touchweight analysis

[Richard Brekne]

Farrell wrote:

> > ...... I got keyed into
> > looking closely at the knuckle. Some were really slanting badly... mostly
> > towards the hammer. Straightening these up solved quite a bit of problem
> keys.
>
> I had not heard of this. (I suppose I just missed it somewhere.) Are you
> speaking of the slot in the hammer shank not being at right angles to the
> long axis of the shank, resulting in the knuckle core being angled back
> toward the hammer - thus effectively increasing knuckle-to-centerpin
> distance and reducing leverage?

Exactly... and I was amazed at the influence on the touchweight really. I
suppose the worst of them actually had the tip of the knuckle moved as much as 2
mm towards the hammer. When you think about this then you say...well of
course.... In anycase its worth a good looking at next time you run through an
action job... Stannwood or not. I have on occasion straightened out some of
these before if they looked bad enough...but I really had no idea what a large
part a millimeter can play here.

>
>
> ----- Original Message -----
> From: "Richard Brekne" <rbrekne@broadpark.no>
> To: <pianotech@ptg.org>
> Sent: Wednesday, May 23, 2001 6:50 AM
> Subject: Re: touchweight analysis
>
> >
> > David Love wrote:
> >
> > > Richard:
> > >
> > > To do the weigh-off I now use Stanwood's Balance Weight/Friction Weight
> > > Table.  It effectively takes the friction component out of the weigh-off
> so
> > > that any variations in downweight through the keyboard can be directly
> > > attributed to friction.
> >
> > Thats really nice isnt it... the predictability that creates is ...just so
> very
> > very handy indeed.
> >
> > > With relatively light hammers, the friction in the
> > > action was lessened, and because the KR made the action feel like it was
> > > fighting you a little, I weighed it off at 34 BW.  I think it was the
> right
> > > choice for this pianist.  I didn't hear directly from Stanwood, I
> usually
> > > copy him directly on these types of queries, but did not on this one.
> Jon
> > > Page, however, was very helpful, especially in terms of a methodical way
> of
> > > establishing capstan location.
> >
> > Yes.. tho I am rather green at this myself,  I have come to rely on Jons
> idea
> > for capstan placement quite a bit. At the very least it creates a sort of
> window
> > you dont really want to go outside of unless you are prepared to deal with
> other
> > problems. Keydip, sharp travel, blow distance, and the like. Course you
> can
> > always create a situation on purpose and this whole idea lets you do that
> rather
> > conciously...
> >
> > > The last two actions I've done have been a
> > > crash course in Stanwood's method of problem solving.  I have found it a
> > > very useful way of quantifying the problems and plugging in possible
> > > solutions.
> >
> > I aggree one hundred percent.
> >
> > > I've recently set it up on an excel table with the formulas
> > > programmed into the individual cells so all you have to do is plug in
> the
> > > numbers.
> >
> > I did too... right off the bat on the first run through. It takes FW, KR,
> WRW,
> > SW, UW, and DW as parameters and spits out the rest. You can see just how
> the
> > ratio to BW developes, and just how much a role friction plays. I think
> this is
> > what helped me get such an even BW and Ratio in that last job I did. In
> > essence... after getting  nice SW and FW curves that in theory should
> yeild an
> > acceptable Ratio... I dinked around with evening out friction as
> neccessary to
> > put the final touch on things. Friction ended up being pretty even too
> really,
> > tho to be honest I had to cheat a bit with hammer flange tightness this
> time
> > around. Still they were all within a 7 to 4 (-) swing window and also
> reacted
> > well to the S&S tap test. Btw, in the course of that process I got keyed
> into
> > looking closely at the knuckle. Some were really slanting badly... mostly
> > towards the hammer. Straightening these up solved quite a bit of problem
> keys. I
> > hadnt been able to get the BW high enough for these...had to look around
> to find
> > the problem.. and there it was...
> >
> > > I'm sure someone has already done this but going through the
> > > excercise of setting it up gave me a better sense of how all these
> things
> > > interact with each other.  I'm working on a "what if" table that
> combines
> > > research taken from Richard Davenport to produce an input/output table
> so
> > > that various solutions to problems can be tried on paper first.  I
> haven't
> > > plugged in the new data from this particular action yet, but when I do
> I'll
> > > send it off to you and you can look at the before and after if you're
> > > interested.  Speaking of Richard Davenport's research, if you have his
> "What
> > > happens if" table, take a careful look at under centering versus over
> > > centering, and what that does to the touchweight and friction.
> >
> > I dont have that, and havent read anything from Richard... would love
> to... do
> > you have anything more on this ??.. I can send you my excell whatiffer if
> you
> > like for ideas..
> >
> > >
> >
> > --
> > Richard Brekne
> > RPT, N.P.T.F.
> > Bergen, Norway
> > mailto:rbrekne@broadpark.no
> >
> >

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no