Tension & compression-- Not lacquer fight

[Erwinspiano@aol.com]

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     To all Hammer Heads
    In the previous thread I was trying to convey the way I see that a hammer 
is made & if you followed that then you see that I have a definition of 
tensioned felt in mind. However what I failed to articulate clearly is that Tension 
& compression go hand in hand in the hammer pressing process.
   As I stated, & piano hammer makers can tell you, that too much tension can 
be achieved during pressing in the outer layers of felt and it can & will rip 
open in the crown. This is the elastic limit of the felt. As the stretching 
of the felt on the outer perimeter happens the inner parts of the felt are 
compressing. It has too because of the stretching of the outer felt, the 
triangular shape the felt strip is cut & the hammer press pressure itself. 
    To prove this to yourself take any kind of tenor or bass hammer & cut 
thru the molding with a band saw small hand back saw  up to the tip at the 
underfelt. Now that the molding is separated if it actually has tension the 2 halves 
of the molding will move away from each other as the tension is released & 
the middle compressed part will unload. Squeeze it back & forth & back & forth & 
you can visually see tension & compression phenomena happening at the same 
time
  Unless heat & pressure keep the felt from approaching its elastic limit 
only so much density/compression can be achieved in the middle of the hammer by 
strictly tension, which can be considerable but not for the kind of hammers 
some prefer. I believe this is one reason why we've had so many bad sets of over 
hard hammers in the past. Manufacturers have simply used heat or steam to 
densify felt & render it's natural properties less or unusable. Hence steam 
voicing, excess needling, voice grips.
  We all want hammers that work the way intended & it seems that in many 
places its getting wwwaaayy closer. That's the way I see it
    WIllis, nice to hear your out there.
  Regards
   Dale Erwin


Erwins Pianos Restorations 
4721 Parker Rd.
Modesto, Ca 95357
209-577-8397
Rebuilt Steinway , Mason &Hamlin Sales
www.Erwinspiano.com

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