Adjusting new repetition springs

[Phillip Ford]

If you install new wippens you know that you can't use them straight 
out of the box because the repetition springs are too strong (at 
least for the hammer weights that I normally use).  I thought I would 
share with you my method of adjusting the new springs when installing 
them on the action to give you either a chance of ridiculing me or of 
sharing with me some other bright ideas of your own.

These days I routinely adjust hammer weights (Strike Weights 
actually) to fit one of the curves on David Stanwood's chart.  I 
have discovered (probably not a new discovery, but new to me) that 
for a Steinway style wippen, the force needed to push down the 
repetition lever at the drop screw contact point is six (6) times the 
Strike Weight.  I've only done this on Steinway wippens, but the 
principle should be the same on other wippens, but the figure of 6 
times might have to be modified somewhat.

1.  I take a new wippen in hand and turn the repetition spring 
adjusting screw (I no longer use wippens without adjusting screws if 
I can avoid it) so that it is about 2 full turns from being fully up 
against the repetition lever (about 1 mm between top of adjusting 
screw head and repetition lever).  This is more or less the position 
the screw is in out of the box.  This allows me to reduce spring 
tension about 10% if necessary.  From this point you can also 
increase tension by 20 - 25% depending on how far down you're willing 
to turn the screw.

2.  Take a Correx 0 - 100 g gauge.  With the arm of the gauge press 
down on the leather at the drop screw point and measure the force. 
This force should be six times the SW for the corresponding hammer. 
I find it tricky to measure the force to just start the rep lever 
moving, so I push down until the rep lever height adjust button lifts 
about 1 mm and hold it there and take the reading.

3.  Bend the spring to reduce the tension so that you get the correct 
reading.  If I get within 5% I call it good enough because I can 
easily adjust that much with the screw after installation.  For 
example, if the SW for note x is 10 g, then I want a measurement of 
60 g at the drop screw point on wippen x, and I will settle for 
anything from 57 - 63 g.

This takes longer to describe than to do.  With a little practice you 
can move along pretty fast.  Also, you soon get so that you don't 
have to do the initial measurement because you can feel with your 
fingers that the spring is a little too strong or way too strong and 
bend the spring accordingly before taking any readings.

For setting SW to the curve I used to read the numbers off the chart. 
But now I use the curve fitting spreadsheet that Mark Davidson posted 
to the list some time back.  I pick four points off the chart and use 
the spreadsheet to generate a table of SW.  I find this easier to 
work with.  I then just have the spreadsheet generate another column 
six times the column of SW and this gives me the numbers to use to 
set rep spring strengths.  I've done this several times now,  and I 
find that the spring strengths are right on the money.  Very little 
adjusting is needed when the action is assembled.

Phil Ford