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Bobbling Upright Hammers

  • 1.  Bobbling Upright Hammers

    Posted 08-17-2022 17:03
    My client owns a new (-ish) Ritmuller full-size upright. Reasonably nice piano. However, many notes tend to have the hammer bobble (multiple string strikes) on very light blows. One can watch and see that the jack simply does not clear the butt leather and the hammer assembly then bounces back and forth between the strings and the jack top. The only thing I can think of to do at this point is to increase aftertouch - either by increasing key dip or lessening blow distance and regulating lost motion. I have key dip right at 10mm and blow at 1-3/4".

    Any thoughts? Anyone run into this type of problem with a newer Ritmuller upright?

    Oh, and don't bother suggesting warranty work - the dealer already "fixed it" - he increased let off to about 3/4" and blow to over 2". Didn't fix anything.....

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    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
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  • 2.  RE: Bobbling Upright Hammers

    Posted 08-17-2022 17:41
    It's a balancing act between Let Off, Blow Distance and Key dip. If there are dowel capstans on wires, you could bend the wire towards the rear to increase Action Ratio, or, which is more involved; relocate the capstans.

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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 3.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-17-2022 17:49
    I would start by increasing dip one puching at a time. Even .005 is often enough to trip the jack.  





  • 4.  RE: Bobbling Upright Hammers

    Posted 08-17-2022 20:59
    Shim the balance rail to increase dip, if the level does not bind elsewhere.

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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
    ------------------------------

    Original Message


  • 5.  RE: Bobbling Upright Hammers

    Member
    Posted 08-17-2022 18:34
    You need a little bit of lost motion so there is clearance between the top of the jack and the hammer butt. turn down the capstan screw and observe if there is clearance between the top of the jack and butt. You also may need to play around with the backchecking distance . Of course others have pointed out blow distance, letoff and key dip so experiment on a few keys . It is a balancing act that can drive you crazy...

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    James Kelly
    Owner- Fur Elise Piano Service
    Pawleys Island SC
    (843) 325-4357
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  • 6.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-17-2022 19:42
    Shorten the blow by shimming the rest rail and take up the lost motion to get more jack clearance.

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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 7.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-17-2022 19:53
    Some of the Chinese upright pianos have very strong damper springs, which on a soft blow slows the key travel and makes it prone to bobbling.  Solution is to weaken the damper spring using a hook or Hart spring tool.  Engage the spring and pull it back to weaken it.  Try one and see if weakening the spring helps.

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    Paul McCloud, RPT
    Accutone Piano Service
    www.AccutonePianoService.com
    pavadasa@gmail.com
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  • 8.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-17-2022 21:17
    Dittos on Paul's post. The Bowman-Carraher class on upright action regulation, mentioned earlier in regard to damper spoon regulation, also covered a very accurate technique to adjust the strong damper springs to their optimal strength.

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    Patrick Draine RPT
    Billerica MA
    (978) 663-9690
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    Original Message


  • 9.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-17-2022 21:09
    Does the bobbling occur when you play the piano lightly or only when the customer plays the piano lightly? I ask because one can make a hammer bobble on both an upright and a grand if one hesitates, consciously or not, even just the slightest amount upon feeling the bump of the jack when it hits the letoff button. At that exact moment the hammer has enough momentum to complete it's throw to the string and bounce off before the jack has had the opportunity to escape fully. When the hammer bounces back off the string, instead of the hammer being caught by the back check, the butt hits the jack and gets thrown a second time when escapement actually completes and the hammer is thrown, correctly this time, striking the string a second time. Or sometimes even more if you hesitate longer. This is a player technique problem and the player simply has to learn how to NOT be aware of that slight bump and instead learn to smoothly follow through the entire key movement until the key bottoms out on the front rail punching. Two things to try, after explaining and demonstrating this to the customer. Teflon powder the hammer butts. Too much friction there will increase the feel of the bump upon jack/letoff button contact. Check to make sure there is enough friction in the hammer flange. If the hammer flange is too loose then the hammer is moving too freely in the first place.

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    Geoff Sykes, RPT
    Los Angeles CA
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  • 10.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-17-2022 23:56
    Like James said, I would start by checking lost motion. To me it sounds like there might not be enough. Here's a list that I've complied over the years for dealing with bobbling hammers. Check in this order:

    1. Is there too much or not enough lost motion?

    2. Is there enough slack in the bridle straps?

    3. Is the action mounted correctly?

    4. Is the hammer blow correct?

    5. Is checking close enough?

    6. Is the damper spring too strong?

    7. Is the hammer return spring too weak?

    8. Is the jack spring too strong?

    9. Is the jack stop rail too far back?

    I'm sure the list isn't all inclusive, but going through them in that order I usually find the problem fairly quickly.



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    Benjamin Sanchez, RPT
    Piano Technician / Artisan
    (256) 947-9999
    www.professional-piano-services.com
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  • 11.  RE: Bobbling Upright Hammers

    Posted 08-18-2022 04:25
    I'm curious about the comments citing that there is potentially not enough lost motion. Generally speaking, if I can see the hammer follow the rest rail a bit when I pull back on the rest rail, I'm thinking that I have enough lost motion. If that is not the case, how much lost motion is generally recommended and where/how is it measured?

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    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
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    Original Message


  • 12.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-18-2022 08:17
    I too am curious about the last motion piece. As lost motion increases, jack deflection decreases. My instinct is to look for excessive lost motion when I have a bobbling hammer, not for insufficient lost motion.

