CAUT

  • 1.  Brodmann upright: bad bobbling

    Registered Piano Technician
    Posted 16 days ago
    I recently serviced a Brodmann BU-128 vertical from 2009, which had some of the worst bobbling I've ever seen.
    I did some regulating, but this piano was especially stubborn. The jacks cleared the hammer butts with plenty of room--aftertouch was not the issue. The tops of the jacks look especially deep, so in a way I'm not surprised. It's kind of like walking through a screen door that closes quickly and nails you on the way out.

    Anyone encountered one of these pianos? I've sent an email to the company describing the issue, but no response. Hence my post.

    Here's a thought though: We can adjust the fore-aft position on grand jacks so that we get the fastest performance but without "cheating." Is it possible to somehow do the same with vertical jacks? Perhaps they lie at rest too deeply under the hammer butts, and if a thicker rest felt were installed, the back of the jack would clear the butt faster? Of course one would have to make sure the jack didn't cheat under a hard blow, just like a grand. What about experimenting by gluing a bit of felt on the back of the jack itself with just a small dot of glue? If it worked, would that extra mass impede the motion of the jack with too much inertia? One could of course replace all the rest felt if something of just the right thickness could be found.
    If the jack were tilted a small bit forward, I suppose it would compress the spring a tiny bit more. Hopefully there would be enough adjustment in the letoff screws to compensate.

    Any commentary on my thought experiment? Maybe I'm reinventing some square wheel that's already been left at the side of the road...

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    Scott Cole, RPT
    rvpianotuner.com
    Talent, OR
    (541-601-9033
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  • 2.  RE: Brodmann upright: bad bobbling

    Registered Piano Technician
    Posted 16 days ago
    Hi Scott:

    I worked for the local Brodmann dealer years ago. The damper springs are too strong. With light touch, the springs slow down the key stroke and the hammers bobble. Use a spring hook on the damper springs to weaken them. Just pull the spring back with the hook, no need to remove the action. Just be a little careful not to weaken too much. Or, remove them and do it. Of course there may be other causes, but that's what I remember about those pianos and similar coming from overseas.

    Good luck.

    Paul McCloud

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    Paul McCloud, RPT
    Accutone Piano Service
    www.AccutonePianoService.com
    pavadasa@gmail.com
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  • 3.  RE: Brodmann upright: bad bobbling

    Registered Piano Technician
    Posted 15 days ago
    Hi,

    What Paul said. (Weaken the spring)

    Plus, yes, you can install thicker hammer butt felts. Before you do, try a couple samples. It may not make a significant improvement on those. 

    Jim



    Sent from my iPhone





  • 4.  RE: Brodmann upright: bad bobbling

    Registered Piano Technician
    Posted 15 days ago
    I have also found making the damper springs weaker can alleviate bobbling upright hammers. Also, having the spoon timing no later than half stroke helps too.

    But I have a question that I also posted over on pianotech; Is the bobbling only in the tenor hammers above the bass/tenor break? Or do all the hammers bobble?

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    Edward McMorrow
    Edmonds WA
    425-299-3431
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  • 5.  RE: Brodmann upright: bad bobbling

    Registered Piano Technician
    Posted 15 days ago
    The damper springs/ damper timing will likely solve the issue. If you still get some bobbling on sharps, may need a bit more key dip. If back checks line up AND check same distance from strings, then dip is fine. These pianos do seem to have action issues. There are 6 BU 125s at Loyola, center pinning has also been a headache, though I think some of that was caused by a misdiagnosis of the bobbling issue by another tech.

    David Graham
    Graham Piano Service, Inc.
    512 S. Main St.
    Sycamore IL 60178
    815-353-5450
    grahampiano1@yahoo.com