Fluid and Gas Transfer

Pipe Organs, Steam Engines and One Historic Valve Solution

18 October 2017

Art and technology often cross-pollinate: art sometimes repurposes industrial technology (like the vocoder) for its own use, for example. In one instance, two very different technologies — pipe organs and steam engines — were undergoing innovative growing pains, and the remedies were surprisingly similar technologies.

Organs

Musical instruments of the early 19th century were seeing major technological advancement. Instrument makers introduced piston and rotary valves on brass instruments and heavier iron frames on pianos for the first time, and both became louder, richer and more versatile instruments. The pipe organ was no exception to this evolution: audiences desired a larger, more “symphonic” instrument with a thicker texture, capable of imitating any instrument in the symphony orchestra.

Organbuilders responded to these desires by building larger instruments that operated under higher wind pressure, but they almost immediately ran into a problem. All organs built before about 1890 used a completely mechanical means to control airflow into the pipes — this is known as tracker action. Each key on the instrument’s keyboard is connected to a thin, vertical wood strip called a tracker, which manually pulls open the pallet valve to the pipe corresponding to the depressed key. The open valve allows air from the wind chest below to flood the pipe and make a sound. Large tracker organs are immensely complex, with thousands of mechanical connections between the keyboards and pipes.

The major disadvantage to tracker action is that the performer opens each pipe by the strength of his or her own finger. Essentially, as the organist pulls out more stops and adds more pipes, they require more hand and finger strength to depress the keys. This was not a problem until about the 1840s — prior to that time, most instruments were relatively small and wind pressures were low, so the force required from the performer’s hands was reasonable. But organists were finding the newer, higher-pressure instruments nearly impossible to play. In 1833, the organist at York Minster cathedral claimed that playing the new high-pressure instrument there would be “enough to paralyze most men.”

Engines

At the same time that organists’ hands were struggling with higher wind pressure, steam engine valves were struggling with higher steam pressure. Steam pressures had steadily increased since Watt’s original steam engine. The Cornish steam engine perfected in the 1820s had reached pressures of up to 60 psi by closing the intake valve midway through the power stroke, allowing the steam in that part of the cylinder to expand through the rest of the stroke to a lower pressure. This resulted in major improvements in efficiency, but Cornish engines were prone to breakdown due to the higher pressures. They also developed irregular power throughout the cycle: the stroke completely paused at one point and was followed by a swift downstroke. This made the engines unsuited to rotary motion and disqualified it from most industrial applications.

Two Similar Solutions

These two disparate problems were solved only a few years apart using similar engineering: a small pressure chamber to aid in opening and closing the valves.

Figure 1: The Barker lever. Source: Shoichiro ToyomaFigure 1: The Barker lever. Source: Shoichiro Toyoma

The organ issue was solved by British engineer Charles Spackman Barker. He invented a pneumatic system that uses the organ’s own wind pressure to overcome the resistance felt by opening multiple pallet valves at once. Barker added a pneumatic lever to each pipe’s pallet valve and an additional “touch box” containing an intake valve and high-pressure air. When an organist presses a key, they mechanically open only the intake valve, which allows air to flow to and inflate the pneumatic lever, opening the pallet valve. This innovation resulted in a much easier keyboard touch since the intake valve physically opened by the organist is much smaller than the pipe’s pallet valve.

Figure 2: The massive facade of the Saint-Sulpice organ. Source: Lukke/CC BY-SA 3.0Figure 2: The massive facade of the Saint-Sulpice organ. Source: Lukke/CC BY-SA 3.0Barker developed his device in the late 1830s, and the lever was adopted and improved by renowned French organbuilder Aristide Cavaillé-Coll throughout the 1840s and 1850s. In 1862, the lever allowed him to build his magnum opus, the massive Great Organ at the Church of Saint-Sulpice in Paris. The instrument has 100 stops, six keyboards, 20 separate windchests and eight reservoirs and over 7,000 pipes, and would be impossible to play without the seven sets of Barker levers installed by Cavaillé-Coll. The organ retains almost all of its original specification today, including its mechanical action. This video of the Saint-Sulpice organ shows the necessity of mechanically coupling the lowest keyboard to the higher ones to obtain the loudest possible sound. Without the pneumatic assistance provided by Barker levers, the many pounds of pressure required to press even one key would be far too much for even the strongest fingers.

Figure 3: An early 20th century Corliss engine. The improved valve gear and pair of dashpots is to the right of the image.Figure 3: An early 20th century Corliss engine. The improved valve gear and pair of dashpots is to the right of the image.

Figure 4: U.S. Grant and Pedro II starting the Corliss Centennial Engine.Figure 4: U.S. Grant and Pedro II starting the Corliss Centennial Engine.At nearly the same time, American engineer George Corliss revolutionized the steam engine with a similar mechanism. In place of Barker’s pneumatic chambers, he used two dashpots as dampers to rapidly close the engine’s valves. Corliss’ improved valve gear, patented in 1849, allowed for variable valve timing and engine speed controlled by varying the steam cutoff rather than opening or closing the throttle valve. As a result, the Corliss steam engine was around 30 percent more efficient than other stationary engines and would remain the most efficient stationary engine until the perfection of the steam turbine in the 20th century. The improved valve gear resulted in more uniform speed and better response to load changes, allowing the steam engine to branch into manufacturing applications like milling and spinning. The improvements also allowed industrial development away from millponds, which were previously necessary.

Corliss’ engine factored into an industrial magnum opus, not unlike Cavaillé-Coll’s massive Saint-Sulpice organ. The Corliss Centennial Engine was a massive rotative beam engine built to power nearly all the exhibits at the 1876 Philadelphia Centennial Exposition. It was 45 feet tall, featured a 30-foot flywheel, had shafts totaling a mile in length and produced 1,400 horsepower. The engine was jointly started by U.S. President Ulysses S. Grant and Pedro II, Emperor of Brazil and was available for public viewing for the duration of the exposition.

Just as many of Cavaillé-Coll’s groundbreaking organs are still working, a number of Corliss engines still operate in museums. These magnificent devices that spectators still flock to see were possible through the innovative use of a lever and dashpot, only a few years apart.

To contact the author of this article, email jonathan.fuller@ieeeglobalspec.com


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