David,
You didn't sound harsh or judgmental at
all! You are very eloquent and intelligent in
your writings. I appreciate you posts always.
I understand what a hammer does when it
hits a string (at least on a superficial level).
I maintain that it is the most easily adjustable
in the equation though. While it's an interesting
puzzle from the design standpoint I wonder if we
can expect that much accuracy from a hammer maker
anyway. I feel that through tried and true
voicing method applied evenly across the entire
scale you can achieve anything you want after
you've designed a predictable outcome in the belly assembly.
I have to question your idea of building
a heavier soundboard spring assembly than that of
the string assembly. It seems to me that either
system will push against the other until
equilibrium is achieved anyway. Lighter or
heavier string tension would in either case
translate into downbearing or the amount of force
(not just angle) the strings were applying
against the upward push of a crowned board.
Sooner or later they would equalize and that is
what resultant angle you would have, no? I think
that what you are designing into a RC&S board is
not only the crown in a predictable amount across
the board but also it's stiffness or resistance
to deflection. In any case it all seems to boil
down to equal opposing forces. Maybe I'm missing
something here. The "nature abhors a vacuum" thing keeps coming to mind.
If my previous assumptions are correct
it seems to me that the only way that you can
design is from the scale/board deflection
outward. A soundboard a string scale can be in a
state of equilibrium regardless of whether
anything ever strikes it or not. Could you not
and do we not often judge a pianos tone and sustain by plucking the strings?
It's late and I'm getting kind of foggy
here. I'm quite sure there's something to your
ideas. I'm just not sure how much.
best,
Greg
At 11:52 PM 3/7/2006, you wrote:
>Gosh, I hope I don't sound that harsh and judgmental. Thanks for your
>response.
>
>For this discussion let's start with the hammer. Let me start with this.
>When a hammer hits a string, it compresses, i.e. flattens out. The degree
>to which it flattens out depends on how firm it is. The degree to which it
>flattens out has an effect on the development and strength of various
>partials. A very soft hammer, for example, on a forte blow will flatten out
>more that a firmer hammer and the development of upper partials relative to
>the other partials between the hammers will be different. So let's assume,
>for a moment, that there is some optimum amount of compression that we want
>in an ideal hammer as we push it through various levels of playing in order
>to maintain a certain balance of partials that gives us a broad tonal
>spectrum from ppp to fff (yes, there will be differences in taste). Maybe
>that's an incorrect assumption. Let's assume for the moment that it is in
>some part true.
>
>Now let's jump to the soundboard spring/string spring interaction. For
>greater ease in talking about it let's just call them the string scale and
>the rib scale respectively (since we are talking about RC&S boards anyway).
>If the springs are equivalent and the string scale is a low tension scale,
>then the rib scale, if it matches, will also be lower tension. Being low
>tension, it will tend to move more easily and therefore will require a
>softer or lighter hammer in order that the attack is not too harsh. As you
>push that hammer to the forte level, as we mentioned before, since the
>hammer is soft it may tend to compress more than you might want and you may
>not get the balance of partials that you want from a forte.
>
>But let's assume that are working on a Steinway like piano and you don't
>want to alter that low tension scale but you want to use that somewhat
>firmer hammer in order to produce the balance of partials in the way that
>you want. Presumably you could do this by increasing the stiffness of the
>soundboard spring. The lower tension string scale now would not be as
>easily capable of moving this heavier rib scale so you would need a somewhat
>harder or heavier hammer in order to impart more energy to the board--which
>is what you wanted. How you calculate this difference is another matter
>which I leave to the experts design experts I am familiar with.
>
>Let's assume that the system does have to be in equilibrium. But to be in
>equilibrium there are three components, not two. It's not simply that the
>rib scale and string scale have to balance. The third component which has
>to be considered is the hammer which will impart a certain amount of energy
>depending on its weight and firmness. That's not to suggest that the hammer
>was ever not in the equation. But what I am interested in is in developing
>the formula with all three components from the start: i.e., I want this
>hammer and this string scale therefore I must have this rib scale--or, at
>least, the rib scale must fall within this range. While the rib scale can
>never be lighter than the string scale because it simply won't be able to
>support it over time, the reverse is not true. A lighter string scale won't
>compromise the rib scale over time.
>
>My point is that we tend to start from the string scale, calculate a rib
>scale and then figure out which hammer sounds best. I wonder whether it
>might not make more sense to start with the hammer and string scale and then
>calculate the rib scale that puts everything in equilibrium.
