felt in hammers

[Delwin D Fandrich]

----- Original Message -----
From: "Richard Moody" <remoody@midstatesd.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: December 10, 2002 6:34 PM
Subject: felt in hammers


>
> ----- Original Message -----
> From: Delwin D Fandrich <pianobuilders@olynet.com>
> To: Pianotech <pianotech@ptg.org>
> Sent: Tuesday, December 10, 2002 11:18 AM
> Subject: Re: digital keyboards
>
>
>
> Heheh, but pathetic is no laughing matter.    I am sure you have
> read the American Steel and Wire transcripts of the meetings of
> the manufacturers from 1906 through 1918.   Now a lot is hype as
> when the felt man says he can feel a fleece and tell the breed,
> the age and which side of the animal it came from.  But I am
> wondering if the quality of the felt that comes to the felters,
> (those who make the sheets that are then cut up and put into
> hammer presses)  is what is needed for a piano hammer.   I have a
> hunch that breed specific wool is what is needed, and I would
> gladly submit the fleeces of Ramboulet or Ramboulet Colombian
> cross, to the felter who supplies the hammer maker. The wool of
> wethers might be even better.  The  springingness of Ramboulet
> wool should make for a very reboundable hammer.  Did you ever come
> across Pfhreimer (sp?)hammers... Weren't they used on 70's
> Wurlitizers and others?   They seemed soft but they were as loud
> as you wanted.  ---rm


Personally I'm not sure the breed of sheep the wool comes from makes all
that much difference. Once it's off the sheep a lot happens to the stuff.

I did all of my hammer making experiments using Bacon felt of various
densities and thicknesses. A good felt maker can blend wool to just about
any specification you want. And a misguided hammer maker can screw it up in
more ways than that. Some of the best sounding hammers I ever pressed were
from a piece of felt the hammer department rejected as too soft.

There are so many variables that have to be tightly controlled. Should be
anyway, I'm not sure if they always are.
    -- Felt density
    -- Thickness & taper of sheet
    -- Shape and thickness of cut strip
    -- Grain direction of cut strip
    -- Moisture content of felt at press time
    -- Heat of press
    -- Time of press cycle (length of time the felt is in the press)
    -- Shape of caul (shape of hammer crown)
    -- Pressure on wood molding (from top rams)
    -- Pressure on side cauls
    -- Type and amount of adhesive used
    -- Type of underfelt (if any)
    -- Shape of underfelt
    -- Shape of wood molding
    -- Species of wood used for molding
    -- Staple type & location (if any)
    -- Amount of post-press shaping
    -- Type of post-press shaping
    -- Press to shape vs. sand to shape
    -- Type of slicer
    -- Sharpness of slicer
And I'm sure I'm leaving out about that many more if I wanted to spend a
little time thinking about it.

I so often hear about some special felt some hammer maker is using and then
I see how they are pressing hammers -- and cringe in compassion for the poor
piece of felt that only wanted to become a nice hammer. You press felt wet
enough and hot enough and I don't care what kind of sheep you start with
you're not going to have felt when you're through. I saw a block of felt at
Bacon that was hard enough to pound nails with (Seriously! You could have
put a handle on that stuff and pounded away.) while other types of felt were
so soft you'd wrap your baby in it. If I had to put numbers on it I'd say it
was 10% felt and 90% what goes on just before and during the hammer press
cycle.

Lamenting what is done to perfectly good wool felt....

Del