hammers: what kind of felt?

[Roger Jolly]

Hi Ron, 
       A quick question and maybe the it will stimulate some thought. How
often have you hardened hammers down pass the killer octave vs just
hardening the top 2 doz or so notes? In fact I have a hard time remembering
when I last juiced the bass on a piano. But I have fequently voiced down a
bass section, done little or nothing in the centre, and juiced the treble.
Just a thought. Roger 





At 08:36 AM 01/09/98 -0400, you wrote:
>
>
>On Mon, 31 Aug 1998, ari isaac wrote:
>
>[snipped "yada-yada"]
>
>> A sheet of hammer felt of graduated density - not merely graduated
>> durometer reading - is a good deal more expensive to have made.  You can
>> see why hammer felt of uniform density throughout the scale tends to be
>> the norm.  Graduated density means, among other things, that the wool
>> fibers have to decrease in diameter towards the treble end. This nice
>> feature of the felt sheet ensures not only a far more musical piano tone
>> but a huge increase in the voicing stability of the hammers.
>
>[playing Devil's Advocate]
>
>Actually, doesn't uniform density, top to bottom, give the technician a
>better shot at making changes in the density (using softeners and/or 
>hardeners as necessary)?  Graduated density might be equated with the
>proverbial moving target, right?  How much gradation might one expect from
>top to bottom?  Is it, indeed, gradual? I suspect that hammer felt that's
>supposedly uniform is actually not as uniform as one might wish. Makes
>things all the more interesting if there's an intentional graduation 
>factor added to the mix!
>
>Something else...how does the manufacturer determine which wool fibers are
>of which diameter?  Weighing each fiber? Weighing a pile of felt and
>figuring an average somehow? I'm amused by the thought that someone
>actually employs a worker who, using a magnifying glass, sorts felt
>fibers.  "Let's see....this one's a .00035, this one's a .00020....HEY!
>Someone's messing with my sorted piles again!!" :-)
>
>Note: This was cross-posted to the CAUT list. Not being subscribed to the
>PIANOTECH list, I don't know where the discussion is/was going on the
>topic. Good reason to avoid cross-posting.
>
>Ron Torrella, RPT
>Piano Technician
>University of Michigan
>School of Music
>
>
Roger Jolly
Baldwin Yamaha Piano Centre
Saskatoon and Regina
Saskatchewan, Canada.
306-665-0213
Fax 652-0505