My work on the development of a MIDI interface valve mechanism has
evolved into two separate projects, a very compact (hopefully cost
effective) valve mechanism, and the interface or sealing device that
would easily connect the valves directly to the tracker bar, without
cutting tubing or defacing the piano in any way.

On the tracker bar, some MMD members feel that a good reliable connection
directly to the tracker bar cannot be made.  I have some good mechanical
engineering friends working on this problem.  Some questions have come up
that maybe MMD subscribers could help with.

Assuming a fairly good operating player mechanism, what portion of the
tracker bar hole needs to be opened to correctly operate pneumatic valve?
Also, is there a 'standard' bleed vacuum level or range that is applied
to the tracker bar tubing?

George Bogatko had an idea of using small tubes that would insert into
the tracker bar holes to help seal the connection from the MIDI valves
to the tracker bar.  I have thought about similar ideas in the past.  My
concern of this is that any reduction to the size of the tracker bar hole
may cause the piano notes to not repeat quickly or not play correctly.

An idea I have is to use this tube-in-the-hole arrangement and to
overcome the partial restriction of the hole by adding air pressure to
the back side of the MIDI valves.  For example, if the tracker hole is
restricted to, say, 25% of the hole size by this tube, then add air
pressure to the space outside of the valve that would compensate for the
restriction.  The result should be that the player valve mechanism thinks
the tracker bar hole is fully open.

If this pressure valve idea is viable, does anyone know how the amount
added air pressure required would be calculated?

I  would appreciate any comments the MMD people have concerning this.

Gary Rasmussen
GRasmus140@AOL.Com