THUD

[Horace Greeley]

Hi, Hans,

At 10:27 AM 12/8/2000 -0500, you wrote:

>They are nearly identical twins for the good and bad, respectively 23 and 
>24 years old.

Indeed, mid-70s boxes...

>They are played year around by our faculty, students and major world class 
>artists. This year's performers Igor Pogorelich, Russell Sherman, 
>Valentina Lisitsa, Ignat Solzhenitsyn, Lee Luvisi.

I've not worked with Luvisi, but the others a certainly fun.  Pogorelich is 
probably the best in the business when he's on.  I have always enjoyed 
working with Russell Sherman very much; an elegant and underrated 
performer, his Beethoven cycle is well worth hearing.

>Both pianos each have 4 adjustable key frame screws to support the frame 
>from knocking on the keybed. They are both close to each cheek blocks, 
>adjustable screws (like reversed keyframe glide buttons) from below the 
>keybed. There are no keyframe guides left or right in the cheek blocks 
>holding the action down and therefore forcing the center section upwards. 
>I need this feature, because of our environment with sudden humidity 
>changes in our school, where the keyframe or keybed seems to change within 
>hours. The idea with the maybe sagging keybed in the middle came to me 
>just lately through all the THUDS e-mails. It said, that it appears to be 
>dominant just with the loud playing. It makes sense, because of the extra 
>force pressing down. No knock or THUD by tapping  gently for a knocking 
>key frame, but holla in the ff or more, you here it in the audience.

A couple of things:

First - and I do not know why this did not strike me before - living where 
you (and the pianos) do, the environment is most charitably described as 
unstable.  So, given the construction of the S&S rim and frame, chances 
are, that as the humidity goes up, the keybeds expand with the grain, and, 
running into the tension of the rim (and the rest of the superstructure) 
are forced down for some reason, instead of up, by the expansion...instant 
gap.

How about the following:  Reduce the moisture content in the instrument to 
around 4 - 6%.  Sand/polish/steel wool the keybed (like, really, really 
smooth).  Carefully bed everything.  Then, taking at least one new can of 
McLube, liberally apply multiple coats, drenching everything in sight.  (A 
couple of coats on the underside of the keybed is in order, too.)  Steel 
wool the keybed in between coats, picking up residue with tack 
cloth.  About one can of McLube ought to do the trick.  Do essentially the 
same thing with the keyframe, using a second can of McLube.  (Yes, a pain.)

Second - Were the front rail glides a factory job?  (Just wondering) - 
Actually, have you considered installing the cheek block system used by 
Yamaha?  It is a relatively painless installation: The cheekblocks need 
some machining, and then the new units can be fit.  The beauty of this 
system is that you can access the tensioning screws from the top (if you 
are careful) and not have to remove the blocks to get to them.  Instant 
moisture compensation...and, much less finicky than the pseudo-Baldwin 
system you seem to have.

(Actually, Sohmer and Haines had the solution about 100 years ago in using 
steel framing and supports for the keyframe...)

I still do think that John's problem may well lie in some pretty flaky 
forefinishing, but there may be something useful for him here, too.

Best.

Horace