S & S 'A' parts, geometry -- shanks and flanges

[Jon Page]

On further thinking this out, I am not sure where the hammer would be
with a larger knuckle compared to a smaller one at the halfway point
since it started from rest when the wippen was lower in order to maintain
hammer blow. I tested knuckle radius changes from the hammer c/p but
not tested larger knuckles to see their effect.

Does anyone have results from such an exchange?

So far, I';m inclined to think that a larger knuckle will induce greater
aftertouch, no hard evidence, just speculation.

No time to test . . .

Jon Page

At 01:44 PM 10/6/98 -0400, you wrote:
>In the Robinson/Baldassin class in Providence "Truth & Consequences"
>they stated that not only was the capstan to intersect a line between the
>b/r and wippen center pin at half-dip (my term) but also the surface of the
>knuckle is on a line between the wippen c/p and the hammer flange c/p.
>
>An involved formula accompanied the drawing on the handout. Which had
>nothing to do with the diameter of the knuckle but rather its proximity to
>the hammer c/p, action spread, key ratio and hammer height.
>
>The height (diameter) of the knuckle will affect the situation of all parts
>concerned. So the appropriate diameter/radius should be selected to best
>accomplish optimal parameters.  A larger knuckle will have the hammer
>closer to the string at this halfway point and will consequently affect
>aftertouch.
>
>In the Renner USA Parts Kit, two different diameter knuckles are supplied.
>
>Jon Page
>
>At 11:46 AM 10/6/98 -0500, you wrote:
>>
>>
>>----------
>>> From: Dave Swartz <dms2000@PIONEERPLANET.INFI.NET>
>>> To: pianotech@ptg.org
>>> Subject: Re: S & S 'A' parts, geometry -- shanks and flanges
>>> Date: Monday, October 05, 1998 11:54 PM
>>> 
>>>.I've taken readings from
>>> .357 to .395 in the same set!!!  Does it not also effect the
>>relationship
>>> from whippen centerpin to hammer flange centerpin?...Where's that
>>knuckle
>>> supposed to be at rest?
>>> 
>>> Dave Swartz, RPT
>>> dms2000@majesticpiano.com
>> 
>>Dave, 
>>	If you mean a varation in the diameter of the knuckle between .357 and
>>.395 I would notify the maker and insist on closer tolerences.  To put it
>>in prospective a varation of .038 is close to a .040 medium thick
>>cardboard br punching, or almost 1mm.    
>>Also where the knuckle is at rest is where it puts the  hammer hammer at
>>the correct striking distance.  Which begs the question, "What difference
>>in striking distance is caused by a varation of .038? If the ratio is one
>>to seven, then the furtherest two hammers will be from each other is 7mm. 
>> 
>>	Now 10mm is .3937, I am wondering what size knuckles were installed. 
>>	I think of where the knuckle is placed on the shank is how far the jack
>>has to move up and down to make the hammer move X distance. I am not sure
>>how the size of the knuckle affects this distance, since every thing is
>>measured from the center line of everything, and distance traveled (which
>>is always circular with levers) is determined by distance from center of
>>rotation. (a radius) 
>>
>>Richard Moody 	
>>
>>
>
>