Weird Frontweights

[David Love]

Richard:

Doesn't this piano have assist springs?  If so then you need to do the weigh
off with them disconnected anticipating that you will further reduce the
balance weight by whatever factor you choose (10-15 grams) when you reattach
them.  You will, of course, have to set the tension.  It is hard to imagine
a 15 gram variance in the front weight from note to note if you have used
the balance weight system for doing a weigh-off.  Friction would then not
effect the leading pattern.  If you have done the weigh off using only the
down weight, then the leading pattern can be all over the place.  Remember
that a change in friction will not effect the balance weight as the upweight
and downweight will move in opposite directions, e.g. UW = 20, DW = 50, F =
15, BW = 35.  If you reduce the friction to 10 grams then UW = 25 DW = 45, F
= 10 and BW still equals 35.  Assuming even a resonable transition in strike
weights from bottom to top, a uniform knuckle radius and straight capstan
line, there shouldn't be that much variation.  It is possible that the KR is
different between the sharps and naturals, I have seen that many times and
that will account for differences.

David Love


----- Original Message -----
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: <pianotech@ptg.org>
Sent: October 08, 2001 11:53 AM
Subject: Re: Weird Frontweights


> Yes.... well all this is fine and dandy Ron and Del.... but if that
results in
> fluxuations in FWs of up too 15 or more grams in neighboring keys.... then
> something is wrong and right here in River city.
>
> That was the origional complaint with this thread.... whether or not
pattern
> leading is too blame I dont know, but someone.... Ed Foote I think said
> something about pattern leading sometimes results in such variations.  I
have a
> hard time thinking that this is acceptable.
>
> One other thing.  Friction does  not present the same problem in a
Stanwood
> setup action. Friction is a sort of left over, and as such a known
quantity.
> You make the point of reasonable dependability below Ron... what could be
more
> dependable then this then ?
>
> The only point left is cost effectiveness in a factory setting. Ok... its
really
> quick to stamp out a set of keys after a pattern. But wildly varying FW's
is a
> big negative. And if one already "knows" ahead of time just how much the
FW
> should be... as in to the tenth of a gram.... then it seems absurd to
allow for
> 15 gram variances when this can be easily avoided.
>
> btw... doesnt Stanwood has worked out a pattern system that fits with his
basic
> method also...?
>
> Ron Nossaman wrote:
>
> > >    Any weighting off of keys, if done on an individual basis, must
first
> > >have all of the other problems of friction, regulation, etc. taken care
of
> > >first. So many of the manufacturers don't seem to be able to do this.
> > >    So, if a piano is made at the factory with these obvious
shortcomings,
> > >and then the keys are individually weighted on an action in that
condition,
> > >when it IS put into the proper, well-regulated condition, then it seems
to
> > >me that the key weighing would no longer be correct, and in fact would
> > >probably be all over the place.
> >
> > That's the whole problem. Keys are individually weighted to produce
uniform
> > static down weight. It's done as a "finishing" step to "overcome" the
> > apparent irregularities in the action, but it doesn't. Weight
distribution
> > from key to key most likely isn't where the problem lies in the first
> > place, so changes in weight distribution from key to key probably aren't
> > going to fix it. Pattern leading is a better approach because it's done
as
> > a foundation rather than a last ditch attempt at disguise. The leading
> > pattern is, of course, established to accommodate anticipated action
> > geometry and hammer weight graduation. With a reasonably competently
> > designed pattern leading schedule, someone doing a "final" weigh off and
> > finding wild discrepancies will know to look elsewhere than at the
leading
> > for the cause.
> >
> > That's why pattern leading is a better idea. It's a known weighting
> > progression, and it helps to have SOMETHING reasonably dependable to
work
> > from.
> >
> > Ron N
>
> --
> Richard Brekne
> RPT, N.P.T.F.
> Bergen, Norway
> mailto:rbrekne@broadpark.no
>
>