Pianotech

  • 1.  Potential for bridge recapping

    Registered Piano Technician
    Posted 03-12-2016 00:17
      |   view attached

    Hello all,

    I am doing an estimate on an old upright that has a bass bridge cap that is falling apart but also has a large crack in the bridge body (picture attached). Is there any reason not to glue the bridge body back together and then recap on top of the original bridge?

    ------------------------------
    Peter Stevenson RPT
    P.S. Piano Service
    Prince George BC
    250-562-5358
    ps@pspianoservice.com
    ------------------------------


  • 2.  RE: Potential for bridge recapping

    Posted 03-12-2016 06:32

    You can make a new single body/cap unit with a scrap of pin block material.

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

    Jon Page



  • 3.  RE: Potential for bridge recapping

    Registered Piano Technician
    Posted 03-12-2016 18:02

    Old upright?  How old and what is it?

    It appears that the crack is limited to the very low end of the bass bridge evidenced by the cap separating only on the lowest two monochords and only on one side.  It's probably been like that for awhile.  If the rest of the bridge is sound and if it is still firmly attached to the SB I would try and repair it first before undertaking a complete recapping.  You can probably do it on site.  Lay the piano on its back with a tilter.  Take the tension off the lowest few strings to give some room to work and just move them to the side.  Pull the bridge pins that are loose on the side where the crack appears. Using a glue injector, inject some epoxy (slow cure type like West System) into the crack.  Also inject some epoxy into the bridge pin holes that you've vacated and using a thin feeler gauge work it into the cap/bridge body joint.  Gently but firmly clamp with pony clamps and try and leave room to reinsert the bridge pins you've removed.  You don't need a huge amount of clamping pressure with epoxy.  Clean up the squeeze out with lacquer thinner (not too much as you don't want to dilute the epoxy with thinner) and make as neat a job of it as possible. If you are careful and if the crack isn't migrating too far up the bridge you can repair this without recapping the entire bridge.

    I've made similar types of repairs on both bass bridges and on the top of the treble bridge where I've seen cracks begin to open up along the pin line into the bridge root.  On the treble bridge you have to be very careful if the split is on the speaking side to insure that the terminations remain sharp and clean and in such cases clean things up with a chisel and redrill, perhaps, before reinserting the bridge pins.  In my case the split was on the non speaking side where it's a bit easier and less critical.  In the bass section the terminations are important too but not nearly as sensitive.

    If the split is migrating up the entire pin line (and it's hard to tell from the picture) then you probably have to recap.  Bolduc gives a class on recapping the bass bridge in an upright without removing the plate.  You might look into that.    

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 4.  RE: Potential for bridge recapping

    Registered Piano Technician
    Posted 03-12-2016 21:58

    Thanks for the responses, Jon and David. The piano is an 1898 C. Bechstein Model III upright. If you look closely at the picture, you can see that the cap is not just cracked, but actually broken into pieces. I expect that if the tension were to be taken off of the strings, the cap would just fall apart in pieces. However, if after taking a close look at the photo you think that it can be epoxied, I would love to hear about it.

    I have actually taken Christian Bolduc's class on bridge recapping without removing the plate, and it is because of that class that I began discussing this with the owner. The piano was recently restrung, and the pinblock and treble bridge seem fine, so if we can fix the bass bridge without having to remove the plate, that would be ideal.

    ------------------------------
    Peter Stevenson RPT
    P.S. Piano Service
    Prince George BC
    250-562-5358
    ps@pspianoservice.com



  • 5.  RE: Potential for bridge recapping

    Posted 03-13-2016 06:53

    I've made many bass bridge body and cap replacements with a single piece of pin block stock. Removing the body can take a little effort but with a MultiTool an even surface can be produced. If it's a little rough, epoxy fills the voids. Once the body is removed, run a line from the front termination to a spacer on the plate (thickness for down bearing angle) and measure to the apron. Measure the treble and bass ends and one or two in between. Fashion the replacement to those dimensions. Remove material from the bottom side so as to maintain an even top layer of wood. Determine any angle or slope needed to account for tilting with the strings installed; measure front and rear of the body from the drawn thread. Before removing the old bridge (strings off), measure with a thread to see how much db was there and any degree of slope.

    Once it's installed, index the new pin holes with a thread drawn between each unison's terminations. Drill the holes, notch the surface, install the pins, install the wire. A template of the old holes is good for the front pin line indexing speaking length but rely on measuring anew for the pin holes themselves rather than the template. The rear pin line is not that important but make it such that the rear notches match the front notches in length, making the top symmetrical looking.

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

    Jon Page