[pianotech] Wandering Capstan Screws

[David Skolnik]

If humidity is the culprit, why don't they all respond the same way? 
Just wondering.
David Skolnik
Hastings on Hudson, NY

At 03:52 PM 12/4/2011, you wrote:
>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