Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Regulation Problem - bouncing keys

Yea that's the humidity changes. If you go 20% up, the capstans will be too tight, 20% down they'll be too loose. The easier way to manage this, is to setup everything for the lowest point of humidity during the dry months, then on the wet months, just shim the hammer rail by 0.25-1mm. This is alot easier than turning all 88 capstans.

I've chosen to do it this way, because I've always wondered how many times can you really turn those capstans before the wood gives out. If it was metal you could put in some loctite, but with wood I just don't know.

Doesn't butter go rancid and have a smell? I guess if you're not using much maybe it's not that bad.

I also regulated the pedals. According to the manual of regulation from Petrof, damper pedal should lift the dsmpers 6-7 mm while fully pressed. The sofr pedal shouldnreduce the hammer distance by 1/3.
So for my 45 mm blow, I regulated the soft pedal at 30mm.
Also, in their manual, they recommend adjusting the bridal straps so that when the hammers has travelled 1/3 the bridal strap should start moving the flange. This was easily adjusted since the soft pedal was already adjusted at 1/3, so when one presses the soft pedal all the way, all the bridal straps should give a small mobement to flanges.

Eberything is measured well now and regulated to specs. No change in any parameter has resulted in bobbling relief, the only solution was changing the butt felt.
So I adjusted everything according to the regulation manual, at least the keyboard is even.

If I will ever have the urge to change the felts, I will, not now though, I need a break from it :))

Zonzi, is your Petrof the same model? Model Opera, 125cm?
Does it have the problem with bobbling when very softly pressed?

more key dip

The key dip is at 10-11mm. Even if I remove the green felt completely, the problem is still there. The bobbling happens halfway through pressing the key, without going to the keys furthest depth. The key dip is such that it allows the jack to escape from the butt fully and some more. The problem is that I as a player when playing softly, tend to not press the key fully. For a smooth butt leather and the butt felt that enables the jack to sit just at the point of escapement, this touch should be enough. But for the worn leather and jack sitting too deep inside, this soft touch is not enough to escape the jack, hence the butt returns back and bounces on the jack second time. If I increase the let off to say 15mm instead of 3mm, the problem is fixed, since the jack escapes much before the hammer has returned, but I do not want to compromise that much.

Mine is this model, but not black.
This one sounds so much greater and even than mine, I think. Can mine be taken to this level?

just put very few butter less than 1/10g probably, so there is no smell at all.

Yes it is Opera, 125cm. there is bobbling problem very softly pressed only for 4-5 keys. It can be resolved by regulate capstan. last regulation more than 4 months ago, there is only 1 key is bobbling again recently.
I also reinstalled one of the hammer butt, everything seems perfect but just for 3 days.

yes put PTFE on the butts and regulate the capstans, it will keep this level for some weeks.

thank you for your tips, but in my case, there are only 4-5 keys had this problem. I put the modelling clay into some of capstans to reinforce and they seem working (they are very stable after 4 months)
The problem is that I put also a lot of sheets, lamps, electronic devices, books on the top of the piano, so it is quite difficult for me to open it.....

Ah, the capstan unscrewing, yes mine had the same problem when I bought it first. My technician put in some small strips of wood and than screwed in the capstans, that got rid of their loosening.

A great post I found on a similar issue on Kawai uprights on another forum, which is completely in tune with my theory too:


"The hammer buts are worn; and the bottom area where the jack contacts the butt skin has become too flat, and the jacks are in too far because the jack rest felt (hammer butt felt) has become compressed. I have attached a screen shot picture from your video; the red circle shows the corner of the butt skin which shows that the butt skin has become flat, and the green circle shows a gap between the back part of the jack top and the butt skin, indicating that the jack is too far back. Also, I don't know if the white stuff is powder or grease - if it is some kind of grease, that should be eliminated, it is a very bad idea. Teflon powder here is OK, but will not solve the problem of course.



Also, two other things:

1. The letoff seems too close. You say it is 2.5mm in the center, but it seems to be much closer, although we cannot see the tip of the hammer to be sure.

