THUD

[John D. Chapman]

On Sat, 2 Dec 2000, Jon Page wrote:

> Can you further describe the 'thud'.  Only on fff, right or on p  ?  Teflon 
> in whippens?

At first I thought the thud/slap could be heard only above forte, but now
that I have been
able to play S&S CD141 back at the dealership in peace and quiet, the
thud/slap is there at
all dynamics.  
No teflon.  It is not the teflon click, but a woody slap along with the
thud usually heard
with an improperly bedded key frame (see steps 4 & 19).
> 
> Heaven forbid that the plate is touching (barely) the back of the bridge in 
> the top section.

Plenty of clearance (see step 12)

> 
> I didn't see that you checked the height of the shift lever above the 
> keybed and the height
> of the notch in which it resides.

I did check that and was surprised to find that as the action is moved
into the piano the
shift lever moves through the notch and passes the back rail entirely so
that its pushing is
done against the front to back connecting piece of the keyframe so there
is no keyframe
wood above the lever.  Now that I write this it seems very odd, and I will
double check
that step.
> 
> !!!!!!!!!!   Front rail pin too high?  :-0
>          I've had that happen.

I have not checked this.
> 
> Balance rail pin hitting wood, loose back checks.  Does it happen with the 
> dampers lifted?
 
I have not checked the balance rail pins.  As for dampers, see step 6.
> 
> Worn damper upstop felt (hitting rail).  Hardened key end lifter felt 
> (damper lifter).

Damper upstop felt OK.  I will check the key end lifter felt.
> 
> ...grasping at straws...
> 
> Jon Page

Thanks Jon,
John Chapman

> 
> At 08:26 PM 12/02/2000 -0500, you 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
> 
> Jon Page,   piano technician
> Harwich Port, Cape Cod, Mass.
> mailto:jonpage@mediaone.net
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~