AOH :: AIRRAIL.TXT|
About pneumatic railways
Last month I wrote in alt.folklore.urban:
> This article deals with facts. [Urban legend] purists, move on now.
> The topic really belongs in rec.railroad, but as it happens, I posted
> an article there very similar to this one not too many months ago.
> (Wish I'd saved a copy...)
Well, it turns out that I did. The two articles, although based
on the same sources, contained sufficiently different material --
and even a couple of conflicts -- that I have decided to edit them
together, merge in some more background, and repost the resulting
article to both newsgroups. If you weren't very interested the first
time around, stop reading now. Followups are directed to rec.railroad.
The ultimate responsibility for this thread :-) belongs to George
Medhurst (1759-1827), of England. During a period of a few years
about 1810, he invented three distinct forms of air-propelled
transport. None of them was implemented during his lifetime;
but all of them saw use eventually, reaching their greatest extent
in the reverse order of their original invention.
Medhurst's first method involved moving air through a tube a few
inches in diameter, pushing a capsule along it; this simple idea
was the pneumatic dispatch tube. Next he realized that if the same
system was built much larger, it could carry passengers (or freight
items larger than letters); it was natural to run the vehicle on
tracks, and so this became known since the vehicle would be large
enough to require tracks, this became known as a pneumatic railway.
But would anyone actually want to ride along mile after mile inside
an opaque pipe? Not likely. So he then thought of having only a
piston moving within the pipe, somehow dragging along a vehicle
outside it. He proposed several versions of this idea; in most of
them the vehicle ran on rails, so this became known as an atmospheric
railway (though a distinction between that term and the pneumatic
railway was not always observed). The key feature of all versions
of the system was a longitudinal valve: some sort of flexible flap
running the length of the pipe, which would be held closed by air
pressure except when the piston was actually passing. Medhurst
did try to raise capital to implement this system, but failed.
Now, while the first operable steam locomotive was built about 1804,
steam-powered trains did not see regular use for passengers for some
25 years after that. It was in the 1830's and 1840's that the steam
railway was shown to be practical in both engineering and financial
But the same technical developments that made possible the practical
steam railway also made the atmospheric railway, if not certainly
practical, at least worth a try. And it offered the prospect of
considerable advantages. Since the trains wouldn't have to carry
their prime mover, they would be lighter; therefore the track could
be built cheaper, and the trains' performance would be better.
The trains wouldn't trail smoke wherever they went (and into the
passenger cars in particular), and they would also be quiet.
And if one section of the route was hilly and required more motive
power, all that were needed would be more or larger pumping stations
along that section; no need to add extra locomotives. In short,
very much the same advantages that electricity gave a few decades
later. (Plus one more: a derailed train would tend to be kept near
the track by the pipe and piston.)
The success of the 1830's railways gave rise to the Railway Mania
of the 1840's, when interest in railway shares reached absurd levels.
In that climate the proposers of atmospheric lines could find the
backing they needed, and four atmospheric lines opened in a period
of about 3 years. In order of opening, these were:
* The Dublin & Kingstown, from Kingstown to Dalkey in Ireland,
1.5 miles long; operated 1844-54.
* The London & Croydon, from Croydon to Forest Hill in London,
England, 5 miles, then extended to New Cross for a total
of 7.5 miles; operated 1846-47.
* The Paris a St-Germain, from Bois de Vezinet to St-Germain
in Paris, France, 1.4 miles long; operated 1847-60.
* The South Devon, from Exeter to Teignmouth in Devonshire,
England, 15 miles, then extended to Newton (now Newton Abbot),
20 miles altogether; operated 1847-48.
I note in passing that while I (as a fan of his) might like Isambard
Kingdom Brunel to have invented the atmospheric system used on the
South Devon, it is wrong to say that he did so. He did choose it
and actively promoted it (well, "actively" is redundant with Brunel).
It was actually developed by Samuel Clegg and Joseph and Jacob Samuda.
Both of the longer, if shorter-lived, English lines used atmospheric
propulsion in both directions of travel, whereas the French and Irish
lines were built on hills and their trains simply returned downhill
by gravity. Since all were single-track lines, the one-way system
simplified the valves needed to let the pistons in and out of the
pipes at their ends (possibly while traveling at speed).
All four lines were converted to ordinary steam railways in the end,
and for the next 130 years the atmospheric system appeared dead.
