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Let's face it. A number of new upright pianos play like trucks. If the right pedal is down, dampers can't be the issue, and if (downweight - upweight)/2 is low, I can't see how friction anywhere in the action can be the main problem either. That leaves us with geometry, butt/jack spring, and moment of inertia of the action as the only possible factors. However, I have seen calculations for a moment of inertia of an upright versus a grand and the difference is striking. In both cases the hammer contribution to inertia is the dominant one but the geometry of the grand action results to roughly twice the overall moment of inertia. So, even if the geometry of the upright is off or the hammer head too heavy or the shank a bit too long, there is so much buffer, so to speak, that the moment of inertia can't be too high.

The conclusion seems to be that those uprights have bad geometry or stiff butt/jack spring. I can't see anything else. It's a shame that the manufacturer, often times Kawai, or Yamaha, can't do better than that when the customer forks out North of $10,000. However, if geometry and/or butt/jack spring is the problem, then, adding lead in the front of the key should compensate for both as it is mechanically equivalent to shifting the balance rail (fulcrum) away from the player. The only side effect is increased moment of inertia but it should be insignificant for three reasons. First, it can be minimized by adding more lead closer to the balance rail. Second, the mass of the key is not the main contributor to the overall moment of inertia. Third, as I mentioned above, the moment of inertia of the action is low to begin with compared to a grand piano.

So, based on my current understanding, lead work is the key in repairing those heavy actions and if lead work does not do it, nothing will. If that is the case, then, I wonder why so many technicians see it as a last resort for uprights and/or as a "risky" solution. In fact, Mario Igrec (in pianos inside out) emphasizes that uprights shouldn't normally have lead in the front of the keys. I am mystified by this.

(Of course, lead work will not compromise repetition since upweight will still be high enough after repair, assuming that friction is low.)

Without using the right pedal, two additional factors come in, namely, stiffness and time of engagement of damper springs. Is bending spoons or easing damper springs usually the best cure? What is the best method/tool to ease damper springs? Is there any information online about how to perform this?

I would appreciate any response on my thoughts and questions.

Thanks!

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“The only side effect is increased moment of inertia but it should be insignificant for three reasons. First, it can be minimized by adding more lead closer to the balance rail.”

If you add lead closer to the balance raise, you have to add more of it to achieve the same result. Which leads to… more inertia. If I’m not mistaken, didn’t Steinway try and abandon that approach?

I’m not sure I accept your generalization that modern verticals “play like trucks.”
How many have you weighed off? Which models? What downweights and upweights did you record?

In my experience, new modern verticals sometimes have issues, especially very tight tuning pins and double-striking, but I haven’t found them to be overly heavy.

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Thanks, Scott Cole. If you half the distance of the lead from the balance rail, you must double the lead mass to achieve the same balance weight change, you are certainly right in this. But the moment of inertia is also divided by a factor of two since it is proportional to the square of the distance from the balance rail and only proportional to mass. I am pretty certain about this and it is also explained in Mario Igrec's pianos inside-out and some online sources. I am not sure about Steinway. But tis approach does makes sense from a physics perspective. Of course, the difference could be marginal since the key inertia has only a 10% or so contribution to the overall moment of inertia of the action in uprights.

Well, I am not a technician so my experience with pianos is limited. Most of the verticals for sale should play all right, but some new Kawai and Yamaha that I played in piano shops had stiff actions, e.g., 60-65 gr downweight and 40-45 gr upweight with the pedal down is not acceptable by most serious piano players. That's why I said that a number of uprights play like trucks. I did not say that the majority of them do. I wouldn't know.

I have at home a new K 500 Aures with 65 gr downweight for the black keys. It is a replacement of another K500 Aures that was marginally worse. Another Aures I played in a shop was also stiff. Somebody from Kawai needs to come out and explain to customers like me why Kawai is selling a 65 gr. downweight action at a premium. Kawai's engineers should be able to control the action inertia and touchweight to plus or minus a gram already at the level of computer simulation at the factory.

I contacted Kawai America and Kawai Japan at different times with technical questions. Kawai America does not seem to have any answers beyond some generic specs that I could also find online. Kawai Japan simply ignored my email. Nice.

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My own belief is that if you cannot handle putting a couple of ounces of pressure on a piano key, maybe you should consider taking up the theremin.


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theremin?

I know, we had this discussion before. There are many professional pianists who can't take the extra weight, not in their everyday piano, practicing for hours a day. I think they should still have the right to enjoy the piano! My ten year old daughter can handle 70gr. downweight, no complaints! But then again, she plays 15 minutes a day ... But I started piano late and had to stop because of severe tendinitis. My technique won't get that great but I still need a piano I can play 5 hours a day ...
I see your point but on the other side you got thousands and thousands of great pianists who would never settle for a truck. So, I guess, I am on that team!

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Oh! Ok, theremin is actually an instrument that can be played without physical contact ... Wouldn't have guessed that such a thing exists! smile

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When the jack spring is the cause of the problem, why is adding weight to the keys the only possibility to solve it?

