Pianotech

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Bass bridge

  • 1.  Bass bridge

    Member
    Posted 07-15-2022 11:09
    I recently installed new h/s/f on a restrung Hamburg M. Ronsen Bacon felt Hammers with WNG s/f (flex 3).
    I really like the new s/f. I bored the hammers .003" larger than the shanks and chamfered both sides on a drill press.
    I dry fit the tapered hammers and applied CA to the front and back. The bevel allowed the glue to wick into the joint. I applied it twice.

    Then I removed them from the rail to cut off the protruding c/f shank and rough-cut the arc on the band saw.
    Spurlock's Hammer Tapering Jig finished the arc. Then graduated their SW. re-leaded the keyset after a survey.
    It came out exceptionally well except for the bass.

    A0 and A#0 sound hollow, nasally. There is excessive (I mean excessive = a lot) d/b in the middle of the bass bridge.
    I think the board is squashed and the s-curve is affecting the low tenor as well.

    There is also excessive side bearing, I'm surprised the cap hadn't split.
    Repairs to the bridge will not happen due to the owner exceeding their budget already.
    I attached photos of the bearing and a video of the tone in a second post.


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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 2.  RE: Bass bridge

    Member
    Posted 07-15-2022 11:10
      |   view attached
    video of the tone:

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    Regards,

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



  • 3.  RE: Bass bridge

    Registered Piano Technician
    Posted 07-15-2022 12:29
    Jon,

    What I noticed in the pics is that the windings are very close to the bass bridge but correspondingly far away from the agraffes. Do you happen to know who made the bass strings? And, did the bridge get recapped to put all that side bearing on there (as well as the high downbearing)?

    Peter Grey Piano Doctor

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    Peter Grey
    Stratham NH
    (603) 686-2395
    pianodoctor57@gmail.com
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  • 4.  RE: Bass bridge

    Member
    Posted 07-15-2022 12:46
    Bass bridge was not recapped.  The wrap does end very close to the bridge, maybe because of the severe angle.

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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 5.  RE: Bass bridge

    Posted 07-15-2022 12:50
    Jon, 
    You didn't ask a question in your post, are you just venting?
    -chris





  • 6.  RE: Bass bridge

    Member
    Posted 07-15-2022 12:59
    Q & V. The excessive d/b and to some degree the side bearing is killing the bass response?

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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 7.  RE: Bass bridge

    Posted 07-15-2022 13:04
    Yes, excess downbearing kills the tone. It's the first thing I check upon first inspection so I can give an appropriate estimate to the piano owner.
    -chris





  • 8.  RE: Bass bridge

    Member
    Posted 07-15-2022 12:51
    Either the bass cap was bored mis-aligned or the hitch pins were installed too far towards the bass. The bridge pins just about line up with the next highest hitch pin.

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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 9.  RE: Bass bridge

    Registered Piano Technician
    Posted 07-15-2022 13:24
    Jon,

    I've seen you install little half rounds under the bass strings near the hitch to deal with db...yes?

    Peter Grey Piano Doctor

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    Peter Grey
    Stratham NH
    (603) 686-2395
    pianodoctor57@gmail.com
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  • 10.  RE: Bass bridge

    Registered Piano Technician
    Posted 07-15-2022 13:36
    Incidentally, what did those notes sound like before replacing the hammers? Same.. worse...better?  Also, what about the rest of the bass...how did it sound prior?

    Do we know the age of this piano? I've seen plenty with what I would consider excessive DB.  Was there a reason given for restringing it?

    Peter Grey Piano Doctor

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    Peter Grey
    Stratham NH
    (603) 686-2395
    pianodoctor57@gmail.com
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  • 11.  RE: Bass bridge

    Member
    Posted 07-15-2022 15:06
    The top treble cap needed replacement. New hammers were to eliminate the noisy knuckles and worn out hammers. The notes were poor prior to new hammers but she said she rarely plays the low bass. A0 was dead and needed replacing. Upon replacing A0 (I got it from her tuner<restringer<string maker), the note was no longer dead but it is nasally, crimped, squashed. Why the rebuilder replaced the treble cap and not the bass is anyone's guess. And why did it leave their shop with a dead A0 and E1 down awful? 4/0 pins, tight with more torsion than I care for; glad I don't tune it.

