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Great video and explanation, thank you very much for this. But how did you find out that friction was a problem in that piano? Do you happen to have (downweight - upweight)/2 measurements for this piano before the repair?
Thanks. I didn't use DW- UW measurments. But just went by feel. In this case, I had gone through the entire action, repinning, lubrication, replace worn out felts, rebushed keys, everything. And it was only by playing it that i noticed that the action was still sluggish. Since i went through everything, the keyhole was the only thing left. -chris
I see. Since you were rebuilding you would go through those many steps anyway. In my case, I have a new piano with nice and low (DW - UW)/2. I gently eased center holes with the appropriate tool (smooth tapered tool) and lubricated the center and front pins so that key fronts fall freely when raised significantly above their rest position and released. After this easing and lubrication, I only reduced DW by 0.7 grams on average. I may be wrong, but I don't think friction is my problem and frankly it does not feel like it is when I play. The action feels smooth. The problem is that it is heavy. I don't feel I have enough leverage at the finger. I almost want to push the balance rail away from me to reduce DW, UW, and inertia, all at the same time. Equivalently, reduce the length of the shanks. Equivalently, reduce the weight of the hammers!!
As the discussion moves forward and some evidence accumulates, I can take a wild but hopefully educated guess: Kawai wants to maximize profit. Duh! What sells is loud. Grabs a heavy hammer and sticks it in. And, yes, K500 is one loud instrument. How much heavier is that hammer? I bet it is 1.5 g too heavy. This is how much it is needed to make the inertia roughly 12% higher than optimal and DW and UW higher by 4.5 g (given a measured action ratio of about 3). But now this is a loud noise and K500 Aures sells like hot cakes. Somebody show me that I am wrong. I'd be happy to hear that!
By the way, I think I now understand why Ambrozy said "Just take out one hammer and measure its strikeweight ...'' At the time, I didn't even know what a rather heavy A1 would be. I think 11-12 g would be heavy, right? (Of course, in theory that depends on the geometry of the action but in practice 12 g should be a heavy key?). So, I guess that's my next step in the absence of better ideas?
Amateur opinion/experience here (though nothing new): Do your dampers lift up half way through pressing the key? My upright was lifting them up as soon as the key was pressed. Adjusting the spoons gave a lot of sense of lightness. If this is all good, than yeah, lubricating everything is your next go. If not, you should try spring tension adjustment. If that won't help, key weight lead adjustment or hammerhead weight reduction should be your last resort.
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. -chris
That's a splendid tool....I had to make mine, is that one commercially available?
Walkman, thanks. I will certainly bend the spoons a little, that was in the plan from day 1 and there is a bit of room for it. Question is what to do about static DW and inertia when right pedal is depressed and so dampers are out of the way. Spring tension adjustment for jack? The problem is before letoff. For butt spring? Perhaps. A stiff butt spring should contribute to both both static and dynamic touchweight (despite not contributing to inertia, strictly speaking) but I am not sure it could be a significant factor. It does not seem easy to adjust those springs but it seems easier and quite effective to balance their extra stiffness with lead in the front of the keys. Of course, if adding more lead is not an option due to an already high inertia, then adjusting hammer weight seems to be last resort.
[=Diver]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?
Teflon can muck up the optical sensors (if there are any). Check with Kawai about what lubricants to use on a hybrid.
I have to ask: you tried three of these pianos and thought they all had heavy actions with high inertia. Yet you bought one and are now twisting yourself into a pretzel trying to re-engineer it. Isn’t that like trying three of same car, declaring that they all handle poorly, and then going ahead and buying one anyway? Why not just cut your losses and look for something you like? You may never be happy with it, and might even void the warrantee and make it less desirable for a buyer or shop for a trade?
As I said, I bought the piano first after I played a K500 (not Aures) at the dealer which I liked. Aures was not available anywhere in my area but I needed a silent piano, so I went ahead and ordered it as a special order without having played it. I thought what can go wrong with a modern Kawai Aures with excellent reviews? At the time my knowledge about the mechanics of the piano was pretty much zero. I surely did not know what downweight means. Later, once playability appeared to be a really a problem, I started looking around and had the opportunity to play the other pianos and compare. Now, I have practically become an amateur technician, which is the bright side of it all ... I also understand that unless you are at least an amateur piano technician of some sort, or bring with you a technician you trust, you are pretty much looking for trouble if you go out there to buy a piano. Had I have the chance to do this again, first, I would certainly play the piano before I buy it. Second, I would open the piano and inspect every little piece. Third, I would request that the dealer adjusted static and dynamic touchweight, if needed, and regulated the darn thing to perfection before purchase. If the dealer refuses, I move on. You bet I would end up leaving with a fine instrument at a good price. But this business is worse than car sales. I know now.