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If you get tired playing a piano, the two most likely reasons are poor technique and lack of exercise. Most energy is expended holding the note, rather than playing it, yet that requires the least amount of effort. Learn to release the tension in your fingers after let-off, and you will save a lot of effort.


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Diver,

If you have been told you have tendonitis and this inhibits your playing I would suggest two different (though amazingly related) avenues to pursue. One is "The Trigger Point Therapy Workbook" by Clair Davies, and the second is "The Divided Mind" by Dr. John Sarno. I'll leave it at that. Been there...done that, which is why I'm suggesting it. YMMV.

"Tendonitis" nearly put me out of the piano tuning field (and piano playing) many years ago. I'm still in it for the 47th year with no complaints.

Peter Grey Piano Doctor


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Peter, Thanks! I have overcome the problem completely after several years. It was the reason why I abandoned piano for ten years just a few days after I started playing for the first time... It had taken only 3 days to damage my wrist tendons for years ... What worked for me in the long run was patience and working out including swimming.

BDB, you got a point. Many players, in fact, like a heavy action. I still need a piano with normal touchweight and inertia for suboptimal technique and physical ability.

Josephine83, makes sense, but in this particular case the jack spring is not the problem. The heaviness is there before letoff.

I still wonder if I got it right about inertia and lead work and whether bending spoons or easing damper springs is usually the most effective way to make the action lighter when the sustain pedal is not depressed.

Thanks!

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Originally Posted by Diver
BDB, you got a point. Many players, in fact, like a heavy action. I still need a piano with normal touchweight and inertia for suboptimal technique and physical ability.

I have not found this to be the case, and I'm around players, all the time. Nobody wants an exceptionally light action on their practice pianos (unless they are prone to some sort of physical problem), but the notion that we want heavy actions on our practice instruments seems to be an all-but-gone generalization, these days.


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Well said.

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I installed temporary weights on keys yesterday mostly on the bass section and brought the touchweight to normal levels (54-53 on the bass, 53-52 on the tenor). However, to my disappointment, I only saw a slight improvement in the touch and a small increase in inertia ...

So, it seems that the problem is not the static touchweight but the net moment of inertia of the action. What a relief when I switched and played a little on an ancient $200 Baldwin upright. It felt like I was playing a piano instead of lifting weights in the gym...

Now the problem I have is to find out how on earth an upright can have moment of inertia considerably greater than a grand. Based on what I know, this is surprising but facts don't lie. The hammers just can't be that heavy, so I believe there is something wrong with the geometry of this action.

Of course, this should be by design and not particular to my instrument. Apparently, Kawai has found that sales are doing well with the current specs. I surely hope so because It's probably time to trade it.

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I can't help you because I just started learning about the piano action myself but topics like this make me curious and I was wondering if the action feels less heavy when you press the soft pedal down. I'm curious about how much effect gravity has on the hammers when starting the movement towards the strings. I would think that the further they are tilted backwards when they are in rest position the more power it will take to start the movement, but the more they will accelerate and therefore hit the strings with more force.

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Thank you Josephine83. Here is my thought:

Yes, when you press the soft pedal, you raise the hammer shank to a more vertical position thus reducing the torque of the weight of the hammer (hammerhead + shank) relatively to its pivot. This implies reduced static downweight at the finger. (Incidentally, this is partly why downweight is reduced a bit when the piano key is slightly depressed. Another reason may be higher static friction in the initial position of the key). Adding felt under the hammer rail is equivalent to constant soft-pedaling by a fixed amount. In either case you are changing the blow distance. However, lost_motion + blow_distance - letoff = strike_ratio * (dip - aftertouch) and so for a piano regulated at specs (dip, aftertouch, and letoff all fixed and only tiny lost motion), there is no play for blow distance. You can live with plenty of lost motion only occasionally, so you may soft pedal from time to time but that's it. Now, if you are not soft- pedaling, that is, if blow distance is at its prescribed maximum value, the greater force you need to apply apply at the finger to get the hammer going will provide increased acceleration to the hammerhead which will strike the strings with higher velocity at the end of the blow distance.

At average to high accelerations of the hammerhead, the force at the finger is essentially determined solely by the moment of inertia of the action at the finger. If the sustain pedal is not depressed, then, the stiffness and timing of damper springs are also of relative importance which declines though with increasing acceleration. Butt spring stiffness and high static downweight are factors of the same order of magnitude and they are both relatively unimportant at average to high accelerations. They are still welcome in piano actions with rather low moment of inertia, that's why high downweight is presumably better tolerated in uprights than grands.

In my upright piano, both downweight and upweight are too high, so I thought that lead work would kill two birds with one stone by bringing both down by the same amount. And that is clearly the case and temporary lead work did that just fine. But reducing them this way does absolutely nothing to reduce the moment of inertia, in fact, it's adding to it (not by too much if the lead is not too heavy and it is placed close to the balance rail, but the small increase is still perceptible). Of course, I knew that the combo of high downweight and upweight is screaming that the action has no friction problems but suffers from high leverage ratio for the given hammer weight. Given that to a good approximation

total_moment_of_inertia = mass_of_the_hammer * factor_depending_on_geometry_and_increasing_with_leverage_ratio

I was still hoping that this geometric factor will not be too large (for the given hammer mass) despite the high leverage ratio. I took heart from a calculation showing that a typical upright can have half the moment of inertia of a grand. Unfortunately, the piano touch after my (reversible and temporary) lead work clearly shows that I lost that bet. This geometric factor is sort of skyrocketing ... for the high leverage ratio of the action. It depends on 4 different geometric dimensions in the action. It's tough to change them.