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    Floyd Gadd RPT
    Regina SK
    (306) 502-9103
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    Original Message


  • 13.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-18-2022 10:48
    Like Floyd, I'm curious how not enough lost motion can cause bobbling. I know it causes unreliable repetition...

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    John Pope
    University of Kentucky School of Music
    Lexington, KY
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    Original Message


  • 14.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-19-2022 00:25
    I've seen some instances where insufficient lost motion caused the hammer to bobble. Or, maybe more accurately, adding just a tiny bit of lost motion caused the hammer to stop bobbling. I think it may be because the jack won't go under the hammer butt all the way but is under far enough to push back on the butt as it's trying to come back (typically on a blow that's not strong enough to engage checking), causing a double strike. I don't know if that's accurate or not. What I do know is that sometimes adding just a bit of lost motion solved the problem. *shrug*

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    Benjamin Sanchez, RPT
    Piano Technician / Artisan
    (256) 947-9999
    www.professional-piano-services.com
    ------------------------------

    Original Message


  • 15.  RE: Bobbling Upright Hammers

    Posted 08-18-2022 08:25
    Technicians who service new vertical pianos should know the following procedure:

    On a relatively new vertical piano, consider the possibility that the keybed has flexed due to humidity change.
    If so, the action irregularities will be in the center of the keyboard. There will be a "problem neighborhood," perhaps the middle third of the keys.
    Key dip in the middle of the keyboard will be different from the end sections.
    A straight edge will show a drop or rise in the key level in the middle section.

    If this is what you find, correct it by raising or lowering the balance rail in the middle. Adjust the same amount as if you were adjusting the balance rail punchings.
    This neighborhood adjustment should result in a neighborhood correction.
    Mark the keys that cover the balance rail screws, as you may need to correct this again when the humidity changes.

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    Ed Sutton
    ed440@me.com
    (980) 254-7413
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    Original Message


  • 16.  RE: Bobbling Upright Hammers

    Member
    Posted 08-18-2022 16:25
    Ed.. I wonder if flexing keybeds on new verticals is a more recent problem and is due to poor environmental conditions at the factory. Years back there was an issue with poor keybeds on Pearl River grands . Not long ago I worked on a new Yamaha P22 that had action issues including the need to ease all of the keys, add some lost motion, adjust backchecks. It was fine after I played it when I finished the work but then the dealer ended swapping it out after the pianist complained. I heard that some of the pianos where being rushed out the door and did not get the usual qa at the factory. Having to make adjustments due to humidity changes seems like it is time to consider piano life savers, room dehumidification/humidification.

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    James Kelly
    Owner- Fur Elise Piano Service
    Pawleys Island SC
    (843) 325-4357
    ------------------------------

    Original Message


  • 17.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-19-2022 00:18
    James,

    I'm seeing the same thing on some of the Yamahas that the local dealer here gets. When asked about it, the Yamaha people told us they're so behind with orders they're having to rely on the dealerships for some of the final prep work. Unfortunate but it's becoming more common.

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    Benjamin Sanchez, RPT
    Piano Technician / Artisan
    (256) 947-9999
    www.professional-piano-services.com
    ------------------------------

    Original Message


  • 18.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-18-2022 17:24
    Hi Terry,

    9 times out of 10, bobbling hammers on an upright is the result of insufficient aftertouch. The other unlikely culprits are backchecks not checking at all, and damper springs that are far too strong.  I say unlikely because these two source problems usually present themselves in obvious ways.  

    It sounds like the dealer who claimed to have fixed the problem by increasing let off to 3/4" actually stood to gain more aftertouch from that adjustment (as ill-advised as increasing aftertouch by compromising the let off may have been), but then they lost the aftertouch they gained by increasing the blow distance to 2"

    Since aftertouch is likely insufficient, you will want to increase aftertouch in one (or both) of two ways:

    • Decreasing blow distance, and/or
    • Increasing key dip

    Since pianists are usually very sensitive to changes in key dip, the choice to get more aftertouch almost always ends up being decreasing the blow distance although it is important to consider a compromise between the two.

    Other people have mentioned lost motion and I want to point out that more lost motion means less aftertouch.  The lost motion should be just sufficient enough for the jack to fully and reliably reset and no more.  Too much lost motion can actually lead to bobbling hammers since the wasted motion of the key is directly decreasing the amount of aftertouch.

    Note that if you decrease blow distance on an upright, you will have to take up the lost motion you created in order to test the results of your adjustment.

    I hope this helps!

    Daniel DeBiasio

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    Daniel DeBiasio
    Brooklyn, NY
    646.801.8863
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  • 19.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-19-2022 00:34

    Hello Terry,
    Daniel is spot on.  The likely culprit is shallow dip but if you are confident that the dip is at 10mm, and that after-touch is correct, shorten the blow distance to whatever it has to be to be,  Ritmullers (Pearl Rivers) have been somewhat flexible about hammer blow..    

    Regards,
    Mark Wisner



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    Mark Wisner RPT
    Cape May NJ
    (714) 337-9074
    MarkWisner
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    Original Message


  • 20.  RE: Bobbling Upright Hammers

    Registered Piano Technician
    Posted 08-19-2022 09:18
    10mm seems fairly shallow on a Chinese vertical.  Many seem to work best with more key dip, in the 10.5-11mm range, but it's been a while since I've worked on one with that type of problem.

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    Tom Dowell
    Hulbert Piano
    tom@hulbertpiano.com
    262-221-0792
    ------------------------------