Capstan Relocation

[Richard Brekne]

Come on Newton... the picture is more complicated that just these
measurements below, submitting them to Stanwoods formula and presto...
solve the problem.

Terry and I, and I assume others, are seeking an understanding akin to that
Stannwood and the like have, and this takes quite a bit of thinking
through, and hands on experience. Especially so since there is so little
written about all this and so little disscussion.

Take my Duysen grand for example. Looking at SWR alone as the overall
leverage, the thing didnt look so bad by the numbers. Even got a couple
comments in private email about that. But this thing was like waaaayyyy off
and felt like it too.

Overall leverage is the result of the component leverages and these have to
stand in a certain relationship to one another. The potential gains from
assuring the best possible geometry / leverage, whatever you want to call
it are quite substantial, and the assumption that factory settings are even
close to optimal proves to be quite erroneous. If this were not the case
then Stanwoods product would be worthless to begin with. Further his own
research into the matter indicates that even the best factories have widely
varying action sets from piano to piano. Given factory production
conditions, this really shouldnt suprise anyone.

So that leaves us in the spot of either seeking how to really,,, and I mean
REALLY, make these things fly, or.... not. Seat of the pants regulation
even at its best will not compensate for a poorly set action.

For the uninitiated, looking at an action and dinking around with moveing
the spread, seeing what happens, is going to be confusing. Trying to
visualize what happens with a capstan whippen cushion move is probably
going to be baffeling. And how many of us have a Boston of our own sitting
around that we can screw totally up, and eventually get right ??

I know this stuff is difficult to help with on-line... but hey... thats
what we are here for... to teach and to learn... (grin and of course to
throw the occasional kilo of walnuts at each other). Would be nice indeed
to get this Action Geometry thread really going... Heck even Stanwood
himself expresses frustration over how hard it is to get folks to
understand what he is talking about.

Terry, get a hold of the old journal reprints of "Hammers and Touchweight".
In particular there is an article series written by one Alan Vincent, and
an article by one Fred Temper (this one bears  striking resemblence to
Stanwoods stuff written in 1989). This will help a bit. Otherwise I find
that haveing an action model to dink with when I have a particular idea and
dont want to pull the whole piano action helps.

Newton Hunt wrote:

> The critical factors in understanding the consequences of
> making a change in an action parameter is to understand the
> leverage of the system in it's entirety.  The measurements
> you need are:
>
> Up weight
> Down weight
> Wippen weight
> Hammer weight
> Key front weight
> Key leverage.
>
> Submitted to David Stanwood's formula permits you to
> determine the actual strike ratio which is the overall
> leverage of the action.  If your action is currently over
> leveraged then moving the capstan makes sense but if the
> action is currently well leveraged then you will have an
> under leveraged action which is as bad to an over leveraged
> one.  Before to start fixing something not broken you need
> to know fully what you are doing by understanding Stanwood's
> system.
>
> Once you understand this system you can analyze any action
> and know where the problems lie.
>
>                 Newton

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway