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I didn't mean to say that you have to play with the soft pedal all the time, or at all, I don't use the soft pedal. But you were saying the keys play heavy before let off. So I thought (but it's very possible that what I thought is completely wrong) if using the soft pedal makes it a lot less heavy then it has probably nothing to do with bushings or the jackspring or what ever. So I thought maybe thin pieces of felt on the hammer rail would make it less heavy. Just a bit closer to the strings but not as close as when you push the soft pedal. But I don't know enough about it, I just like to think about it as if it was a puzzle, and read the things others have to say about it.

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Agreed, some new pianos do play like trucks. I just keep wondering why people buy them.

Last edited by Mark R.; 04/22/22 05:38 AM.

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Naturally ..... aside from design constraints associated with pianos .... not just uprights, they need also have variety to satisfy various customers expectations.

So ..... the general approach should be to try first .... then choose.

And the manufacturer may have a few things to say if sonebody asks them. And their answer might be along the same lines. Pretty sure they get lots of experienced people testing during the design development stage. And market research etc.

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Perhaps most new buyers are just thumpers!
(Ducks for cover...)


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Originally Posted by SouthPark
sonebody asks them.

Typo. Pushed the 'n' on the phone screen instead of 'm'.

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Originally Posted by N W
Perhaps most new buyers are just thumpers!
(Ducks for cover...)

It's always like that. It's only when hypothetically - just hypothetically, that you're tasked with the job of designing a single upright piano by yourself - under the same conditions as the designers at (put brand name here) are given - and to be later put on sale, under same conditions. And need to sell lots of them and face the feedback from people, like you, and me etc. And then everything becomes clear. The light bulb turns on.

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Diver,
Just wondering: have you removed the keys and checked for tight bushings and/or balance holes? I often see pianos that need extensive key easing, which takes less than an hour. Another thing that can help the feel of the action is lubrication, including the wippen heel/capstan interface and the jack/hammer butt. Damper systems also benefit—it all adds up.

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Originally Posted by Scott Cole, RPT
I often see pianos that need extensive key easing, which takes less than an hour. Another thing that can help the feel of the action is lubrication, including the wippen heel/capstan interface and the jack/hammer butt. Damper systems also benefit—it all adds up.

These all make a lot of sense, and I have seen benefits from something as simple as easing tight key bushings myself. Has the OP had these things checked? All I recall is reading a lot of downweight numbers, which (even as a less experienced tech) I know doesn't tell a definitive story of what all is going on here. What Mr. Cole is suggesting is all fairly standard stuff, and I'm wondering if it has been done on the OPs piano.

Seems like we've been seeing too many threads recently where we're getting into seemingly complicated solutions and interventions to what should be fairly easily solvable problems with the help of an experienced tech.


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True. We also don't know for sure whether those particular pianos are operating 'normally'. They may well be operating normally. Hard to say right now.

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Peter, Scott, and All,

pulling from my data:

Key 28 (white) is nice and loose at the center. It has downweight 60 gr and upweight 45 gr. Calculated friction is 7.5 gr.

Key 70 (black) is a bit too tight at the center. It has downweight 64 gr and upweight 43 gr. Calculated friction is 10.5 gr.

I had measured downweight and upweight for all keys and the high average upweight of about 42 gr seemed far more striking than the average friction of about 9 gr.

I think that friction can be tricky and the action can benefit from easing/lubrication but it is the high upweight that made me think early on that the action has heavy parts and/or stiff springs.

So, I just now calculated the moment of inertia, assuming:

1. an ultra heavy hammer of 16 g (all placed at the hammerhead which exaggerates the moment of inertia).
2. a standard 15 mm distance between hammer butt center and jack / butt leather contact.
3. A wippen moment of inertia 60% heavier than the wippen of the C4 in Yamaha U1 in Yuji Nakamura' article.

I was able to directly measure other parameters.

I got a net moment of inertia at the finger 22% less than that of a typical Steinway D grand and I am not surprised. This is what I expected from the beginning and that is why I was not worrying about moment of inertia in uprights (it's all about the geometry) and tried to make a point on that in a separate thread.

