Hammer Shanks

[Don Mannino]

Jim,

People do say amazing things.

I was mistaken - the Kawai shanks have eight sides, but like most they
are not really evenly octagonal.  It appears they simply start out
square and then trim the corners to give 8 surfaces.  I knew they were
not round, and thought they were hexagonal without really looking
closely.

I also don't agree with those who say that there is any one shape which
is 'better.'  The combination of shape and wood type will combine to
provide a shank flexibility which matches the hammer mass and the
acceleration profile of the action to give a particular tone.  Shanks
(and their action centers) most definitely affect the tone of the
instrument, and simply watching the high speed films shows why pretty
clearly.  The old Kimball film showed very poor control of the hammer
head on a forte blow.  The current Kawai film that I have shows perhaps
too stiff of a shank (it is of our current RX action in the bass area),
but the hammer is very well controlled.

I have demonstrated shank thinning in some of my voicing seminars, and
the tonal change has sometimes been pretty obvious (like last Saturday
in Denver), and at other times not very obvious (because the particular
shank probably didn't need to be thinned in the first place).  But the
way the shank flexes can have a very noticeable affect on the tone.

Any discussion which focuses on something being "Better" or "Worse" can
never be resolved.  Similarly no one can ever "prove" that one will be
better or worse.  But one can prove differences, then state whether they
prefer the difference and why.  Here is my take on it:

- A medium weight or light hammer with a stiff shank gives a reliable
and voicable tone.
- A heavy hammer with a flexible shank gives a poor tone that never
really sings well and doesn't give good power.
- When the hammer weight and the shank stiffness are well matched, then
the piano really gives a sensation of great power and effortless tone
production to the pianist.  Voicing becomes much easier, and getting
good projection is not as hard.

There are other complications to discussing thinned shanks.  Ideally the
shank flexibility should be tapered to match the hammer mass, from bass
to treble.  This is very difficult to do, and there is no published data
showing the optimum mass to stiffness ratio.  Kawai has this data in the
laboratory (at least as it pertains to the kind of tone Kawai wants),
but we do not publish it.  We have to work empirically, which means hit
or miss.

So my conclusion from the standpoint of the technician in the field
would be; use shanks that are stiff enough, and if you like light weight
hammers then you might experiment with shaving the stiff shanks to see
if there is an improvement to the tone.

Don Mannino RPT



> -----Original Message-----
> From: James Ellis [mailto:claviers@nxs.net] 
> Sent: Sunday, November 23, 2003 6:08 AM
> To: caut@ptg.org
> Subject: Hammer Shanks
> 
> 
> Years ago, I was told that there was a famous piano teacher 
> in New York who taught her pupils to play with the soft round 
> parts of their fingers when they wanted round tones, and the 
> ends of their fingers when they wanted bright tones.  There 
> was another not-so-famous teacher who taught her pupils to 
> wiggle the keys when they wanted to produce a vibrato.  I 
> almost lost it when I saw one of the kids doing this.  (I'm 
> talking about a piano, not a clavichord.)
> 
> There have been dozens and dozens of recent posts to this 
> list asserting that firm pinning makes for better tones 
> because it does not allow the hammer to shake and wobble when 
> it hits the strings.  That was followed by the assertion that 
> "hex" (sic) shanks produced better tones, for similar 
> reasons, because it was believed they were lighter and more 
> rigid, and did not bend as the hammers approached the strings.
> 
> I just proved that the "hex" shanks are in fact octagonal, 
> and that they are in fact not any more rigid than round ones, 
> and not any lighter.  If fact, the round shanks that are 
> tapered toward the end are just as light where it matters 
> most, and much more rigid than the octagonal shanks that are 
> not tapered.  (I'm talking about shanks that are available on 
> the market, not theoretical unavailable shanks.)
> 
> Now, the argument has suddenly shifted.  Some just make a 
> joke of the discussion.  Others say that the octagonal shanks 
> just sound better, for whatever reason.  Prove to me that 
> this is so, and I will be the first to go to work to find out 
> why - but you must first prove it to me - otherwise I will 
> consider it just one more absurd notion that took wings and flew.
> 
> Jim Ellis  
> 
> 
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