2. The damper lift is too late, which is making the problem worse. I can see in the video that when your finger is being stopped the damper lever just barely winks. This indicates that the damper spoon is helping to stop your finger. Since it is timed very close to point where the jack toe touches the letoff button, you have made it want to bobble much worse.


To verify if the dampers are causing the key to stop, simply hold the damper pedal down. If the bobbling stops or is better, then this shows that the dampers are contributing to the problem.



Solutions:



- Fix the worn hammer butts

- Set the regulation back to specifications





As a temporary test, try this test:

- remove one hammer butt

- Pull some thin flange bushing cloth under the butt skin from the side to make it round again. Trim with a sharp knife.

- Insert a long single needle through the butt felt square from the side enough times to make it thick again.

- Install the hammer butt, and regulate the capstan and letoff. The bobbling should be gone.



If this solves the problem, then you have a couple of choices. You can pull thin flange bushing cloth through all of the hammer butts like the same, and replace the butt felt on all hammer butts. You should apply some glue to one side of the bushing cloth - preferable to the back side, so that it becomes glued to the underfelt, not glued to the butt skin. For the butt felt, use PVC-E or PVC-A glue to



If the butt skin is not too worn, then this might work as a repair. If the skin is also worn, then the full repair is to remove all of the hammers at the flanges, peel off the butt skins, remove the butt felt and under felt, and replace them with the correct dimensions of new materials. Once again, PVC-E or PVC-A glue works well.



Finally, regulation:

- Set capstans for no lost motion at all _once the hammer butts are repaired_. The jack springs are strong, and the hammer springs are weak, so during normal play the jacks will return as long as the butt skin is shaped correctly.

- Set letoff to a real 3mm in the center area. Verify with something that is 3mm thick

- Set key dip to about 10mm, or slightly more if needed to get the jacks to clear the hammer butts. It looks in the video like the key dip is a little too deep based on the jack clearance when the key is down.

- Set damper lift to begin with the hammer 1/2 way to the strings, or a little sooner. This forces the pianist to push their finger through the damper springs, and once they have overcome the damper spring resistance the jack springs will not be such a problem to play through. This is the most common cause of bobbling in Kawai and Yamaha actions - late damper lift and strong damper springs.

- The low tenor damper springs are often set too strong in the factory. From the tenor break up to about G#4 is a strong spring, and from A4 up they are more weak. So in this section you can use a grand repetition spring tool to pull the springs back and weaken them a little - but only a little! After weakening the springs you will most likely need to do some damper adjusting to get them to work. Don't make them too weak! Just slightly lighter than original.



Good luck!



-------------------------------------------
Don Mannino RPT
Kawai America Corporation"

as PTFE on the jack rest felt does improve much more the key touch, I think this is the most important part to improve overall experience.
I think this problem is quite common on upright piano, just they are not at the point to have "bouncing keys".
I tried 20 years old Schimmel 125 and the touch is similar but not bouncing.
With a fresh regulation and PTFE, the touch of my Petrof Opera 125 is better than music school's Kawai baby grand.
This piano is better than I have expected.

Finally, I spent some time in the Saturday to regulate the action and tune some notes, here is the result.

Thank you for sharing this! Chopin Nocturnes are indeed so nocturnal.... I love the Earl Wild recording of the complete Nocturnes, on his beautiful Baldwin SD10 (before he switched to a ravishing Shigeru Kawai).

Zonzi, gently and respectfully, I think you are needing to practice tuning nice clean unisons....

Thank you David for your suggestions! I listened Earl Wild's recording, it's beautiful.
After a careful check, the bouncing keys are much more than I have expected.
As I mentioned previously, I was on rush, so I just tuned few notes very out of tune quickly. In addition, I cannot wait for try the fresh regulated action. This is a very bad idea, because the contrast makes the unisons of some notes even worse...
the capstan regulation brings this piano to great condition, I just don't know how long it will stay. I will put modelling clay in case they keep very short.