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

[Dave Swartz]

At 10:08 PM 10/6/98 -0400, you wrote:
>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
>
Jon and all,

This is a good question...hmmmm....now I'm thinking aloud here (in print of
course..he..he):  Using a 17 mm shank results in greater dip...  .420 to
.430..sometimes even higher (depending on the action).  I think partly
because of the extended distance from knuckle core to c/p but also think the
diameter of the knuckle itself (which is larger on higher leveraged shanks)
plays a role in the dip correction as well.  Of course aftertouch is
effected by this change.  I tend to believe that a larger knuckle surface
creates more friction at that particular arc but not as highly realized
simply due to a higher leveraged action system.  

Now, if you lower the upper leverage of the system but do not reduce one of
the components that contributes to friction (oversized knuckles) then your
dw & upw grow farther apart (hence friction increase) and forcing
dip/aftertouch to deviate from optimum. Also the Strike Weight Ratio should
increase.  Another iron in the works is that of hammer blow... 1 7/8" vs. 1
3/4". A lower leveraged shank (15.5 mm) houses smaller knuckles, dip is
shallower (.385 to maybe .400 with .045 aftertouch) but hammer blow can only
be 1 3/4" to work properly.  Higher leveraged action can allow for 1 7/8"
blow distance  (most actions) because the leveraged shank is higher (don't
know of any other manufacturer who used 15.5 mm)...and the knuckles are larger.

There should be a way to determine exactly the correct knuckle size for a
particular leveraged shank...no??? or better yet, a determining calculation
that would give proper specifications on knuckle size dependend on the
action's leverage....wow, this is getting groovy.   I think Richard
statement is thought provoking  when he said: "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)" .  Would not a larger radius in this application
differ from a smaller one?      

It will be interesting to install the smallest knuckle to the higher
leveraged shank and visa-versa without changing anything else and come up
with results.  

SINCE golf season IS coming to a close........(yes Wim, I'm an 11.6 USGA
handicap...nothing great but consistent) and you've got my curiosity on
level 5, I suppose I'd better go mess around with it.

I'm retrofitting a Mason action next week (these use high leveraged
shanks)...going to do some testing with a Steinway B as well (have 2 of
them: one with modified 16.3 mm and the other with 17 mm).  I guess my first
complaint (expressed many times BTW) is that inconsistencies within one set
is not so cool....Kind of like having to repin a whole set of rep levers or
hammer flanges fresh out of the box...Gee, isn't this craft labor intensive
enough already?

If you guys and gals get to do this experiment first, let us know....Thanks
for a very interesting discussion...Hey Vince, are you out here...give us
your nickels worth.

Dave Swartz, RPT
dms2000@majesticpiano.com