Scruffing -was - Over-Strike vs Under-Strike

[ed440 at mindspring.com]

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
>>
>>
>
>