When to do it

[Tony Caught]

Hi Clyde

You are talking about my nightmare.  Decreases with humidity, increases with
the lack of.

Not being scientific by nature or having substantiated proof with
measurements, hydroscopic readings and all that jazz, I can only give you my
thoughts and observations.

During the humid periods in the tropics the moisture gets everywhere. Not
only does it cause the wood to swell it also causes felt to swell even
further.  Hammer felts pop of the woods, dampers swell etc.

But what you asked is this,

The backtouch felt swells thus decreasing the lost motion, the hammer butt
felt and leather both swell further decreasing  lost motion, the keys also
swell, the accumulation of this swelling can and does cause a change in
motion equivalent up to 4mm in hammer / string travel.

Yes, I have been caught on the same problem on many occasion.  The main
problem is that I think that we are trying too hard to make the piano feel
just right and our pride won't let us take the humidity factor into
consideration as when we regulate, we want the piano right at that time, not
three, six months later.

In a non controlled environment in Darwin (where the humidity varies from
30% to 95%, the variation is 4mm in hammer travel.  If I fine regulate the
key capstains in the dry (35% to 40%) to just a 'wink' in a Yamaha U1 (the
most stable) the variation is about 2mm in hammer travel in the wet (75% to
95%) (The hammers are proud of the hammer rest by 1.5mm.)  In an European or
other piano the variation will be up to 4mm.

The reason for the difference between the pianos are, I believe, the type of
felt used in the back touch. Yamaha backtouch felt in not wool.  Thus I
guess that I have to say that the non wool felts do not swell with humidity
as much (if at all) as does the woollen backtouch felt.

The smaller variation in the Yamaha's variation to me means that swelling is
still a factor in the key, wippen / capstain felt & hammer butt felt and
leather.

But Clyde, you are not going to know which piano is going to do what or by
how much. Sometimes it just has to take two goes to get an acceptable
standard, or, when the humidity is low, leave it loose. If the humidity is
high, make it tight.  But also remember, in an upright, it takes about 3
weeks for the humidity to have the effects.

The reverse of course is also true.  I completely regulated a piano in the
wet in Darwin to  total specs., the customer took the piano to Alice Springs
(humidity drops to 10%) and not only was every screw loose, hammers
chattering on the strings, there was 2mm of lost motion to take up on the
capstain to wippen.

Enough ?

Regards

Tony Caught ICPTG
Australia
caute@optusnet.com.au
Clyde Hollinger  Wrote,


> Friends,
>
> What happens to lost motion, particularly in spinets and consoles, when
> the humidity changes?  When does it increase or decrease, and why?  I
> should know by now, but I don't, and I did run into trouble once by
> doing it at the wrong time.  Since things seem pretty quiet on the list
> at the moment I thought this might be a good time to ask.  (Don't talk
> to me about humidity control; I already know.)
>
> Regards,
> Clyde
>
>