[pianotech] Regulation mystery

[Tony Caught]

Hi David,

 

I have worked in both Darwin and Alice Springs for over 20 years, Darwin
humidity varies from 90% to 18% Alice springs Humidity from (at present) 75%
to 5%. These readings are for outside so you have to take into consideration
the variations in the buildings that house the pianos. Experience has taught
me to regulate according to the present climatic conditions in these two
places, thus when the air is dry leave the capstains with a big wink (about
1/3 to ½ mil loose) and when the humidity is high, the capstains should be
tight. Clearance only for the jack to return on a slow lift of the key.

Your capstain has about 6mm lift and the hammer goes forward about 48mm.
Moisture in the cross grain of the timber and moisture in the back touch
felt will cause the capstain to vary in hight by about  ½ mm.

 

Another reason for Dampp-Chasers in pianos.

 

Regards

 

Tony Caught

acaught at internode.on.net

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of David Lawson
Sent: Sunday, 24 October 2010 6:33 PM
To: pianotech at ptg.org
Subject: [pianotech] Regulation mystery

 

I regularly service about twenty pianos at a Conservatorium, both uprights
and grands. The uprights are mostly Yamaha U1 models about 15 to twenty
years old, with a couple of Kawai KS models also. I regulate the lost motion
on these instruments so that the capstan holds the wippen so there is no
lost motion, however, it is not holding the hammer off the rest. I have just
finished the regular maintenance of these this week, and discovered that all
but one had increased the height of the capstans to hold the hammers off the
hammerest by about 1/4 inch or 6cm. My first reaction was that someone had
been at them, turning up the capstan. However, this is not possible as I am
the only tech. who attends to these pianos.

So, my question is this: Would the sudden change from drought,(about ten
years) to very wet conditions, have brought on this amazing change? I find
it difficult to believe that this much change could be brought about by
humidity. Let's face it, the metal pin holding the capstan is tight into the
rear of the key, which would surely not increase the height by this much
with humidity! I checked the back touch on the key-frame, and it seems quite
normal.The only piano that did not have this happen to it, had an additional
heater in that room, which may give us a clue.

Your thoughts please.

David Lawson Wangaratta Australia

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