Touchweight Metrology Question

[David Love]

Terry:

I think you should carefully reread Stanwoods 3 or 4 articles that he
suggests with the kit.  Though he seems to be an advocate of choosing heavy
hammers for tone purposes, there was a memorable post a few days ago by Bill
Ballard quoting Del Fandrich on the tradeoff between power and quality when
it comes to tone.  I think hammer weight falls into this category.  Heavy
hammers produce more tone, but not necessarily better tone.

Analyze the system to see what strike weight it will accomodate and keep the
FW's under maximum, would be my advice.  It's not as if inertia problems
suddenly start at 1 gram over the maximum.  An action at the  FW maximum
will  have greater inertia than one 10% under the maximum.  Unless you want
to install assist springs and create a perfectly smooth front weight curve
allowing the assist spring to compensate for differences in SWR due to
manufacturing irregularities to get an even BW, then target a slightly lower
FW to insure those irregularities won't put you over the max on some notes.
Figure out the maximum SW for that system and decide whether that is
attainable with a hammer of reasonable weight.  As Jon Page suggested, then
take the hammers off, taper, tail, to get the SW you need and while your at
it, repin the flanges. The Stanwood system need not be such a great mystery.
Read the articles carefully, do the math.  It's all there.

David Love
----- Original Message -----
From: "Farrell" <mfarrel2@tampabay.rr.com>
To: <pianotech@ptg.org>
Sent: May 15, 2002 5:02 AM
Subject: Re: Touchweight Metrology Question


> Richard wrote:
>
> "Basically what I do is to pick a SW curve based on the target ratio I
want,  install FW to fit the FW max table ...."
>
> How do you relate/figure SW to SWR? I thought target SW should be based on
piano tone, and then geometry and FW and whatever adjusted to accomodate the
desired SW?
>
> Unfortunately, this piano appears to have new Yamaha hammers on it. But
they are not tapered, or arced. Friction in the hammer-shank flanges is all
over the place. Is it reasonable to try the water/alchohol thing to
shrink-size the bushings before repinning the whole shebang? I wish the
hammers and knuckles were more worn, then it would be easy to recommend a
new top half of the action.
>
> By installing FW to "fit" the FW max table, are you suggesting that FW
should be at or near that maximum value? If so, why? Doesn't "maximum" in
this case mean that "at that value or below is fine"? Or not? Thanks.
>
> Terry Farrell
>
> ----- Original Message -----
> From: "Richard Brekne" <richard.brekne@grieg.uib.no>
> To: <pianotech@ptg.org>
> Sent: Wednesday, May 15, 2002 3:11 AM
> Subject: Re: Touchweight Metrology Question
>
>
> > Farrell wrote:
> >
> > > I am taking my second stab at touchweight metrology analyses of an
action (my first was half-hearted and incomplete). Yamaha G5, 1963, action
in very good condition. Complaint: action heavy. It is indeed with DWs all
over the 60 to 80 gram range (mostly around 65 grams). Some notes do have a
lot of friction, but many measured notes only have 10, 11, 12 grams
friction, so clearly there is a problem with either too much weight hanging
out somewhere, or bad geometry. KR is 0.49, BWs are mostly around 50 to 55
grams or so. I have not measured strike weights and wippen radius weights
yet.
> >
> > KR of 0.49 is down there quite a bit... which means the capstan is in a
good ways and you should be able to lift all kinds of weight, but need lots
of key dip to get things to work.  So if you are in addition experiencing
medium heavy to heavy DW then you probably have a fun job on your hands.
> >
> > But this is real sketchy just with KR and vague DW, BW and Friction
hints.
> >
> > I like to take a few (10-12) samples of all parameters to get an idea of
where the action is, then plan what I want to end up with a "least work
possible" perspective. I aggree with David that ending up around 5.75 SWR is
a good generic solution that seems to work well with most actions.
> >
> > Basically what I do is to pick a SW curve based on the target ratio I
want,  install FW to fit the FW max table David includes with his kit, and
adjust leverage as neccessary to make a decent enough fit.
> >
> > Make sure the action spread and friction issues are taken care of ahead
of time.
> >
> > > Maybe too early yet to even be asking questions. Just wondering if
anyone that is familiar with this process has any recommendations. Thanks.
> >
> > This proceedure makes for a decent generic solution, and gets you
started along the Stannwood path. It gets you looking at and using his
formula in a few different ways, and you start routines in his practical
methods. It doesnt allow for much "design" work tho as you are pretty much
stuck with a very narrow set of SW and FW parameters. But its a good and
easy place to start.
> >
> > In your case, if your KR is indeed only 0.49,  I would guess you might
end up moving the capstan line back a bit
> >
> > > Terry Farrell
> > >
> >
> > Grin.. Ed will correct me if I am thinking backwards again. It gets
worse when I think upside down :)
> >
> >
> > --
> > Richard Brekne
> > RPT, N.P.T.F.
> > Bergen, Norway
> > mailto:rbrekne@broadpark.no
> > http://home.broadpark.no/~rbrekne/ricmain.html
> >
> >
>