Ted Barnett asks about return spring calculations in 130723 MMDigest.
I looked at US patent 1,711,989.

I'm not sure what the problem is here.  According to the patent, the
force of closure on the valve is approximately due to the difference
in cross section area between the pouch diameter and the disc diameter
at the wind pressure of 10 inches of water.  This pressure needs to be
able to carry the weight of the valve system.

To make the system more responsive, a 'helper' spring could be used to
carry the weight of the valve.  This spring needs to be calibrated not
only for its 'closed position force' but also its rate of force change
with length, so one would need to know the distance of travel of the
valve.

Being an organ, it is probably the case that the travel is quite large
compared to that of a pianola.  In the case of the Ampico 'A' crescendo
box, a return spring is used in the pouches, but this spring is used to
guarantee a _very_ low leakage of the valve because this valve is part
of a pneumatic timer with very low air flow rates.

It is not clear whether Ted wants to obtain a replacement spring or
just to duplicate a system for himself.  Either way, a spring calculation
could be done but more information is needed.

Regards from Melbourne, Australia.

Paul Rumpf