CAUT

  • 1.  Thinking through action spread

    Posted 06-10-2019 11:30
    I am working through the regulation of a 1966 Yamaha G3.  At some point in the past, the wippen rail was apparently moved forward, reducing the action spread.  I understand the spec to be 112.5 mm.  The action spread is 110.5 in the bass and 111.5 in the treble.

    In the regulation process, I discovered that the backs of the sharp keysticks were clacking on the back of the wippen rail when the sharps were set at a height of 12mm above the naturals, and when dip was set to equalize aftertouch with the naturals.  I presume that the problem would be worse if the wippen rail were to be located in its original position -- in other words, I think I can see the logic that led a previous tech to move the rail.  The origin of the clacking problem is not clear to me, though I suppose the back key rail cloth may not be original, and too thick.  I am thinking that if the proper action spread were restored, the clacking could be eliminated either by using a thinner back rail cloth, or by removing material from the wippen rail.

    In any case, I am working to think through the implications of a reduced action spread.  Here's what I am thinking thus far:

    • The capstan is contacting the wippen heel at a point closer to the wippen flange center.  This will increase the action ratio.
    • The jack center is now further out from under the knuckle, in the direction of the front of the keyboard.  This will reduce action ratio.  I think.
    • In some cases, the jack itself is contacting the knuckle at a point closer the the keyboard than optimum, though not so far as to cause the jack to cheat.  I think this slightly increases action ratio.
    • The repetition levers have little marks, presumably to indicate a theoretical ideal positioning of the jacks.  Predictably, the jacks are not aligned with these marks -- they are closer to the wippen center.

    Is my thinking on track?  The action is functioning acceptably, though I have reduced the key dip, and thus the aftertouch, on the sharps where clacking is a problem (primarily in the lower half of the keyboard).  What would be the likely net effect on action ratio if the action spread were restored to 112.5mm?

    Thanks for any insights you have to share!

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    Floyd Gadd
    Regina SK
    306-502-9103
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  • 2.  RE: Thinking through action spread

    Registered Piano Technician
    Posted 06-21-2019 21:20
    Floyd,

    How's it going on that thing?

    Are there any telltale signs that the back rail cloth was changed? Is there a bumper felt underneath the back rail cloth as in Steinway? If it is too high, that would probably require thicker BR punchings which would further exacerbate the problem. 

    Pwg

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    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
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  • 3.  RE: Thinking through action spread

    Posted 06-22-2019 07:33
    The knuckle core should be aligned with the jack center at rest. Spread should be 112.5 mm.  the Magic Line, this may indicate improper b/r cloth thickness. Measure another Yamaha's key end height. Is there an inordinate amount of b/r punchings?

    While working on a M&H player install trouble-shooting; M&H said that at the underside of back of the key is 15/16" above the key bed.

    Look at the underlever's position relative to key lift. This can indicate too thick of b/r cloth.

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    Regards,

    Jon Page
    mailto:jonpage@pianocapecod.com
    http://www.pianocapecod.com
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  • 4.  RE: Thinking through action spread

    Posted 06-24-2019 15:32
    Thank you, Peter and Jon, for your responses

    The piano will be accessible for service again after this weekend.  I will dig into it again then.

    I did not seem obvious to me that I was dealing with something other than the original backrail cloth, but there were some challenges in establishing simultaneous damper lift with the tray that pointed in that direction.  I did some really conservative nipping of the bottoms of some damper wires.  As I think through a plan of action, I am inclined to remove some material from  the sharp keysticks where they hit the wippen rail, probably using a small router.  The slot would not need to be very deep at all, and would not significantly weaken the key stick.  I will then be able to restore the 112.5mm action spread and restore full key dip on the sharps so that the aftertouch more closely matches that of the naturals.

    Jim Iileggio's article in the April Journal was helpful to me in the process of thinking about this action, and the points he made about the limits of possible action spread reduction were spot on in terms of what I encountered in this piano.  The point of the article, however, was something different that discussion the relationship between action spread and action ratio.

    I will be interested to see how changing the action spread affects damper timing.  The spread on this action was reduced more in the bass than in the treble, and the damper lift with the keys is earlier in the bass than it is higher up in the scale.  This is in the context of a simultaneous (well . . . pretty simultaneous) lift of the dampers with the tray. 

