The "unit valve" for the Ampico pneumatic is secured to the stack (the
windway/manifold) using a semi-elliptic pressure spring.  The intent is
to maintain a constant force through the unit valve and against the
cork gasket and the stack, while the wood of the unit valve shrinks and
expands slightly with changes in moisture content.

The Ampico A used pressure springs made of flat cold-rolled iron,
formed into a shallow curve, and with a hole punched in the center
through which the threaded stud passes.

Dr. Clarence Hickman redesigned the spring, based upon his experience
designing bows for archery!  Instead of flat iron, the pressure spring
for the Ampico B unit ball valves uses thin spring-steel, punched and
formed to resemble a pair of archery bows.  The B spring has much more
compliance and seems to work very well.

Is there any reason why the Ampico B spring should not be used to
replace the A spring when rebuilding an action stack for an Ampico A?
Where can a set of B springs be purchased?

• ----------------------------------
|         Robbie Rhodes            |
| Return-Path: rrhodes@foxtail.com |
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