Wippen support springs and action geometry

[David C. Stanwood]

Chris writes:

>In your opinion, am I barking up the right tree with these turbo wips?
>Will I need to change the key weight?  Will I have problems with bubbling
>hammers?

>Thanks for our help.

>chris

Dear Chris,

The bubbling I think your refferring to is the sort of bouncy key?  When
the key comes up it bounces and bubbles as it comes to rest?  We've found
that this occurs when springs are asked to do too much work.  We set up
actions so that springs work 25 grams off the touchweight at most, Tops!
Many actions are found with springs that are working as much as 40 grams
off the touch. That's too much!   I've found this on pianos from Samick to
Bluthner.

To measure how hard a spring is working just measure upweight with the
spring disengaged.  Now engage the spring and measure upweight again.  The
difference is haow hard the spring is working.  When upweight rises by 15
grams, then balance weight and downweight will also rise by 15 grams.  (The
difference between up and down will remain the same because friction
doesn't change.)   Take the time to do this metrologic study on a piano
that you take care of.  The infromation is useful and may lead you to ways
to improve the action by improving uniformity of the proportion of balance
between the spring and key leads.

The turbo wip I measured on the model at the CA State conference was
working 17 grams and they had study which states what happens to up down
with spring on and off and 17 seemed to be the number that Renner was
speaking alot.  Any comments Loyd?  Oviously the one with the spring had
fewer leads.  17 grams is a good medium tension for wip suuport springs.
Don't assume that they are adjusted accurately "Out of the box".  The only
way to tell is to measure the touch then hook up the spring and remeasure
the touch.  

The balance weight of the keys (Balance weight is the average of up and
down wt) should be even with the spring disengaged and when engaged.  The
best way to treat springs is to balance the keys with the springs
disengaged then hook them up and adjust to final balance.  The biggest
mistake people make is to hook up the springs without accounting for how
tight or loose the spring tension is, then balancing the keys and making up
for variations in spring tension with key leads, thereby making for
inertial discontinuity and uneven front key weights.  In other words
measure up and down wt with the springs off and check the balance of each
key as the average of up and down (Balance Weight).  If it's not even then
adjust the key leads to make it even.  The only way to tell is to measure,
so you have to commit to the value of taking the time to measure and
analyze the data.

There are other ways to adjust the feel of the action as well as the sound.
 The hammer weight which may be measured on the shank as Strike Weight.
The action ratio which may be assessed by looking at the strike weight
ratio.  PTG Journal June 1996 "The New Touchweight Metrology".  I'm not
blowing my horn so much as I am inviting all of you to learn how to take
advantage of newly available ways of looking at our work.  

Touch weight is made up of components.  Look at the components.  Hammer
weight and action ratio make a foundation that will not be rocked by any
spring.  Springs only allow you to balance the action with less lead than
would be otherwise needed,... that's it!  There is advantage to using them
in all cases but they should be used with a full understanding of their
specific effects.  I'm all for them!

I hope this answers your questions and sparks some new ones.


David  C. Stanwood

http://www.tiac.net/users/stanwood

>Hi David,
>
>I caught your post and am very interested in what you had to say about the
>turbo wips.  I have a faculty member whom I believe would really like the
>feel of these.  She likes a very quick and light action with as little bump
>from let off as possible.  What she calls a "European feel".  (She has a
>Bechstein at home.)  She also, however, desires the ability to play very,

>very softly.  I have to have let off and back check as close as possible.
>In your opinion, am I barking up the right tree with these turbo wips?
>Will I need to change the key weight?  Will I have problems with bubbling
>hammers?
>
>Thanks for your help.
>
>chris