Great. So, friction is not a problem, moment of inertia is not a problem (unless item 2 above is 12 mm or less but I can't imagine there are pianos with less than 14.5 mm), static touchweight or butt spring are not a problem assuming lead work, and dampers are no issue assuming right pedal is depressed.

So, I am thinking one viable option is to carry on with lead work to bring downweight to a tapered 54-50 (bass to treble) and then bend spoons a little and leave it there. The lead work I tried so far makes it slightly lighter in a way and slightly heavier in a moment-of-inertia sense (and rather unexpectedly so, given its percent increase) but overall it improves playability, I think.

Maybe I got ticked off by the high static touchweight and then became biased against this action. I have been playing some old and small uprights and a digital in a nearby music department and don't have an access to a grand to compare on the spot and that has not helped. One thing I am almost certain about is that, for an upright, this piano action has quite a high moment of inertia. It is higher than the moment of inertia of some grands I have put my hands on in the past. However, as long as it does not exceed the normal values for a good modern grand, I should be able to get used to it. This action does have some good qualities after all.

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Diver,

Do the following as a test:

Choose a few notes randomly. Pick up the whippen to remove it from the power train. Now rock the key back and forth (i.e. normal travel) with only your fingertips at the center, straddling the balance rail pin. First notice if there is ANY friction whatsoever in the key (doubtlessly yes...some). Then, as the key comes to rest (both forward and backward) try to sense any increased resistance immediately prior to coming to the stop position. What you are trying to determine is if the BR hole itself is binding at all on the pin. If so, this can add a tremendous amount of perceived touchweight (in essence it becomes an additional spring in the power trainthat you must overcome) but does not show up usually in a touchweight measurement. The factory drills a straight hole through the bottom of the key. If tight, the upper part of the hole can press on the pin through the arc of travel. Proper hand fitting of the keys to the pins involves using a tool that tapers the hole (wide at the top) to eliminate this potential problem. To my knowledge little (if any) of this is performed at the factory on this level of instrument. I have found this particular issue to be consistent on Kawai pianos (more so than other makes). This is why expert fitting of the keys to the pins (holes and bushings) is so important before messing with other stuff. (I can only surmise that the reason they do this is to allow for a "break in" period, knowing that they will gradually loosen up).

So, we don't want floppy, sloppy and loose keys. We want "firm but free" keys. This takes some time to accomplish, buy once it's done (usually) its done. I wouldn't go changing anything till all the keys are perfectly fitted to their respective pins.

Peter Grey Piano Doctor


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I see what you mean! Let me try this right now because I don't seem to be happy with compromising. I tried adding lead (only in a reversible manner, of course) and did that to many keys. Great improvement for slow play but the increased moment of inertia REALLY shows in fast play and it's just not working well. I still don't know why but it is what it is. I am sure about what I experience at the finger! (Something must be wrong not necessarily with my calculation of moment of inertia per se but perhaps with some of my underline assumptions or with how I interpret the result.) The effect of increased inertia after lead work is quite perceptible and unpleasant. I can see now how lead work is useless unless moment of inertia is at least a bit low to begin with.

As I am testing for friction, I wonder if anybody is familiar with typical values of moment of inertia for upright pianos or grands. I start thinking that maybe grand pianos somehow deal better with higher values of inertia than uprights. Theoretically, for a given acceleration, force (more specifically torque) at the finger is uniquely determined by the moment of inertia of the action, but I can't think of anything else.

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I completely agree with Peter. I very rarely see a new midrange upright piano with properly fitted balance rail tolerances.
My simple quick test is to lift each key a mm at the front and see if it drops back properly. They almost never do.
But, as Peter says, it's not just about making the hole larger as that leads to unwanted movement. They have to be shaped from within for an excellent result. I do not think an amateur could tackle this easily sadly.
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Of course the bushings need very careful sizing. With the whole key visible check that there isn't sticking of the bushing at the top of the balance rail pin. Similarly try depressing the B and D keys either side of C and hold them down.
Grasping the C at the front there should be a minute amount of sideways play to be sure the front bushing isn't binding.


