Re: Venting Slides


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Posted by Rick Denney on November 15, 2002 at 19:05:19:

In Reply to: Venting Slides posted by Keith C. on November 15, 2002 at 16:11:54:

Any check valve that would open automatically would have to have a very weak spring--the vacuum is not substantial. Such a valve might leak during play, depending on the acoustic characteristics at that location--sound is a series of pressure variants, with pressure fronts separated by negative pressure (i.e. vacuum). Probably any spring known to man would be sufficient to prevent it from opening because of sound, but I'd suspect if it was stiff enough to avoid that problem, it wouldn't work as a check valve.

But it's moot in any case, because venting valves is done to relieve pressure when the slide is pushed in as much as vacuum when it's pulled out. Check valves only go one way.

Valve venting works by opening the valve branch to the atmosphere when the branch is not being used, and thus has no effect on the air-tightness of the horn. The vent doesn't open into the horn when the valve is not pressed, and doesn't open into anything when the valve is pressed. If venting is done improperly on a rotary valve, it can leak, but that is an execution rather than design issue.

Rick "who has vented all the valves of his piston tubas and the first valve on his rotary tuba" Denney


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