>
>David Love
>davidlovepianos at comcast.net
>
>-----Original Message-----
>From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
>Of Greg Newell
>Sent: Tuesday, March 07, 2006 7:07 PM
>To: Pianotech List
>Subject: RE: laminated ribs
>
>David,
> Your questions are certainly very
>astute. I'd have to say from the onset that I
>have no idea as to the correct answer so if you
>consider the rest of this a pure blather you can
>stop reading here. I can only speculate based on
>ideas I have not yet tried or have experience with.
> If we proceed under the assumption of a
>system that will not deteriorate appreciably over
>time I would, personally, lean toward a system of
>equal opposition of forces with a medium density
>and weight of hammer. That alone, in my mind,
>would seem to lend support to the hope of little
>or no deterioration over time. My take is that of
>the systems we speak of here, the hammer is
>certainly the easiest to change out. Naturally we
>can only theorize about what kind of result we
>should achieve until we actually try it. Those
>who have studied this is much greater detail have
>a better educated guess than I could ever hope to
>gain. That being said I wonder, from a laymans'
>point of view, if building a strong spring system
>on either end wouldn't cause, eventually,
>premature failure in the other thus rendering the
>effect of returning to where we started with a CC
>system in the first place. Unless I miss my guess
>the longevity is at least 50% of the appeal of
>the RC&S system. The other being predictability
>of result (in case some who are reading this
>weren't paying attention). ((Definitely NOT you
>David). What I wonder about is specifically to
>what level are we making fine tuning adjustments
>in the opposing forces here. You can't really do
>this on a string by string basis, can you? Then
>again isn't that exactly what the vertical hitch
>pins are all about? Carried further, how
>customized can we hope to make this throughout
>the entire scale? Assuming predictable crown
>throughout which follows the design we've made
>for ourselves Is there any reason that we might
>vary from 1.5 degrees in the high treble to 1 or
>1.25 degrees and then perhaps back up again
>before going down to 1 degree or lower in the lower tenor areas?
> By studying relative beam strengths and
>deflection rates (something I have not done) we
>should be able to determine what opposing
>downbearing would be required to render the
>system inert until the force of the hammer
>disrupts it. My question is if the system is set
>up this way what kind of attack and sustain can
>be expected from, say, simply plucking the string
>my guess is that sustain would be good but attack
>weak. I'm not sure what I base that on, however.
>Which would we favor (soundboard spring or string
>spring) if we wanted more attack? Another guess
>.... I'm thinking the soundboard spring.
> Regarding the choice of hammers I'm not
>sure it matters as much as we might think. I
>postulate that since the belly system is, or we
>hope it to be, as dialed in as it can be for
>predictable response then even an average hammer
>will sound great! Hard or soft, dense or not, any
>will be easy to voice to smoothness across the
>scale. That seems to be the reason all this
>effort is put into the belly in the first place.
>I maintain that this is even possible in a CC
>soundboard system, it's just much harder to get and even harder to keep!
> I'm certainly not the guy to answer any
>of your questions David. Actually, it seems that
>I only serve to add to the pile. Thanks for your kindness.
>
>best,
>Greg
>
>
>
>At 07:41 PM 3/7/2006, you wrote:
> >I'm glad you responded because no one else did. I'm not sure whether
>that's
> >because the information is proprietary or the answer is unknown. What you
> >responded to didn't really address my question but I appreciate it.
> >
> >I understand the benefits of RC&S boards. The question has more to do with
> >how the opposing strings should be matched. Should they be relatively
>equal
> >or not? Under what circumstances might you want a slight mismatch of the
> >two springs? How does the choice of hammer density and mass fit into this
> >equation?
> >
> >Typical CC boards seem to start out with a soundboard spring that is
> >somewhat stronger than the string spring (I like the sound of that), at
> >least hopefully, and end up with one that is somewhat weaker. This seems
>to
> >produce an interesting relationship to the hammer. A soundboard with a
> >heavier soundboard string than the string spring seems to require a denser
> >of heavier hammer. That's not surprising since the relatively weaker
>string
> >spring will require more energy imparted from the hammer to move the
> >relatively heavier board.
> >
> >A soundboard with a relatively weaker soundboard spring seems to require a
> >softer and/or lighter hammer. Interestingly, older soundboards where the
> >soundboard spring has weakened tend to sound better with a softer hammer.
