THUD

[John D. Chapman]

Jon,

On Sun, 3 Dec 2000, Jon Page wrote:

> Roger,
> The Damper upstop rail slapping on the belly rail is a good candidate.
> 
> Hardened guide rail felt is another possibility along with the damper head
> itself being a bit loose on the wire.

I think step 6 would eliminate this possibility.
> 
> Hmmmmmm...
> 
Thanks,
John


> Jon Page
> 
> At 11:50 PM 12/02/2000 -0600, you wrote:
> >Hi John,
> >           Guess we could be grasping at straws, but a couple of other
> >things to try.
> >
> >Is the damper guide rail secure to the belly rail?
> >
> >If the board is flat in this area, that can cause some thud like tones.
> >Measure the bearing with a compound gauge, and check the board for some
> >curvature.
> >
> >If the glue joint on the inner rim or belly rail is loose similar
> >result.
> >Take an artist pallet knife, (.010" thick) and see if you can find any
> >looseness between the board and liner.
> >
> >Just some thought's
> >Roger
> >
> >
> >John D. Chapman wrote:
> > >
> > > Remember THUD?
> > > Here is the history.  I had not seen this piano until last month.
> > > While tuning I noticed that notes 50, 51, 52, and 53 (top four notes in
> > > agraff section,  just below the treble break) had an unpleasant
> > > knock/slap sound, the same percussive knock which is in the background of
> > > all piano tone, but in notes 50-53 it dominates the tone.  These are the
> > > four notes between A440 and the treble break.  The orchestra conductor
> > > asked me if I had noticed those four notes, as did the pianist, so I knew
> > > it wasn't just my imagination. I have checked it out both upstage and back
> > > stage (wood floors), and back at the dealership (concrete floor).
> > >         Here is what we have done so far:
> > > 1.  checked hammers for loose glue joint, flange pinning, and screw
> > > tightness,
> > > 2.  visually checked the action frame joints between notes #53 & #54,
> > > 3.  checked the wippens for sufficient felt at the front to keep the
> > > jack from slamming into the rep lever,
> > > 4.  checked key frame bedding, front, back, and glides, with and without
> > > damper pedal, and with and without shift pedal,
> > > 5.  pressed down the back key frame with a long screwdriver to see if it
> > > was slapping up against the dag,
> > > 6.  played notes with dampers held all the way up by hand and by pedal,
> > > 7.  moved the action in and out to see if the tone improved,
> > > 8.  switched some hammers from the octave below to see if it could be the
> > > hammers,
> > > 9.  switched some whippins from the octave below to see if it coulb be the
> > > whippins,
> > > 10.  seated the strings,
> > > 11.  applied firm pressure on the bridge cap at the end of the section to
> > > see if there was a loose glue joint between cap and bridge body,
> > > 12.  checked for clearance between the bridge and the plate,
> > > 13.  checked for loose ribs,
> > > 14.  checked for clearance between nose and bell bolts and soundboard,
> > > 15.  checked that the bell bolt nut which was one turn past finger tight,
> > > 16.  checked for foreign object lodged between soundboard and frame, and
> > > between soundboard and plate,
> > > 17.  tightened the end screws of the diagonal plate bar, which could be
> > > turned another half turn to snug,
> > > 18.  checked key leads and underlever leads,
> > > 19.  checked the key bed with a straightedge front to back.  I found that
> > > the board just beyond the board on which the balance rail glides rest was
> > > high.  Chalked it where it passes under the front to back board of the key
> > > frame which is just under notes 50-53 and found that is was just barely
> > > touching. Sanded key frame there until there was adequate clearance.
> > > Playing the note by pushing up on the whippin from underneath with my
> > > finger without moving the key still produces the THUD, so I guess that
> > > eliminates the keyframe anyway.
> > >
> > > None of this has changed the THUD.
> > > What have I missed?
> > > Why these four consecutive notes  with no sign of the problem above or
> > > below them?
> > >
> > > John Chapman RPT
> > > Wake Forest University
> > > Winston-Salem NC
>