Swing Test (Was Tension gauge)

[stanwood]

>     Someone earlier drided the swing test saying that he preferred the
>guage for measuring hammer flange tightness.  I would disagree.  Since the
>weight of the hammers graduates from one end to the other, having the same
>resistance on each flange will not give the same response withing the action.
>On the other hand, if all hammers swing the same number of swings on the
>swing test, than the resistance within the flanges has also been graduated
>to match the weight of the hammers.  That's an automatic match.
>     Using a spring guage is not wrong, it simply doesn
>'t automatically adjust to the changing weight effect within the action.
>Of course it makes perfect sense to me to use the guage on wippen, jack, and
>other flanges since they do not benefit by being graduated from one end of
>the action to the other.

>Ed Hilbert RPT


If you take an action and set each flange to uniform friction with the gauge,
the frictional touchweight will decrease from bass to treble by about 4 grams.
The decrease comes naturally due to the decrease in hammer weight and the
corresponding decrease in forces normal to the sliding surfaces between the
action parts.

Using the swing test to set hammer flange friction creates an additional
decrease in friction from bass to treble thereby exaggerating the overall
decrease in friction from bass to treble.  I would argue that there is no
need or motivation for creating this exaggeration in respect to what
pianists want in a piano.

For historical perspective look at the touchweight specs that Steinway used
to use.

Roughly:

Downweight:  50 - 46
Upweight:    20 - 24

These specifications were friction specific.

The fraction of touchweight due to friction may be calculated as half the
difference between downweight and upweight or: (DownWt - UpWt)/2;

I call this value friction weight for short.  Apply this formula to the
traditional specs and you have a friction weight of 15 - 11 or a decrease in
friction weight of
4 grams from bass to treble.  This would imply that Steinway used to believe
that
flange friction should be uniform from bass to treble because to achieve a
four gram difference in friction weight you need uniform flange friction by
the gauge.

Furthermore to achieve and overall friction weight of 15 - 11 you will find
that you need flange friction's in the area of 5 grams rotational as well as
snug key bushings.

It is interesting to note that the current Steinway Specs which state that
the upweight may be 20 grams plus any amount or minus 2 grams, are
frictionally nonspecific.


David C. Stanwood