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"Frozen" register slides

  • 1.  "Frozen" register slides

    Registered Piano Technician
    Posted 02-13-2020 03:52
    A few days ago I was asked to examine a single-manual Neupert, that had been knocked off its legs a few years ago and fell to the floor. It has since been moved from New York to Jerusalem (yes, that's where I live now) and sat unused for a few years. The tuner who tried to tune it said that strins would not hold tension, even though the tuning pins feel plenty tight enough.

    I found that the 4' hitchpin rail has split in half around 2 octaves from the top, and the top part is partially unglued - which explains the above. I didn't see anything else that would explain instability in the rest of the instrument, and the two or three strings I "tuned" in other parts of the harpsichord appeared to hold.

    Anyway, the two (brass?) register slides are frozen solidly in place (where the pluck the strings). The hand lever for the 8' and the knee lever for the 4' move in and out of contact with the slides, but they remain stuck - their springs to not seem to be able to move them.  Applying sideways pressure by hand or tool does not budge them - they are wedged in pretty solidly. I am wondering if the blow that the instrument sustained shifted something to pinch in on those slides, or maybe it is due to wood swelling? Or some other reason?

    I am trying to decide whether or not to try and get this thing working again - it happens to live two block away from my home. The hitchpin rail shouldn't be hard to repair, but does anyone have any ideas about how to free up those register slides?

    Israel Stein





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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: "Frozen" register slides

    Registered Piano Technician
    Posted 02-13-2020 08:34
    Has the soundboard and/or the stretcher come loose at the treble end? If the 4' hitchpin rail is not mortised in the casework somehow (below?), it would not be a surprise to find the treble end of the soundboard has come free and is binding the registers. This can also happen when PVA glue lets the soundboard drift under tension over the years.

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    Ed Sutton
    ed440@me.com
    (980) 254-7413
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  • 3.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-13-2020 09:50
    Thanks, Ed

    The soundboard or stretcher do not appear to have come loose, but I suppose I would need to let down the string tension completely to know for sure - no? I didn't quite want to do that without taking on the job, but maybe I'll just have to do it, if the owners agree. If it's only treble drift over the years, how does one fix that?

    Israel

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



  • 4.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-13-2020 10:03
    About the 4' hitchpin rail, what you are seeing is what is on top of the soundboard, and there is a corresponding rail beneath. I repaired a split one a couple years ago, made inquiries before proceeding, and that's what I was told by the most reliable person I found who was willing to provide an answer. The pins didn't seem to penetrate very far through the board, which probably contributed to the problem. When I finished the repair, I drilled deeper and confirmed the presence of the mirror rail, and installed longer pins.

    To free the registers, the first step would be to remove all tension from the strings. Then remove all the jacks onto some kind of rack or tray (to keep them in order). And then you just do what you can to figure out how to get one of the registers out of the gap. I've done several over the years, usually gently prying them upwards from one end or the other, bit by bit until I get the whole register up. Then, if there is a hole in the side of the instrument for the purpose (with a screwed on cap), remove the one that is still in place, followed by the other. Alternately, finagle the freed register so it is parallel to the spine (I'm assuming you probably have a bent side spinet, no?) and remove it from the gap to the bass side of the lowest bass strings. 

    And then see what's there. Your guides are presumably metal (brass with inserts), so you'll be looking at removing material from the face of the belly rail or pin block, or finding a way to spread the gap and install a longer gap spacer, or shim the existing one. Easier to to if you remove the strings.

    IOW, quite likely a can of worms you don't want to open.
    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








  • 5.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-13-2020 10:11
    If the soundboard is drifting, you should see a gap or crack along the case. Does the harpsichord have a braid or molding along the case you can lift?
    Can you pull the keyboard and jacks and get a camera or phone inside the instrument?
    There's probably a hitchpin rail under the soundboard, and if so, it should be mortised into the stretcher for support. If not, maybe you can add a little wedge.
    If you can stabilize things, just trim the edge of the soundboard.
    You might also add a few gap spacers if there's room between the jacks, some flat brass or aluminum bars to hold the gap open.
    If the case or wrestplank are warping and squeezing things tight, maybe you can jack the gap open with bolts or small screw jacks and then add gap spacers.

