Capstan angle

[David Love]

I'm not sure why that wouldn't improve the key ratio.  You have a
straight up capstan with a key ratio of, say .52 (using the Stanwood
method).  You relocate the capstan keeping the contact point with the
wippen heel the same but moving the capstan key contact point closer to
the balance rail by angling the capstan.  The measured key ratio will
now be less than .52 and the overall SWR will have decreased as will.  

I'm not sure I even understand what is meant by  

"What they have accomplished is to move the
contact point between the top of the capstan and the
wippen heel a little closer to the balance point, so
that the key ratio has changed."

Do you mean by virtue of the capstan leaning it now contacts the wippen
heal on the front edge of the top of the capstan?  I would say that is
probably insignificant.  Much less, anyway, than the repositioning of
the capstan/key contact point.  



David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of V T
Sent: Monday, April 18, 2005 4:50 PM
To: pianotech@ptg.org
Subject: Capstan angle


Hello Phil, Michael, List

>    I would also caution you against being deceived
by >anecdotal evidence of people who say that they
have >'improved' the key ratio by angling the capstans
back.  >What they have accomplished is to move the
contact >point between the top of the capstan and the
wippen >heel a little closer to the balance point, so
that the >key ratio has changed.  That change resulted
from >moving the contact point, or point of force
>application, a little closer to the balance point.
Not >from angling the capstan so that it contacts the
key >closer to the balance point.

I agree. Some people angle the capstan in order to
reduce the overall action ratio because it's less work
than moving the heel.  I agree that this only works
because the angled capstan can be pushed closer to the
end of the heel.  The disadvantage is a smaller
contact surface between the capstan and the felt.

The relationship between the key/capstan and the
wippen is that of a pair of gears.  In this case, the
two gears mesh only with one tooth each, so you can
eliminate the bulk of the gear mass and teeth.

Regarding the post by Michael Gamble:

>On this subject I have already posted an extract from
>Max Matthias book "Steinway Service Manual" published
>by Verlag Erwin Bochinsky. Relating to Steinway
>uprights, page 165 it states (inter alia):
>- Modifying the wippen lever. This is done by
>adjusting the capstan screws to the rear or front.
>(13mm factory    setting on  Model K, 10 mm on Model
>V, front edge of the capstan screw to front edge of
>wippen heel).  Adjusting the capstan screw to the
>front results in lighter touch. This tends to reduce
>after-touch.
>Hope this helps!
>Michael G.(UK)

This is an interesting point, but such a design puts
the technician in a situation where one adjustment has
to satisfy two requirements; the capstan height is
normally adjusted to get the proper hammer strike
distance.  If we use the capstan adjustment to change
the strike ratio, the hammer strike distance may not
be in the right range.

Best regards,

Vladan



		
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