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Measuring String Height

  • 1.  Measuring String Height

    Registered Piano Technician
    Posted 07-01-2015 14:58

    New question - using the Blue Schaff damper tool discussion as a "springboard":

    I am pretty sure that PLUNGER from my 933 is completey gone/lost forever. I never really had much success using it as a string height gauge anyway--although the tool is VERY handy to have in the "tune mo bill".

    Therefore my question is, what are some of the niftiest ways (is niftiest really a word?) you all have found to measure string height accurately, and easily transferred to the bench for regulation. (those of us without the fancy Chris Brown/TPR bench!)

    I have had some fairly good success just grabbing a few manilla folders and cutting off the back edges, to make one individual height marker for the low bass, then upper bass, then 2 for each section and labeling them as I go. Then I have a fairly accurate set of guides to set up the Jaras or whatever, for each section, on the bench. Something tells me this is going to create a small STORM of much BETTER AND FASTER IDEAS!! GO!

    Kevin

    ------------------------------
    Kevin Fortenberry
    Registered Piano Technician
    Lubbock TX
    806-778-3962
    ------------------------------



  • 2.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-01-2015 15:38

    Hi Kevin,

    I record my string height measurements on the action itself:

    1. Lightly sand off the string grooves from the hammers located at the top and bottom of each section.
    2. Put the action back into the piano and adjust the letoff of these sample hammers to 1/16” below the string.
    3. At the bench use the sample hammers to adjust the height of the jig. I use the Jaras jig.
    4. Write the numbers down someplace. As soon as you start working with the action the measurement will be lost.

    When I return to the piano with the action I am always very close on my letoff and drop measurements so I know this is a successful technique.

    It is also great for determining bore distance.  I glue balance rail punchings right onto the strike point of my old sample hammers. I keep adjusting the stack of punchings until they barely touch the Jaras jig when the shank is level. Then just measure the distance from top of the punchings to the center of the shank. Foolproof. (That is important for fools like me!)



    ------------------------------
    Ted Kidwell, RPT
    California State University, Sacramento
    Capistrano Hall, rm. 153
    6000 J Street
    Sacramento, CA 95819-6015
    916.278.6737

    ------------------------------




  • 3.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-01-2015 17:40

    Thanks Ted,  I like it. I've done samples before, but this does seem more foolproof and makes perfect sense. 

    Do you pay attention to the dip in the piano and them try to duplicate on the bench or does this eliminate that need?

    Kevin


    ------------------------------
    Kevin Fortenberry
    Registered Piano Technician
    Lubbock TX
    806-778-3962
    ------------------------------




  • 4.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-01-2015 18:54

    No, I don't try to duplicate dip on the bench. That way lies madness. The value of my technique is that it is not dependent on going to extremes to try to recreate the keybed on the bench. I just need enough keydip for the hammer to go up and drop down. Usually that is not a problem. If dip is too shallow I just crank down the glide bolts to raise the keys enough to give me sufficient dip.

    On the bench I set the blow distance arbitrarily to 1-3/4" below the jig. I don't know what the final number will be at this point but this is close enough for me to set jack position and rep lever height. Then I set letoff, drop and spring tension and I am done at the bench.

    Then, when I return the action to the piano, I set the glides and verify that my letoff is correct. Then I set the dip on all the naturals to 10mm. Then I adjust blow to give me the aftertouch I like. Next I set the sharp dip such that the aftertouch is the same as the naturals. Finally I set the checking and touch up the drop as needed. Then, usually after a little tweaking here and there, it is time to tune and voice.
    ------------------------------
    Ted Kidwell, RPT
    California State University, Sacramento
    Capistrano Hall, rm. 153
    6000 J Street
    Sacramento, CA 95819-6015
    916.278.6737

    ------------------------------




  • 5.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-01-2015 22:20

    Ted, 

    What you have described is essentially my approach, although I don't bother with the jig. I always found that with a jig I have one more opportunity to make a slight error in transferring a measurement, and in getting the jig precisely set to a stable spot, although your method of setting one to let off that has been set in the piano removes that problem a bit.

    In any case, I set sample let off in the piano, then use a Spurlock/Laroy let off jig (sits on the wipp cushions or whatever is that, and adjusts to raise the shanks all to the same height, which is that of the sample let off). Then do drop from let off - carefully controlling the key so the hammer just lets off and adjusting the amount it drops, definitely not pressing the key down to the bottom. 