    The situation now is that she would like to sell it but I told her the low bass is a deal-breaker. I gave her a price to replace the cap with new bass strings.

    70's or 80's vintage. Cracked polyester finish. Nice one-piece ivories. Overall, it looks great at first glance.

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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 12.  RE: Bass bridge

    Member
    Posted 07-15-2022 15:24
    I installed shims (.060") under a few notes but when I needed to double their height, I gave up. A new cap would be the best solution.

    I have installed shims to correct bass d/b multiple times with success but was the wrong approach in this case. Vertical hitch pins are the way to go.

    I have an idea for a tool to measure for shim thickness needed, it involves a spring-loaded dial plunger, measuring the distance from the front bridge pin to the hitch pin and compute the angle of deflection read in thousandths of an inch (or mm). I got the idea from John Hartman's d/b tool. I have all the stock/items needed; I just need the time/ambition to assemble them.

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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 13.  RE: Bass bridge

    Member
    Posted 07-15-2022 15:30
      |   view attached
    One more photo, As I approached the top of the bass, the shims became thinner.

    Edit: oops sorry, it didn't show up at first. It took a while to load I guess.
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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 14.  RE: Bass bridge

    Posted 07-15-2022 16:12
    The gauge or idea you describe doesn't work, because you don't know the whole load on the board, nor how much load the board can accept. You have to Zero out then follow a downbearing plan that applies the correct dB in one pass.

    Chris






  • 15.  RE: Bass bridge

    Member
    Posted 07-15-2022 21:59
    I have usually started on A0 and placed zero bearing because as I came up the scale the bridge rose and the lower notes ended up having .5 degrees.
    The top end has come from a negative bearing to zero. Maybe not perfect but not too bad for work in the field. There was a noticeable improvement.
    Making the best of a bad situation.

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    Regards,

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



  • 16.  RE: Bass bridge

    Registered Piano Technician
    Posted 07-15-2022 22:11
    Is it the original board?

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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 17.  RE: Bass bridge

    Member
    Posted 07-15-2022 23:41
    original board

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    Regards,

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



  • 18.  RE: Bass bridge

    Registered Piano Technician
    Posted 07-16-2022 08:45
    I would doubt the excessive side bearing is causing any tonal problems. It's egregious, but it isn't your enemy here. Ruling out a problem with the bass strings themselves, I would suggest this is a downbearing problem. I would create zero downbearing across the entire bridge, from #1 to #26 to free up the bottom end of the soundboard. Also, I would look at what kind of downbearing exists at notes #27 and #28. If it is excessive shim them up, too, to zero. There are other factors potentially at play, but this is where I would start. And here comes the ultimate response (he stated humbly): will the piano's owner complain about the tone at notes #1 and #2? Did it sound like this before your fine action work, Jon? We can get ourselves into real trouble "correcting" problems that the owner was never aware of until we point them out. At this point we have dug our own graves. If you're already over-budget, put the piano back together, return it to the owner, and let him/her bask in your glorious new action. Mention nothing about notes #1 and #2.

    David G. Hughes, RPT
    Baltimore Chapter
    ​​​​​​​​

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    David Hughes RPT
    Vintage Case Parts
    Glyndon MD
    (443) 522-2201
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  • 19.  RE: Bass bridge

    Member
    Posted 07-16-2022 20:20
    The windings look real close to the bridge pins as Peter mentioned but it almost seems that the hammers are almost blocking the strings on A0 and A#0- if not blocking the strings are having some contact with the hammers and not vibrating freely. The other thing is what is with the A0 damper dancing all over ? loose screw ? too close damper lift from the key ?  how does it sound when the damper pedal is held down and A0, A#0 is played ?   I would not fuss too much more with things. Whats there now is an improvement over what was there before...

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    James Kelly
    Owner- Fur Elise Piano Service
    Pawleys Island SC
    (843) 325-4357
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  • 20.  RE: Bass bridge

    Member
    Posted 07-17-2022 12:38
    nothing blocking. As for A0 damper, loose pinning on the underlever? Loose guide rail bushing? Small potatoes compared to the constrained tone at the low end of the bridge. I can hear a deficiency in the tone from the mid tenor down.

    ------------------------------
    Regards,

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