One Question

[Richard Brekne]

Newton Hunt wrote:

> Non checking upright.
>
> The backcheck felt should not be curved unless the wooden block is
> curved as well.  If the block is straight then replace the felt.

The wooden block is indeed curved, and the curvature matches the curve in
the felt. Doesnt look too awfully muched used really, tho the hammers
needed filing (not horribly, but they were packed and a bit grooved), so
the piano has seen some use.

>
>
> THe letoff rail has a strip of felt glued to the back side to act as a
> jack movement limiting rail, or liberty rail.  If this rail is too
> close to the jacks the butt can bounce off the top of the jack causing
> non checking.  If it is further back the jack can become wedged
> between the rail and the butt and can cause the action to not return
> to rest position.
>

I checked this right away before removing the action. It is at an
acceptable spot. No problem here.

>
> The theory of backchecking on an upright is that the backstop will
> have an arc of such and such a radius and the angle of the backcheck
> will be such that the backstop will be wedged into and held by the
> backcheck.  So the angle of the backcheck to the horizontal is
> critical to functioning.  Likely in this case is that the backcheck
> needs to be tilted back slightly at the top then adjusted so it
> catches at 15 mm.  The wire should act as a spring to help retain the
> backstop under a hard blow.

I did a few spot checks here and there before removing the action.
Regulated letoff in on a few, checked dip, etc to see if I could isolate
the problem to regulation related things. Nope.. Made no difference.

>
>
> If there is any lose of mechanical integrity such as wires loose in
> backcheck or wippen or broken glue joint at backstop shank and butt
> checking will not work.  Check the glue joints carefully.

I suspect that herein lies the problem. The outside two action mounting
bolts (the ones that screw into the piano thru the plate) are bent way up
to accomodate the brackets. The middle one is bent way down and doesnt
really reach the bracket. The "U" of this center bracket just goes around
the threaded part of the bolt, but there is about a quarter inch of space
between the bolt and bottoming out on the bracket. The screw for this
pushes the bracket in tight, but it is susceptible to upwards movement.
Also the stabilizer screw on the back side of the action (where the "V" in
the plate is) shows signs of being too far in. There is obvious marking on
the plate where the screw head has moved around abit scraping the paint
off the plate. So.. I am hoping this is it.

>
>
> If all else fails try some 220 (very fine) sandpaper lightly on the
> buckskin to raise a nap.
>
> Poor checking can be caused by poor regulation.  You indicated that
> the letoff was way off.  Regulate the action completely first then
> determine in the problem remains.
>

I am delivering the action tommorrow, and have set off 4 hours to set it
up. I will let you know what I find out. Thanks as always for the reply
and interest.

>
>                 Newton

Richard Brekne
I.C.P.T.G.  N.P.T.F.
Bergen, Norway