I am developing an electric vacuum valve for use in reproducing pianos
that I hope will be cheap to build and reliable.

My design, which is a single inline valve, is easily adapted to
manifold mounting.  It is .5-inch in diameter and from .75-inch long,
depending on the mounting option.  There is one moving assembly and no
hinges.  It works on gravity without springs.

I hope to be able to offer the parts as a kit for do it yourself
construction as the tedious job of assembly does not require skills
or tools beyond the abilities of the average rebuilder.  All critical
dimensions are built into the few parts that can be made on an
automatic screw machine.  I hope that the parts cost will be less than
$5 per valve.  Of course this depends on the quantity produced.

I have a working prototype that shows promise but hope to improve it
still.  The units are undergoing reliability tests and are not ready
for production but I am interested in hearing from interested
individuals in order to determine how much time I should dedicate to
this project.

At reasonable duty cycles, that I believe are suitable for reproducing
piano applications, it has the following specifications and limits
which I hope to improve upon.  Orifice size of .074" with large open
passageway to nipple or integral insert tee.  It is designed to work
continuously at 82 milliamps (ma) current with no overheating and can
work at higher currents at less than 100% duty cycle.  A reliable 10 Hz
repetition rate against 40 inches of suction with equal on and off
times requires 82 ma.  For 32 Hz it climbs to 100 ma for reliable
operation.

I have not determined if the valve closes or opens completely at this
rate but since no device that it will be connected to can achieve this
repetition rate (other than a minimal mass pouch that is doing no
actual work) it is probably not important.  It will modulate a stream
of air at much higher frequencies too, but again I do not have figures
on the degree of airway opening or closing.

At 60 inches of suction the required current is 125 ma and at 80 inches
it is 150 ma (repetition rate of 5 hertz).  At a duty cycle of less
than 50% the valve does not overheat at these current draws.  Of course
most of these times will improve with less than 50% "on"-cycle time.
This is just the easiest to test with a simple function generator.

My main reason for writing is that in order to optimize the use of this
valve for reliable quiet and long lived operation I would like to
control it with a pick and hold controller.  Before Laurent Corey died,
he was planning on adding this feature to his well known Octet
controller.  I have been unable to obtain information on whether this
will be provided by the current manufacturers of the controller.  I
have a schematic (actually several) for add-on circuits to provide this
feature, but I would prefer to not build one, if possible, especially
as it would not be necessary for most applications.

Does anyone have information on a ready-built MIDI solenoid controller
with programmable pick and hold, or know if this is to be an option in
the near future for the Octet controller?  I would like to continue
work on the valve knowing that I do not have to build this part myself.
I have searched the Internet extensively and have found nothing.

Spencer Chase
http://nt.mcn.org/spencer/

 [ What operating voltage is the new electric valve, Spencer, and
 [ what is the "pick and hold" technique?  -- Robbie