Renner "Turbo Wippens"

[David C. Stanwood]

>BW=(DW + UW)/2...What does that show us?  I am not particularly 
>up on Stanwood's "balance weight" work.  Was there a recent 
>article in the Journal I missed?  With a 50 gram DW and a 25 
>gram UW we have 37.5 BW which I would assume is a good balance 
>weight?  With a 60 gram DW and a 30 gram UW we would have a 45 
>gram BW.  A 60 DW and 20 UW would be 40 BW.  
>
>Thanks in advance...
>
>David ilvedson, RPT
>Pacifica, CA

David,

38 is a good "Normal" BW for modern pianos.

On the subject of Balance Weight.  Friction causes DownWt and UpWt align
themselves around a point in between.  As friction is reduced, DownWt and
UpWt converge on this point.  As friction is increased they divirge from
this point.   The point is: that if there were no friction in the action it
would take one weight to balance the key like a beam balance.  That amount
of weight is the balance weight.  We can only infer this by measuring
Down/Up and computing BW = (Down+Up)/2;

Friction Weight is found as (Down-Up)/2.  This tells how much weight added
to the Balance Weight it would take to make the key go down (DownWt), and
how much weight taken away from the BW it would take to make the key go up
(UpWt).

So a key with a 50/20 D/U would have BW/F of 35/20.  To change D/U you work
on the BW/F.    I personally find it impossible to deal with Up/Down
without using the components of BW/F.

If anyones in Houston this week? I'll be teaching a workshop:

     "Changing from one Up/Down Weight to another Up/Down Weight"


Here is an excerpt from my handout.  We are all going to work the weight
and friction on action models to change up/down to our desire:

Three Steps:                  

  I. Measure old Up/Down Weight, then calculate old Balance Weight and
Friction Weight.
     Pick a New Up/Down Weight, then calculate new Balance Weight and new
Friction Weight

II. Change the old Balance Weight to the new Balance Weight by adding or
subtracting keyleads,
     or by increasing or decreasing support spring tension.

III. Change the old Friction Weight to the new Friction Weight by adding or
subtracting friction in the 
      hammer flanges, wippen flanges, or key bushings.
         

When talking about key balancing it is always preferable to talk BW because
it separates out friction as a separate issue.  Sorry to get carried away
here but this is an area that most of us can't deal with.  I hope to change
that.  It's not rocket science, it's seesaw science!  

On the subject of Turbo wips:  One mistake that makers make is asking too
much of a wippen support spring.
The highest BW Balance to for use with support spring is 54 grams.
Attaching the spring and achieving a final BW of 35 means the spring is
working 19 grams off the BW.  The spring can be adjusted to as low as
30gram BW for a very light touch, in which case it would be working 24
grams.  This is our red line.

We almost always use wippen support springs in all our action work.  I
think they are great and they are an underutilized resource in piano
making.  Piano makers just don't know how to use them the right way.  
An exception is the Hamburg Steinways of the 1920's who set spring to
support the weight of the wippen on the bench and then balanced the keys
using Up/Down.  Unfortunately there are piano makers out there, some very
good ones, who ask as much as 40 grams or even 50 grams of the support spring.

Ed, I agree that hammer weight can be a big problem.  So can overall action
ratio and I feel that this an even greater culprit contributing to heavy
actions.  In Steinway the big culprit is Key Ratios: they vary all over the
Map!  yet this is hardly ever mentioned in discussion of trouble shooting
heavy action.

David C. Stanwood