[pianotech] Wandering Capstan Screws

[David Skolnik]

DavidB -

Some concurring or additional observations:
If the screws were loose, it's unlikely that they would move 
counterclockwise, to lift the hammers from the rail.
The cloth on the rail is old (look at indentations in picture 
3).  The indentations do not look even and the cloth likely has no 
resilience left. DavidB says:
>So I regulated the screws back down, leaving the hammers on the 
>rail, without lost motion
which means it's possible, if not likely, that the distribution of 
weight between 'capstan' and rail was inconsistent, all the more so 
because of the nature of this type of  hammer rail, which would seem 
to limit, if not preclude, the technique of pulling back on the rail 
to gauge the degree of hammer-follow.  There's too much potential for 
inconsistency here to derive a grand (or upright) unifying 
theory.  BUT WAIT! THERE'S MORE!

As Wim points out, there have been a series of renovations to the 
space that could have allowed the introduction of significant 
variations in temperature and humidity, and he also makes reference 
to new carpeting being, or soon to be installed.  The piano, is 
seems, is getting moved around.  Any variation in the way an upright 
sits on the floor can cause a change in the way it flexes, affecting 
both tuning and regulation.

Wim suggests waiting until renovation work is done, which is a lot 
more reasonable than my alternative:   A new piano AND a new house.

Good luck
David Skolnik
Hastings on Hudson, NY



At 03:51 AM 12/6/2011, you wrote:
>David
>
>The first question: The round sticker w/cloth against the round 
>capstan. That is the ideal situation. The two round surfaces work 
>very well together, without creating any friction.
>The other question/concern, about the screw moving. I don't 
>understand how a screw could turn in the wood, unless it was loose 
>enough that it could be turned by you fingers. There is nothing on 
>the felt that would be able to turn it.
>
>You mentioned new carpets and new windows. Have these people been 
>doing lot of renovating in the house? New carpets give off a lot of 
>moisture. New windows mean there is a lot of moisture coming in the 
>house while they are replacing them. Any painting going on near the 
>piano? All of those things will create a lot of swings in humidity 
>and temperature.
>
>If there is a lot of renovating going on, perhaps you need to ask 
>the customer when all the work will be done. Then, when the house is 
>stable, check the hammer line again.
>
>Wim
>
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>-----Original Message-----
>From: david <david at piano.plus.com>
>To: pianotech <pianotech at ptg.org>
>Sent: Mon, Dec 5, 2011 11:23 am
>Subject: Re: [pianotech] Wandering Capstan Screws
>
>Thanks for those further thoughts, folks.
>
>I made a silly mistake, wasn't thinking (am on a course just now and it's
>quite intensive).  The piano action DOES have stickers.
>
>Thinking then about putting action cloth on the ends of the stickers, and
>replacing the screws with capstans:
>
>Might there be a concern about the two curved profiles? Would the
>relatively narrow-radius curve of the now action-cloth-clad sticker ends,
>bear OK, and be stable enough, against the radius of the capstan surface?
>
>I am still kinda feeling that the blue felt on top of the capstan screws
>can't be swelling THAT much, to cause all that lifting. Could the wood of
>the keystick be of some particularly "soapy" variety, that shoves the
>screw threads around, with cyclical changes in humidity?
>
>With regard to humidity changes, I have wondered for a while if there is
>some cyclical change going on in that room even thought it doeosn't feel
>damp.  The answer, I think, is yes.  The room, a study/spare bedroom is
>just across a corridor from the kitchen, and very near the back door. It
>is quite possible that there could regularly be brief bursts of
>moisture-laden air, which then gets cleared in some way, but in the
>meantime has condensed inside the piano.
>
>An additional factor at the moment is recent replacement of the windows,
>which meant the room was cold and damp for a day or two.
>
>But its still an intriguing question as to whether the screws move.
>
>I will be returning soon to tune the piano (my recent visit was just to
>check out a problem following the window replacement - the half-blow pedal
>rod had become dislodged) and I suggested leaving the tuning until the new
>carpet was laid and the piano placed where it's to go in the room.
>
>I will check out the undersides of the blue felt and see how
>dimpled/ridged they are.  If I don't replace the screws with capstans,
>then I will mark them and the keystick, and see if there is any movemment.
>
>It occurs to me also to suggest a Dampp Chaser, so that if there is a
>sudden surge of moisture-laden air into the room from the kitchen, it
>can't condense in the piano.
>
>Best regards,
>
>David
><http://www.davidboyce.co.uk/>www.davidboyce.co.uk
>

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