    Some users have commented that the bass feels heavy.  I understand that early damper lift with keys will contribute to this.  I have calibrated the weighting of the action in keeping with the average action ratio, ending up with a Stanwood 7  strike weight profile, and keys that are weighted at Stanwood Frontweight Ceiling minus 3 grams.  This matches another Yamaha G series from the same era that I reworked last summer, so I don't think I'm out of the expected range.  It will be interesting to re-measure action ratio by the Stanwood protocols after the action has be regulated with the proper spread.

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    Floyd Gadd
    Regina SK
    306-502-9103
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  • 5.  RE: Thinking through action spread

    Posted 07-03-2019 14:06
    Several factors point to the thickness of the back rail cloth being excessive - keys clacking on the wippen rail, damper wires too long, and the need to shim the ends of the key upstop rail.

    I have had an opportunity to analyze the action today, and here's what I found:

    The back rail cloth has three layers.  The base layer is .038 inches (1mm = ..040"), the next is .055 inches, and the top is between .24 and .25 inches (ie. just over 6mm).

    Ratio of length of key (front to back rail contact point) to the back part of the key (measured from the center of the balance hole) is 2.04 for naturals, and 1.96 for sharps.

    Samples of balance rail punching stack (paper) taken between notes 1 and 53 ranged from .040 to .070 inches in the bass section, and between .030 and .050 inches in the tenor.   (Cloth punchings are .044")

    Given the ratios involved, reducing the thickness of backrail cloth by .040 inches (1 mm) would require a reduction in the height of the paper punching stack of .020 inches.  This is achievable, given the existing height of the stack.  Reducing the thickness of the back rail cloth by an additional millimeter would get me into trouble with my ability to level the keys.

    My options, then, are to replace the top layer of the back rail cloth with material with a thickness of 5mm (vs the existing 6mm), or else to remove the base layer of the back rail cloth, which indeed has a thickness of 1mm.  The layers are glued at the front edge (closest to the balance rail) only.  Removing the bottom layer is the simplest solution.  Is there any reason I should consider keeping three layers and replacing the top one with 5mm stock (which I would have to order in)?

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    Floyd Gadd
    Regina SK
    306-502-9103
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  • 6.  RE: Thinking through action spread

    Registered Piano Technician
    Posted 07-03-2019 15:30
    That's a very puzzling situation. One wonders what one or more previous techs was trying to accomplish. Multiple layers will help quiet return noise, certainly. The bottom 1 mm layer might make some sense if it had been added semi-temporarily, as a way to reduce dip and blow proportionally, but if it is glued together with the other two layers, that doesn't make sense (one would normally just lay it in, leaving it easily removable). 

    If you can conveniently remove the 1 mm material, I'd certainly go that route. Two layers is preferable to one, in general (at least IMO), but I'm not sure three layers gets you much better. While the keys are all out, do a general removal of .020 punchings from all the pins.  
    Regards,
    Fred Sturm
    University of New Mexico






  • 7.  RE: Thinking through action spread

    Posted 07-03-2019 17:30
    My guess, Fred, was that having three layers was original, and that an original 5mm top layer was replaced with what was most easily available, which would be 1/4 inch stock.  There was a lot of green cloth in this piano.  The color of the bottom two layers fits the rest of the scheme.  The color of the top layer is slightly different.  Why the cloth was changed out?  Who knows?!  I'm guessing it happened at the same time as replacement hammer assemblies were installed, and new bushing cloth was inserted deeply into the key mortises. (Well, at least deeper than I would have done it.)

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    Floyd Gadd
    Regina SK
    306-502-9103
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  • 8.  RE: Thinking through action spread

    Registered Piano Technician
    Posted 07-03-2019 17:53
    Ah, that would explain it, just replacing the top layer with slightly thicker than original. Interesting that tolerances are so tight that 1 mm thicker back rail means backs of keys hitting the action rail, though. I wonder if the shanks were replaced with a slightly longer knuckle placement, lowering the action ratio, leading to deeper dip. Kawais of that era tended to be weighted heavy, at least those I have run across. 

    Forensic piano technology. 
    Regards,
    Fred Sturm
    "Art is not a mirror held up to reality, but a hammer with which to shape it." Brecht