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    Ed Sutton
    ed440@me.com
    (980) 254-7413
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  • 6.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-20-2020 12:45
    Well, Ed, this is really getting interesting. Photos attached. There is a big gap between the soundboard and the case along the cheek, but there is absolutely no indication that there was ever a glue joint there - there is no trace of glue or any kind of line indicating previous contact between the board and the rim. The sides of the gap are perfectly parallel to each other, and the soundboard appears to be firmly attached to everything else around there - the belly rail, and the shelf thats visible beneath the board (inner rim?). The belly rail also appears to be solidly attached to the cheek and to the harpsichord bottom - there are three screws in the bottom that appear to attach it to the belly rail. The gap between the soundboard/belly rail and the wresplank measures 36 mm. at the treble end, 36 mm. in the midrange and 37 mm. at the bass end. So, is that "drift" or simply sloppy workmanship? Would it make sense to simply glue a shim into that gap, just in care?

    Another problem I found is that the 8' hitchpin rail appears to have separated from the bentside at the treble end. It is tight to the bentside in the midrange, but separates gradually toward the treble end, and there is a glue line on the bentside even with the top of the rail. The soundboard under the rail appears to be firmly attached to the bentside - I stuck a small ruler down there and felt all along the joint. It is pretty solid. So I'll just have to unstring the treble (I'll have to do it anyway in order fix the 4' hitchpin rail) and check the glue joint between the 8' hitchpin rail and the soundboard. Right now it appears that the front edge of that rail hasn't moved. So, again, did the glue join let go, or is it just sloppy workmanship?

    Any ideas on how to clamp the hitchpin rails for the glue to dry? (I'm not about to build a go deck... :-)  )

    Attached photos of 4' hitchpin rail, 8' hitchpin rail, a peek at the soundboard/bellyrail glue joint through the gap and "gap" between soundboard and cheek




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



  • 7.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-13-2020 13:00
    Thanks for the warning, Fred :-)

    And for all the good information. It's actually a Neupert "Telemann" single - there's an identical one listed for sale on the Harpsichord Clearing House website for $2500. I'm still tempted to look a bit further into it - call it boredom maybe? Getting a bit tired of aged European uprights and gray-market Yamahas, I guess...

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



  • 8.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-13-2020 13:17
    If you are intrigued by exploring something like this, go for it. I'll add that Neupert is typically overbuilt, so I doubt you'll find the sort of structural creep that is present in many kit instruments. It may be as simple as the brass rails became somewhat corroded and sticky, so once you get them out, clean, and polish, they'll work fine. On that theory, you might want to bypass lowering tension and just remove jacks and see if you can finagle one of the registers out of the gap. If it is just plain frozen solid, drop tension and try again.

    And warn your customer that you can't guarantee success, so they need to be willing to pay you enough for an hour or two of exploratory work to determine if it is salvageable. It could turn out to be a fairly quick and easy job, or could be quite time-consuming, so any estimate would need to be open-ended.
    Regards,
    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    www.artoftuning.com
    "Education is not preparation for life; education is life itself." John Dewey






  • 9.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-13-2020 13:38
    True enough about it being overbuilt. I did take off the nameboard, trying to see what it looked like underneath - but that 27-ply, 2 1/2 - inch thick wrestplank (well, I am exaggerating a bit, but you get the idea) obscured most of the view. I'll try to get over there next week - these people are almost neighbors - take some photos and maybe get a better idea of what's going on based on your and Ed's suggestions. Thank you both.

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



  • 10.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-20-2020 03:13
    Speaking of overbuilt harpsichords, check out this wrestplank - thicker than many piano pinblocks I've seen... So to take a look inside the action cavity, I had to pull the keyboard. Having unscrewed every possible screw in front and underneath the keyframe, the thing still wouldn't budge. But I noticed that the front legs have been moved, because at their pre-breakage attachment place the wood was compromised. So we improvised a "leg jack", took off the legs and - sure enough, the last two keyframe screws were covered by the consoles. With all that extra disassembly I ran out of time, so, will go back later today to check a few more things and take a few more photos. The good news is that letting down the string tension somewhat (not completely) released the slides to the point that I can move them manually. But there's still too much friction, so that the return spring does not push the slide back to the original position. There does appear to be some crud on and between the slides that may be contributing to that - I believe that some cleaning and polishing might help. It appears that they are supported underneath by two wood blocks that can be unscrewed, and they should drop down to the keybed once freed from the return spring and the control levers.

    As far as stabilizing the gap, there's very little room for gap spacers, but I have a few ideas I'll double check later today. Whether or not the soundboard/bellyrail got detached somewhere is still not clear, another thing I'll check again later today.

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



  • 11.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-20-2020 13:30
    Israel-
    Is it possible the instrument is developing a cocked cheek on the right side?
    You can check by comparing Wixey level measurements or left, right and bent sides the case.
    This little twist might account for what has happened.
    I have tried, unsuccessfully, to straighten cocked cheeks on two instruments using clamps and braces.
    Richard Kingston (fine harpsichord builder) said "Just turn it over on some two by fours and smash the bottom with a maul until it cracks open, then you can reglue it.
    I don't know if he was serious, I didn't try.
    If that is the problem, it is probably very slow moving, and you might just sand a little clearance in the gap.
    Fred has  hands on experience with Neuperts, and may have other thoughts.

