I agree that standard procedures for measuring key ratio
should be discussed. Here are some thoughts on the subject:
Key ratio may be described in either of two ways; as lever ratio
or as a weight ratio.
The "key lever ratio" is the ratio of the actual measured length of
the -capstan/balance rail- lever arm to the -balance rail/key front-
lever arm.
The "key weight ratio" is the ratio of downward force to the
corresponding upwards force at the front of the key. For instance: in
a key with a weight ratio of 0.5 a hundred grams of downwards force at
the capstan would translate to 50 grams at the front of the key.
In touchweight and key balancing work we use weight ratios. The weight
ratio closely relates to the actual lever ratio. This assumes a normal
displacement of the action parts. Since most actions are of similar
construction and orientation of parts, the assumption holds true.
If, for instance, we had a key with a 0.5 lever ratio but the capstan
was positioned vertically over the balance rail, the weight ratio
would be zero (or iz that infinite?), and the assumed relationship
between the lever ratio and the weight ratio would not hold true. In
this absurd scenario, any amount of weight placed on the capstan would
show no static weight effect at the front of the key.
To measure key weight ratio, measure the distances between parallel
lines that intersect the vertical axis of the capstan line, the
balance rail line, and the a defined "front" line of the keys. Divide
the back leg by the front leg and you have my definition of key weight
ratio. This can be done for an individual key by laying the key on a
piece of graph paper. I think Bill Ballard described this. Anyway,
I'll try in the near future to provide my own synthesis of the
technique. For now I have to go to work!!
More later!!
____
David /||||\ Stanwood Stanwood@tiac.net
(o o) West Tisbury, Massachusetts USA
--oOO--( )--OOo----- On the Island of Martha's Vineyard
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