One can reduce the hammer weight instead by 10% or so.

Peter Grey once wrote that everything can be adjusted and fixed given enough money, time, and talent. Sure thing. Well-regarded technicians in my area talked about lubrication, easing, lead work, and regulation, when I clearly spoke of high downweight and upweight and the elephant in the room is almost always inertia when the problem is really a problem ... I also got both a bad lead work on the first piano and a bad regulation on its replacement (my current K500 Aures). I had to educate myself, buy tools and fix the regulate the piano really well by myself. That does make me a very patient guy but not a professional technician.

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You inspire me to write this...
I'm a technician not a concert pianist. So this is where I'm coming from. Pianists can have a better time understanding what happens under their fingers than they can analysing and labelling the exact weights.
In the same way they get a better sound from an expert tuning than they can analysing the exact frequency of each note.

Upright piano soft pedal should not be called soft pedal at all. It should be called "can't play loud".
Here's why. All it does is is reduce the the hammer blow distance which means the hammer cannot reach as high a speed at contact with the strings. And the speed is what controls the volume. So it doesn't cause softness, rather it limits the loudest possibility.
There is absolutely no way to play a note more softly than overbalancing a key. A key which the player has an intimate relationship, across the keyboard and leading to this moment of "soft" playing.

But wait, that's not "all it does" at all. I misspoke! The soft pedal depression also introduces a great load of lost motion. So now when the player touches the keytop the response is massively different. The key drops it's first part far more lightly than before the pedal was pressed. The expert player's fingers are body sensitive in extreme, no intellectual analysis takes place in this millisecond. What actually happens is that the player plunges harder and loses that intimate relationship with the setoff and back check. It kills the continuity of touch which controls the player's expressive capability.
Continuity of contact and use of players skill is what creates softness.
In an upright. Quite a different pedal in (most) grands of course.


I may not have expressed this perfectly but I hope you will consider this view and see how much sense it makes.


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Just take out one hammer and measure its strikeweight instead of overthinking it for the last two weeks...

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Nick thank you for your note, it certainly makes sense to me.
Ambrozy, I only became familiar with the piano action and its physics quite recently.
As I explained above, based on inspection I thought I had reason to believe that no measurement is necessary (moment of inertia of an upright much less than that of a grand). It's been only a few hours now that I realized that this thought was naive (mostly wishful thinking because messing with hammers or action is difficult and can affect tone) and that it's time to look into the inertia more closely. I don't see the two weeks you are talking about. I really don't mean any disrespect, but if my details in this and other posts have offended your taste you could have tried to enlighten me instead of letting me discover everything on my own. A nicer way to put this is that I am not trying to be a smart ass, I am just seeking answers. For your information, I have never taken an action or a hammer out but I will figure it out. Let's say I find a 10-11gr hammer at the bass. What does this mean? Nothing. But, yes, as we both know now there is a formula to calculate the moment of inertia based on this and several other measurements. Let's see what number I will get and how it compares with a typical Yamaha U1 upright and a Steinway D for which I got numbers thanks to Yuji's Nakamura's work. It would be interesting if the moment of inertia does not come out exceedingly high ...

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Diver,

I am not recalling whether the issue of fitting keys to key frame (pins) was discussed in your case. If not, there can be a significant amount of friction particularly at the balance rail on new Kawai's due to their tight fitting protocol at the factory. Several grams can often be locked up in this as friction. Very careful easing of these points can make a big difference.

Peter Grey Piano Doctor


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I guess you're somewhat technically inclined and looks like you like to think a lot and "be" in abstract world, if that's true, I'm no different, but I have some experience with the subject and I've learned the hard way that my idealized, usually mathematically correct, ideas and assumptions were very often wrong when I tried them out in reality, some things that seemed important, turns out to be barely perceptable, and other things that I didn't even think of were actually very important. The main reason for this was that human is a part of this system, and humans unfortunately cannot be described by simple newtonian physics, for example different voicing of hammers can change how you preceive heaviness of the action despite mechanically it will be the same...

Any idea you have, you should ideally check with reality first because it may turns out to be completely wrong and you will just waste time overthinking it. Measure the most important things on your action and work from that, not from something that someone wrote about some random piano you've never seen, you are trying to fix your piano right? When you have some measurements then we will see if your action is in the ballpark or you have some serious problems. We have downweight/upweight, try to measure strike weight of couple of hammers, blow distance, action ratio... If you want to diagnose your piano this has to be done, otherwise we talking about an imaginary one, and you won't get any valuable information from this.

And yes, many new pianos plays like a truck, I personally don't get it why they are set up like that, but it just how it is.

Last edited by ambrozy; 04/21/22 08:58 PM.
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