action ratios

[David Love]

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Dale Erwin wrote:

...A Case in point, if you take stwy player grands with that extra long =
key (3 inches)? with low amounts of lead it would be possible to carry =
any amount of hammer weight you wished. It's a better lever or has the =
potential to be with appropriate stack geometry.
  Hey the real problem is that keys in general are just to danged short. =
But really on smaller pianos they are and that's why more action =
balancing gymnastics are required...


I think that the role of short keys is somewhat misunderstood here.  The =
length of the key will make no difference in the leverage from the point =
that the measurements are taken (presumably out near the end of the =
key).  The key ratio is all that matters in this case.   A key with a =
.50 key ratio that is 36 inches long will produce the same action ratio =
as a key with a  .50 ratio that is 12 inches long all other things being =
equal.  The difference lies in what happens as you play the key in from =
the measurement point.  A longer key will show less difference in force =
required to move (or balance) it per increment of distance traveled =
toward the balance rail than a shorter key.  Since pianos tend to be =
played "into" the keys more than on the tips, a short key will feel =
heavier in the course of normal playing than will a longer key even if =
the ratios, strike weights, front weights, etc., are all equal.  But as =
far as approaches in setting up the action, there would be no real =
difference.  That is, unless you felt that because of this particular =
difference it would be better to set up a shorter key with lower balance =
weight, front weights or strike weights, which, in fact, might not be a =
bad idea. =20

Yet another way to think of all this might be to figure out where on =
average the key is actually depressed from and take measurements and =
make calculations from there.  This would factor the length of the key =
into the equation.  On actions with very long keys, such as concert =
grands, little change from current designs would be necessary, but on =
shorter keysticks, lighter weights would tend to prevail.  This also =
might help to explain how actions set up with the same ratios, strike =
weights and front weights feel different.  Differences in key length =
create larger variances in balance weight as you move in toward the =
balance rail. =20

David Love

=20


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