whippen weightlessness

[stanwood]

>When the grand whippen has a spring at the flange, how does that figure
>in weighing off?  I'm working on a Korean grand that seems to have
>insufficient upweight because of those buggers.  Hamburg Steinway uses
>them too, so there must be something good about them.  Any hints out there?
>Benjamin Treuhaft

Increasing wippen support spring tension has the same effect as adding
keylead but without adding mass.  Increasing support spring tension reduces
downweight and upweight equally.  It sounds as if your springs are too
tight, or you have excessive friction.  If it's not a friction problem,
reduce spring tension.  Disengage the spring and flip it up so that the
short tab end protrudes.  Pushing up or down on the tab will loosen or
strengthen the spring tension.

The problem with Korean pianos is that they add keylead to the keys with the
springs engaged, usually without much concern for pretensioning them.
Sometimes they are so tight that keylead is added to the back of the key to
get the key to come up.  This is not intelligent.

Hamburg Steinway in the early 1920's used these springs and from what I can
tell they used them very intelligently.  The method was related to me by Jim
Christopher.  Prior to balancing with the stack on the bench, the hammers
are lifted up and the spring tension adjusted so the the wippens hang level.
By doing this the wippen weight is taken out of the equation.

Referring to my article on the New Touchweight Metrology in the June PTG
Journal.  You will see that the amount of weight needed to balance the
wippen (wippen balance weight) is the radius weight of the wippen taken at
the capstan contact point times the key ratio.

With a typical wippen weight of 18 grams and a typical keyratio of 0.55:

WipBW = 18 x 0.55 = 9 grams

This is how much you would expect the springs to be working.  Last summer I
had the opportunity to measure a Hamburg with springs.  I measured Up/Down
with the springs engaged and disengaged.  I calculated the balance weight
(average of Up/Down) of both data sets, and found the difference to be very
uniform - 13 grams on average.

If you do the same exercise on your typical Korean piano you will find the
difference between spring engaged BW and springoff BW to be very
inconsistent from note to note.

Again, the simple answer to your problem is to gain upweight by weakening
your spring.

David C. Stanwood