Richard West writes:
>Someone mentioned overstriking hammers and it reminded me of our Belt
>fortepiano which was evidently built to have overstriking hammers.
>Since the piano is a copy of a Walter instrument of Mozart's, maybe
>they didn't worry about whether the hammer hit at a 90 degree angle to
>the string.
This is an interesting observation. I have worked on a number of
Viennese flip actions as you describe and didn't really consider whether or
not the hammers hit at 90 degrees. One of the differences between Walter's
design and Johann Stein is that Walther employs a much longer hammer
molding. Since the hammers are mounted in reverse of the modern piano
action the longer molding of the Walther might well induce a hammer strike
where the hammers tilt toward the player.
>In any case, our fortepiano needs some regulation and voicing. Does
>anyone have any information on doing the job efficiently? The
>mechanism is the Viennese style and the hammers are wood with a thin
>layer of leather across the crown. I've heard threading string/yarn
>between the leather and wood will soften the tone. I am not sure how
>durable the leather is. The wire is thin and has grooved the leather
>significantly. The leather isn't cut through yet, however. The
>piano is around 10 years old so maybe new leathers are in order. Any
>help anyone has would be appreciated.
Here are some instructions that you and others may or may not find useful.
Its kind of a long post.
I recommend that you do all of the leather work before you carry out
the adjustment operations as you would with a modern piano. Take a look at
the condition of the beak leathers at the end of the hammershanks as well.
They may need wholesale replacement. The interface between the escapment
lever and the beak leather is critical to good reliable let-off and
repetition. Another area to check is the attachment of the escapement
levers at their base. It is common for the leather and or parchment piece
that hinges these to the action to wear out and need replacement. Note the
type of hinge material used and if any levers lean from side to side or are
any whose tops are higher than the others.
For materials:
Check with David Way or his reps at Zuckerman Harpsichords, P.O. Box
151, Stonington, CT 06378 (203-535-1715) for leather supplies - beak
leather and outer hammer coverings as well as hinge material. Also, he may
have a guide taken from their kit instructions on regulating their
fortepiano. Most of their instructions will apply to your Belt. Phil Belt
had a hand in developing the Zuckerman and Hubbard kits ( both Stein and
Walther types).
Another approach to getting hammer covering material is to simply go
to a Tandy Leather store or other craft place and buy a few small pieces of
leather that you see. If the existing leather on the Belt sounded good
over the years take a piece of it or a hammer with you and look for leather
that is of similar density and thickness. Note that the high treble
hammers may have a thinner covering than the middle and lower ones. I
would then experiment with groups of hammers in different parts of the
scale, attaching new leather from you samples to adjacent hammers for
comparitive purposes. Cut some small rectangles of leather of different
types and attach with titebond to one side. After 10 minutes, apply a
little glue to the other edge and stretch the covering over the hammer and
sweeze to the other side for a minute with your finger. It should hold
just fine. You don't need to trim these. You should get a pretty good
impression of sound differences as they are. Practice stretching them all
to the same tension - this will be critical later. If some sound too
bright, or too tubby, detach the leather from one side (just pull it off)
and stretch the leather tighter or looser and note the change.
After you have arrived at a schedule of leather I would detach *all*
hammers from their capsels and lay them out. Remove outer coverings to be
replaced. Note if any look like they need more underleather. This must be
applied and taper cut - the adjacent hammers can be a guide. I would cut
all of the squares of leather for the outer coverings and lay them out
(just like a good compulsive techy). I would sort them by feel placing the
thicker one of a type toward the bass and I would test the stretchability
of each piece and discard any that are stretch like rubberbands. Then
using the same titebond approach as before, go down the line gluing all
squares to *one* side of their respective hammers. Then, go back to hammer
#1 and come down the line stretching and gluing each piece of leather over
the top of the hammer. I would do this last operation in one sweep paying
close attention to getting equal tension on the leather from one hammer to
the next. Then you can trim the leather. I would trim only the sides of
the hammer. You will need a lot of single edged blades for this or some
very good little sissors. Later, when you have tested your hammers for
voicing (after you regulate) you can once again detach them from their
cappsells and with a sharp blade tapper cut the ends of the leather strips
front and back. I find that restretching to different tension is the most
useful way to voice the leather coverings. Needles may be used as well. If
you have a few real problem leathers it is easy enough to just try another
piece or look at the shape of the underleather.
Next, beak leathers.
If they all look a bit tired and ragged on the ends I would replace
them all. I would leave them over length if there are no screw letoff
adjusters on the escapement levers. If you have screw adjusters I would
trim all the beak leathers to a uniform length. Note the old ones that
look original and use their amount of overhang as a basic guide. The final
cut though needs to been square and clean - very sharp blade. You want the
end face to slide down the polished face of the escapment lever cleanly.
(I would reburnish the face of the escapement levers a little -carefully so
as not to tear their hinges, they shouldn't require a lubricant, but if you
use one I would use the clear McLube or a little dry teflon -just like they
did in the 18th Century).
Some notes on regulating (this is off the top of my head so it may not be
the most organized account and I just may have left out some stuff. As in
all regulating certain things you do affect things you already did - so be
forwarned):
1. I would check the bedding to be sure nothing is tipping. Level the
keys so that they are even. I would leave the dip until later. I tend to
go for a very shallow dip on these pianos in order to promote pianissimo
control. I would see that there is no difference in height between the
natural and sharp key sticks as that much of the action is directly mounted
on the key (no capstans. The key balance holes need to be regulated so
they don't rattle. They are not bushed with felt so careful reaming is in
order or little glue sizing for the loose ones.
