Grand Rolers "knuckles"

[Don Mannino]

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Hello!

While I was working for another company, they did very extensive,
thorough testing of noise and durability of grand knuckles. This was in
response to complaints of action noise and overly hard knuckles.  I was
not involved in the testing process, but was shown the results.

The conclusion they came to was that the hard core felt was required for
the knuckle to hold its shape. To keep the noise down, the skin has to
be soft, fairly thick (1mm) and not stretched too tight or heated too
much during installation.

Sometimes noisy knuckles can be made quieter by stretching the skin a
little (a fine screwdriver between the skin and the core works), and
freeing it up from the core. This will probably be temporary, though,
unless the skin is thick and spongy.

The artificial skins used in some oriental pianos are very durable and
quiet. Real doe skin that is thick and soft enough is rather expensive,
but is still available, and it also works extremely well and does not
squeak as readily as the artificial skin.

In the tests, the quietest knuckles were those with artificial skin on
soft core - but these self destructed in reliability tests.  1,000,000
hard keystrokes is a very telling test! The best knuckles hardly showed
any wear, while the worst (made by very reputable makers) became badly
flattened and misshapen.

Don Mannino RPT


> -----Original Message-----
> From:	Barrie Heaton [SMTP:Piano@forte.airtime.co.uk]
> Sent:	Friday, May 22, 1998 7:38 AM
> To:	pianotech@ptg.org
> Subject:	Grand Rolers "knuckles"
> 
> Dear All,
> 
> I have just installed a new set of Japanese rollers, these rollers
> were
> so hard when installed, it sounded like I had left a screwdriver on
> the
> keys in the top treble. This was just prominent in the last octave or
> so
> I believe it was due to the light hammers at this end if I swapped a
> hammer from the middle to the top treble no noise, if I moved one of
> the
> top hammers in to the middle section noise.  
> 
> I had to needle the under felt to soften them up this cured the
> problem.
> I inspected some new Yamaha, Renner  and HerbugerBrooks rollers.
> these
> rollers varied in firmness.   I have noticed that rollers seem to be
> getting harder these days.
> 
> Have any of you come across this problem before.  Also, has anyone
> done
> any tests on softness or hardness of new rollers.
> 
> Barrie.
> 
> 
> 
> 
> 
> --
> 
> Barrie Heaton                                  |  Be Environmentally
> Friendly
> URL: http://www.airtime.co.uk/forte/piano.htm  |  To Your Neighbour
> The UK PIano Page                              |  
> pgp  key on request                            |  HAVE YOUR PIANO
> TUNED

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