    With brand new parts, I don't bother with samples in the piano or measurements for the first rough regulation (lots of turning), I just regulate to the stack itself. First, capstans so the shanks are just off the cushions (normally this means a full 360 degree turn of the capstan, which I rough in with the stack off, a stiff wire through the hole and spin a full turn - first do a couple samples to see the best amount, could be 1 1/2 turns.) Then I set let off so that it will be just below the shank being horizontal, so I find out how many times the drop screw needs to turn on average to allow let off to happen at that level, turn all the drop screws by a little less than that amount, then use the Spurlock jig as described above, and readjust drop as needed. I usually find I am within a couple mm when I put it in the piano to check.

    Next is setting check to be something like 10 mm below drop, which is just an intermediate step. I don't care how accurate it is, just try to make it reasonable. With check fairly regular at this level, rep spring strength can be set (inconsistent check, and spring tension will also be inconsistent - behavior is different at different compressions of the spring). And then rep lever to jack top, jack to knuckle core. Everything to be refined later. A good, quick ballpark job.

    Basically, I just regulate everything to let off, which is done relative to the piano: if I rough in with the Spurlock jig (which I do if there is more than 1/2 turn of the let off button), I always refine in the piano. With some inventiveness and skill, that doesn't have to involve too much leaning over. Top two sections are done with a mirror (dampers removed from the next to top section) for instance. Turning the button is always done by feel (learn to find the hole or the wire loop by feel). The best visual angle varies a good bit depending where the plate struts are, but usually there are at least some sections where you can be sitting comfortably looking under struts, watching the approach from an angle close to horizontal.


    ------------------------------
    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    http://www.artoftuning.com
    "We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
    ------------------------------




  • 6.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-02-2015 12:46

    Thanks to all for indulging my string height question. I really like Ted's and Fred's posts and methods--printed off and plan to use/experiment/continue improving my methods. I'm interesting in that article Ed--look forward to that.

    Michael, would you be willing to send me a link or more info on that engineering gauge? offline if fine too-in clueless but my tool junkie side wants to know more!

    ED: When you mentioned the TPR thing--I just stuck my fingers in my ears and began saying... "da da da ca-la la la la" Just kidding! (sort of .. grin..) All in fun! Hashtag: no SPACE and too much $$$

    I made my own grand regulating jig using plexi-glass, aluminum angle strips, and some wood for the base, etc--using Barbara (Richmond's) post and detailed pics. Thanks Barbara! It works really nice on hammer replacement jobs, particularly those far away jobs. But for simple regulations and touch ups here at school, I either do in the piano or use the Jaras, etc

    ALSO: I bought the little string height tool made of just quality string and bendable wire with green coating on the ends. I think it was from Pianotek, but it's been really handy for quick/small jobs so far.

    Thanks again-love this stuff! Kevin


    ------------------------------
    Kevin Fortenberry
    Registered Piano Technician
    Lubbock TX
    806-778-3962
    ------------------------------




  • 7.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-02-2015 16:20

    Hi Fred,

    Thanks for bringing the Spurlock letoff jig to my attention. I was unfamiliar with this tool. It looks very good.

    I will likely stick with my Jaras jig. A big advantage of that tool is that it registers at the strikepoint of the hammer rather than at the shank. So, as I am looking hard at the hammer as it approaches the jig, I can see if the strikepoint is not square. It is very easy to see and correct while I am right there at the bench. This dramatically cuts down on the time spent mating hammers at the piano.
    ------------------------------
    Ted Kidwell, RPT
    California State University, Sacramento
    Capistrano Hall, rm. 153
    6000 J Street
    Sacramento, CA 95819-6015
    916.278.6737

    ------------------------------




  • 8.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-02-2015 17:11

    I see those strike lines all along during regulation. I see them while setting drop, capstans, all the time. And I always have a strip of sanding film ready to correct. I might as well describe some of my regulation procedure in more detail, as that is what I have been doing this week. I'll assume let off has already been done, either with the Spurlock jig or, preferably (for fine work) in the piano.

    Hold down the neighbor key so that hammer is up - presumably about drop or let off distance. If not, I adjust the front rail so there is enough key travel to put the hammer that high. This is just a reference mark, and it doesn't have to be precise, but must be close to let off and drop height. I then lightly press the key to be regulated. I feel the moment of resistance, when the drop screw is contacted. I hone in on that precise spot (light finger, feeling for the spot), I notice where that is in hammer height relative to the neighbor hammer. I go slowly and controlled from there through let off, JUST through let off and no farther, and observe drop. How high did the hammer go relative to the neighbor? How far did it drop? What is the distance between the initial drop contact and let off? I am aiming at drop contact being about 3 - 4 mm below let off, and drop itself being 1.5 - 2 mm below. Watching contact, let off, and drop helps to hone in. When I turn the drop screw, it changes both the lower and the upper measurement, brings them closer together or farther apart. I am also feeling the drop, which can tell me if it is too much, too little, or just right by the bounce back at the finger.

