Pianotech

  • 1.  Specs for Damper Lever Springs in a 1907 Stwy O

    Registered Piano Technician
    Posted 12-13-2019 13:09
    The damper levers on my home piano return with too much force, adding to the force required for pedaling. I've never measured damper return springs (and intend to use either the Bolduc DW balance beam or one of my P.K. Neuse spring gauges). But there's always a first time.

    The question is more like: what's the lowest that spring pressure can get before promptness suffers. And that depends on wire size and speaking length, and if a figure could be developed for the bottom and top notes of each damper felt configuration, there should be a straight-line taper between these two. Developing a figure for any of these guideline notes would mean muting out all other notes (backrail-felt-on-iron bar) and doing a lot of in&out at different increments of spring pressure. So that's why I like to start with someone else's work <g>.

    It's well understood that this is one of many details in the damper and trap work system. (In the immortal line from the movie "Body Heat", discussing arson: ""There are fifty ways to screw up on this job. If you can think of twenty of them, you're a genius......and you aint no genius". This is the only one I know nothing on.

    TIA</g>

    ------------------------------
    William Ballard RPT
    WBPS
    Saxtons River VT
    802-869-9107

    "Our lives contain a thousand springs
    and dies if one be gone
    Strange that a harp of a thousand strings
    should keep in tune so long."
    ...........Dr. Watts, "The Continental Harmony,1774
    +++++++++++++++++++++
    ------------------------------


  • 2.  RE: Specs for Damper Lever Springs in a 1907 Stwy O

    Registered Piano Technician
    Posted 12-13-2019 21:28
    Did a little hunting an came up withe the proper set-up for measuring damper lever return weight (the wood and the spring pressure), and also turned up the page in the Renner back action installation guide with the table of recommended spring pressures. The latter wasn't much help, with the "Underlevers" column listing what could be a range of levers but followed by a "g". (Maybe there are individual levers weighing 52g, but with that weight, they'd do fine without any springs.)

    So I'm simply going to measure what is there (with and without springs), see patterns and smoothed-out curves, and try some samples (at section ends, maybe two levers with a trial lightening, surrounded by two "control" levers) to see what's really required for prompt damping. The only specs already existing are probably those arrived at this same way.

    ------------------------------
    William Ballard RPT
    WBPS
    Saxtons River VT
    802-869-9107

    "Our lives contain a thousand springs
    and dies if one be gone
    Strange that a harp of a thousand strings
    should keep in tune so long."
    ...........Dr. Watts, "The Continental Harmony,1774
    +++++++++++++++++++++
    ------------------------------

    Original Message


  • 3.  RE: Specs for Damper Lever Springs in a 1907 Stwy O

    Registered Piano Technician
    Posted 12-14-2019 10:49
    I'm cross-posting this from (of all places <G>) FaceBook's NBSS Piano Tech Alum group, which begins with Debbie Cyr's very helpful starting point:
    "Damper springs usually taper from 35g in the bass to whatever you have on the first one without a spring.

    Now the dilemma is a little clearer than just "Does someone have a scrap of paper from the Steinway Factory of 110 years ago, with a schedule of damper lever weights". <G> I did preliminary reading, with a digital scale, an adjustable parallel on the platen set to raise the underside of the lever just 1mm off the tray, and with the damper post vertical, and got confusing results. Hopefully a few more people will chime in.

    In setting the lever down on the platen, how it hits the scale will vary the readings by as much as 1g. The digital scale can easily be driven too far down by any deceleration occurring with too fast a lowering, and doesn't reset itself to a stable, static reading. So, setting the lever gently enough to be silent is what I came up with.

    All this is my fine-tuning the measuring technique to yield reliable results at 0.1g resolution. But I also want to "get on the same page" with conventional techniques to get an opinion on where my preliminary readings lie:
    #1: 16.3g
    #30 (mid-scale): 16.2g
    #54 (end of springs): 12.4
    #55 (no spring): 6.0

    These readings confuse me; of three readings which don't make sense, which should I choose to evaluate the other two? #1 @ 50% of conventional, #2 the same as bottom of the scale, or #54 which is double what it should be.

    What is clear is that during the pedal play before the pittman hits the damper tray, the pedal feels fine. And friction at the back action mounting blocks is fine. I've also take a slice out of the tray return coil spring upper mounting block, to lessen its pressure.

    I'd be grateful for any advice.






    ------------------------------
    William Ballard RPT
    WBPS
    Saxtons River VT
    802-869-9107

    "Our lives contain a thousand springs
    and dies if one be gone
    Strange that a harp of a thousand strings
    should keep in tune so long."
    ...........Dr. Watts, "The Continental Harmony,1774
    +++++++++++++++++++++
    ------------------------------

    Original Message