> >That’s not surprising either for the same reasons. Since tone is a
>function
> >of both the relationship between the two springs as well as the
>density/mass
> >of the hammer, one could conceivably manipulate the relationship between
>the
> >two springs in order to gain a certain tonal effect desired from a
> >particular style hammer. My personal tonal preference (at the moment)
>seems
> >to come from a soundboard that requires a hammer that is medium firm and
> >medium mass. While that might work best on a soundboard designed for a
> >medium tension scale (say 160 - 170 lbs) matched with an equivalent
> >soundboard spring, one might also have the option of combining a relatively
> >low tension scale on a somewhat heavier soundboard spring in order to be
> >able to use a medium firm hammer.
> >
> >Looking at your average Steinway, for example, you have a relatively low
> >tension scale (on the smaller models). When the soundboard spring is
> >matched to the string spring, in these cases, the soundboard seems to work
> >fine with a relatively soft hammer. The heavier the soundboard spring
>comes
> >out for reasons of the unpredictability of compression crowning, the firmer
> >the hammer needs to be (i.e., more lacquer). Some of the nicer sounding
> >Steinways that I've heard are those that needed a somewhat firmer hammer
> >suggesting that the strength of the soundboard spring was somewhat greater
> >than the strength of the string spring.
> >
> >Thus, to repeat my question: How should the two springs be matched up?
> >Clearly, having a string spring that is stronger than the soundboard spring
> >is not a good thing. But that leaves (assuming stability in the system for
> >a moment) soundboard and string equal or soundboard spring stronger and if
> >so, to what degree. The further question is what sort of hammer in terms
>of
> >density and mass should we shoot for and how does that influence our
>choice.
> >Also, in terms of overall longevity of the system, wouldn't we be better
>off
> >with a somewhat lighter string spring than soundboard spring with a
>slightly
> >firmer hammer to mitigate that difference.
> >
> >David Love
> >davidlovepianos at comcast.net
> >
> >-----Original Message-----
> >From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On
>Behalf
> >Of Greg Newell
> >Sent: Tuesday, March 07, 2006 3:52 PM
> >To: Pianotech List
> >Subject: RE: laminated ribs
> >
> >Folks,
> > Sorry I wasted bandwidth. This was an
> >old question from David Love that I saved. Looks
> >like I found it again by accident and this time
> >decided to respond. Please disregard.
> >
> >Greg
> >
> >
> >At 06:17 PM 3/7/2006, you wrote:
> > >David and others,
> > > I understand your questions and they are
> > >good ones. Perhaps my answer is simpler than
> > >anyone is looking for but ........ The board is
> > >designed in such a way as to be in direct
> > >opposition to the downward force of the
> > >individual and combined force of the strings.
> > >There isn't any magical relationship that I'm
> > >aware of as a carryover from a CC setup save that
> > >the opposing spring of the board is still in
> > >direct opposition to the strings. It seems to me
> > >that the beauty of the RC&S system is the
> > >achievable predictability of the result not
> > >necessarily the added potential in it's strength
> > >capabilities. Just because the capability exists
> > >does not necessarily mean it is exploited.
> > > Consider that in many cases where a RC&S
> > >system is used it is also coupled with the other
> > >design elements of an adjustable plate support
> > >system and a roll pin type arrangement both of
> > >which assist in setting a micro-adjustable down
> > >bearing. This is a real part of the beauty of
> > >this overall plan. Taken alone these two would
> > >serve to provide a much better result even in a
> > >CC board system since it is so fully adjustable.
> > >The preference for RC&S in my mind seems to be
> > >one of longevity. Since the compression / tension
> > >relationship is mostly or wholly residing in the
> > >ribs the panel is far less likely to crack over
> > >time resulting in a much happier customer in the
> > >long run not to mention the possible elimination
> > >of the killer octave scenarios and bridge roll
> > >scenarios that we all know and love.
> > > Please know that I am somewhat a
> > >neophyte in this and my opinions mean very little
> > >if anything at all. This is all just my current
> > >take on the subject and hey, you asked!
