[pianotech] Adjustable Repetition Spring

[Don Mannino]

John,

I thought I would pull this out of the previous thread, as it's a different
topic.

There are other issues with the adjustable screw for the "butterfly" style
repetition springs.  Not issues that make them bad or unusable, but they do
affect the feel and the performance of the action.

In the original system, the repetition spring normally slides out the groove
on the repetition lever.  This changes the point of contact of the spring on
the lever, moving away from the lever center and towards the knuckle, while
gradually increasing the spring resistance.

In the screw-adjustable system, the contact point of the spring on the lever
remains the same, but the spring length becomes shorter as the spring is
compressed.  This changes the rate at which the spring stiffness increases,
and also does not "soften" the affect of the spring's stiffening by sliding
the contact point closer to the knuckle.

Finally, the spring force ratio between the repetition lever / knuckle and
the jack is also affected.  This is of less consequence than the rate of
spring tension increase, but has an impact on the overall force which the
spring applies to the capstan during repetition.

The end result of all this is that the touch is affected in a small way.  I
installed 3 sets of these wippens in the 80s when they were first offered by
Renner, and went back to the normal design because I didn't care for the
touch, and felt that the repetition was not as good unless the springs were
regulated strong enough to make the hammer rise quite fast. The hammer lift
was then bothersome during soft playing at times, detectable by the player. 

So, for these reasons, many people (and piano companies) prefer to use the
old "PITA" style of wippens, even though the new design is certainly much
simpler to regulate.

Don Mannino


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of John Delacour
Sent: Tuesday, June 22, 2010 9:58 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] WNG Parts Question


I met Bruce Clark in England a few weeks ago and had a long chat with 
him.  . . . . . . I was also critical of his decision to stick with the most
primitive 
and PITA type of repetition spring, and the reason he gave me was 
that an adjusting screw would add weight.  Yeah, and a fat lot of 
weight it would add compared with the added convenience of an 
adjustment such as used by Ibach, Grotrian, Schimmel etc. for 
donkeys' years.