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

[Keith Roberts]

On 10/30/07, Richard Brekne <ricb at pianostemmer.no> wrote:
>
>
> In anycase, moving the whippen rail is a matter of creating this
> alignment and not a matter of changing touch weight.


Sorry Rick but that doesn't agree with the data. The action I was just
working on Dale weighed off yesterday and he had been trying to squeak an
extra lead out of the keys. It was weighing off with 4 leads in the bass
when regulated. After the rail move it weighed off with 3 leads. This is
because the resistance arm when measured to the top of the jack is not a
direct ratio to the effort arm. The force has to be translated through the
jack first. Remember weigh-off is only to let off so miss alignment of the
core to the knuckle core will make no difference as long as the jack is
pointed at the center of the knuckle.

So to figure the force directed out the jack, you make the line from wippen
center pin to the jack center pin the x axis and then the tangent line is
the y axis. By the number of degrees you calculate the amount directed back
down the x axis and then you figure the resultant force vector directed
down the jack. Then resolve the force at the end of the jack to the tangent
line of the arc from the top of the jack to the wippen center pin. There
will be a slight movement of the magic line but when 2 mm is translated in
degrees back to knuckle it is nothing.

In any event like David Love said and what my mentor thinks agrees with the
data: there is a change in the amount of weight needed to balance an action
and there is no measureable change in friction. Personally I don't see how
you can change the effort arm of the wippen and not effect a change in
leverage.

That's my story and I'm sticking to it.

Keith Roberts
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