> > >
> > >best,
> > >Greg
> > >
> > >
> > >At 11:03 AM 2/22/2006, you wrote:
> > > >There is another issue to be raised. How should one match the scale
> > > >tensions and anticipated downbearing angles to the rib scale. There
>are
> > > >choices to be made. I presume that you want a certain amount of
> >deflection
> > > >of the soundboard assembly and that given a certain scale with a
>certain
> > > >downbearing load, you can calculate the panel assembly stiffness and
> >preset
> > > >crown (in and RC&S board) to achieve that amount of deflection. But
> >there
> > > >are yet various ways to achieve that amount of deflection. For a given
> > > >assembly you could increase the scale tension and lower the downbearing
> > > >angle or decrease the scale tension and increase the downbearing angle.
> >You
> > > >can design an assembly with greater stiffness to go with a lower scale
> >and
> > > >greater downbearing or a lower stiffness to go with a higher scale and
> >less
> > > >downbearing, for example. Each combination, I presume, will produce
>its
> >own
> > > >unique tonal characteristics and, probably, require a hammer of
>different
> > > >density and/or mass. Those of you who are designing boards, how would
> >you
> > > >characterize your goals and why?. If we can produce a RC&S board that
> >will
> > > >be able to accommodate any particular variation in load, what is so
> >magical
> > > >about the .5 - 1.5 degrees of downbearing that seems like it came
>about
> > > >mostly due to the limitations of compression crowning. Further, in an
> >RC&S
> > > >board, what combination is most likely to give the general tonal
> > > >characteristics of your successful CC board. And let's allow ourselves
> >to
> > > >speculate even if we haven't actually built each variation.
> > > >
> > > >David Love
> > > >davidlovepianos at comcast.net
> > > >
> > > >-----Original Message-----
> > > >From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On
> >Behalf
> > > >Of Overs Pianos
> > > >Sent: Sunday, February 19, 2006 3:15 PM
> > > >To: Pianotech List
> > > >Subject: Re: laminated ribs
> > > >
> > > >Richard,
> > > >
> > > >The downbearing (vector) force on the sound board
> > > >is equal to the SIN of the angle of deflection
> > > >times the string tension.
> > > >
> > > >If there was absolutely no down bearing angle, it
> > > >follows that there would be no downbearing force.
> > > >The SIN of zero is zero so the string tension
> > > >vector component force would be zero.
> > > >
> > > >If the down bearing angle was 90 degrees, with
> > > >the speaking length segment parallel to the board
> > > >and the back scale heading vertically downwards,
> > > >the down bearing force would be equal to the
> > > >string tension, ie. the speaking length segment
> > > >would be contributing nothing to the down bearing
> > > >force, while the back scale segment would be
> > > >contributing its full string tension. The SIN of
> > > >90 equals 1.0. String tension X 1.0 equals string
> > > >tension. You can see how it all works.
> > > >
> > > >So if you have 160 lbs unison string tension with
> > > >a downbearing angle of 2 degrees, the downbearing
> > > >vector force for this unison string would be;
> > > >
> > > > Downbearing = 160*Sin2.0
> > > >
> > > > Downbearing =5.583 lbs
> > > >
> > > >The downbearing force for the whole note would be
> > > >3 X 5.583 if the note was a trichord, at 16.75 lb.
> > > >
> > > >If you are using an excel spreadsheet for your
> > > >calculations, remember that the downbearing angle
> > > >will need to be converted to radians.
> > > >
> > > >Yes, there is a large variation in what people
> > > >believe is an appropriate level of downbearing.
> > > >If you measure a few pianos around the place
> > > >you'll find that there is a lot of variation in
> > > >the downbearing angle also.
> > > >
> > > >The 2 degree figure you quoted I would consider
> > > >to be too high for a real world piano.
> > > >Bösendorfer have typically set their pianos with
> > > >angles approaching 2 degrees strung. This is a
> > > >little higher than I would feel comfortable with.
> > > >When Ron N was here a couple of years ago we
> > > >looked at our no. 5 with a Lowel gauge and it
> > > >measured almost right on 1.3 degrees over the
> > > >whole piano. This yields a total downbearing
> > > >force on our no. 5 of 427 Kg (941 lb). I wouldn't
> > > >recommend these figures for an older or weaker
> > > >panel but it works just fine for our I-rib
> > > >design. Setting the downbearing angle is a
> > > >balancing act between how much the board will
> > > >sink and how much force we wish to apply.
