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Last year, 2018, I purchased a 2007 Kawai K5 upright. I love the piano. Currently I’m working on Moonlight Sonata and am having some issues with my pianissimo. Some hammers sound like they’re “rebounding” off the strings. My teacher said this is part of the limitations of a verticle’s action, but part of Kawai’s documentation regarding their Millenium III action specifically mentions the added control with pianissimo. Question: Does this sound like a regulating issue? Is it possible to play pianissimo on a vertical successfully? The piano is very clean with hardly any indentations on the hammers. It was not beat up. I doubt it has ever been regulated. Is it time? How can I tell? Is there a “test”?

Your teacher isn't right.

When you say "rebounding", do you mean it sounds as if the hammers are double-striking? (the phenomenon is called "hammer bobbling"). You will be able to see this happening (it happens especially in pianissimo playing) if you take the top panel off the piano and watch the action in motion as you play.

I had a client a few years back, with a Kawai upright (I forget which) that was only a couple of years old, and had this problem, and others techs had not fixed it. I had attended Don Mannino's excellent Kawai upright regulation class at MARC in Bethlehem PA in 2011 and I took the upright regulating sheets with me. Everything seemed to be to spec, but still the "bobbling" on tentative or pianissimo playing. In the end, the thing that completely solved it, was slightly tightening the bridle tapes by slightly bending the bridle tape wires.

I hate hammer bobbling - it ruins any feeling of control, and takes away much of the pleasure of playing.

Regulation will fix this, and you will have a super piano.

Agreed with David on this.
Without seeing what you are talking about, it is hard to definitely answer that what you are feeling is in fact regulation issues...BUT- definitely- IF the piano has never been regulated, then yes, you need to get it regulated. It will probably solve the issue you are trying to explain. It will certainly greatly improve the play of your instrument.

And, you should not only be able to play p, but also pp on the vertical, without a bobbling hammer...ppp might be a bit too much to ask of a vertical without getting those "ghost notes" once in a while.

This man seems to be able to accomplish teaching pianissimo play on a vertical without too much difficulty:
https://www.youtube.com/watch?v=Hxb8juWQdcQ

That's a really good video Rick. Thx for posting it. Gotta work on that myself.

On the Kawai, I have had this problem consistently, and I "believe" it is primarily due to the ecsaine leather substitute. I have found it far less on pianos with good leather on the catches.

I'll have to try the bridle strap adjustment though. Good idea.

Pwg

This is a result of the stupid way that vertical actions are made these days, with the spring loop butt springs. I posted a method of springing the hammer butts that takes less labor than the spring loops, that nobody seems to have thought of using during manufacture.

One of these days I will have to get hold of an upright and rebuild the action with springs put in properly. I think I could even put in the extra spring like the old Mason & Hamlin actions to get a real repetition action.

I also feel that part of the problem is the use of ecsaine synthetic leather rather than good quality real leather (though I understand why the manufacturers use it).

BDB, can you show that again? I remember it vaguely but would like to review it. Seems to me I thought it was a decent idea.

Pwg

Thank you all for your advice. I’ll set up an appointment with my tech.

Yes. I’ve watched his video. He has a good technic. Thanks

I don’t regulate too many upright actions but if you tighten up the bridal tape to eliminate double bounce isn’t this an indication of possible excess friction in the hammer flange?
Usually setting checking close and squaring the check with the catcher is a remedy, assuming letoff and key travel and hammer travel are correct. You want to be certain the jack clears the hammer butt at the end of the key stroke.
All the bridal should do is keep the jack from falling to far allowing it to jam on the butt.
Upright regulators correct me if I’m wrong.

Yes David. That's exactly what I'm talking about, "bobbling." I've never noticed it while playing at louder volumes. This is the first time I've come accross it. In fact, the feel of the action along with the sound of the piano, was what sold me. It just really spoke to me, so I was a little disappointed when this situation came up. Thanks for your input. Much appreciated.

What happens in these actions is that the hammer overbalances the spring and falls towards the string before letoff at soft volumes. It leaves the jack, hits the string, and bounces back to the top of the jack, which lets off and makes the hammer hit the string again. Bending the bridle wire will hold the hammer back a little more, at the cost of the keys going all haywire if you use the soft pedal. Increasing the weight of the catcher might help.

When I spoke of the instance where I corrected bobbling by bending bridle wires, it was only by a very very small amount. That was on a quite new piano, with all other distances - key dip, blow, set-off, check, all being to specification.

BDB, I think I can see how your butt spring works, but I can't see how this would work any differently to a normal spring rail system. The only difference is that the spring is attached to the butt and bears on the rail rather than attached to the rail and bearing on the butt. Therefore, how can it change the bobbling problem on very soft strokes. I think I do see however that a spring system that does have a definite force variability across the stroke from weakest at rest to strongest at the point of string contact should in theory reduce bobbling, but spring rail systems have that anyway.

I can however see how it could be used to retrofit an existing butt/loop system.

The problem with the loops is that the loops move along with the spring, and so instead of the steadily increasing pressure of Hook's Law, you get a variable pressure.

My method can be used to retrofit spring rails, as well.

Isn't it interesting that bobbling hammers on old upright pianos are a rarity and they are commonplace with veritcals from about 1980 on.

What has changed?

Yes. the loop springs are weaker than the hammer rail sping type typical of the standard American upright action. But the hammers are heavier too and this alters the center-or-gravity of the hammer and butt assembly so much that they easily fall towards the strings rather than away. The CG is worst starting just above the overstrung section.

In addition the to bridle wire mentioned above, it helps to reduce lost motion to a minimum and set the escapement 4mm or more from the string.

I have not been able to confirm that hammers are heavier than they were in old pianos, which is a vague statement at best. Hammers have not been uniform since uprights were made, so if the weight of the hammers were a factor in this double-striking, it would be more of a factor at one end of the piano, which is not the case. Old pianos with spring loops were less prone, but they often had things like auxiliary jack springs, or a short bore with extra mass behind the shank which helped.

An auxiliary jack spring could be added fairly easily in the same way that I added the spring to the butt, and that would improve repetition.

Many older German overdampers have no butt springs at all and do not have the ppp bobbling problem. In these pianos the action rail is positioned closer to the strings compared to under dampers. This causes the hammer centre of gravity to be always causing the hammers to fall backwards when the action is in the piano. Hammers could still possibly race away from the jack on ppp strokes in this case however. If so then why does it not happen with with those butt spring-less overdampers?

BDB, I am expecting to do another Yamaha butt loop job some time soon. I am willing to try your butt spring idea. However, I would like a better explanation of why your idea is better than a normal American spring rail at reducing ppp bobbling.

It is not better than the spring rail at reducing bobbling. It is just easier to do. In the example, I just drilled a hole at a 45° angle from the back of the butt through the side, inserted the spring and bent the tail to hold it in place. Bending the spring to center it behind the shank locks it in position.It struck me that the spring grove on the butt that I photographed was holding the spring in place, so I sanded it off and tried it again. It holds in place reasonably well, but if you have a problem, a dab of glue from a glue gun will make it more secure.

You will need to make a grooved back to put on (or replace) the damper stop rail (corresponding to a spring rail), but that is just a piece of wood with holes drilled in it at the position of the hammers, cut in half. So you will have two of them, and you can save the extra for the next time you do the job.

I think I will try it out with a Schwander action Kimball studio we picked up for a non-profit. Springs keep breaking on their pianos, because of the lousy storage facilities, so it makes sense to try it.