    That's a lot of detail, but it isn't all that complicated. It's just a matter of focus and sensitive fingers.

    Capstans, I adjust a few at the ends of each section in the piano: jig (cheap yellow plastic one is fine) held between a hammer and its strings by pressure of finger on key. The neighboring hammers on each side are then brought to that height. Those pairs of hammers serve as guides, and I just do the rest on the bench, making a straight line. And boy do those tiny inconsistencies in strike line (crown not being quite square to the molding) show up like a sore thumb. I put on my reading classes, or sometimes even my magnifiers.

    Well, that's probably about enough for now. I think that using a jig would get in my way: I wouldn't notice nearly as much, and much of the detail would get lost. I find it better to train myself to be sensitive and observant, and the results are as good or probably better, done at least as fast if not faster. But that's me, and my comfort zone. That's how I like to work, what I have come up with over the years.

    ------------------------------
    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    http://www.artoftuning.com
    "We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
    ------------------------------




  • 9.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-02-2015 18:52
      |   view attached

    I have attached a picture of the strikepoint of the hammer approaching the Jaras jig. You can see, in my vanity, I have pictured one that is pretty good. Note that I have painted the wall behind my bench flat black to make this sightline pop out. I can't imagine seeing the strike point contour this clearly without a straight and level point of reference directly above.

    ------------------------------
    Ted Kidwell, RPT
    California State University, Sacramento
    Capistrano Hall, rm. 153
    6000 J Street
    Sacramento, CA 95819-6015
    916.278.6737

    ------------------------------




  • 10.  RE: Measuring String Height

    Registered Piano Technician
    Posted 07-02-2015 22:06

    I haven't painted the wall, but I do have a large piece of black fiberboard that I prop up behind the action for various operations involving needing to see something clearly (setting a hammer line, judging spacing when squaring hammers on their shanks, etc.) Which includes setting a straight edge above the hammers after I file them. Just about 1 mm above works best to judge - if it gets too close, the fuzz confuses the matter. I find, though, that looking from different angles I see somewhat different irregularities: back side or front side could be off a bit. So I continue to refine as I notice things.

    Obviously great minds think similarly <G>

    ------------------------------
    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    http://www.artoftuning.com
    "We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
    ------------------------------




  • 11.  RE: Measuring String Height

    Posted 07-01-2015 17:40
    I used the 933 for a long time with a manilla tag as the recording
    medium, punching a hole with the tool for each section end. I tried a
    few new and improved alternatives and eventually decided the Jaras was
    very handy. I could transfer measurements by scale readings to the
    letoff rack rather than physically. After I replaced the inch scales
    with metric, it was much nicer.

    Not very magic, but it worked for me.

    Ron N




  • 12.  RE: Measuring String Height

    Posted 07-01-2015 21:33

    For a long time I used John Hartman's string height tool described in the August/sept 2000 Journal. It will be reprinted in August. I also put index cards under the glides and rails to recreate keydip, usually getting very good regulations on the bench.

    Now I have Chris Brown's regulation station, a big investment in money and space. It allows me to do all action work in the shop at eye level, rotating the station to work from front, back or sides. It let's me do good work while limiting my bent-over-the piano time to a minimum.


    ------------------------------
    Ed Sutton
    ed440@me.com
    704-536-7926
    ------------------------




  • 13.  RE: Measuring String Height

    Posted 07-02-2015 05:27

    For measuring 'String Height' (in a Grand, obviously!) I use an engineering 'Depth Gauge' which, because its overall length is a bit more than 6", I stand on a block on the keybed and gently push the moveable/lockable gauge to the underside of the strings at each end of each section. I transfer my readings to a record sheet and can thereby replicate the distances for use on the portable adjustable Bridge (home-made, of course) Works every time! Very reliable.    Michael   UK

    ------------------------------
    Michael Gamble
    semi retired
    Brighton
    01273813612
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  • 14.  RE: Measuring String Height

    Posted 07-02-2015 19:51

    Pianotek has a tape measure with a reader window on the side. It's perfect for measuring string height.
    ------------------------------
    Regards,

    Jon Page