To be or not to be: a heavy hammer

[Richard Brekne]

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David Love wrote:

> The question was put to me off list about why I reject the
> idea that heavier hammers are necessary on a concert
> instrument.  I thought I would put my reply on list
> because I think it is an interesting discussion. The
> practice of putting heavier hammers on a concert
> instrument comes from the idea that more mass will produce
> greater force and therefore greater volume of tone.  But
> mass is only part of the equation.  Force = mass x
> acceleration.  While it is true that if hammers of varying
> weights are accelerated equally, the one with more mass
> will have more force, it is also true that a hammer of
> lower mass will be accelerated to a higher velocity more
> easily.  This is especially true in a piano where lower
> mass in the hammer results in lower inertia at the hammer
> end as well as in the key.  Whether you have more mass and
> less acceleration or more acceleration and less mass, as
> long as the mass of the lighter hammer is not so much less
> that its deficiency cannot be compensated for by increased
> acceleration, the potential force in the two examples can
> be equal.

This is the heart of Ed McMorrows thinking. He would also
add that friction is quite reduced with lower hammer
weights, though he does not formally work this into his
equation.  However, while F=m*a is quite simple in itself
and has led Ed and others to believe that the mass reduction
of a lighter hammer can be sufficiently compensated for by
increased acceleration, many years experience with this
approach has not born that claim out. One need do no more
complicated experiment then to take a hammer from key 88 and
lead it to the same weight as key 1 and exchange the two to
begin confirming that things are not so simple. Voice all
you want, or use different hammers all you want, and there
is still a difference in sound. Perhaps its as simple as
saying velocity simply does not compensate for mass in the
sense we seem to assume here.


> Because pianos are played from pppp to ffff, the only area
> of concern is in the potential force at the highest end.
> You don't benefit from a more massive hammer at the pppp
> level.  In fact, since there is a point below which soft
> playing cannot be reliably controlled, a lighter hammer
> will give greater dynamic range at the bottom end.  So the
> only concern is at the top end.  Assuming that the
> difference in hammer weight can be compensated for by
> greater acceleration, the heavier hammer will actually
> have a narrower dynamic range.

Thats an interesting claim, tho I dont see it qualified in
any sense. And I have heard the opposite being stated,
equally unqualified I might add. I wonder if you might try
and justify all this a bit in terms of the mechanics
involved. Just why do you think a more massive hammer
effects no change (or a negative one perhaps) at pppp ? And
how can you show that a light hammer can be more reliably
controlled ?

very curioius.

> As I already mentioned,  a lighter hammer will reap
> benefits in terms of lower inertia both due to lower
> hammer weight and lower front weight of the keys.  Lighter
> hammers will rebound off the strings more quickly
> increasing sustain and improving clarity.  Lighter hammers
> will also allow you to maintain an action ratio that
> doesn't require compromises of key dip, blow or both.
> One final concern with very heavy hammers is the
> deflection of the shank at high level of acceleration.
> Though I haven't looked into the research in any great
> detail, I know that Renner has given this a lot of
> consideration in the design of their shanks.  If, in
> trying to accelerate a very heavy hammer to high levels,
> the shank deflects to the point that the hammer is
> striking fairly far from top dead center, how much force
> and tonal quality are we losing because of this and,
> therefore, is there any real benefit to trying to increase
> the upper range limit anyway.

I dont think it has been shown that hammer rebound from the
string is mostly a function of its mass. Rather I think it
has been shown that the hammers resiliancy has the most
determinant function in this regard. Neither do I understand
that a lighter hammer allows any particular greater freedom
in terms of key dip, or blow. These parameters vary quite
enough as a matter of course already. We see everything from
a little over 9 mm dip to circa 11 mm dip coming out of
factories, and from as little as 42 mm blow to as much as
50. There is in fact no standard by which to define what a
"compromise of keydip, blow or both" is.

Lowering the ratio will make it lighter at the key, and yet
it will it will travel less distance with equal key
movement, and thus more slowly at equal key speed. But
because it seems lighter at the key..... the finger playing
will have a tendancy to compensate in order to achieve
similiar degrees of sound volume.

And its the pianists fingers this is in the end all about.
It might be instructive to simply change the ratio and
compensate the action regulation with a change in blow. This
would keep key dip and hammer mass constant in an attempt to
better identify the effect of a change in ratio on the
perception of touch.

>  Those are my thoughts.  Feel free to comment.David Love

 me too :)

--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html


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