hammer "throw" on hard blow

[David Nereson]

Conrad Hoffsommer wrote:

> At 07:23 AM 8/26/2005 -0400, you wrote:
>
>> Could it be caused by unequal friction on each side of the bushing?
>>
>> --Cy Shuster--
>> Boston, MA
>
> Sorry, I've lost the initial post, but when I find that inconsistent 
> striking, it is due to unevenly worn bushings or a broken/splitting 
> birdseye or flange. Were the centerlines of jack and knuckle/butt 
> lined up?
>
> I suppose a loose flange screw could do it, but the noise of that 
> would have been very noticable.
>
> Conrad Hoffsommer
> I tried to get a life once but they were all out of stock.
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> pianotech list info: https://www.moypiano.com/resources/#archives
>
>     Yes, the jack alignment to butt is OK, and the pinning seems OK, 
> too, that is, as good as any of the other butts/flanges that do NOT 
> wobble when striking.  I don't have a way to scientifically check that 
> the center pin torque on each side of the flange is exactly equal -- 
> just the usual methods of checking "by feel," clamping in a vise and 
> checking for wobble, hanging upside down and checking number of swings 
> (there were 3 or 4).  I pushed the hammer lightly to the unison to see 
> if it's striking all three strings simultaneously, which it appears to 
> be doing -- except on a hard blow, some of these shanks twist, I 
> think, or the ears of the flange twist, or the bushing "gives" a bit, 
> causing the hammer to strike at an angle or to the left or right of 
> the unison.

       Occasionally I encounter this on grands also, when tuning -- play 
it soft and it hits all three; play it loud and it misses a string, or 
vice versa.   --D.N.