hammer travel

[Marcel Carey]

Just to correct you David, it's not the hammer that we are traveling,
it's the shank and flange. This is easy to understand if you just
imagine the center pin to be a hinge. When the hinges are not all
aligned, the shanks are going to come up all over the place.
 
Marcel

-----Message d'origine-----
De : pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] De la
part de David Ilvedson
Envoyé : 19 septembre 2006 22:26
À : pianoguru at earthlink.net; pianotech at ptg.org
Objet : RE: hammer travel



Frank,

 

When I talk about traveling, I'm not talking about does it look like
it's moving one way or the other.   Does the space on one side of the
hammer compress and other expand?   If so, you need to travel that
hammer.    

David Ilvedson, RPT
Pacifica, CA 94044




  _____  

Original message
From: "Frank Emerson" 
To: "ilvey at sbcglobal.net, "Pianotech List" 
Received: 9/19/2006 9:57:56 AM
Subject: RE: hammer travel



If all shanks are perfectly traveled, and all hammers mounted perfectly
perpendicular to the keybed, while the shanks are parallel to the
keybed, the bass hammers will APPEAR to travel to the bass.  The lower
tenor hammers will appear to travel to the treble.  This is a function
of the angle of the hammer bore and the width of the larger hammers
toward the bass.  Once you get into the treble where the hammers are
bored parallel to the sides of the hammer, they will appear to be as
perfectly spaced when one is raised between its neighbors, as it did
with all the hammers were at rest. 

 

Next time you replace a set of hammers, try this.  Knurl the shanks for
note 1, 2, and 3 just enough so that their respective hammers fit with
sufficient friction that the hammers will stay in place without gluing.
Do not taper the hammer tails yet.  Mount the shanks for these three
hammers.  Travel the shanks as perfectly as you can.  Mount the first
three hammers on these shanks.  Position these hammers along the shank
to the achieve the correct strike point.  Rotate the hammers on the
shank so that the center lines of the hammers are plumb, and
perpendicular to the keybed, while the shank is parallel t! o the
keybed.  Verify that the spacing between the first and second hammers,
is the same as between the second and third hammers.  With the first
three hammers dry fitted in this fashion, lift the second hammer between
the first and third hammers, which remain at rest.  As the middle hammer
rises, it will appear to move away from the hammer to its right, and
closer to the hammer to its left.  While the hammers are all at rest,
the adjacent faces of the sides of the hammers are parallel.  You can
measure the distance between the hammers at the crown, at the tip of the
molding, or at the widest part of the felt.  These distances will all be
equal for both pairs of hammers, if all has been done correctly.  Once
you lift the center hammer, thes e faces are no longer parallel.  With
the middle hammer shank held parallel to the keybed the point of closest
proximity between the middle hammer and its neighbors has changes.  As
the hammer rises in its arc of rotation, any given point on the hammer
is moving away from the keyboard, as well as upward.  The point of
closest proximity between the first and second hammer is the lowest
point of the second hammer’s molding, and a point on the felt of the
first hammer beyond its centerline.  This point beyond the centerline of
the first hammer is further to the right than the centerline of the
hammer, due to the angle of its bore.  Nothing has moved left or right,
but the hammer tail of the second hammer has moved enough away from the
keyboard to place it closer! to the felt of the first hammer angling in
its direction.

 

Now, rotate all three hammers on their shanks very slightly toward the
bass.  Changing only this, you can find an angle where the distance
between hammers are equal, while the middle hammer is raised between its
two neighbors, at rest.

 

Tapering the hammer tails mitigates this condition, but does not
entirely eliminate it.  Over time, with misalignment of hammer spacing,
shank warpage, etc., there is a greater risk of bass hammers rubbing the
hammer to its left, since it is inherently closer to this hammer when
the first is elevated and the neighbor to its left is at rest.  

 

Recognizing this, many manufacturers deliberately tilt the bass hammers
slightly to the left, and the tenor hammers slightly to the right.  The
degree of this tilt is calculated to precisely correspond to the angle
of the hammer bore.  In smaller pianos, with greater hammer bore angles,
this condition is exaggerated, and more apparent.  As the tenor hammer
bore angle becomes less and less, so does the tilt to the right.  Once
you get high enough in the treble that there is no bore angle (parallel
to the sides of the hammer), there is, correspondingly, no further tilt
to the right.  This creates another problem.  If hammers are tilted in
this fashion on a piano that was not designed for it, the hammer shanks
will have to be moved out of perfect alignment to the whippens in order
to center the hammer under the strings.  However, when the piano has
been designed for this left to right tilt, the action scale is altered
to correspond to the exact amount of tilt intended for the hammers.  You
can determine if this is the case by measuring at the point with the
difference is the greatest.  In the bass, where the hammers tilt left,
the hammer flange screw are shifted to the right, corresponding the
degree of tilt.   In the tenor, where the hammers tilt right, the hammer
flange screws are shifted to the left, corresponding the degree of tilt.
This makes the spa! ce between the highest bass flange screw and the
lowest tenor flange s crew less that the corresponding distance at the
strike point at the strings.  If you carefully measure the distance
between the strike points of these two notes at the strings, and find it
to be greater than the distance between the corresponding flange screw,
the foregoing explains why.  If you propose to replace the hammers on a
piano designed in this way, you must tilt the hammers right to left, as
the original hammers were installed in order to maintain perfect
alignment between the shanks and whippens, while maintaining perfect
spacing of the hammers to the strings, and also optimizing the clearance
between hammers as they move between the at-rest position and the fully
elevated position.  If you, on the other hand, you find the spacing of
the strike point at the string to be identical to the spacing of the
flange screws, you can still til! t the hammers left to right to
optimize the clearance of the hammers in motion, but it will be at the
expense of perfect alignment of the shanks to the whippens.

 

I am sure that this is difficult to visualize from my feeble attempt to
describe it, but demonstrate it for yourself with the three hammers, as
described above.  You will clearly see it for yourself.

 

Frank Emerson

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