Swing Test

[Charles Ball]

At 07:52 AM 4/20/96 -0600, you wrote:
{snip}
>    In regards to the manner in which factory pinning is set;
>the difference between graduation of friction,(by swinging the hammers), and
>pinning all the flanges to one specific tension, seems to be far less than
>the inherent inconsistancies in many factory jobs.  i.e.,  upon taking all
>the hammershanks off several new high quality grands, it is not unusual to
>find ranges from two to 6 swings from one note to the next!  (there have been
>several reasons I have removed whole sets from new pianos, all of them
>unflattering, but that is a different thread).
>    My point is,  any technician that carefully and properly repins a set of
>hammer shanks by either swinging the hammers, or using one gram spec. for all
>of them, will probably be closer to an ideal median,  than what the factory
>has sent out originally!!
>
>    {and for another  $.02 worth},  the pinning on the balancier, and the
>friction involved with the repetition spring contact will have a greater
>influence on how well the action can be regulated than the friction in the
>hammerflange,( within a reasonable range, of course)
>
>regards to all,
>Ed Foote,
>(Spring is here, I can hear them soundboards swelling!)

Greetings Ed,

This is an important point.  This occurred to me several days ago when Don
Mannino asked whether anyone could name one manufacturer who uses the swing
test.  For that matter, can anyone name one manufacturer who uses fine metal
polish on key pins and coats them with a film of teflon lube, or who does a
really fine job of detailed string voicing.

Did you ever see a film that was once in the PTG library that showed slow
motion photography of a hammer and shank striking a string? It was
remarkable just how much the hammershank flag poled upon impact. It may be
because of this phenomenon that I have found that professional instruments
have a clearer, rounder, more focused tone when loose pinning is tightened up.

Of course the heavier the hammer, the wider the arc of the flag poling; yet,
if the top soprano hammers are pinned as tightly as the bass hammers want to
be, they can become sluggish.

Another phenomenon that I have observed is that on some actions the pinning
has to be a bit tighter in the lower registers in order for the repetition
lever to support the weight of the hammershank assembly, as demonstrated by
the dropping of the hammer when the jack is winked.

I meant to do some measurements before writing this post, but basically I
agree with you that either method gives better results than just taking what
comes out of a box or from the factory, and only attending to the obviously
problem centers.

Charles





Charles Ball
School of Music
University of Texas at Austin