About Checking

[William R. Monroe]

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Paul, and list,

I think I'm starting to get a grip on it.  My suspicion now is that the =
arc is perhaps to large and needs to be sanded down.  I think this =
because of the fact that the hammers do not increase in friction when =
pushed through the backchecks, regardless how I alter the angle of the =
head.  Sometimes it seems that there is some improvement with head angle =
change, but not significant, or consistent.  Suggestions on tightening =
this arc? (I know, I know, someone already posted  a suggestion, but it =
has gone away from my 'puter.

One other issue that I'm still not convinced is not part of it, is the =
jack to knuckle placement.  There is still plenty of room in the window =
to allow for more aftertouch, and thus more clearance of the jack from =
the knuckle, but I already have about .055" of aftertouch (measured by =
placing .055" of punchings on top of front rail felts and seeing that =
escapement just barely occurs when the key is depressed).  I hesitate to =
think that more aftertouch would be appropriate.  Oh yeah, I forgot, I =
tried increasing it last night, and it didn't improve checking anyway.  =
It's late.  I don't like it, but it seems the jack does get bumped out =
of the way a little bit by the knuckly before checking, but I'm at a =
loss as to how to solve this.  As I said, the jacks really can't be =
moved farther forward, and increasing aftertouch does not seem to help.

Also, these are new wippens, repinned upon arrival at 5-7g.  Hammer =
shanks also repinned on arrival.

Thanks again,
William R. Monroe
Madison, WI
Assoc.
  ----- Original Message -----=20
  From: Paul McCloud=20
  To: Pianotech=20
  Sent: Wednesday, November 10, 2004 9:15 AM
  Subject: Re: About Checking


  Hi, William:
      If your hammers don't find increased friction when you push them =
down into check, your angles may not be correct.  If you take a wedge =
shaped block and force it into a crack, you'd expect it to get tight, =
right?    The tail is arc-ed in a radius which is less than the radius =
of the hammer shank length, so that when the tail meets the backcheck, =
it acts as a wedge.  It's possible that the radius arc of your tails is =
too long (you may need to sand a tighter curve into them).
  The backcheck is bent so that the tail will be caught in it.  The =
movement of the keystick is also in an arc which intersects the arc of =
the hammershank.  The movement of the hammer and keystick and their arcs =
causes them to meet and interfere with each other (a good thing!).   =
Where these two arcs intersect should be around the middle of the =
backcheck head.  The bottom of the backcheck should be closer to the =
hammer, and the top should be farther away (this is your backcheck =
angle)  This angle insures that the tail finds more friction as it goes =
down into it.  It sounds like your backcheck angle is insufficient to =
cause this to happen.  See if you can angle the backcheck back a little, =
and regulate the backcheck height again, while making sure it's not =
rubbing on the tail on the way up. =20
  It's too bad we can't see the action up close.  Sounds like a good =
subject for a Guild meeting/demo.
  Hope this helps,
      Paul McCloud
      inSaneDiego


    ----- Original Message -----=20
    From: William R. Monroe=20
    To: Pianotech
    Sent: 11/10/2004 6:15:31 AM=20
    Subject: Re: About Checking


    Joe Garrett,=20
    I have already bedded the keyframe, and double checked to make sure.

    Tom,
    Already repaired the balance rail holes (Onesti system - great =
tool!).

    Joe Goss, and Paul,
    Rep Springs really don't seem too strong, they have definite rise, =
but do not "jump-up" from check.  I will try weakening them more, =
though, and see what that brings.]

    Terry F,
    Double checked jack position, by bringing it out to the point of =
cheating, then just in enough to function, and no change (Drat!).

    Paul,
    Great ideas.  Checks are aligned, spaced, etc.  I resurfaced them =
prior to regulation.  Checking occurs about 1/3 of the way into the =
backcheck, and backcheck height is just about even or a little below the =
backcheck tail at drop, checks do not rub on tails on the rise.  The one =
thing that is giving me concern is that when the hammer is in check and =
I push them further into check, it does not happen.  I can push the =
hammer pretty much through the range of the backcheck without much =
increase in friction.  As as mentioned earlier, maybe the hammers being =
hung at a different angle are to blame (if indeed that was done).  I =
will be checking that, but any other thoughts on why the hammers won't =
go deeper into check?

    Thanks everyone for your input!!!
    William R. Monroe
    Madison, WI
    Assoc.



      ----- Original Message -----=20
      From: Joe Garrett=20
      To: pianotech=20
      Sent: Tuesday, November 09, 2004 11:35 PM
      Subject: Re: About Checking


      William asked: "Also tried varying the backcheck height, which =
showed no noticeable
      improvement with either higher or lower backchecks.  Also tried =
changing the
      backcheck angle - again no improvement one way or the other, =
hammers simply
      will not check on soft blows."

      Lost in Wisconsin:
      William R. Monroe
      Madison, WI

      William,
      If you've tried all of that, then it has to be something you =
didn't try.<G> Have you checked to see if the keyframe is bedded =
properly? I've known that to mess up checking.
      Best Regards,


      Joe Garrett, R.P.T.
      Captain, Tool Police
      Squares R I
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