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    Ed Sutton
    ed440@me.com
    (980) 254-7413
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  • 12.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-20-2020 14:44
    The lack of glue joint between soundboard and liner at the treble is by design. The bridge extension goes to the edge of the board, so the board needs to be floating. Kind of like many harpsichord bridges are undercut at the bass end so it bears on the board farther from the liner and glue joint.

    I think your gap is probably OK, and unlikely to be a problem, if you get the registers nice and smooth. You could improvise a spacer or two to place in the mid range, to help maintain the gap, but that is troublesome to do successfully in retrofit. 

    A precisely cut piece of rectangular cross section brass or steel or the like (say 3 mm x 20 mm) would serve, placed so it doesn't interfere with jacks (precisely between two jacks), but getting it in place is the challenge. I have found that rounding the edges is necessary. You get one end located and held in place, then drive the other until they are straight across the gap. Holding in place is a bit of a challenge, and the rounding is necessary to get it to slide. The geometry of having initial right angles would mean that the effective length will decrease as  you finally get it perpendicular, leaving a loose fit. If it is rounded, it will make a small dent in the wood and be tightest when it reaches perpendicular.

    You don't need a full go bar deck to clamp your hitch rail, just create a small emulation. Eg. clamp a board across the rims in an alignment that mirrors the section of hitch pin rail. Cut a couple pieces of wood to go between that board and the rail - they could be flexible, as in using it as a true go bar, or could be fixed size. Have the board resting loose without clamps as you set things up, then slowly clamp it down.

    Alternately, build a kind of rectangular rack from something like 2 X 4 material, two uprights and top and bottom, so that the top will be high enough above the sound board to use flexible bars. The bottom of the rack is placed against the bottom of the instrument (build up underneath the instrument with a horse and spacers to support it against the bottom). The top serves as your go bar deck. The top can be attached with screws after you have the bottom and sides in place. 

    Or use wedges between the clamped board and the pieces of wood contacting the rail, one wedge in either direction, maintaining one fixed and driving the other to apply pressure. 

    IOW, there are several ways to improvise a means to clamp at a distance, if you use a little ingenuity. 
    Regards,
    Fred Sturm
    University of New Mexico






  • 13.  RE: "Frozen" register slides

    Member
    Posted 02-20-2020 15:46
    Another means to clamp bridges and such is to make spring-loaded go-bars (for lack of a better term). The amount of tension can be adjusted by the length of the dowel. A curved end on the dowel aids in getting it situated.

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    Regards,

    Jon Page
    mailto:jonpage@pianocapecod.com
    http://www.pianocapecod.com
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  • 14.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-21-2020 06:49
    Thanks, Fred. I sort of suspected that the "gap" between the soundboard and cheek was by design - it just looks too clean and neat to be "damage" - but it's good to get confirmation. And I read about the "simulated go deck" procedure somewhere years ago, but your clear exposition of the  procedure is much appreciated - I would have been floundering around without it. Besides, I am dreading the need to remove the main lid - why do they insist on attaching it with a long hinge and umpteen screws?   :-(

    And yes, I plan to thoroughly clean and polish those slides - hope it does the trick. I am wondering if brass rod would work as a gap spacer. There really isn't much room between the jacks, or above the slides. Luckily, I live a few blocks uphill from the Talpiot Industrial Area, where there's a bunch of tool and hardware stores (besides all knds of garages, workshops and all kinds of outlets besides the Motor Vehicles Authority and their driver test facility) and I remeber seeing a good selection of metal stock in a couple of them. And at least two carpentry shops that will cut boards of all kinds to size. Glad I didn't leave my clamps behind in California with most of my shop equipment...

    With your and Ed's advice I feel competent enough to undertake this. Starting a week from Sunday.

    Thanks again...


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



  • 15.  RE: "Frozen" register slides

    Registered Piano Technician
    Posted 02-20-2020 16:35
    Here is a sequence of photos of the hitch rail I repaired. Unfortunately, I failed to photograph the downward clamping, but in this case it was close enough the the case side that it wasn't that much of a challenge. I frankly don't remember my solution. I kept the wires on their strings, and managed to reuse them all. A little troublesome to get the coils neat, but it was only six unisons each, 4' and 8', and I managed OK.

    You'll notice the gap at the treble side of the soundboard, just as you described and photographed.