <
> richard at karlquist.com> wrote:
>
> > I fail to understand why these would be more jam resistant due
> > to the mere fact that "the pulley rim is even with the frame of
> > the block."  That is only true for part of the pulley rim.  The
> > top quarter or so of the rim (near the "R" in Harken) is exposed
> > to a tall frame similar to conventional pulleys.  You could also
> > have the rope come off the lower part of the pulley and wrap
> > around the frame, which cannot happen with conventional blocks.
> >
> > I don't claim to know anything about pulleys; just trying to
> > understand what you are saying.
> >
> > 73
> > Rick N6RK
> >
> > On 3/10/2021 9:23 AM, Mickey Baker wrote:
> > > If you look at the 22mm Harken block, you'll see an example of a design
> > > that is difficult to jam - the pully rim is even with the frame of the
> > > block. Agreed that they're relatively expensive at $10 or so each, but
> I
> > > have never had a pulley jam. These are designed for sailing where a jam
> > > could be a true disaster.
> >
> > > Mickey Baker, N4MB
> >
> >
> >
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