Cutting my losses and selling was the plan. After all, technicians in the broader area would either not help or be very expensive while offering no convincing prospects. The downside was that I live in a somewhat remote area and trading or buying a new piano would be a pain and a significant loss of both time and money. Another problem is that I need a silent acoustic piano and so my choices are limited. Finally, K500 Aures is indeed a good quality reliable piano with powerful sound, excellent bass, and a long list of digital capabilities.
In the end, I started figuring things on my own and managed to regulate the piano to my satisfaction. I also came up with an alternative reversible procedure for lead work which works for me. It may all end up well because I think I finally found a way to reduce DW, UW, and inertia at the same time, so today is a good day! I noticed just a couple of hours ago that there is still a tiny little room for capstans to bend toward the player to reduce leverage ratio. I tried it on key #58 and that immediately shaved off 3 g from DW and UW and reduced inertia (which is essentially proportional to the square of the distance between the top of the capstan and the key center hole). A few minutes before that I tried the key balancing punching method, which I had ignored so far, and it worked like a charm shaving off another 3 g from DW and UW while further reducing leverage ratio and inertia. Between these two methods and some light lead work, I think I have the tools now to bring this instrument to a good shape.
Incidentally, I folded a piece of lead around a super thin screwdriver and cut it in the shape of Chernobieff's tool's ending to test the key holes of my piano. They look fine, so yet another indication that friction is not the problem. I already started bending capstans slightly and cutting punching felt and the action is coming alive. At last. many Thanks to all of you for your generous comments and advice.
Schaff sells the "balance pin hole reamer", item no. 3156, for $49.00. (ouch)
Be aware that a balance pin hole reamer is used for a specific problem: The hole was improperly cut by the manufacturer, causing the balance rail pin to run into the wood as the key is depressed. There is a characteristic feel of resistance with key travel. This is more a problem with cheap spinets and consoles from the past, but it should not be an issue with higher-quality pianos like modern Kawai and Yamaha.
Don't get this tool and start scraping away material unless you are sure that this is indeed the issue. Balance holes can be fixed; better not to cause problems in the first place.
Thank you Scott, you are right. That's why I checked the geometry of the hole with this shape I built before doing anything to it! I found out that no adjustment is necessary in agreement with your experience in this.
I've been thinking about this bal rail hole / too thick key thing. Only thinking so would appreciate comments from techs only please based on that. But what if one used a conical shape from the bottom which would enlarge the hole at the underneath surface of the key but leave a really perfect fit at the top of that thickness (i.e. the part of the key that the Schaff tool cuts away.) Wouldn't that, by transferring the point of contact higher whilst completely freeing the lower surface, reduce friction alot? I wish I could draw it but imagine the pivot 1/8th inch above the balance rail. There would be a conical depression in the base of the key. Expressed as best I can, maybe not very well. Hoping you can see where my thought experiment is going...
Taking the pivot point away from the punchings would cause the key to rub forwards and backwards over the punchings when pressed and released. I would expect higher wear on the punchings. (And possibly, increased friction.)
Autodidact interested in piano technology. 1970 44" Ibach, daily music maker. 1977 "Ortega" 8' + 8' harpsichord (Rainer Schütze, Heidelberg)
In the end, I started figuring things on my own and managed to regulate the piano to my satisfaction. I also came up with an alternative reversible procedure for lead work which works for me. It may all end up well because I think I finally found a way to reduce DW, UW, and inertia at the same time, so today is a good day! I noticed just a couple of hours ago that there is still a tiny little room for capstans to bend toward the player to reduce leverage ratio. I tried it on key #58 and that immediately shaved off 3 g from DW and UW and reduced inertia (which is essentially proportional to the square of the distance between the top of the capstan and the key center hole). A few minutes before that I tried the key balancing punching method, which I had ignored so far, and it worked like a charm shaving off another 3 g from DW and UW while further reducing leverage ratio and inertia. Between these two methods and some light lead work, I think I have the tools now to bring this instrument to a good shape.
Diver, I'm having the same issue but with a Yamaha piano. Thanks for sharing your experience!
May I ask what you mean by key balancing punching method? Also, how does your reversible lead work procedure work? The capstans idea sounds great. Unfortunately, Yamaha uses quite thick screws that don't bend. Too bad!
