Action Geometry

[Diane Hofstetter]

Great idea about a thread on action geometry, Rob!  It seems that that is 
the most useful
thing for a _real_ understanding of what we are doing when we regulate.

We are currently working on a JC Fischer grand, converting the action to a 
modern one.
The old whippens have no balancier, but a large circular spring that 
attaches to a thread on
the hammer butt (that's right, hammer butt on a grand).  The old action 
parts are
considerably lighter in weight than the new ones we hope to make work.  
Catch is the
customer never liked the piano because it felt so "heavy".  Another issue is 
that the new
hammertails are 3/16" shorter than the originals.

We put a new whippen and hammer assembly on a note and weighed it.  We got a 
down
weight of 85g and an upweight of 53g.  This results in a friction reading of 
16 and a
weight reading of 69.  Then we weighted the key with leads to result in a 
downweight of
48 which gave us an upweight of 19, friction  of 14.5 and weight of 33.5.

Hoping to improve these results we experimented with moving the capstan 
forward.  We
tried two new positions, .2” and .4” forward (toward the front of the key.)

Results:

	Original position	Original position	.2” forward		.4” forward
	no leads		with leads		with leads		with leads
-----------------------------------------------------------------------------------------------------
Up
weight		85			48			48			48

Down		53			19			21			22
weight

Diff.		32			29			27			24

Friction	16			14.5			13.5			12

Weight		69			33.5			34.5			35


So...   what should we do?


Thanks,

Diane Hofstetter
Jeff Williams
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