Harpsichord

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Neupert progress: hitchpin rails

  • 1.  Neupert progress: hitchpin rails

    Registered Piano Technician
    Posted 03-01-2020 14:52
    Yup, Fred, a can of worms it is. It appears that since the last time I examined this harpsichord a week ago, the 8' hitchpin rail decided to to start moving. Last week it looked solidly attached both to the rim tail and the soundboard, today there was a gap between it and the rim, and the back side of it appeared to be lifting (see photo). So I unstrung that section, and a little pressure with a Jorgensen clamp cleanly broke the glue joint and I was able to lift that section out. But a 2 inch section of the soundboard also appeared to have come loose from whatever it was glued to underneath, and the bass end of the bentside section of the 8' hitchpin rail had also come loose. I chiseled some of the loose soundboard section free, so as to be able to work glue under it with a feeler gauge and clamp it down, so there will be something solid to glue the rail back onto tomorrow. I also glued and clamped the bass end of the bentside section of the 8' hitchpin rail both to the soundboard and the rim at the same time.

    Before doing that, however, I rechecked the treble end of that rail after unstringing that section, because there is also a gap there between the rim and the rail but the rail appeared to be solidly attached when I examinedit last week. Applying sidways pressure with a Jorgensen clamp to close the gap does appear to narrow it slightly, but when downward pressure is applied to the back side of the rail (closest to the rim) there is no movement at all, suggesting that the rail is still firmly attached at its bottom there. At the front edge the glue joint appears to be solid - no poking with the thinnest feeler gauge made any headway underneath. However, since pressure toward the rim makes the rail move slightly in that direction, wouldn't string tension make it move in the other direction? Would it make sense to glue a shim into  the gap between it and the rim, to prevent that possibility?


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    Israel Stein RPT
    P.O. Box 68141
    Jerusalem, Israel 9168002
    510-558-0777
    istein248@gmail.com
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  • 2.  RE: Neupert progress: hitchpin rails

    Registered Piano Technician
    Posted 03-01-2020 18:26
    I don’t generally worry about the top end of the 8’ bridge, because it is captured by a piece of molding along the cheek. It doesn’t have hitch pins, but it seems to always be there, and I always figured that was the reason. The bend in the bridge probably is wanting to unbend, and that is there to keep it from happening.

    On the bass end, there is a similar stop gap in most harpsichords, where there is a tail portion of the hitch rail that helps wedge the bass end of the curved side rail, and also a piece of “decorative” molding along the spine, which holds the tail portion of the rail in place.

    Neupert seems to have omitted both those pieces of “decorative” molding, which is a little worrying. I never cared for the model of the hitch pin rail being glued mostly to the soundboard. Hard wood to soft wood, and bearing a good bit of tension seems like a recipe for disaster. It should be glued to the rim as well, though that joint may tend to fail.

    All in all, I think there is ample cause for concern. While those hitch rails have never seemed a problem on the few Neuperts I have dealt with over the years (and one over a period of nearly 40 years), if the joints on yours are failing, I’d hate to stand behind simply gluing it back to the board. I’d feel happier attaching it to the rim, perhaps glue and add a couple screws, both to pull it tighter and to make a tighter glue joint.

    On the treble end, I don’t see anything to be gained by filling the gap, unless the shim was glued both to the back of the rail and to the rim, again perhaps with a screw reinforcement.

    This is all pure speculation on my part, not having run into it.
    Regards,
    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    www.artoftuning.com




  • 3.  RE: Neupert progress: hitchpin rails

    Registered Piano Technician
    Posted 03-02-2020 01:14
    Thanks again, Fred, I was thinking of adding screws to counter the string tension - you helped make up my mind. My thinking about shimming the gap between the rail and the rim is simply to provide a stable surface onto which to glue and screw the rail. I have several very thin sheets of plywood in several thicknesses to get just the right thickness shim.

    BTW, the 4' hitcpin rail got glued to gether with no real problems. In the process I discovered that the loose section of rail did not get unglued from the soundboard - the rail simply split along horizontal grain, its bottom part remaining firmly glued to the soundboard. I was wondering if a few screws through that rail might be a good idea...

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    Israel Stein RPT
    P.O. Box 68141
    Jerusalem, Israel 9168002
    510-558-0777
    istein248@gmail.com
    ------------------------------



  • 4.  RE: Neupert progress: hitchpin rails

    Registered Piano Technician
    Posted 03-02-2020 09:15
    Israel-
    What's under the soundboard and 8' hitchpin rail? Is it a liner or is it a full inner case, intended to be the real support structure while the outer case is, well, just an outer case? Is it possible that the outer case is separating from an inner rim?
    How long are the hitch pins? Do they go down far enough to get support from the rim, liner, whatever-it-is that supports the soundboard, or do they mostly pull on the hitchpin rail?

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    Ed Sutton
    ed440@me.com
    (980) 254-7413
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  • 5.  RE: Neupert progress: hitchpin rails

    Registered Piano Technician
    Posted 03-02-2020 10:27
    Ed,

    It's an inner case - the outer rim is too thin to be structurally relevant. Today I screwed and glued down the tail section of the 8' hitchpin rail. Drilling the screw holes felt like the bit was going deep into a rim - not some sort of liner. The inner/outer rims are not separating, I checked with a feeler gauge. The glue joint is solid. The hitchpins protrude out of the bottom of the rail enough to maybe traverse the soundboard and maybe tickle the top of the inner rim. - and they 1" hitchpins. The rail is tall...

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    Israel Stein RPT
    P.O. Box 68141
    Jerusalem, Israel 9168002
    510-558-0777
    istein248@gmail.com
    ------------------------------



  • 6.  RE: Neupert progress: hitchpin rails

    Posted 03-02-2020 02:42
    Can anyone please describe: Jorgensen clamp? It sounds like the veritable answer to a 'sky hook'

    Michael  UK


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    Michael Gamble
    semi retired
    Brighton
    01273813612
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  • 7.  RE: Neupert progress: hitchpin rails

    Registered Piano Technician
    Posted 03-04-2020 12:41
    Jorgenson Clamps:

    A company in the USA makers of a variety of specialty clamps.
    Not sure which type he was referring to.

    No relation to the late great RPT and author Owen Jorgensen who could clamp 3 pure thirds into an octave.





  • 8.  RE: Neupert progress: hitchpin rails

    Registered Piano Technician
    Posted 03-04-2020 12:49
    Israel was referring to hand screw clamps, wooden jaws. Google it. 
    Regards,
    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    www.artoftuning.com
    "Art lives from constraints and dies from freedom." Leonardo








  • 9.  RE: Neupert progress: hitchpin rails

    Posted 03-04-2020 15:23
    Hello Jonathan Moberg
    Thanks for the information about the Jorgensen clamps. I have found the UK version of Bar clamps (made by Jet Clamps) particularly useful and have used them when laying tongue and groove floor boards - but in the opposite way! Both heads are turned round so pressure can be applied 'outwards' so as to clamp the boards together for nailing. Maybe the Jorgensen bar clamps can be so used. I'm impressed by their 'deep throat' clamp. As to getting three pure 3rds into one 8ve - that certainly takes some clamping I agree!! I have been tuning to the Farley-Serkin temperament for piano/Orchestra in Gerschwin's 'Rhapsody in Blue' - the strings liked the 5ths in that!
    Michael  UK

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    Michael Gamble
    semi retired
    Brighton
    01273813612
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