Electric Valves for Reproducing Pianos
By Robbie Rhodes
Sorry I'm tardy responding. I had a garage fire last Friday, 1 Dec, which destroyed much of my fixtures and pumps for pneumatic measurements. Fortunately the critical and valuable instruments were spared. It will be a few months before the structure is repaired and I regain a normal life!
Herr Josef Grosssteiner, in Austria: Willkommen zum Automatic-Music! Do you have any valves for testing? What is the valve installed in the small Dreyhorgeln? Is it the same as those used in European pipe organs?
This discussion concerns the evaluation of small electric valves, in order to determine their suitability for application to vacuum pneumatic controls, specifically: the Reproducing Pianos. Two designs are available: (1) the solenoid valve, used extensively in industry at high pressures (several atmospheres), and (2) the "magnet valve", traditionally used in pipe organs at low differential pressures.
Because there is limited space for about 100 valves under a Reproducing Grand Piano, the valve should be physically small and generate minimal heat. Unlike a pipe organ system, the valve must operate over a wide range of pressure: from about 4 to 70 inches of water column vacuum, without leaking or sticking. And it must be quiet -- piano music should not be accompanied by "tinkle-tinkle" or "click-click"!
The arrangement for testing should duplicate the conditions of a typical piano installation, and the IMI Cassette Converter installation in an Ampico or Welte piano is a good example: the assembly of 100 valves is mounted under the piano to the rear of the pneumatic action. The test setup should have tubing of similar size and length, and also duplicate the effects of the pouch and bleed inside the piano's valve.
The turn-on and turn-off delay times may be measured with an oscilloscope and a strain-gage pressure transducer. I think Richard Tonnesen has one like mine, which responds up to 1000 Hz. When I measured the delays on my Ampico piano years ago I could see the delay time due to the long tubing from the tracker bar, and also little "bumps" in the pressue when the piano's valves changed state.
Wayne Stahnke, who developed the IMI Cassette Convertor 20 years ago, says: "It is imperative to use a very well regulated and filtered supply of direct current. The power supply must provide enough current to operate 40 to 50 valves simultaneously at regulated voltage."
Karl Petersen, I received your little valve sample in the mail yesterday. Is this a standard catalog item? It looks like a solenoid design, with three ports, made by Pneutronics, USA, part number 991-00008-001, coil 12 volts dc, rated 100 pounds per square inch pressure.
Mike Ames, do you have an Aeolian Concertola valve for testing?
I will provide a "magnet valve" from the IMI Cassette Convertor (and send Karl's Pneutronics valve). I think Richard has a typical Reisner valve; if not, perhaps Mike Ames can provide one.
Richard Tonnesen, could you test these valves for all of us?
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(Message sent Fri 8 Dec 1995, 18:09:58 GMT, from time zone GMT-0800.) |
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