Hammer weight/density

[Tom Servinsky]

Del,
Seems to me I read about the use of a "resolometer" ( I think that was the
spelling) which even though rather primitive, measured the resiliency of
hammers.  It was a crude vice which could measure the hammer at rest, then
under pressure, then back at rest. The end result was the amt. the hammer
did not return back to the original size would be the resiliency
rating..i.e. 80%,90% etc.
Seems to me this was printed in great book entitled "The American String and
Wire Conference of 1913), which was basically the minutes of this conference
with the likes of Chickering and other great  mines of the day.
Is this the type of gadget you were thinking of?
Tom Servinsky,RPT
----- Original Message -----
From: "Delwin D Fandrich" <pianobuilders@olynet.com>
To: <pianotech@ptg.org>
Sent: Tuesday, October 16, 2001 1:30 AM
Subject: Re: Hammer weight/density


>
> ----- Original Message -----
> From: "Joseph Garrett" <joegarrett@earthlink.net>
> To: <pianotech@ptg.org>
> Sent: October 15, 2001 7:10 PM
> Subject: Hammer weight/density
>
>
> > Del,
> > You stated that the pound designations really are meaningless and I
agree.
> > Is there a meaningful way of measuring the density? I have seen "Density
> > Meters", (my description), designed for measuring the density of metal.
> Are
> > these a viable means of measuring something as soft as felt? Inquiring
> minds
> > want to know.
> > Best Regards,
> > Joe Garrett, (Oregon)
> > -------------------------------------------------
>
> None that I am aware of. Baldwin (and probably others) used a durometer to
> test the felt sheets before cutting and pressing hammer sets, but this was
> not really very useful. It measured the hardness of the surface of the
sheet
> of felt as it came from the felt maker, but this told us very little about
> how finished hammers made from this felt would perform--there are just too
> many variables in the hammermaking process.
>
> I'm not really all that interested in just a hammer's weight or density
all
> by itself. What I would really like to see is a method of rating a
hammer's
> resilience--that is, it's ability to deform on striking something like a
> piano string and then to recover from that deformity. This, combined with
a
> general ranking of the actual weight of the finished set of hammers, would
> at least get us in the ballpark of being able to predict their
performance.
>
> The actual rating system wouldn't have to be elaborate; perhaps just a
mass
> rating of light, medium and heavy coupled with a resilience rating of low,
> medium and high. That would give us nine choices and the ability to match
> hammers to just about any piano made. Getting there could be some
difficult,
> however.
>
> To be meaningful a rating system will have to consider the rate of energy
> transfer over time as measured by some standardized test blow against some
> standardized energy absorber. Coming up with an appropriate test mechanism
> is not going to be easy. And then, once the test mechanism is developed,
how
> are we going to use it? Are we going to check just one hammer out of a
set?
> Or several? Do we check each set? Or do we trust the manufacturer to test
> samples and label them accordingly? As you can see, this could quickly get
> complex and expensive. Some years ago I worked on this problem just enough
> to learn that it was going to take a lot more time and effort that I could
> devote to it at the time.
>
> The problem will be coming up with that resilience ranking--bearing in
mind
> that soft and resilient are not the same thing. Consider that dropped
> against a hard surface from some given height both a golf ball and a
'super
> ball' will bounce quite well but one is very hard and the other is rather
> soft. And I don't even want to think about 'silly putty.' Marshmallows are
> soft but they don't regain their shape after being deformed. Foam rubber
is
> also soft but bounces back quite well after being deformed.
>
> As may be, one way might be to clamp a test hammer in a fixture with the
> hammer's tail resting against a solid and massive surface. A striker of
> known shape, mass and velocity could be dropped against the strike point
of
> the hammer and its rebound characteristic measured. I'm not sure if the
> result would tell us enough about the performance potential of the hammer,
> but this would be a fairly easy place to start.
>
> Another way might be a mechanism which would easily and quickly clamp a
test
> hammer and then accelerate it to some standardized velocity. The hammer
> would impact against a standardized length of string set at a standardized
> pitch. An accelerometer would measure the impact and, using the signal
> generated by the accelerometer, we could come up with some way to rate the
> hammer's performance.
>
> As I said, it might not be easy.
>
> Del
>
>
>
>