Adjusting wippen assist springs

[David C. Stanwood]

>>As a general rule it's safe to work the springs so that they just support
>>the weigh of the wippen.  This would take about 9-11 grams off the touch
>>weight.  17 grams is generally considered the upper limit to working
>>springs without significant risk of comprimising normal feel.  Some
>>pianists are more sensitive to the effect than others.
>
>Thanks.  I was hoping for a number.  So, that is 17 grams of spring assist 
>at the capstan?

No, that's at the front of the key.  BTW when I refer to TouchWeight it
means Up/Down/Friction/Balance Weight.

>On the particular action that I'm working on (old Hamburg Steinway) I 
>measured the angle of the wippen at key rest and also at full keystroke.  I 
>then measured WW at these two angles.  It varied significantly, or in other 
>words, the spring assist varied significantly.  With the springs working in 
>the general ballpark of where I thought I was planning to use them I 
>noticed a change of 14 g in WW from rest position to full keystroke (an 
>increase of 14 g of WW when going to the full keystroke position from rest 
>position).  Have you observed this yourself?  If you set the spring for
>17 g assist at rest then you would only be getting 3 g assist at full 
>keystroke.  This isn't much assist.  Is that OK?

I and many of my associates have been using support springs in various
applications for many years and the force variations through the stroke
have never been an issue.  This can be seen by the fact that the motion of
the hammer when measuring up/down wt is of a similar character as with or
without the spring hooked up.

>>How much the spring
>>can work depends on the diameter of the spring.  Renner makes three sizes,
>>0.7mm, 0.6mm, and 0.55mm.  If you are going to work as much as 17 gram off
>>the down/up wt then use the 0.7mm, for up to 12 grams use the 0.6mm, and
>>for up to 6 grams use the 0.55mm spring.
>
>Thanks.  I wasn't aware of that.  I just ordered a set of turbo wippens 
>from Renner, but didn't specify.  I wonder what I'll get.

Turbos come with springs up to #70 or there abouts. They are 0.6mm and they
will sell you an extender kit if you want fill the set out to 88.

>I normally don't use assist springs.  This is an old Hamburg Steinway O
action.
>It currently has assist springs which I am assuming are original.
>Also somewhat low key ratio.  

It's the overall ratio that you need to know...

>Someone at some point set the springs very strong

What's "very strong"?  How many grams effect on U/D?  Overlifting the wippen?

>and took some of the weight out of the keys.  I am planning to put on new
parts.
>My intention was to use 3/4 medium to top medium hammers.  

What's the average StrikeWt Ratio?  An important question! 5.7 is good for
3/4Med SW, 5.5 for TopMed SW.

6.0 won't do very well dynamically speaking unless the SW level is closer
to 1/2 med.

The original set up was probably like a 6.0 ratio with 1/2Med SW.

If you copy the old parts you'll probably get a ratio like 6.0.

How far from the center pin to the center of the knuckle?

David Stanwood

>and current action geometry if I don't 
>use assist springs then I would have to lead beyond max FW.  I'm willing to 
>change the geometry, but my thinking (and at the customer's request) is to 
>keep something of the original character of the action.  By using some 
>moderate assist I can keep the current geometry (perhaps changing knuckle 
>location slightly) and keep FW well below max.  I would also be putting 
>back springs which were there to begin with.  Thanks for your comments.
>
>Phil Ford