[CAUT] Digest, Vol 1103, Issue 85 Moving Wippen Rail

[Keith Roberts]

On 10/31/07, Richard Brekne <ricb at pianostemmer.no> wrote:

> Hi Keith
>
> I'm not about to argue the point of the change in leverage. Thats been
> hashed through already and you've made some very good points for
> ponderment.  But I deem you have it wrong about the friction.  Friction
> between the jack and knuckle has to do with the interface between jack
> and knuckle top.  It makes no difference to this interface that the jack
> is being supported by the jack center... the interface still sees its
> own condition.


Ok Rick, the only problem I have is the friction is measurable is it not? It
was measured. There was no change in a wippen move of 1 to 2 mm. The action
was weighed off. Not to the DW but the BW. Dale Erwin custom balances his
actions. He said there was change in the weight of the keys due to a change
in leverage. He did not believe friction had anything to do with the change.
I'm not arguing, I'm only reporting actual measuring. You will have to
discuss with Dale how he weighs his action and why he thinks friction had
nothing to do. Me, I'm going to take his word that he measured and
interpreted the data properly.

Sure alignment has a lot to do with friction but friction is exponential. It
won't change much if you are within the lines of convergence window but it
will change rapidly as you move outside the window. Your bore distance is
what dictates where the knuckle/jack contact point sits in relation to the
proverbial magic line. If you got that right, the horizontal move of the
wippen center pin doesn't move the magic line at the knuckle enough to move
it out of that window. I drew this on the attachment Jon Page posted at the
start of the disscussion. The friction comes in as the hammers wear. If
having to raise the hammer to maintain blow distance and letoff created such
a change in friction most actions would be unplayable after a year.

I really have no problem with Stanwood figuring the action ratio the way he
does. It doesn't change the action as it sits if you measure it my way. It
only gives you a perspective as to where it sits in relationship to where
you want it to be. It's like an aural tuner using different checks than
another. He just like the view better and the method does not have to use
all the same checks to come up with a great tuning. If you measure the
action ratio like Mr Stanwood, you have to make all the other assumptions he
does to achieve the proper result. He has a great system that can be
followed step by step by most technicians and achieves wonderful results. It
does not have to take into account this minor detail. To some, five leads in
a key is ok. Hey, the proof is in the pudding and there are a lot of great
recipes and a lot variety in taste.

Namaste,
Keith
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