Knocking keyframe

[RobertD429@aol.com]

In a message dated 96-02-15 17:10:26 EST, Avery Todd writes:

>   My question was about a problem I'm having with our Hamburg D. A knock
>develops, periodically, in the low bass end of the keyframe. The last time
>was an hour or so before a recital. Am I correct that Steinways use a
"pinch"
>system on the cheek block to keyframe fit? It should press down on the pin
>in the keyframe?

Avery,
It's true that Steinways are designed so that the guide plate presses down on
the guide pin, but the second half of the equation is that the front rail is
intended to be bowed upward enough to knock (very slightly) at the ends when
the pressure is released. This sprung front rail stays in better contact with
the keybed with minor humidity variations, as well as when the keybed bows
downward as the pedals are stepped on.

Since you said all the shims are gone, I'd wonder if the frame or pin is too
low rather than the plate being too high. I don't know how old this piano is,
but is it possible that a previous technician planed or sanded the front rail
too vigorously in an attempt to "fit" it by stopping the knock when the
blocks weren't screwed down? I would check to see if there is evidence of
this: is most of the original lip still there? I ran into a case where
someone had planed so enthusiastically that the BACK of the front rail was
knocking. If the front looks severely planed, you also have the choice of
gluing a 1/2" wide maple shim to the front rail to return it to the original
height, and re-fitting. I've only had to do this once. I used Tite-Bond, and
wouldn't again. I expected some warping from the water content of the glue,
but was surprised (shouldn't have been) that it took weeks to stabilize. I'd
probably consider epoxy or CA glue next time. Anyone else have thoughts on
this?

With the gliders up, fit the rail so that there is a knock for the last ten
or twelve inches, which you can stop with moderate downward hand pressure at
the end (if the center levers up you've taken too much). The Kluge keyframes
are a little more flexible than the old ones. Screwing the blocks in place
should provide only enough pressure to stop the knock under all conditions.
With them screwed down, you should be able to apply (a lot of) upward
pressure with your thumb on the end of the frame and just barely be able to
get the knock to return.

If the front rail looks okay, I might move the pin up, especially if the
guide plate doesn't show a lot of wear. If you are using the original type
non-adjustable plate, you need the adjustability of the shim (or adjustment
screws, whatever you decide) under the keyblock. If you have checked the
guide pin and it is not bent down, you can remove it, plug, and redrill the
frame a little higher. You can't just bend it up, as it must remain parallel
to the keybed.

Don't forget to re-set the gliders !

Best wishes,
Bob Davis