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Crash Valves in Exhauster Assemblies

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Crash Valves in Exhauster Assemblies

    What is a Crash Valve? Basically, it's a valve that senses a sudden increase in the vacuum pressure inside of the Exhauster Assembly (or pumper assembly). What is the purpose of a Crash Valve? It's purpose is to make it easier for the user to accent specific notes or passages in the music. How does the Crash Valve work? Most simply stated, the Crash Valve redirects the vacuum being generated by the exhauster bellows (the foot pumps) from the reservoir bellow/s directly to the stack (or windchest), bypassing the reservoir. Where is the Crash Valve located? The crash valve is always located somewhere between the foot pump bellows and the reservoir bellows. Let me explain.

    Under normal circumstances, the vacuum being generated by the exhauster bellows (or foot pumps) is stored in the reservoir bellow/s. The reservoir bellows are spring loaded bellows, and as the vacuum level generated by the foot pumps increases, the vacuum level inside the reservoir increases and bellows collapse more. Also, the volume of the music is controlled by the level of the vacuum pressure inside of the reservoir bellow. The higer the pressure, the louder the music. However, when the user wants to accent a note or a short passage, they can push on the foot pedal/s faster or quickly, and the volume of the notes being played will increase. Generally speaking, the majority of player system manufacturers found this method of controlling the volume of the music adequate.

    When a crash valve is added to the system, the crash valve senses the sudden increase in vacuum pressure, being generated by the foot pumps, and it automatically bypasses the reseroir bellow and applies that increased vacuum pressure directly to the stack (or windchest). Below is a very detailed description of a crash valve. The graphics and explanation below were found in the 3rd Edition of the Standard Player Action Service Manual, which was published in 1925. Click on each image to see the full size page.

For more detailed information about the Standard Crash Valve, click here

    Some crash valves, like the one explained above, are quite simple. Others, which all claim to be better than someone elses design, can look quite complicated. But, they all perform the same basic function. As I get pictures of various crash valves, they will be added to this webpage along with the name of the company that made the device. Personally speaking, I don't like crash valves. I find that they limit my ability to add expression to the music and make it sound more life-like. The way I pump the pedals, to get the expression I like, is demonstrated in the video below.

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This page was last revised January 17, 2019 by John A. Tuttle, who Assumes No Liability
For The Accuracy or Validity of the Statements and/or Opinions
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