Capstan Angle

[David Love]

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OK.  Here's a good illustration.  You are, of course, correct.  KR1
shows the KR taken at the capstan key contact.  The KR measures .51.
KR2 shows the KR taken at the top of an angled "capstan".  The KR
measures .59.  KR3 shows the KR taken at a point directly below KR2.
The KR measures .59.  That was pretty simple.  I'm convinced.  I guess
it's three to one now.  

David Love
davidlovepianos@comcast.net 

If I understand Phil's explanation (and my small experiment), the KR 
> is a function of the combination of the contact point with the key and

> contact point of the top of the capstan with the wippen heal.  On a 
> straight up capstan there is not difference.  If the capstan is angled

> back at a 45o angle, the KR as measured from the very top of the 
> capstan will not be equal to the KR as measured from a point on the 
> key directly below the point of contact with the wippen heal.  It will

> be something between the contact point with the key and the point 
> directly below the contact point with the wippen heal.  Therefore, 
> angling the capstan does lower the ratio (assuming the the same 
> contact point on the wippen), you just don't get the full benefit of 
> the new position vis a vis the contact point with the key.  But maybe
someone can provide the math.
> 
> David Love

There is no math. The moment arm is the straight line between the 
fulcrum and the contact point, regardless of whether the beam 
support between the two meanders through Sandusky, Minot, or 
Will-e-findit. The point at which the capstan enters the key is of 
no importance whatsoever, other than the angle it imposes on the 
capstan, and the angle at which the capstan contacts the wippen. The 
difference between the distance from the fulcrum and the point at 
which the capstan enters the key, and the distance between the 
fulcrum and the contact point between the capstan and wippen is 
utterly unimportant. The fulcrum to contact point is the measurement 
you need. If the angle between the capstan and wippen pad is such 
that the moment arm changes length through the key stroke, then the 
action ratio will change through the keystroke. That's it. It's 
really simple.

Ron N
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