(from An Illustrated History of Air Pumps, © David L Brittain, 2014)
In the middle 19th century in England, steam locomotives were
having trouble climbing some grades with full loads due to slippage of the
wheels on the tracks. In addition, they were noisy, dirty with soot, slow, and
mechanically unreliable. An inventive and quite ingenious solution came in the
form of an atmospheric railway, and believe it or not, it used vacuum to
lower the pressure in a tube so that atmospheric pressure could drive a piston
connected to a railroad car to power it without an engine—even uphill.
Several variations of this design were made, with some put into
actual use. The most successful—though rather short-lived—line was built in
1846 and ran between Exeter and Starcross on the South Devon coast of England.
It worked like this: The system used an
8.5-mile long continuous line of cast-iron tubes about 20 inches in diameter
and 10 feet long with a continuous slot about 2½-inches wide at the top. Other
rail lines used 15-inch diameter tubes (for low gradients), or 22 inches in
diameter (for steeper gradients). The tube was laid between the rails. A 15
foot-long dumbbell-shaped piston ran inside the tube, with a connecting plate
extending up through the top of the tube. This was sealed with a continuous
line of leather to act as a valve, which was weighted with iron plates to seal
it against a channel filled with a mixture of tallow (made from animal fat) and
beeswax, or soap and cod oil. The piston had small wheels before and after it
that opened and closed the valve.
A section of the South Devon Atmospheric Railway
by Chowells
Illustrations of the operation of the valves
The piston was driven by the differential pressure of the
atmosphere (hence, the technically correct term of atmospheric railway)
pushing against a vacuum created by large air-pumps driven by approximately 80
hp steam engines spaced at about 3 mile intervals. As the train car passed
along the track, the connecting plate lifted the leather valve, and the weights
closed it after the car passed, thus—in theory—keeping it from leaking air into
the vacuum side of the tube. The only thing that kept that theory from working
was the elements (the leather tended to dry out and crack, or rot from chemical
reactions); the sun, which melted the tallow mixture; and rats, which ate the
tallow (and, I’m assuming, got a great thrill when they got sucked—excuse me,
atmospherically pushed—into the tubes). Further problems were associated with
the lack of communications between the pumping stations in order to advise when
a train was approaching so that they could turn on the air pump, and
under-sizing of the pumps, which were sized for the 15-inch tubes, not the
22-inch tubes. The latter was never used.
An Atmospheric Railway car used in Saint Germain,
France.
Interestingly, in separate tests, one train actually reached a top
speed of 68 miles-per-hour, and averaged 64 MPH over 4 miles while carrying a
load of 28 tons; another hauled a load of 120 tons! The average travel time
between the two cities was 28.8 MPH. The vacuum level in the tubes averaged
about 16 inches of Hg. A report was given of a man named Frank Elrington,
sitting on the piston car without any passenger cars attached. When he released
the brake, the car shot off at a very high speed, averaging 84 MPH over the
entire 2 mile distance, much of it uphill.
Alas, in 1860, the last atmospheric railway of this type closed.
It was near Paris, France, and ran for 5.5 miles.
“Like a Sail-Boat Before the Wind”
In 1870, in New York City, Alfred Ely Beach (founder and editor of
The Scientific American) proposed an atmospheric railway that he called
the Beach Pneumatic Transit. It was to be the first subway in NYC and it was
constructed in secret at night, because he knew that Boss Tweed would oppose his
effort. It was a 312 feet long, 8 feet diameter tube constructed (in only 59
days!) under Broadway from Warren Street to Murray Street to demonstrate the
pneumatics-powered subway. 40,000 tickets were sold to curious customers in the
first two weeks, and over 100,000 in its first year of operation. A huge
100,000 cfm “fan”, called The Western Tornado, drove the car in one
direction; then, the louvers were reversed, creating a vacuum, which powered
the car in the other direction. The fan was manufactured by Roots Patent
Force-Blast Rotary Blowers. This is the same company that invented of the type
of blower known by its name, which is today a generic term: Roots, (Connersville, IN). (The blower
was referred to in news reports and documents as an æolor; not having
ever heard this description I tried finding a meaning to this word, with no
success until I looked in an old copy of the Oxford English Dictionary
(OED). Æolus (l.) is the god of Wind, and an æolist is a worshiper of that god.
That would make an æolor a wind machine; a quite appropriate description for a
100,000 cfm blower used to make wind.) With a
pressure of only ¼ psi, the blower theoretically generated enough force to
drive the car at a speed of from 60 to 100 MPH (though it normally travelled at
7 MPH)!
Journalist Helen C. Weeks commented on this
blower in her article “What a Bore!” 6, “Down we went into a basement,
where we faced at once, the greatest blower ever yet seen on this continent.
Not, however, a New York politician, as you may have supposed, but a rotary
blower … “
The exterior of the blower was covered with frescoes, although
many reports incorrectly state that the frescoes were on the walls of the
station.
Though it operated for nearly three years, the Pneumatic Railway
never became a reality, killed by a stock market crash that caused investors to
withdraw from the project, and other issues.
In 1976, a song by the band, Klaatu, titled Sub-Rosa
Subway, made it to #62 on Billboard’s Hot 100. Part of the lyrics:
Back in 1870 just beneath the
Great White Way
Alfred Beach worked secretly
Risking all to ride a dream
His wind-machine
His wind-machine
New York City and the morning sun
Were awoken by the strangest sound
Reportedly as far as Washington
The tremors shook the earth as Alfie
Blew underground
Blew underground
...
As for America’s first subway
The public scoffed, “It’s far too
rude”
One station filled with Victoria’s
age
From frescoed walls and goldfish
fountains ...
To Brahmsian tunes
Written by John Woloschuk and Dino
Tome
Beach Pneumatic Railway under
Broadway, in NYC
A humorous anecdote is that when Beach entered his pneumatic
tube, he thought to himself, “tu-be or not tu-be”.
The Pneumatic Railway and all its offices moved out of its
building at 260 Broadway Ave. in December, 1875. It is interesting to know that
in January, 1876, the station and the tunnel for the Pneumatic Railway became a
100-yard rifle range for a newly formed New York organization named the
National Rifle Association.
Adapted from: Scientific American, March 5, 1870
But the story does not end there; in the late 1970s, Brazil built
a “people mover” named the Aeromovel. Lightweight cars ride on rails on
an elevated hollow concrete box girder that forms an air duct.
An Aeromovel pneumatic train in
Indonesia. (The blue air duct is visible below the track.)
by Gunkarta Gunawan Kartapranata
Each car is attached to a square
plate—the piston— within the duct, connected by a mast running through a
longitudinal slot that is sealed with rubber flaps. A stationary air pump blows
air (vacuum is not used here) into the duct to create the differential pressure
necessary to drive the car—just like the system more than 200 years earlier.
The Aeromovel systems are still in production and are used in theme parks and
airports.
Sources:
The Remarkable Pneumatic People Mover, by Alan Bellows; www.damninteresting.com
Atmospheric Railway; www.wikipedia.com
The Applications of Vacuum, from Aristotle to Langmuir; by Theodore E. Madey; Journal of
Vacuum Science Technology, April-June 1984.
The Atmospheric Railway; Mike’s Railway History;
hppt://mikes.railhistory.railfan.net/r027.html
Unless otherwise noted, all images are in the public domain. Images so marked are used
with permission according to the Creative Commons Attribution-Share Alike 3.0
Unported license. 
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