[pianotech] Wandering Capstan Screws

[david at piano.plus.com]

Thanks for those suggestions, Joe and Wim.

Joe, I know the system is archaic - I tune lots of archaic pianos! All in
this area, in the same climate, lots of them have this system, and this is
the only one that moves in this manner.

Wim, the suggestion about the cloth is very interesting.  Could it really
get THAT much thicker and thinner  Maybe.

It occurs to me that I could test whether the screws move, by marking a
dot on the screw head aligned with one on the keystick. If the dots get
out of alignment, then the screws are moving.

Most of the other pianos I tune with this sytem, have action cloth over
the screws. I wonder if that is less susceptible to swelling. The cloth in
this piano seems to be some kind of felt material.

If the problem is all with the felt, and the screws are not moving, then
it would not be necessary, would it, to replace the screws; just remove
the cloth and glue action cloth to the wippen heels/feet (no stickers).
(though there may be an issue with the flat heads of the screws as opposed
to the gently domed heads of new capstan screws).

It is certainly possible that in this particular room there is some kind
of  cyclical change in humidity taking place. But the room never feels
damp.

Thanks for these thought-provoking suggestions folks, you are making me
think it through!

Best regards,

David
www.davidboyce.co.uk



>David,
>This system is archaic. And, was long since abandoned for good reason.
>There are too many different expansion ratios involved. My solution would
>be to install standard capstan screws and put action cloth on the stickers
>bottoms. Once, settled, I suspect the problem will go away. Also, I'd take
>a long, hard look at the temperature/humidity situation in the piano's
>area. (Leave a recording Temperatur/Humidity gauge inside the piano for 6
>months.) I suspect a combination of bad things, all working together to
>make your life miserable.<G>
>Regards,
>Joe

>David

>The problem is not the screw but the cloth on top of the screw. As thick
>as it is, and without it being glued to a surface, every time the
humidty >changes, the thickness of the cloth changes.

>I would cut the cloth off the key, and glue a small piece on the bottom
>of the sticker. Then replace the screws with standard capstan screws.

>Wim