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MMD > Archives > July 1999 > 1999.07.26 > 16Prev  Next


Solenoid Players in Upright Pianos
By Craig Brougher

Andy Taylor was telling how he modified the striking system of his
upright solenoid system to be more efficient and to play the piano
better than the way the solenoid stack was designed to contact the
action.

The end of a whippen does have some leverage advantages over the key
capstan line (possibly 30% in a few cases of whippens designed for
player contact, and about 10-15% otherwise), but that presupposes that
the solenoid armature travel gives better results with the extra travel
leverage.

Even though it would seem that since a small, relatively weak solenoid
magnet should profit from a bit more travel and less weight to lift,
Since the  optimum position of the solenoid armature -- when fully
activated-- is at the place in the bobbin where the coil exerts its
maximum force, then the extra 15% travel required in a different posi-
tion other than the capstan/sticker line, just places the armature 15%
further away from its minimum power (start) position.  That in turn
means that its start power, governed by the square law effect, weakens
the initial armature start-up more than 15%, for sure.

The only two mechanical advantages you gain by not operating the
keys directly in the sticker line, would be (1) that you bypass key
friction, which otherwise simply follow the stickers up and down,
anyway, and (2) you bypass a few points of lost motion (which
otherwise can be taken up by regulating out the lost motion).

I have no doubt that what Andy has done has improved his player action,
but I think it is possibly because when he first installed the stack
under the keybed, other variables came into play, possibly rough front
rail pins, resistive and sticky key bushings, and all those factors
which make keys want to raise off their balance rail pins, instead of
rotating smoothly at the balance rail.  That slows things down, since
solenoids are marginal in lifting power and cannot compensate for
constantly changing resistive keys and a keybed that is bowing under
the weight of many notes playing at once.  These solenoid players are
designed to play a new or like-new, easy action piano with very little
added friction and regulation problems.

I personally cannot see how this change in the player action mounting
should make such a "huge" difference if the piano parts are clean and
fitted, easy to play, and well-regulated.

The main detail I don't care for in retrofitting solenoid stacks is
the fact that in many pianos, the keybed support nose molded into the
plate has to be sawn off.  That happens to be a crucial element in an
upright's mechanical stability and regulation, preventing the keybed
from sagging over the years, which it surely must, without its main
support.  Remember, the action brackets get their support from the
keybed, and there is a lot of weight concentrated in the middle  that
it must support for generations.  That center support nose is all it
has.  When you saw it off, it's gone forever.  I really think this is
ruinous and destructive.  Even though possibly not to someone who
thinks in terms of 10 years max.

So for that reason alone, I think that over-the-key mountings of
solenoid stacks make a great deal of sense, and I also don't see that
the performance should suffer (or change), or that the guarantee should
be voided on the piano or the player action.

My observations are strictly from a personal viewpoint, not from
experience with solenoid stacks.  I have not started installing them.
But in my opinion, any new piano with its keybed support sawn off
should have its guarantee voided, and any old piano treated the same
way should be fitted with a hanger brace to the plate.  The
manufacturers of retrofit player actions can avoid sawing off the plate
nose if they choose.  For every problem, there is a solution.

Craig Brougher


(Message sent Mon 26 Jul 1999, 17:30:33 GMT, from time zone GMT-0500.)

Key Words in Subject:  Pianos, Players, Solenoid, Upright

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