Pneumatic Valves
By John Rhodes, forwarded by Robbie Rhodes
Doug says that the rule for adjusting the bleed size in a primary or single-acting pouch valve is so that the pouch trips when 1/6 of the tracker hole is uncovered. This is the point where the bleed plus pouch_leaking equals the flow through the tracker hole and tubing. Note that this is a _static_ adjustment. I would guess that a repetition test would be the better way to wring maximum performance out of any particular installation.
Over a year ago, I described to Doug how to build a pneumatic Whetstone Bridge using adjustable needle valves purchased at the Tropical Fish Store! The setup helped him decide if the pouch leather required replacement, and if larger or smaller bleeds were needed. Bleed-size adjustment was necessary in some piano restorations where particularly "tight" pouch leather was replaced with the currently-available "leaky" variety. I can supply description and theory of this test setup if someone wishes to try it.
-- John Rhodes
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(Message sent Mon 1 Jan 1996, 23:57:35 GMT, from time zone GMT-0800.) |
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