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Thanks a bunch Peter and NW and All,

I eased the center key holes in the treble, using the appropriate tool, to the extent that keys can be lifted at the front and freely fall back to their rest position. That was indeed a daunting task since, as Peter emphasized in a previous thread, every hundredth of a millimeter counts! It is pretty easy to mess up but I hope I didn't .... I also lubricated the center pins. The combined effect reduced downweight by a meagre 0.7 g average. The gains are not to be completely discounted though since the heaviest keys were some black ones at around 65 g and those came down by 1-2 g which is welcome.

Sometime ago, I noticed that the keys, in a bunch of old uprights I have access to, wink downwards, upon lifting the wippen out of the power train, with a negative downweight of approximately 5 g at the finger (which I measured by placing 5 g at the very back of the key in order to balance it). In my K 500 Aures, the only keys that wink downward (albeit with less than 5 g weight) are the three lightest ones between 51 and 54 g. So, last night, to ensure that friction at the pin is not the culprit, I removed several keys from the piano and balanced them carefully on a ruler edge right at the middle of the center hole. Sure enough, all but the lightest ones have their front part rotating upward instead of downward. This is the 5-10 g downweight difference relatively to the aforementioned old uprights right there!

It seems to me that somehow the keys of the piano are not forward balanced appropriately and that is the main cause of high static downweight and upweight. Since I cannot shift the balance rail, adding lead to the front of the keys seems like the only solution, except that the moment of inertia of the action is borderline too high and it will become even worse, so I will also have to remove say 1 g from the hammers which will keep the inertia at bay while also dropping the touchweight by an additional 3g. (I estimated the strike ratio to be approximately equal to 3, remember this is an upright.) Note that capstans cannot be bend any further toward the player (that was already done by Kawai presumably to reduce touchweight) and I know there is another method of sticking half a felt punching on the key at the center hole with the potential of reducing the touchweight by 2-3 g but it sounds like an unstable cheap fix so I am leaving out for now.

In sum, 1g down by easing/lubricating + 3g from lead + 3g from hammer = 7 g which will bring the current downweight of 59.5 g down to 52.5 g. I am not happy with this plan because I have no clue whether the hammer job is safe and predictable (it is an irreversible modification ...) and whether I can do it myself.

What do you think? Any ideas? Thanks!!

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As a related footnote, I am pretty forgiving in the way I have been measuring the downweight of my keys. Somebody else could have easily measured 60-61 g average downweight instead of 59.5 g. Anything above 55 g, I really feel it, especially in slow play and messes up the pianissimo as well which is not the greatest in an upright anyway. Similarly, any amount of lead at the front exceeding 3-4g at the finger is perceptibly a drawback in fast play. I am quite surprised with that, as I noted above, and I can only understand it as a further indication that the moment of inertia of this piano is already critically high.

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Did you try lubing: Capstan/wippen and jack/hammer butt interfaces with teflon? Also, lube spoon/damper interface. (There are techs who don't like Teflon, but I find it does a good job, especially on jack/knuckle area in grands.) Polish capstans with Flitz or other metal polish, and apply Protek or another drying lube?

Also, you said you eased the balance holes--what about front and balance bushings? Hammer return spring tension? I'd investigate every other option before changing the weight. You're proposing brain surgery for a headache before trying aspirin. Sometimes brain surgery is eventually required...but there are risks to that too.

Also, if you do decide to add weights, do you have the equipment and skills to do a clean job? If you've never done it, maybe look for some spare keys, maybe from a technician, so you can practice doing a neat job. It's not as simple as you'd think.

PTG member Chris Brown advocates for using copper weights due to lead toxicity.There's probably a different technique involved. I've never used copper, but I don't think you really swage it in place; I think he glues it in. Something to consider. Not sure about the weight difference per size.

