Hammers (long)

[Delwin D Fandrich]

Stephen Birkett wrote:

> Some interesting comments on hammers from John and Del.
>
> "Resilience" or compliance is a tricky one to describe, but even harder to
> measure effectively. There are the complications of the compliance
> relationship changing dynamically (Del's hardening spring is a good
> analogy)...this is the cause of the fundamental principle of the "piano
> sound." Microscopically it is related to the ease with which the layers of
> fiber can slide over each other as they are compressed...obviously easier
> at first, then progressively harder. Initial density distribution is
> important, as is the initial distribution of felt layers according to high
> or low pressure, heat or cold etc....as observed by Del. Doping alters
> this sliding relationship and hence the compliance curve. Internal
> friction is another consideration that is observed in hysteresis effects,
> whereby different curves are followed according to relaxation and
> compression...bad doping can make the hysteresis gap too large, causing
> undesirable effects. Last has not been hinted at this time...what I would
> term resilience failure, the gradual decline in resilience or
> flattening of compliance curves as the hammer is subjected to repeated
> cycles of compression and relaxation (= regular playing). Manufacturing
> technique will probably have a big influence on this lifetime aspect of
> the hammer...I think a place where doped hammers have the edge.
>
> Stephen
>
> Stephen Birkett Fortepianos
> Authentic Reproductions of 18th and 19th Century Pianos
> 464 Winchester Drive
> Waterloo, Ontario
> Canada N2T 1K5
> tel: 519-885-2228
> email: birketts@wright.aps.uoguelph.ca

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In actual life tests, hammers that had been hardened with both lacquer and with the truly gruesome mixture of keytop scraps &
acetone wore faster than did unhardened hammers. We attributed this effect to the harder hammers inablility to flex under
impact, but that is not a conclusion I'd want to have to defend with any vigor.

Del