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Persistently tight damper guide rail bushings

  • 1.  Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 12:54

    Esteemed Colleagues,

    A client has a Boston grand that has had problems with sluggish dampers since day one. The cause is tight damper guide rail bushings.

    A smooth tapered broach, heated with a soldering iron has been used repeatedly.  Pressure has been applied from both ends (top and bottom) of the bushings with an awl. Even the dreaded "umbrella stave" tool has been dug out and used. And yet, on certain particularly stubborn notes, the problem persists.

    So, the question is: What is the next (more drastic) step? Applying VS Profelt, using bridge pins that are considerably larger than the diameter of the damper wire as cauls, and allowing it to sit overnight? Reaming with a similarly oversized bit chucked into either a drill motor or a Dremel (or Foredom) tool? Something else (hopefully, short of re-bushing the entire guide-rail)?

    Also, I would be curious to know if others have encountered this problem on other Boston grands.

    Thanks,

    Alan



    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------


  • 2.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 16:41
    Alan, you didn't mention simply trying to shrink the bushings with water/alcohol.
    It is a puzzler though. I've had some problems with the back action centers but not the guide rails.
    Perhaps they used a batch of too thick felt.

    ------------------------------
    Steven Rosenthal
    Honolulu HI
    808-521-7129
    ------------------------------



  • 3.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 16:46
    Steve,

    No, I have not tried shrinking the bushings. What is your recipe, and how do you apply it?

    Your guess that the cloth used in these bushings is too thick may well be correct. If that is indeed the case, then it is doubtful that this is the only piano with this problem.

    Thanks,

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 4.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 17:27
    Alan, I imagine the same formula used in "watering" the action. 50/50 water and alcohol? It's not something I've done much since the newer lubricants have come on the scene. I use a plastic pipette to apply CPL directly on the guide rail bushings.
    It's hard to believe that the multiple methods you've used have failed to relieve the problem. As I mentioned, I have run into quite a few damper wire flanges that are too tight on Kawai products, both wooden and plastic varieties. These need to move freely backwards and forwards or you will get symptoms similar to tight guide rail bushings. Lubricant usually does the job.

    ------------------------------
    Steven Rosenthal
    Honolulu HI
    808-521-7129
    ------------------------------



  • 5.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 17:39
    Steve,

    It may be hard to believe that the approaches used so far in addressing this problem have not solved it, but that is indeed the case. They have each, in turn, yielded improvement, but, on this piano, not permanently.

    Alcohol and water applied to center pin bushings have the pin in the bushing to function as a caul. Have you applied water/alcohol to guide rail bushings with the dampers in? With the dampers out, but using something else as a caul? With the dampers out, no caul?

    Thanks,

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 6.  RE: Persistently tight damper guide rail bushings

    Posted 06-24-2019 18:22
    I have spent inordinate amounts of time on an occasional new keyboard, shrinking and easing and what-have-you bushings. But if the bushings are too big, the bushings are too big. I ended up rebushing...sad I know, but that's the only thing that worked. All the easing and shrinking worked for a max of a week or so.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 7.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 18:26
    Thank you for your characteristic clarity of thought, Jim. (Not to mention those hard-won scars of experience! ;-)

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 8.  RE: Persistently tight damper guide rail bushings

    Posted 06-24-2019 20:05
    If you're in an experimental mood, you could make a damper bushing broach, something like a Mannino action center broach made larger.
    An appropriate size steel rod, roll with a file to make teeth over a 3 cm section. Or use a small rat tail file to remove some cloth, then burnish with a capstan tool.

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



  • 9.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 20:26
    It is rare that I am not in an experimental mood, Ed! When Steve suggested sizing the bushings with alcohol and water, it got me thinking in the direction of treating these guide rail bushings like center pin bushings. I wonder if the much thicker cloth of the guide rail bushings and the much looser fit of the moving part (the damper wire) to the bushing would respond like a center pin bushing to reaming and burnishing.

    First, I plan to try a more aggressive approach with heated broaches and cauls. If that doesn't do the job, then sizing. (So, no one so far has reported having tried VS Profelt on guide rail bushings...) If all of that still falls short, then my plan would be to rebush. But before rebushing, there would be nothing to lose by experimenting with your idea.

    Thanks!

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 10.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 20:42
    Mr. Eder,

    Sorry to be late to the conversation. I have used profelt on guide rail bushings for years. I've posted about this in years past. First thought : use a #8 bridge pin instead of a #7 pin as a caul. Be prepared to do a little wire bending if this works too well. Second consider adding a bit of de-nat alcohol and small amounts of distilled water to the profelt but use caution in the mixture. Something in profelt reacts with de-nat to heat up the mixture but not so much as to cause a runaway reaction. The more water you add to the mixture the more the felt will shrink. Also don't take the smoothness of the wire for granted. 10 minutes polishing will pay for itself very quickly.


    ------------------------------
    Karl Roeder
    Pompano Beach FL
    ------------------------------



  • 11.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-24-2019 21:41
    Thank you, Karl.  Thought I'd seen something about Profelt being used in this situation. Appreciate you chiming in about it.

    You recommend adding distilled water and denatured alcohol to the Profelt, but cautiously. Could you give some idea approximately what proportions you have worked with?