> > > >
> > > >When looking at a given piano, I suggest that you
> > > >set up a spreadsheet to calculate the downbearing
> > > >force you are planning to set up per rib. Note
> > > >also that setting an unstrung angle of say 1.5
> > > >degrees won't result in a downbearing force of
> > > >tension X SIN(1.5). Its the resultant string
> > > >deflection angle when the piano is at pitch and
> > > >the board has stabilised (sunken to equilibrium)
> > > >under load which will determine the actual
> > > >downbearing force. So you need to make an
> > > >educated prediction on how much a board will sink
> > > >under tension to get an idea of the resultant
> > > >downbearing force.
> > > >
> > > >A common scenario with new pianos is for techs to
> > > >measure a down bearing figure which on the face
> > > >of it looks OK, but very often the sound board
> > > >has sunken to a state where it is pushed almost
> > > >completely flat by the down bearing angle which
> > > >was set into the piano. In these instances the
> > > >board is too weak for downbearing loads which are
> > > >being applied or the unstrung angle wasn't set
> > > >properly. Either the downbearing unstrung angle
> > > >should be reduced or the board strengthened to
> > > >withstand the setting angles to which it is being
> > > >asked to resist. So often technicians will look
> > > >at a sound board and declare that it is fine
> > > >because the downbearing angle measures some
> > > >wonderful figure. But if the board has been
> > > >pushed inside out before the customer's ink is
> > > >dry on the cheque, things ain't too good,
> > > >regardless of what the downbearing gauge might
> > > >indicate.
> > > >
> > > >Get an accurate downbearing gauge and a thread
> > > >length for looking at crown, and measure a few
> > > >pianos old and new. You'll develop a picture of
> > > >what's happening.
> > > >
> > > >Ron O.
> > > >
> > > > >Please correct if this is entirely wrong... but
> > > > >I thought that since the string was being
> > > > >measured in terms of its tension (pounds) one
> > > > >could simply the problem as a like sided
> > > > >triangle with half the pounds on each leg. Since
> > > > >the measurement is taken in the deflected
> > > > >condition... you have basically the hypotenus
> > > > >and all angels of a right angle triangle
> > > > >available to figure the amound of deflection..
> > > > >pounds in this case. So 160 pounds with a 2
> > > > >degree deflection at the bridge yields
> > > > >
> > > > >Sin 1 x 80 = 1.396192515 lbs downbearing,
> > > > >which is 1.745 % of the string tension.
> > > > >
> > > > >er... yes ??
> > > > >
> > > > >RicB
> > > > >
> > > > >
> > > > >-------------
> > > > >> So knowing all of the above, what is the equation that will
> >calculate
> > > > >> an approximate string bearing load under the conditions I
>describe?
> > > > >
> > > > >Beats me. I use the SIN(RADIANS(degree measurement))*tension
> > > > >per unison, and add them up in my spreadsheet.
> > > > >_______________________________________________
> > > > >Pianotech list info: https://www.moypiano.com/resources/#archives
> > > >
> > > >
> > > >--
> > > >OVERS PIANOS - SYDNEY
> > > > Grand Piano Manufacturers
> > > >_______________________
> > > >
> > > >Web http://overspianos.com.au
> > > >mailto:ron at overspianos.com.au
> > > >_______________________
> > > >_______________________________________________
> > > >Pianotech list info: https://www.moypiano.com/resources/#archives
> > > >
> > > >
> > > >_______________________________________________
> > > >Pianotech list info: https://www.moypiano.com/resources/#archives
> > >
> > >Greg Newell
> > >Greg's piano Forté
> > >mailto:gnewell at ameritech.net
> > >
> > >
> > >_______________________________________________
> > >Pianotech list info: https://www.moypiano.com/resources/#archives
> >
> >Greg Newell
> >Greg's piano Forté
> >mailto:gnewell at ameritech.net
> >
> >
> >_______________________________________________
> >Pianotech list info: https://www.moypiano.com/resources/#archives
> >
> >
> >
> >_______________________________________________
> >Pianotech list info: https://www.moypiano.com/resources/#archives
>
>Greg Newell
>Greg's piano Forté
>mailto:gnewell at ameritech.net
>
>
>_______________________________________________
>Pianotech list info: https://www.moypiano.com/resources/#archives
>
>
>
>_______________________________________________
>Pianotech list info: https://www.moypiano.com/resources/#archives
Greg Newell
Greg's Piano Forté
mailto:gnewell at ameritech.net
www.gregspianoforte.com
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