No Power Yamaha Revisited

[Dave Nereson]

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Ok guys and gals...

I gots to eat crow here...  I think anyways. As it turns out I managed
to finnally solve the hammers bouncing all over the place thing by
turning up all the bed screws so that the key frame was solidly bedded
with the actuall wood of the balance rail a full 2 mm elevated over the
key bed.

=20

So?  That's OK.

=20

 Huge increase in power, but this also caused an increase in
keydip to 10.5 mm (!)

=20

Well, Yamaha's official spec. for grand key dip is 10 mm, so 10.5 isn't =
outrageous.

=20

 and forced a drop in blow to just above the
cushions... perhaps the shanks are about 2-3 mm off.=20

=20

That's not way out of line, either

=20

However....
absolutly no bouncing of neighboring hammers any more, and that feeling
of loosing power is gone.

=20

Great!

What I dont get is why the Balance Rail needs to be elevated so much.
And how are we supposed to determine the proper balance rail height to
begin with ? I was always told that glide bolts need to just make
contact with the key bed... not to lift the whole darn middle of the key
frame up.

Explainations please ?

RicB

--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html
http://www.hf.uib.no/grieg/personer/cv_RB.html


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=20

We're not "determining proper balance rail height", we're first, bedding =
the keyframe - and, yes, in some pianos the glide studs barely touch, =
but the point is to eliminate any knocking of the balance rail against =
the keybed when you tap on it.  If the rail "floats" at all, then the =
keys don't have a solid fulcrum. =20

Depending on flatness of keybed, accuracy of keyframe joinery, stiffness =
of the slats that connect the three keyframe rails, and any distortion =
the tightening of the stack down onto the keyframe causes, the balance =
rail will sit at different heights above the keybed in different pianos. =


 Second, we're setting an optimum key height, then leveling keys and =
setting key dip.  This is done with punchings and assumes the balance =
rail is already bedded.  I know you know this, but....

   At the Little Red Schoolhouse (Yamaha's technician seminar in =
California), LaRoy Edwards likened the keyframe to a bridge:  with the =
keys (the load) out but the stack screwed on, the front rail and back =
rail are bedded first (the two abutments at either end of the bridge), =
then the balance rail studs are turned down to just contact the keybed  =
(strip of newspaper pulled between stud and keybed has just a slight =
drag), then the keys are put back in.  There's no spec. for "height of =
balance rail", just for key height, which is determined more by the =
keyslip and the fallboard.

            The height of the balance rail is determined by bedding the =
keyframe and it ends up where it ends up.=20

                    --David Nereson, RPT        =20

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