Bill:
That seems all very well reasoned. Does that suggest, though, that the
dilemma can't be resolved by simply going to a higher ratio to yield a
greater sense of control, coupled with an assist spring to allow for a
little more mass in the hammer which also serves to maintain coupling? Or
will the increased inertia as a consequence of the higher ratio and more
hammer mass not be adequately compensated for by the 9 or 10 grams of FW
removed by virtue of employing the assist spring. The general belief has
been that higher ratios must be combined with lower strike weights and vice
versa for that action to feel "normal". To what extent will the assist
spring "normalize" the feel in the case of high ratios combined with high
strike weights? Is this where we need the dynamic model!?
David Love
----- Original Message -----
From: "Bill Ballard" <yardbird@pop.vermontel.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: October 31, 2002 5:59 AM
Subject: Re: Fw: Patent Notice
At 5:31 PM -0800 10/30/02, David Love wrote:
>Though each installer, as you mentioned,
>can presumably request that designs follow their own specifications, it is
>my assumption, from limited observation, that Stanwood installers are
>following his design preferences. I could well be wrong about that.
You have to check on an idividual basis. I happen to set the SW
according to what I know I can easily trim off or weight up, in the
current set of hammers. That's David's starting point with anything
which I send him, SWs not set according to an inclination towards the
steroid, but what is practically possible with the hammers on hand.
At 5:31 PM -0800 10/30/02, David Love wrote:
>I am inclined to think that anything that causes
>separation of the wippen from the key can't be a good thing. This idea
>seems to be loosely supported by the number of people who gasped at the
>thought of my changing an old Bechstein rocker arm action to a more modern
>capstan system. The consensus seemed to be that the old system performed
>better. If it does, then it seems that the connection to the key is key,
as
>it were. With respect to the wippen-key connection, the assist spring's
>function is exactly opposite.
That's not to say that in an action with the rocker/sticker coupling,
a rep helper spring would seriously compromise this coupling. That
combination would be an interesting one to examine, because the
coupling would be enforced by the "stiff-hitch" sticker. Any extent
to which
The helper spring by itself may appear to reduce a gravity based
coupling. By reducing the effective weight of the rep (and the SW it
carries), it may slow the return of the key. That allows you to
reduce FWs which speeds up the return of the key. The net of this
transaction will depend on how much the BW is moved. If it isn't,
then I'd bet that the return of the key is not being affected by any
loss of coupling. Remember that in the dynamic situation (ie. under
all conditions of mass and acceleration) the big player in coupling
the rep to the key is the force and momentum with with the hammer is
rebounding from the string. I'll bet that dwarfs the few tenths of a
gram that individual SWs get moved up or down, of the ten or so grams
which would be carried by the helper spring.
Another reason why I wouldn't be worried about the effect of coupling
is that it hasn't been shown to me that spring-balanced parts behave
any differently than gravity-balanced parts. (Rumored, but not
shown.) Certainly we can agree that the spring gets weaker the
further upwards the rep moves, and certainly anything which lowers
the Top Action Weight (BW-FW) will lower the top action's gravity
coupling to the key. Certainly, you and I can point to actions in
which the SW/SBR set is is reasonable enough not to require helper
springs in its solution. But for those which do require some drastic
solution, that solution will be either gravity-based with Cristofori
hammers or LHTR, or spring-based (oops, I forgot about magnetic field
based). In either case, The top action weight is being reduced, and
by consequence, the key/rep coupling. These actions needed their
balance problems solved, and in solving them, these actions have been
brought back to normal Top Action Weights, and by consequence normal
key/rep coupling. It doesn't seem to make much difference whether
returning these actions to normal is done by spring balancing or
gravity balancing.
Magnetic balancing is another world entirely; it's based on a force
which is completely independent of gravity. Conceivably, you
magnetically balance take your worst-hung action, by-passing the
gross gravity/inertia issues, and please the pianists.
At 5:31 PM -0800 10/30/02, David Love wrote:
>But now that we
>have turned our focus that way and explored the lower limits, I am finding
>that the actions that are appealing to me and to my customers are
measuring,
>not surprisingly, somewhere in the middle: not enough to fight you, but
>enough that you can easily feel what is going on out at the end of the
>system of levers.
I would agree, that once the lower limits have been explored we'll
return to look for a sweet spot in the middle. I also feel that a
certain amount of inertia is required, if not for the coupling (about
which my ideas standing ready for correction), then at least because
that's what pianist have learned is part of the feeling of an action.
>What I am beginning to think is that the original designs with slightly
>higher action ratios (6.0 - 6.1) delivered something that the more modern
>trend of 5.5 or lower cannot, that there is something inherent in the
>relationship between key and hammer movement that is critical in imparting
a
>sense of control. While this necessitates relatively low strike weights
(by
>today's standards), I am more and more inclined to think that this dilemma
>represents the Sophie's choice of action design.
Again, agreed. Action ratios amplify the angular motion of the key,
and higher ratios provide for more gradations of hammer shank angular
motion per incremental-unit-of-individual-pianist's-key-motion.
Remember that in the formula for the force delivered to the string by
the hammer (F=m*a), it's the acceleration which is the pianist's
variable factor. Adjust the formula for lower SW and higher
acceleration (by bumping the leverage up), and you've increased the
portion of the transaction in which the pianist's input has an
effect. More control for the pianist.
It is a Sophie's Choice, and more so to the extent from which we
stray from the sweet spot.
Bill Ballard RPT
NH Chapter, P.T.G.
"No one builds the *perfect* piano, you can only remove the obstacles
to that perfection during the building."
...........LaRoy Edwards, Yamaha International Corp
+++++++++++++++++++++
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