"Oval or Round Shanks" or to bend or not to bend

[Bill Ballard]

On 9/4/97 1:48 AM, Richard Moody <remoody@easnetsd.com> wrote:

>miniscual

"miniscule" (adjust your Spelch-Ecker according <g>.)

On  09/04  6:16 PM, Delwin D Fandrich, pianobuilders@olynet.com ,wrote:

>Most of what I have to say on this subject I've already said. See
>"Action Power" Part 1 (August, 1996) and Part 2 (December, 1996)
>published in the Piano Technicians Journal. May I respectfully refer the
>reader to those articles?

Hats off to Del for this and many other wonderful articles.

On 9/4/97 1:48 AM, Richard Moody <remoody@easnetsd.com> wrote:

>	On the other hand, a bent hammer shank may possess potential energy
>just as a bent bow ready to shoot the arrow.  So perhaps after let
>off, the bent shank tends to spring back and actually accelerates the
>hammer onto the string.

Yes this is what is happening. However this temporary ricocheting of the 
action's energy into the springiness of the shank is worth considering 
only if it is complicating our measurement of the hammer's final velocity 
as it meets the string. The shank's whip is a complication only in that 
it modulates a direct  correlation between the key and hammer velocity. 
If the shank has restored itself (ie. straightened out) before let-off, 
then it is not complicating the reading of the ham,,hammer's final 
velocity. More importantly, how the springiness of the shank may affect 
the acceleration curve of the hammer head is moot if the shank has 
restored itself by let-off. What I mean is that if you have two keys with 
identical parts in their lever trains, excepting that one has a shank 
which will bend under the rabbit-punch at the knuckle and the other which 
won't, AND if the flexible one has restored itself by the time let-off 
occurs, AND if both keys are both driven by the same striking force, both 
hammers will have taken the same time interval to travel to let-off. 
Never mind that they'll have different acceleration curves to arrive 
there, they'll both arrive with the same velocity.

Now while acceleration is in the "moot bin", velocity is the salient 
factor, as it combines with the hammers mass will determine the hammer 
head's deceleration when up against the opposing force of the steel 
wire's springiness.

All of which is to say that if the flexible shank has restored itself by 
the time the hammer reaches let-off (minus of course energy lost as 
frictional heat during the mechanical flexing), the flexing will have no 
effect on the hammer's momentum. If the shank hasn't finished its 
restoration by let-off, then the flexing will have a significant effect 
on our knowing what the hammer's momentum is, going into the interaction 
with the string.

Hey, I've only got a HS diploma (and barely that). Corrections, please.

Bill Ballard, RPT
New Hampshire Chapter, PTG

"No one builds the *perfect* piano, you can only remove the obstacles to 
that perfection during the building."    ...........LaRoy Edwards