CAUT

  • 1.  Treble Bridge Crack in a 1994 Yamaha C3

    Posted 08-21-2024 19:02

    Hello PTG community, thanks in advance for offering experience or advice regarding my following questions! This is my very first online discussion post. I have cross-listed to the CAUT forum, so apologies if you see it twice.

    I am curious how to proceed with the following piano that is located at UCLA (one of the institutions where I work). This piano has fairly severe bridge cracks in the high treble section. The cracks appear to only affect the rear bridge pins. The bridge looks to be made of two pieces: a root (apparently laminated) and a cap. It was difficult to photograph the end of the bridge, but it looks to me like the crack goes through the cap and even into the root at the very edge.

    The first question I asked myself was: should I attempt to do this repair? Sustain in the affected area is not bad, and tuning stability is also better than I expected given the amount of cracking. Advantages to making the bridge repair include improved tuning stability and possibly improved sustain in high treble.
    Does anyone have experience repairing this kind of damage without recapping the bridge or removing the string frame (AKA plate)? If you did, I am curious:
    1. How did you do it?
    2. What adhesive did you use? 
    3. Did you remove the bridge pins or keep them in place? If you removed the bridge pins, did you fill the holes and then drill them out when the glue hardened?
    I can foresee the biggest challenge in this repair being not enough space between bridge and plate to provide adequate clamping at bridge root and cap. Additionally, the wood looks very "chewed up" (the tearing of the wood has left it ragged) and I am unsure that the clamping pressure from both sides of the bridge would align all the wood splinters to their original position.
    Please see attached pictures for reference, and do not hesitate to ask more questions! I will answer as I am able.
    Kindest regards,


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    Joshua Sadinsky
    Santa Clarita CA
    https://pianojosh.com/
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  • 2.  RE: Treble Bridge Crack in a 1994 Yamaha C3

    Registered Piano Technician
    Posted 08-21-2024 19:27
    Joshua

    This is actually a pretty straight forward bridge repair. 
    1. Remove the string, looping them on a piece of cloth string to keep them in order.
    2. Remove the bridge pins. (put them in a nut cup of small bowl so as not to lose them.)
    3. Mix up a batch of PC7 or other slow curing metal epoxy. 
    4. With an awl or small screwdriver, put as much of the epoxy in the cracks.
    5. Take a bridge pin and put a little of the epoxy on the end and insert the bridge pins. Start with the ones at the middle of the bridge, (string 14.5), where the holes are pretty obvious. When you get to the upper part of the bridge, you will need to find the holes in the bridge core. 
    6. When all the pins are in, use spring clamps to pull the bridge crack together, and squeeze as much of the epoxy out of the gap. 
    7. Remove as much of the epoxy from around the bridge pins with a small screwdriver, making sure the speaking edge of the pins are completely free of epoxy, and, of course, make sure the top of the bridge is also flat. 
    8. Wait 36 - 48 hours. 
    9. With a small file, remove an excess epoxy you might have missed.
    10. Put the strings back on and tune. 

    Even though you're using a slow curing epoxy, you still have to work fast because the epoxy sets up in a bout 15 - 20 minutes. It takes at least 24 - 36 hours to sure completely. 

    Good luck

    Wim  




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  • 3.  RE: Treble Bridge Crack in a 1994 Yamaha C3

    Registered Piano Technician
    Posted 08-22-2024 02:18

    Uncured epoxy washes off with alcohol.  If  you allow yourself some time to clean up the work you can remove most or all of the excess epoxy with denatured  alcohol (assuming your state has not made it illegal).

    This saves on filing and clean-up after it sets.



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    Blaine Hebert RPT
    Duarte CA
    (626) 390-0512
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    Original Message