2. The capsels (stem with metal ears that hold the shanks) need to be
checked to be sure that the hammers swing freely but that none of them
rattle (they make a very distinctive rattling sound when they are loose.
The most elegant way to deal with these is to get a pair of reverse circlip
pliers from an auto supply store. They will allow you to open the ears
slightly in order to dismount the shank. Then if it is too loose you can
just squeeze the ears with your fingers a little and then remount the shank
using the pliers again. After you do a few of these you should pretty
quick at it. This however, needs to be checked and rechecked. Some pianos
have wooden capsels and and they are set-up like modern pianos with
centerpins and bushings.
3. The spring tension on the escapement levers is critical but easy
to adjust. Changes in the spring tension may also affect let-off so you
may have to muck around with this a second time as you do the let-off. The
criteria for correct adjustment is as follows: They must apply enough
tension so that the lever is held lightly but positively against its stop.
You must be able to release the key very slowly and have the beak leather
slide down the face of the lever and slip smartly under the lip. If the
beak leather rides down the face of the escapement lever and stops before
it gets to the bottom, lighten the spring tension a little. (Just take the
spring and flex it a tiny bit backwards or forward). If the slow release
test still fails and now the escapment lever isn't against its stop there
is friction at another point (cappsell, or key, most likely) or the beak
leather hasn't been cut cleanly. Also, be sure that the grove where the
spring contacts the lever is smooth. A little graphite or whatever is ok
here.
4. With the keys at rest, observe the beak leathers and their
position under the lip of the escapment levers. They should be low enough
that they clear with just the tiniest (RHCH) amount of free play. If this
is uneven, recheck the attachment of escapment levers be be sure that they
have been all set at the same *vertical* height. Then, you can turn the
capsels in or out to change the beakleather's height at rest. To much and
you get a lot of freeplay in the key - sucking up keydip - and not enough
and the beaks won't slip under the lip. Be aware that because the capsels
are tilted, as you screw them in or out the horizontal distance between the
beak and the escapment lever changes and this alters let-off (Often, this
can be used to advantage).
5. Let-off: I would set the letoff at about 1/16" or so. I would
account for the fact that the soundboard is going to rise and fall
considerably. If the weather has been humid for a time when I am setting
this I would set a wider letoff to compensate. Traditionally these actions
were not provided with any kind of screw adjusters in order to set let-off.
However, a lot of modern fortepiano makers put an adjustment screw in the
escapment lever so that its point of rest can be altered. If you have *no*
adjusters then altering the length of the beak leather, screwing the
capsels in or out, or shimming the escapement levers comprise the threefold
method you will have to apply. In some cases you can tweek the letoff a
tiny bit by bending the capsel stem slightly with your fancy Yamaha wire
bending pliers. As to beak leather length, I would not have them overhang
much more than 1mm. To carry out letoff I would do end hammers and one
center hammer as guides. I would also center these hammers from side to
side under their strings. Then mark a wood batten for string spacing to
act as a letoff guide. Clamp the batten in a couple of Jorgensen clamps
and position the action underneath so that the guide hammers are center
under their corresponding string marks. As you do the letoff - especially
if there are no letoff adjusting screws, you will have to monkey with the
capsels and reset height under the escapement lever lip. Having the string
spacing marked on the batten is essential as you go twisting the capsels.
6. Backchecking: There are a variety of backcheck systems. In some
pianos the hammers checked on a leather strip or strips glued to the back
of the wrestplank (a pain in the garbonzos to adjust). In most there is at
least a single leather covered batten attached directly to the action frame
and which comes out with the action (adjustment of individual ones by
shimming under the leather strip where needed or by shaving leather from
the back of the hammercovering). This is the most common variety although
some modern makers have devised batten with individual back checks on wires
(adjusts like a modern piano).
7. Key dip: Aftertouch is *not* desired. There may be some
controversy here but I generally set the dip pretty shallow. Some players
like the piano set-up so that the dip is such that, in pianissimo playing
the action doesn't achieve let-off, but rather the beaks are held under the
lip of the levers and hammers close to the strings for quick repetition.
This may sound a bit wierd and impossible but, I have gotten it to work.
There is a stoprail at the back of the action that controls the setting.
Shims on individual key ends or under the felt on the rail may be necessary
as I recall.
7. Dampers: Make sure they all pick-up uniformly (same length stem)
"Oinking" is the big problem. Regular chamois cloth is the leather of
choice where leather is used. Some makers have been using felt. A little
poking with needles or gently sanding one side of a leathered wedge may
serve to get it to seat more reliably. Otherwise, replacing the covering
is in order. The new leather must me glued only at the top edges of the
triangular wood molding and not on the surface where it touches the string.
The procedure is just like gluing on hammer coverings. The wooden wedge is
removed for recovering and then reinstalled with the damper action in place
to that the wedge will be held in the proper location while the glue dries.
Well, that's all I can remember at present. I hope that these instructions
will be helpful. There is a short tract by Nannette Streicher, in
translation, on regulating this type of action which I may have somewhere.
If I can find it I will send you a copy.
Bill Darst, RPT
Music Dept
UC Santa Barbara
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