---------------------- multipart/alternative attachment To: "PTG" <pianotech@ptg.org> Subject: Re: Key Lead Placement Since nobody bit on this one I'll chip in with my 47 cents worth. I like to place my leads out as far as posible.Tho I have been back and forth on this a few times in my life. And I like to use a healthy amount of lead. I am not convinced of this low mass approach and dont particularly like the feel of such actions as I have run into that were set up such. In short.. I like mass levels ranging from around 35-40 graduating down to 2-4, and I like to use as little lead as possible to get there. RicB Farrell wrote: >I have read material that suggest placing key lead close to the center >rail, and other material that suggest to use a minumum of lead and place >it out near the front of the key. For a given balance weight, what >guidelines do listy folks use for lead placement? > >Perhaps just do the 3-2-1-0 arrangement and let them fall where they will >placement-wise to get the job done? Any rules like "no closer than X mm >from key end.....? > >Terry Farrell At 02:49 PM 4/1/2001 -0500, you wrote: >Ric, > >The short answer is, you're right about isolated weights undergoing the same >change in motion. But in the case of keyleads, we're interested in the >reaction force perceived by the pianist at the front rail, when he/she >applies a force hoping to causes a given acceleration of the key. So the >effect of the lever arms on both the acceleration of the lead, and on the >reflection of the reaction force back to the pianist's finger at the front >rail, must enter into the calculation. > >The long answer is: > >Inertia is the tendency of a body to resist a change in velocity, otherwise >known as acceleration. The greater the mass, or the greater the >acceleration, the greater the resisting force. The governing formula, for >linear motion, is F = m*a. (Force equals Mass times Acceleration) > >The formula we looked at earlier in this string (I=M*r^2) applies to >rotating bodies. The rotational formula is T = I*alpha (Torque equals >Moment of Inertia times angular acceleration). It's neat 'cause it takes >the lever arm lengths into account within the values for torque, moment of >inertia, and angular acceleration, but I always get bogged down in the units >conversions, lb-in^2, radians/second^2, etc. etc., so where possible I try >to see every problem in the linear model. > >Let's take the key weight example, and we'll round off the numbers to make >it easier, if not necessarily correct for your specific piano: (You may >find it makes more sense if you sketch this as you read through) > >The key measures 8" from front rail pin to balance rail pin. You want to >increase the keyweight by 4 grams, and are considering putting the weight at >4" (4 grams times 8" divided by 4" = 8 grams required) or at 2" (4 grams >times 8" divided by 2" = 16 grams required). > >Let's let A equal the acceleration of the key, at the front rail pin, for a >mezzo-forte blow. The acceleration at 2" would be A times 2" divided by 8", >or A/4. The force at 2" would be M * A/4, or 16*A/4, or 4*A. > >The acceleration at 4" would be A times 4" divided by 8", or A/2. The force >at 4" would be M * A/2, or 8*A/2, or 4*A. > >So, in both cases, the force AT THE WEIGHT is equal to 4*A. But the force >felt by the pianist, AT THE FRONT RAIL, is reduced by the leverage: For the >weight at 4", the force is reduced by 4" divided by 8", so the pianist feels >2*A. For the weight at 2", the force is reduced by 2" divided by 8", so the >pianist feels A. Bottom line, the closer the weight can be placed to the >balance rail, the less inertial resistance the pianist will feel. > >Mike > > > > >----- Original Message ----- >From: Richard Moody <remoody@midstatesd.net> >To: <pianotech@ptg.org> >Sent: Saturday, March 31, 2001 1:46 AM >Subject: Re: Ideal leading pattern: > > > > >Putting less lead further out will result in more > > > inertia than more lead closer in........ > > > > I thought more mass meant more inertia. Perhaps I lost the meaning of > > the terms. Inertia is the "force" needed to move (or change the > > motion of) a body? Momentum is the force of a body in motion? > > You can balance a lever (Key) with one weight near the end, or with 4 > > weights near the fulcrum. Both are in balance but one with 4 times > > the mass. Wouldn't the one with more mass require more force to move > > it? As piano keys, both would still have the same down weight, but one > > would feel harder to press. That would be the key with more mass in > > it, right? ---ric? > > > > ----- Original Message ----- > > From: Mike and Jane Spalding <mjbkspal@execpc.com> > > To: <pianotech@ptg.org> > > Sent: Thursday, March 29, 2001 11:47 AM > > Subject: Re: Ideal leading pattern: > > > > > > > Paul, > > > > > > I believe you are mistaken regarding the inertia. (As a former > > machine > > > design engineer who recently jumped out of the frying pan and into > > piano > > > tuning, I have some experience with this). It does indeed vary with > > the > > > placement of the lead: Putting less lead further out will result in > > more > > > inertia than more lead closer in. Half the weight, twice as far > > out, same > > > static downweight, but twice the inertia. (For those of us old > > enough to > > > remember phonograph records, this is why the counterweight on the > > tone arm > > > is very large and very close to the pivot point.) Doesn't change > > your > > > conclusion: all other things being equal, keep the lead near the > > pivot > > > point. > > > > > > Mike Spalding > > > > > > > > > ----- Original Message ----- > > > From: <larudee@pacbell.net> > > > To: <pianotech@ptg.org> > > > Sent: Thursday, March 29, 2001 10:15 AM > > > Subject: Re: Ideal leading pattern: > > > > > > > > > > David, > > > > > > > > As a matter of simple physics, it makes no difference whether you > > put less > > > lead > > > > farther away from the balance rail or closer in, with one > > stipulation. > > > The > > > > stipulation is that the key is perfectly rigid and has no > > flexibility. > > > > Otherwise, both the momentum and inertia will be the same either > > way. > > > > > > > > Of course, we know that the key is not perfectly rigid, so > > placement of > > > more > > > > lead closer in is probably preferable, all else being equal. This > > reduces > > > the > > > > sense of inertia in the key because the part that takes the force > > of > > > depression > > > > has less mass in it than otherwise, and applies leverage to the > > part that > > > has > > > > the mass, closer to the balance rail, after some momentum has > > already been > > > > gained in the key. Along with the use of cylindrical key > > bearings, I > > > think this > > > > design is part of what Steinway calls its accelerated action, but > > I am > > > prepared > > > > to be corrected. > > > > > > > > Paul Larudee > > > > > > > > David Love wrote: > > > > > > > > > I run into this sort of situation frequently and I would like > > some > > > opinions. > > > > > Steinway model S ca 1936. I am replacing hammers and shanks > > only. I > > > use > > > > > Steinway hammers full taper, Abel shank 16.5 mm knuckle gives me > > the > > > best > > > > > combination of regulation/downweight from which to work. The > > strike > > > weight > > > > > is medium and consistent throughout. Key weight ratio is 5.0. > > When I > > > > > install the hammers, I will still want to take 2-5 grams off the > > > downweight > > > > > throughout much of the piano (though it is somewhat erratic) to > > get a > > > 52-48g > > > > > taper. Doing so does not compromise the upweight. The present > > front > > > > > weight of the keys allows me to add lead without exceeding the > > maximum > > > > > recommended front weight (according to Stanwood charts). But... > > the > > > keys > > > > > already have a fair amount of lead grouped mostly toward the > > balance > > > rail. > > > > > Though the front weight is not excessive, the keys themselves > > weigh a > > > lot > > > > > because of the amount of lead in them (e.g. C16 = 163g , C40 = > > 144g, C64 > > > = > > > > > 133g). I have the option of adding a small lead, or removing > > two or > > > more > > > > > large leads from near the balance rail and replacing them with > > one large > > > > > lead out toward the front of the key. The latter will produce a > > more > > > > > conventional leading pattern--and involves a lot more work. > > > > > > > > > > My questions are: > > > > > > > > > > 1. Which one will produce a better feel? > > > > > 2. Will the difference be significant? > > > > > 3. Do front weight parameters change with the overall length of > > the > > > key: > > > > > i.e., is the allowable front weight greater for a model D than > > for a > > > model > > > > > S, or there other factors. > > > > > 4. What additional information will be helpful in making a > > quantifiable > > > > > decision? > > > > > > > > > > David Love > > > > > > > _________________________________________________________________ > > > > > Get your FREE download of MSN Explorer at > > http://explorer.msn.com > > > > > > > > > > > > > > > ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/94/4f/8e/ff/attachment.htm ---------------------- multipart/alternative attachment--
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