Function of the rim

[John Ross]

Hi List,
Not one of the answers, but by angling the pin, we cut down the chances of
the wire overlying itself. If it crosses over itself, we have a weak point
that is prone to breakage. I have seen this in a lot of apartment size
pianos.
The wore in a lot of cases is distorted so that even disengaging the coil,
and trying to raise the pin height, still results in string breakage.
I tend to curse the designers, or workmen that installed the pins in too
verticle a position. They didn't realize the problems for the future, they
were causing.
Regards,
John M. Ross
Windsor, Nova Scotia, Canada
jrpiano@win.eastlink.ca
----- Original Message ----- 
From: "Cy Shuster" <charter1400@charter.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Monday, September 01, 2003 6:45 PM
Subject: Re: Function of the rim


> I don't know, and I don't understand the rationale.  My understanding is
> that the typical angle is 3 degrees back, away from the hitch pin.
>
> If a tuning pin were a foot long, and only had the bottom 2" in the
pinblock
> (and the string was attached at the top of the pin, way up in the air), I
> can see where a truly vertical pin would perhaps lever the pinblock
> backwards towards the keys (at least, the bottom layers of the pinblock).
>
> My best guess (having never driven a pin, just measuring my piano) is that
a
> pin is about 2" long, and is in the block about an inch.  The strings on
> mine are about 1/4" above the (bushed) plate.  So, let's see, the part of
> the pin above the string doesn't really count, so we have a lever 1/4"
long
> (the part in the air that can move sideways...easily, anyway...), with the
> fulcrum being the top of the pinblock (way oversimplified: I'm sticking my
> neck out here with this expert crowd, so be gentle!).
>
> Angling the pin back 3 degrees means there's now some forward (towards the
> hitchpin) component to the force vector, as applied to the top of the
block.
> If it were 90 degrees back, it would be 100% horizontal resistance, so
this
> gives it 3/90ths more horizontal resistance.
>
> Assuming the pin doesn't flex that much, I guess there's not as much
> difference in resistance to the string tension, as there is a difference
in
> how the part of the pin in the block puts pressure on the block.  Does
this
> analysis make sense?
>
> And by "plate flange angle", I assume they mean the "v" in the plate that
> opens towards the hitch pins, that the block mates to?
>
> --Cy Shuster--
> Rochester, MN
>
> ----- Original Message ----- 
> From: "Avery Todd" <avery@ev1.net>
> To: "Pianotech" <pianotech@ptg.org>
> Sent: Monday, September 01, 2003 3:58 PM
> Subject: Re: Function of the rim
>
>
> > Cy,
> >
> > And your answer is????????? Mine would be 'B'. Of course, that's
probably
> > wrong. :-)
> >
> > Avery
> >
> > At 01:43 PM 09/01/03 -0500, you wrote:
> > >Charles raises a good point: it specifically mentions the outer, not
> inner,
> > >rim.  Do they function differently?  The outer rim contacts the lid
while
> > >the inner rim doesn't...  And, David, certainly it has an acoustic
> function,
> > >but certainly not by resonating...
> > >
> > >Here's another head-scratcher.  I didn't find any other clinkers.
> > >
> > >75) The tuning pin hole is drilled at a slight angle to the pinblock
> > >primarily in order to
> > >
> > >                 A. create an orderly row of pins
> > >
> > >                 B. resist the pull of the string under tension
> > >
> > >                 C. create a better lock of the pinblock to plate
flange
> > >angle
> > >
> > >                 D. satisfy tradition
> > >
> > >
> > >
> > >In their answer key, the right answer
> >
>
>is.........................................................................
> .
> > >............................................................. C
> > >
> > >
> > >
> > >--Cy Shuster--
> > >
> > >Rochester, MN
> > >
> > >
> > >----- Original Message -----
> > >From: "David M. Porritt" <dm.porritt@verizon.net>
> > >To: <pianotech@ptg.org>
> > >Sent: Monday, September 01, 2003 12:16 PM
> > >Subject: Re: Function of the rim
> > >
> > >
> > > > Cy:
> > > >
> > > > If the written test is supposed to be given to see if someone is
> > > > qualified to take the other tests, that's not an appropriate
question
> > > > in my mind.  There are too many "correct" answers there.  I
> > > > personally think it has a cosmetic function, it does add mass to the
> > > > rim to provide an acoustic function, it obviously does give a place
> > > > for the top to rest.  Provide a support for soundboard crown seems
to
> > > > be the most incorrect of all the answers to me.
> > > >
> > > > Are there any other obvious clinkers in that test?
> > > >
> > >
> > >
> > >_______________________________________________
> > >pianotech list info: https://www.moypiano.com/resources/#archives
> >
> >
> > _______________________________________________
> > pianotech list info: https://www.moypiano.com/resources/#archives
> >
>
>
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