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Hammer tail shape

  • 1.  Hammer tail shape

    Registered Piano Technician
    Posted 05-07-2021 17:18
      |   view attached
    My new/old set of Yamaha hammers has the tails already shaped, but the checking surface of the tenor and bass hammers is not perpendicular to the shank.  As I have done before, I will glue some wood into the coving notch to give to give me more leeway in adjusting that angle.

    Is the existing tail shape going to give me the close checking I desire, or is there a modification of the shape that is possible, given what material is already removed, that will be more amenable to my goal?

    Thanks for any input you can offer!

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    Floyd Gadd
    Regina SK
    306-502-9103
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  • 2.  RE: Hammer tail shape

    Registered Piano Technician
    Posted 05-07-2021 19:44
    Hi Floyd -
    I'm not familiar enough with Yamaha checking to give you precise numbers... hopefully someone who is will share information with you shortly.  In the meantime, I have a couple of questions:
    You are addressing two issues: 1) off-set tail facing; 2) tail radius for high checking
    - Have these new/old hammers been filed?  If so, how much?  Compensating for significant filing in the let off will, as you know, increase the passive distance between the bottom of the tails and the top of the check.
    - Have you assessed what the checking distance is at present, with both the straight and angled checks?
    - I know we've been taught that the angled tail/backcheck configuration is flawed in that it purportedly stresses the action centers.  Not addressing that question full-on right now, it strikes me that there are still manufacturers that use this setup.  If it's executed well, do you have to change it to get the checking height you want? Just wondering.
    - In general, I prefer a larger tail radius ('straighter', with less 'bump') with appropriately shaped backcheck.

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    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
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  • 3.  RE: Hammer tail shape

    Registered Piano Technician
    Posted 05-07-2021 19:50

    Floyd,

    How much tail material you need to accomplish your checking goal may vary according to the length of the keystick, plus the radius of the arc and placement of the fulcrum. This checking problem came up some time ago, (I believe you raised the question) with some controversy. The conflict arose, (which was not finalized), when you couldn't attain proper checking no matter how much you changed the backcheck angle and/or timing. The issue that didn't get resolved was the role the keystick length played in your checking dilemma. With longer keysticks, the backcheck travels a comparative short distance toward the tail arc, hence giving you greater latitude for checking adjustment. With shorter keysticks, the backcheck travels faster toward the hammer tail. If the tail arc radius and fulcrum are incorrectly calculated, one is forced to backoff the backcheck starting point adjustment to prevent upward checking. That "backing off" now prevents one from obtaining the close checking when the key is fully depressed because the location of an improperly placed arc and arc radius is too far away from the backcheck.

    To answer your direct question. If it is truly a Yamaha hammer, you're probably Okay without the need to add more material because your superimposed circle indicates that the fulcrum is properly offset from the hammer shank. I believe it will give you the leeway you're seeking.



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    Roger Gable
    Gable Piano
    Everett WA
    425-252-5000
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  • 4.  RE: Hammer tail shape

    Registered Piano Technician
    Posted 05-08-2021 08:26
    Floyd -
    Hopefully you know how to access older posts to this list... it's not clear to me, however, if you find the discussion 'backcheck regulation' initiated by Eric Johnson on 8/29/20, it has an extensive examination of the geometry issues, in detail.  Great thread. If you know how to locate it easily, let me know.

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    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
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  • 5.  RE: Hammer tail shape

    Registered Piano Technician
    Posted 05-08-2021 18:14
      |   view attached
    Hi David,

    Readers can either type eric +johnson +backcheck +regulation in the search box, or follow the following link:

    https://my.ptg.org/communities/community-home/digestviewer/viewthread?MessageKey=0b5a2071-7399-4d75-adc5-66ee8522c97a&CommunityKey=6265a40b-9fd2-4152-a628-bd7c7d770cbf&tab=digestviewer#bm0b5a2071-7399-4d75-adc5-66ee8522c97a

    In answer to your earlier question, these hammers are new-out-the-wrapper, though they have been in storage here for a lot of years.  They have never been filed.  The set I am replacing are set up the same as this new set, but, I must confess, I did not evaluate the checking before disassembly.  I did regulate this piano a few years back, but I do not recall what I achieved in terms of checking.  I'm attaching a photo of my modified hammer tail.  In shaping, I followed the the existing profile, but changed the orientation with my benchtop belt sander.

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    Floyd Gadd
    Regina SK
    306-502-9103
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  • 6.  RE: Hammer tail shape

    Registered Piano Technician
    Posted 05-08-2021 20:49
    Hi, Let me ask you a question that will bring more problems.  I can't be sure but is the hammer glued on at a 90 degree angle?  Why wasn't it if my eyes don't deceive me?  Is there a problem with the hammer distance in the treble ?  Are they all glued like that?  I guess what I am saying is that the tails might be grabbing to low because of this.  Could you try correcting it to a 90 deg angle and see what happens in the worst checking area?  Also if the bore distance is standard that doesn't mean that the piano is or that the originals should work from the factory. What if the string height is farther in your poor checking area.  A lot of things to check before one removes wood. That is usually something I consider to lighten the touch not to fix checking.  I've had to reposition by bending and Change back Check angles on many pianos to make them work properly.  
    Jessica Masse RPT
    --
    Sent from Gmail Mobile





  • 7.  RE: Hammer tail shape

    Registered Piano Technician
    Posted 05-08-2021 20:56
    This is hammer 31 in the low tenor. The modification is simply to establish a perpendicular relationship between the checking surface and the shank.

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    Floyd Gadd
    Regina SK
    306-502-9103
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  • 8.  RE: Hammer tail shape

    Registered Piano Technician
    Posted 05-08-2021 21:33
    Floyd -
    I haven't had a chance to read through Eric's thread yet, but if it doesn't address the question I raised as to whether the angled backcheck configuration is as bad as we think, I'm wondering as to its efficacy, given that you also have to re-face the angled backchecks and likely respace as well. But now at least it's easier to work on the terrible checking that you don't know if you have.
    Keep at it.  And thanks for the search information.

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    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
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  • 9.  RE: Hammer tail shape

    Registered Piano Technician
    Posted 05-08-2021 22:18
    Thanks for your input, David.  The project parameters are as follows:  55 year old Yamaha G3 piano with (as far as I can tell) original parts.  Action work:  new Yamaha hammers and shanks (parts fresh out the wrapper, but maybe 35 years old?), new back checks, new key bushings, re-pinning of repetition levers, fine tuning of touch weight.  Other:  Restringing, including re-pinning and re-notching of the bridge.  Soundboard issues will be addressed if any appear, but thus far, the board is looking pretty good.  I worked through this piano's twin sister a couple of years ago, and the result was very satisfying.  On the other piano, the hammers had already been replaced with Yamaha parts, but, if my memory serves me correctly, a more recent set of hammers with tail surfaces perpendicular to the shanks.

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    Floyd Gadd
    Regina SK
    306-502-9103
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