Capstan angle

[V T]

Hi David,

Stanwood uses weight measurements to determine his Kr,
because it is a convenient way to get repeatable
numbers that one can plug into the equation.  Since
Stanwood is concerned with touch weight, this is a
very practical method to use.

In contrast, Phil used the radii of the arcs described
by the capstan and heel.  This method of measuring the
key ratio is more convenient if you are interested in
ratios of arcs (angle of the arc described by the
hammer vs. the angle of the arc described by the front
of the key).

It's important not to switch from one method to the
other while discussing this.  Both methods are valid,
but the ratio numbers you will get are different.

In either method, the point where the capstan enters
the key is not significant as long as the contact
point with the heel is unchanged.

Vladan

==============================
David Love wrote:
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



		
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