Touch Weight

[David Love]

I agree that knowing how and how far to move the capstan can be very
useful, and it's not that difficult.  I think the best way for determining
placement is with a Stanwood style platform that allows you to locate the
capstan uniformly by measured key ratio, placing a ten gram weight on the
back of the key and reading off the digital scale for the desired target.  
Measure the end keys (naturals) of each section and draw a line.  You can
make a dummy capstan arrangement with a small block of wood and a shortened
capstan that can be moved around in order to determine proper placement. 
But I think this goes slightly beyond the initial inquiry about a simple
way to tackle action problems.  Nevertheless, it should ultimately be part
of the arsenal.

David Love
davidlovepianos@earthlink.net


> [Original Message]
> From: Fred Sturm <fssturm@unm.edu>
> To: College and University Technicians <caut@ptg.org>
> Date: 1/5/2004 12:54:33 PM
> Subject: RE: Touch Weight
>
> Nice summing up, David! I think what you describe should be within the 
> capabilities of anyone who is replacing hammers on a quality grand. And 
> certainly that should include any caut.
> 	In cases where "original weight" hammers are available, and reliably so, 
> reproducing original conditions is no problem. But hammer weights are all 
> over the place. There are a lot more options available to us now, but it 
> takes a lot of knowledge to select an appropriate set, and even then
there 
> is no guarantee, unless one has the budget and/or time to have many sets 
> available. In any case, it is necessary to know how much weight to remove 
> from whatever set you have (tapering and tailing) to get good results. So 
> you have to have the basic abilities David describes to come up with good 
> results.
> 	I would add that an action rebuilder should also have knowledge and 
> experience to use (if needed) wipp's with assist springs (with
accompanying 
> adjustments), and possibly to do minor capstan movement. This is not 
> extraordinarily complex stuff - though you do have to be on the ball and 
> skilled in precise work. But again, that _should_ describe any caut. at 
> least on a good day, ;-).
> Regards,
> Fred Sturm
> University of New Mexico
>
> --On Saturday, January 3, 2004 9:56 PM -0800 David Love 
> <davidlovepianos@earthlink.net> wrote:
>
> > Jim:
> >
> > I agree with you generally.  But there are times when modest redesigns
are
> > in order and to fail to consider them will often lead to bad results.
> > While a thorough understanding of design elements will always give you a
> > better result, there are some simple ways to approach things if you
don't
> > yet have that type of expertise that will often give you a better result
> > than what is there.
> >
> > An overall look at the action before it is disassembled can give you a
lot
> > of information without taking the extensive measurements that Stanwood
> > suggests.  I do think it is important to adopt the balance weight as a
> > standard rather than simple downweight, but understanding that is not
> > difficult and is outlined well in one of Stanwood's articles in the PTJ
a
> > few years back.  (You also mentioned the formula in you previous post.)
> > )Measure the knuckle to center distance, a few sample hammer weights
(try
> > measuring all the C's to give you a sense of the weight curve), the up
and
> > down weights and look at the number of leads in the keys and their
> > placement.  That information will give you a lot with which to make
> > decisions about changes.
> >
> > If you don't have extensive knowledge, then the simplest changes that
can
> > be made, if you think there is a problem with the action set up, will
> > involve adjusting hammer weight or selecting a knuckle-to-center pin
> > dimension that is different than the existing one.  If the old action
> > weighs off where you want it to and there aren't an excessive number of
> > leads in the keys, then you can try to simply duplicate what is there,
> > weighing the hammers and following the procedures you laid out in your
> > previous post.
> >
> > Without weighing the front weights of the keys it is difficult to
> > determine precisely what constitutes excessive front weighting, but as a
> > general rule no more than four in the low bass, three in the low tenor,
> > two in the mid treble and one in the high treble.  That's assuming they
> > are placed toward the front with moderate spacing between them.   If the
> > leads are placed back toward the balance rail, then you can add one more
> > lead and probably not get excessive.   If your desired hammer weights
> > will cause you to have to add more leads to achieve the balance weight
> > you want, then consider using a knuckle to center dimension that is 1 mm
> > longer than the existing one.  A move of the knuckle by 1 mm will
usually
> > change the BW by about 5 grams ( a longer knuckle to center pin
dimension
> > will also reduce friction slightly).   Try a few samples to make sure
> > that they will regulate properly.   If you are unable to alter the
> > knuckle dimension and your existing hammers are producing excessive
> > balance weights then you will have to reduce the hammer weight.
> > Depending on the action leverage, a reduction in the hammer weight by 1
> > gram will cause a reduction in the BW of 5-6 grams, or it will allow you
> > to take one 12 gram lead out of the key from midway between the front of
> > the key and the balance rail.  Not hard stuff.  I use a balance weight
> > range of 36 - 40 grams (lighter - heavier).  While there are times when
> > one might want to go lower or higher, I would generally recommend
staying
> > in that range.  I default most actions to around 38 grams.  Of course,
be
> > sure whatever you do that you test for regulation with samples.  It is
> > likely, however, that an action that requires a modest number of leads
to
> > achieve a medium balance weight will, by definition of action ratios,
> > regulate properly.
> >
> > These sorts of simple design changes are routinely made and usually
> > without any problems.  I don't think technicians who aren't well versed
> > in action design need fear these types of changes.  Just sample things
> > methodically and take care to create a smooth hammer weight curve by
> > whatever your favorite tapering system is (mine is with a table saw).
> > Though I prefer a more thorough approach as is offered by Stanwood
> > methodology, you can get good results making modest changes to the
action
> > without  all the platforms and detailed formulas.  Just work carefully
> > and think through cause and effect before you glue it all together.
> >
> >
> > David Love
> > davidlovepianos@earthlink.net
> >
> >
> >> [Original Message]
> >> From: James Ellis <claviers@nxs.net>
> >> To: <caut@ptg.org>
> >> Date: 1/2/2004 4:21:11 PM
> >> Subject: Touch Weight
> >>
> >> David Love's point is well taken, and I agree.  However, my previous
post
> >> titled "Touch Weight" was in response to Paul Legard's request for a
> > simple
> >> routine to follow that would produce good results.  From reading some
of
> >> the posts on this list, it seems to me that many technicians out there
do
> >> not have a sufficiently clear concept of action dynamics to attempt any
> >> sort of re-design of an existing action.  Hammer weight (mass) is
> >> dictated by string mass and the sound one wants to produce, but
> >> constrained by the mechanical limitations of the system.  John
Hartman's
> >> description of
> > moment
> >> of inertia is correct.  You must look at the entire compound lever
> >> system, but it all boils down to static weight, leverage ratio, time,
> >> mass, and distance traveled.  No matter how you describe it, the basics
> >> remain the same, and it is not just "theoretical".  It is very real,
and
> >> provable. The simple point I am making is:  If you really know what you
> >> are doing,
> > go
> >> ahead and re-design the action.  If not, don't do it.
> >>
> >> Sincerely, Jim Ellis
> >>
> >>
> >> _______________________________________________
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> >
> >
> >
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>
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