Scruffing -was - Over-Strike vs Under-Strike

[Frank Emerson]

Ed

OK, you point out an extreme condition that clearly would not be desirable.
Extreme conditions are rarely solutions, but they are useful in making a
point.  Your point is well taken.  I have said before, the most common
mistake in piano building is thinking that if a little is good then a whole
lot more must be better.

There are wonderful sounding pianos out there, even some of the uprights. 
I expect that scruffing is something that occurs, to some extent, in all
pianos.   The question is:  Can we make the less wonderful sounding pianos
sound a little better by understanding and controlling this variable just a
little better?

Frank Emerson
pianoguru at earthlink.net


> [Original Message]
> From: <ed440 at mindspring.com>
> To: <pianoguru at earthlink.net>; Pianotech List <pianotech at ptg.org>
> Date: 11/25/2006 12:18:50 PM
> Subject: Re: Scruffing -was - Over-Strike vs Under-Strike
>
> Frank-
>
> All hammers damp upper partials, and thank heavens for that!  To avoid it
we would need knife-edged hammers on inflexible shanks.  Not a sound I
would work very hard to produce.  
>
> Ed
>
>
> -----Original Message-----
> >From: Frank Emerson <pianoguru at earthlink.net>
> >Sent: Nov 25, 2006 10:49 AM
> >To: "ed440 at mindspring.com, Pianotech List" <pianotech at ptg.org>
> >Subject: Re: Scruffing -was - Over-Strike vs Under-Strike
> >
> >> What does scruffing do to the sound?
> >I think there are two questions here.  What does shank flex do to the
> >sound, and what does scruffing do to the sound?  Regarding the first, if
> >you have a shank made of rubber, as you might suspect it were, from the
> >slow-motion photography, there is a huge amount of energy lost that would
> >otherwise transfer into a more powerful sound.  Regarding scruffing, it
> >broadens the "strike point" into a "strike range," damping upper
partials.
> > 
> >> If the hammer did not scruff, would the piano sound different?
> >I expect so.
> >
> >> How hard do you have to play to have significant scruffing in a
vertical?
> >I did not conduct the study, so I do not know what the controls were for
> >the forces applied to the key.  I think there was a fairly wide range of
> >forces, representative of normal playing.  I suspect that if the key is
> >struck with enough force to produce a sound, there is some flex, and some
> >scruffing. Significant   .... I don't know.
> >
> >> Is it more significant in a particular range?
> >The heavier the hammer, the more inertia will influence the flex of the
> >shank.  On the other hand, the longer the string the less,
proportionately,
> >the "strike range" deviates from the "strike point."  Another
consideration
> >is that as the strings progressively move to a greater angle to the
action
> >motion, ... well, who knows what effect that has.
> >
> >Hey, I never said I had answers.  I do better at raising more questions.
> >
> >Frank Emerson
> >
> >> -----Original Message-----
> >> >From: Frank Emerson <pianoguru at earthlink.net>
> >> >Sent: Nov 25, 2006 1:00 AM
> >> >To: Pianotech List <pianotech at ptg.org>
> >> >Subject: Re: Scruffing -was - Over-Strike vs Under-Strike
> >> >
> >> >It's been a while since I have seen the slow-motion photographic
study,
> >but to the best of my recollection, the shank flexing due to impact with
> >the strings seems to overpower other considerations.  Uprights could
> >certainly benefit from more substantial shanks.  I said that my drawing
was
> >exaggerated, but not by much.  It is amazing how an upright hammer flops
> >around before coming to rest.  
> >> >
> >> >Frank Emerson
> >> >pianoguru at earthlink.net
> >> >
> >> >
> >> >----- Original Message ----- 
> >> >From: Steve Fujan 
> >> >To: Pianotech List
> >> >Sent: 11/25/2006 12:02:22 AM 
> >> >Subject: Re: Scruffing -was - Over-Strike vs Under-Strike
> >> >
> >> >
> >> >Wow Frank, great sketch!  
> >> >
> >> >Hmm......
> >> >So, if the shank flex causes upward scruff, and the offset axis causes
> >downward scruff, then could they be "tuned' to cancel each other out?
> >> >
> >> >Intuitively, it seems like scruffing and flex are both power and
clarity
> >robbers.  Could super stiff shanks help minimize both? 
> >> >
> >> >Steve Fujan
> >> >
> >> >
> >> >
> >> >
> >> >On 11/24/06, Frank Emerson < pianoguru at earthlink.net> wrote:
> >> >How can scruffing occur unless the hammer shank flexes?  It does flex,
> >and it does scruff, but always upward.  As the flagpoling of the shank
> >reverses, the hammer begins to scruff downward just as it is rebounding
> >from the string.  The proximity of the axis of rotation to the string is
> >less significant than the length of the hammer bore from the strike
point. 
> >This can be seen in slow-motion photograph of action movement.  It is
> >amazing how much an upright shank flexes.  You would think it would break
> >before flexing as much as it actually does.  A grand shank flexes also,
but
> >not nearly so much.  The drawing below is simplistic and exaggerated, but
> >illustrates the point. 
> >> >Frank Emerson
> >> >pianoguru at earthlink.net
> >> >
> >> >
> >> >----- Original Message ----- 
> >> >From: Steve Fujan 
> >> >To: joegarrett at earthlink.net;Pianotech List
> >> >Sent: 11/24/2006 12:47:45 PM 
> >> >Subject: Re: Over-Strike vs Under-Strike 
> >> >
> >> >
> >> >Shifting slightly to the concept of scruffing...    The hammer contact
> >will always "scruff" towards the hammer pivot axis (unless the pivot axis
> >could somehow lie in the plane of the string).   The closer the pivot
axis
> >is to the string, the less "scruffing" will occur. 
> >> >Steve Fujan 
> >> >
> >> >
> >> >On 11/24/06, Joseph Garrett < joegarrett at earthlink.net> wrote: 
> >> >Upon reading the follow-ups of Jons query, I'd like to wonder which is
> >> >which. I've always considered "Over-Strike" as the Downward angle of
the 
> >> >hammer, which would put the hammer Beyond Perpendicular. ??? Am I
> >correct 
> >> >on that? If so, then, "Under-Strike" would be, where the hammer does
not
> >> >achieve Perpendicular, on contact?? The "Over-Strike" hammer, (on an 
> >> >Upright), would "scruff", (for lack of a better word), downward, at
> >impact. 
> >> >The "Under-Stike" hammer would therefore "scruff" upwards.
> >> >Do I have all of this backwards? Confused minds need to know what the 
> >> >consensus is.<G>
> >> >
> >> >
> >> >Joseph Garrett, R.P.T.
> >> >Captain, Tool Police 
> >> >Squares R I
> >>
> >>
> >
> >
>
>