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 12.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 00:10
    It might be that the vertical alignment of the hole is skewed from the one defined by the damper wire. This will cause binding like you describe. Perhaps the guide rail is "tilted" front to back somehow?

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431
    ------------------------------



  • 13.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 07:49
    Mr. Eder

    I'd probably start with 60% profelt 30% de-nat and 10% water. I'd also use a #7 bridge pin to start before I tried the #8.

    Happy experimenting​​

    ------------------------------
    Karl Roeder
    Pompano Beach FL
    ------------------------------



  • 14.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 09:48
    Thanks for the 411, Karl. Looking forward to trying out sizing these puppies your way!

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 15.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-26-2019 11:48
    Follow-up question for Karl,

    You mentioned trying a #7 bridge pin before trying a #8 in your post with the proportions of Profelt, water and denatured alcohol that you use. In a previous post, you suggested using a #8 bridge pin rather than a #7 (which, stubborn as these bushings have been, would be my own inclination). Does this represent an evolution in thinking, or are you recommending the smaller bridge pin for the concoction and the larger one for Profelt neat?​​​​

    Make sense?

    Thanks,

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 16.  RE: Persistently tight damper guide rail bushings

    Posted 06-26-2019 15:17
    99% cases with sluggish Demper on Kawai and Boston I had , becouse tight center pins on underlever.

    Alexander Brusilovsky




  • 17.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-26-2019 15:20
    Good to know, Alexander. Thanks for your input.

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 18.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-26-2019 22:14
    A final thought: if you do end up removing the guide rails, while you have the dampers out, be sure to tighten all the screws that connect the tray to the belly. They work their way out in heavy use situations, and are a real pain to get to.
    Best wishes,
    Linda

    Sent from my iPhone




  • 19.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-27-2019 08:07
    Alexander,

    I realized that I missed the opportunity to say that I always wondered what it was like to be part of the 1% we hear so much about...

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 20.  RE: Persistently tight damper guide rail bushings

    Posted 06-27-2019 08:48
    And you didn’t built your business! Somebody( Government? O. Hussein Himself?) did it for you.

    Alexander Brusilovsky




  • 21.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 09:41
    Hadn't considered that, Ed. I'll look into it. If the situation you describe obtains, how is it that a tilted guide rail would cause the binding to keep coming back after easing?

    Alan

    P. S. It is reassuring to know that I can always count on you to come up with possibilities unimagined by the minds of most!

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 22.  RE: Persistently tight damper guide rail bushings

    Posted 06-25-2019 17:55
    We had four Yamaha GB1 grands that had the "tilted rail" problem in 2005.  The serials were very close together, so I would imagine it was a limited problem.  We haven't seen it since.   Ted

    ------------------------------
    Ted Rohde
    Central Illinois
    ------------------------------



  • 23.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 18:33
    Alan, how about this scenario? The damper assembly ends up being a little farther in toward the belly rail. The guide rail is installed a smudge forward toward the player. The damper wire would end up leaning toward the player at the top which might cause it to bind in the guide rail as the damper assembly rises. (It would also look like what some have diagnosed as a tilted guide rail, when it may not actually be tilted). In other words the top flange hole is not directly beneath the guide rail hole. Add in Paul Klaus's suggestion that the pinning may not appear tight until a bit of friction created in the guide rail bushing comes into play and causes sluggishness. In other words there may be a combination of two things, neither of which by themselves is a problem.

    Possible? Improbable? Just a thought.

    Richard West








  • 24.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 22:44
    Richard,

    What you describe certainly could be possible. Is it improbable? What difference would that make, if it is indeed the cause of the problem. If it is a combination of two or more things that are close to being what should be, but not quite there, that can be trickier to identify.

    Maybe I've got tunnel vision, but I am still focused on the the guide rail bushings themselves.

    Thanks,

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 25.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 22:29
    Good on you for figuring out that the problem with those GB1s was what Ed McM. described, Ted. I had not heard about this problem until now.

    Thanks for the 411,

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 26.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 10:40
    I've done the Profelt/bridge pin cure.  As a final step, i set it on top of an electric griddle with the pins touching the surface, supporting each end, long enough for the bridge pins to iron the bushing surface and slide out.  It's always been a very stable fix.

    ------------------------------
    Linda Scott, RPT
    Portland, OR
    503-231-9732
    ------------------------------



  • 27.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 11:01
    Thanks, Linda. Good to know.

    What piano brands have you had to do this to?

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 28.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 11:05
    A few afterthoughts, Linda...

    Did you use straight Profelt (without any of Karl's additives)?

    Were the bridge pins in the bushings when you applied the Profelt?

    And it sounds like you removed the guide rail to do all that you described. Is that correct?

    Thanks,

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 29.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 11:39
    Yes, yes, and yes.
    Good luck!
    Linda

    PS damper wires are smooth and clean (make sure nobody has applied stuff to 'fix' the pribkem)

    Sent from my iPhone





  • 30.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 12:15
    Roger that, Linda!

    Alan

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
    ------------------------------



  • 31.  RE: Persistently tight damper guide rail bushings

    Registered Piano Technician
    Posted 06-25-2019 12:17

    Long shot: If one/both of the damper underlever pins are slightly too tight they might temporarily be sympathetically eased by work at the guide rail and return later.