"In my K 500 Aures, the only keys that wink downward (albeit with less than 5 g weight) are the three lightest ones between 51 and 54 g..."

Are you talking about lost motion?

"Sure enough, all but the lightest ones have their front part rotating upward instead of downward..."

Yes, vertical keys (in good-quality modern pianos) have weights on the back end of the keys, specifically to help them and the wippen to return.
A common complaint with low-quality consoles and spinets is the lack of back-weighting, which causes poor return and reset. The weight of the wippen should push down on the back of the key, but all too often it's just not enough and needs help.The slightest hesitation of the key can impede it.

That's why people install jiffy weights behind the balance point. But by adding weight to the front of the key, you may actually solve one problem--downweight--while adding another: poor action return. Most pianos, especially verticals, have compromises engineered into them.

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Diver,
Is the piano originally mentioned the Aures? It's not clear from your post, although you mention you have one.
If that's the case, don't use Teflon or other powered lubricant.

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I didn't read through the entire thread, but from what i did read, i would suggest that before adding keyweights i would look at friction problems first. Here is a big source of friction i was having and fixed in an upright i am currently rebuilding. A real eye opener how a keyhole can cause problems.
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Thank you very much, Scott. Yes, my piano is the Aures. I have only used Protek CLP for center pins and front pins. Why would Teflon be bad for Aures?

Since friction always opposes local motion, it should be reflected by the (downweight-upweight)/2 quantity which in my piano's case is pretty low. The only conceivable exception is of the form that Peter suggested: A high friction somewhere in the action in the beginning of the motion of the key, which would raise the downweight by an amount X, combined with an extra spring resistance (not a friction) at the end of the motion of the key (e.g., extra stiff butt spring whose restoring force increases significantly at a 10 mm dip or just an effective spring due to a tight center hole/pin contact or similar trapping elsewhere in the action), which would raise the upweight by approximately the same amount X. In that case (downweight-upweight)/2 could have a normal value despite the important contribution of friction to the downweight at the beginning of the key travel. However, first, note that I measure the upweight just before letoff that is roughly 1.2 mm before the key hits the front felt. The upweight is still high even, say, 3 mm above the front felt. In addition, the downweight is high even if I start the key, say, from 2 mm depth instead of 0 mm depth. Because of these observations, I believe that the low (downweight - upweight)/2 truly shows that friction in this piano is not the problem. Nevertheless, Ambrozy's point, that theory may not always be detailed enough to account for phenomena, is obviously correct and important, so I will certainly look into further lubricating what I can lubricate without removing the action.

I see what you are saying about brain surgery. Irreversible lead work is a risk. Removing weight from the hammers would of course be an irreversible change too and I am guessing a complicated one to perform.

No, I am not talking about lost motion regarding the wink. It's a downward wink of a key in old uprights when the wippen is taken out of the way. It's comforting that my keys behave the way they were supposed to in this sense. Too bad though this does not help with the touchweight.

Finally, I did (temporary, reversible) lead work on the bass section to bring the downweight all the way down to 53 g and repetition is still going strong since upweight is still above 29 g. If the lead did not increase inertia beyond what feels acceptable I would be a happy camper. But, it does, this is why I start thinking hammers as a necessary part of the solution.

As I mentioned in a previous post, all three Kawai K500 Aures that I had the chance to play (after I bought one without playing it first, yes big mistake, I know now ... but in some way I did not have a choice at the time) had a high touchweight and a high inertia too. I am still puzzled with the inertia part as my calculation says that even a high-inertia upright should have a lower inertia than a typical grand. But my point is that somehow Kawai may want it this way. If that is indeed the case, it would help to know why. But I do have a key at 50 g, another key at 51 g, another key at 65 g, and another key at 67 g. That observation alone may be telling a different story. That Kawai customers should not be entitled to an even and playable action at $22,095 MSRP. If that is the case, then we will know why surgery is unavoidable.


ps. Copper is of course 21% less dense than lead but still heavy enough for weighing off keys.

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