Touchweight

[David C. Stanwood]

To All,

I know I'm not a University Tech but I was just having a look at the
archives thought I would make a few comments on this thread.  First of all
I'd like to say that twenty years ago, when I was hard at work refining the
rebuilding skills I had learned at North Bennet St. School, there was no
comprehensive information about touch weight available.  Things are really
so much better for all of us now thanks to so many who have devoted time
and thought to sharing their ideas and experience on the subject, thanks to
the internet!

>Best thing so far is Stanwoods Method. Tho it does not directly deal
>with inertia issues, it does insure very even key to key inertia
>characteristics.

>RicB

Richard, thanks for the support, Tho I do deal with the inertia issue by
matching hammer weight and ratio.  This does, in a crude but effective way,
deal directly with inertia.  For instance, we know pretty well from
experience what combinations of hammer weight and ratio will produce an
action dynamically appropriate for the customers needs.  For instance if we
find an average weight ratio of 6.0, I wouldn't go with a Strike Weight
level above 1/2 medium unless the client wants a heavier-than-average
action.  For a medium dynamic feel with a 5.5 ratio I would specify a top
medium strike weight.  

A simpler low-tech approach has been taught by Renner for years, that is to
copy the original parts and by trial and error find a hammer weight that
produces a normal down weight.  This would assume that things were ok with
the key leading in the first place, and the word ass-u-me is one to be wary
of!  

Thank you David Love for your comments, especially on what is an acceptable
limit for key leading pattern in this thread and on your intelligent and
straight forward alternative key balancing approaches that you've mentioned
in other threads on the pianotech list.

> 3.  Use the recommended parts for that particular action.  We assumed a
> well-designed action to begin with, so maintain the original design,
> ratios, spread, clearances, etc.

> Sincerely, Jim Ellis

Thanks Jim for your well engineered discussion and thoughts... looking
forward to your seeing fully developed approach when it's published!  I
differ with your comments here, as well as the Renner USA approach, which
is to say that, for instance, in older Steinways one should always copy the
old parts when replacing with new.  This usually means using a knuckle that
is mounted 15.5mm out from the hammer center pin.  This approach usually
spells disaster with modern weight hammers which are often normally in the
high zone.  The solution is to use "light" (say 1/2 medium or less
depending on the tapering) hammers which Renner USA now supplies, or use a
light reproduction hammer say from Ronson, (an excellent choice!).   

One may also get fine results by using current parts, with the knuckle
mounted further out at 17mm, with current hammer weight levels (which
themselves vary quite a bit.)  A little trial and error will indicate if
things will work well.  Sometimes (such as on many older model O
keyboards), the key ratio is too low and using the current parts will
produce an overall ratio that is too low.  This will show itself by having
to regulate to an overly deep dip and short blow.  The problem can be
exacerbated by "noncompliance" issues including inappropriate action
elevations, bore distance, key height, etc.

There is no substitute for measuring and knowing the hammer weight or
strike weight levels and this should be (and is becoming) part of the
accepted discipline...  It would be so helpful if every time we mentioned a
hammer as being "light" or "heavy" to qualify the meaning of those terms by
refering to the specific weight zone:

http://www.stanwoodpiano.com/SW-HWstandards3.pdf

Just some thoughts... carry on!

David Stanwood