For one thing, steam locomotive technology had too much of a head
start in development over the atmospheric system; steam railways
might have delays due to engine failure but they never had to shut
down for 6 weeks while a new design of longitudinal valve was
installed along the entire length of the route!
(The valve involved metal and leather parts and a greasy or waxy
sealant "composition". Although stories were told about rats
eating the composition, and this probably did happen sometimes,
it wasn't really a serious thing; the biggest problems in fact
were freezing and deterioration of the leather, and corrosion
of the metal parts.)
Also, the atmospheric system was inflexible, in that if the power
requirements for a section of route were greater than estimated,
very little could be done short of splitting the section and adding
a whole new pumping station. (All the lines used vacuum rather
than positive pressure in the pipes, which limited the pressure
differential to about 0.9 atmosphere in practice; but the valve
designs were marginal anyway and likely wouldn't have stood up
to greater pressures if they could have been used.)
What today might be seen as the most serious disadvantage of all,
the requirement for long interruptions of the motive power at
junctions, was not so noticeable in those days. If the train
didn't have enough speed to coast across the gap, well, the
third-class passengers could always get out and push, or maybe
there would be a horse conveniently at hand. At some stations
a small auxiliary pipe was used to advance the train from the
platform to the start of the main pipe.
There were many other proposals in those days for atmospheric
lines, but in view of these early failures, none of them were
ever built as atmospheric railways. The next atmospheric railway
to open actually appeared in 1990!
While the atmospheric railways were vanishing, the first
pneumatic dispatch tubes were beginning to appear; I'll get
into that later. But from that start, the pneumatic railway
idea began to return also. At first these were designed for
freight. Engineers J. Latimer Clark and T. W. Rammell formed
the Pneumatic Despatch Company, which built a demonstration tube
above ground in Battersea in 1861. This line successfully carried
loads up to 3 tons... and even a few passengers, lying down in
the vehicles in the 30-inch tunnel! The pressure used was up
to 0.025 atmosphere, and speeds up to 40 mph were reached.
The Post Office became interested in the system and had several
tunnels built for it. They were used from 1863 to 1874, though
interrupted for a time by the financial crisis of 1866.
(At this point they decided that the system didn't gain enough time
to be worth the cost, not to mention the risk of a vehicle becoming
stuck in the tube. In the 1920's, when electricity was available,
they returned a driverless trains system, using tunnels of similar
size to the old pneumatic tubes. This is the Post Office "tube"
Railway, which continues in use to this day. Such systems also
exist in Switzerland, which had it first, and in West Germany.)
Meanwhile, while these lines were moving the mail from the streets
of London to tunnels underneath, the first underground railways
were doing the same with passenger traffic. The first section of
the Metropolitan Railway (from Farringdon, now Farringdon Street,
to Paddington station) opened in 1863. It was promptly followed
by extensions, as well as competition in the form of the Metro-
politan District Railway, a subsidiary that got away. (Their
routes in central London today form the London Underground's
Metropolitan, District, Circle, and Hammersmith & City Lines.)
Now there was no thought of operating the Metropolitan with
anything but steam locomotives, despite the line being mostly
in tunnel. Sir John Fowler, who later co-designed the Forth Bridge,
did have the idea of a steam locomotive where the heat from the fire
would be retained in a cylinder of bricks, and therefore the fire
could be put out when traveling in the tunnels. One example of
this design, later called Fowler's Ghost, was tried in 1862.
It was thermodynamically absurd: as C. Hamilton Ellis put it,
"the trouble was that her boiler not only refrained from producing
smoke, it produced very little steam either".
In the end both the Met and the District were worked with condensing
steam locomotives: these emitted smoke as usual, but their exhaust
steam, while running in tunnels, was directed back into the water
tanks and condensed. The tanks were drained at the end of the run
and refilled with cold water.
So people were not only willing to travel in what amounted to an
opaque tube after all, but in one filled with smoke at that!
Why not one *without* smoke? And so the pneumatic railway was
now tried; but it never got past the demonstration stage.
The longest line to carry passengers was opened at the Crystal
Palace in London in 1864. It used a tunnel about 9 by 10 feet,
1800 feet long. The driving fan was 22 feet across, generating
about 0.01 atmosphere of pressure -- the larger the tube, the
lower the pressure you need. The vehicle was a full-size broad
gauge railway car ringed with bristles; it carried 35 passengers.
The trip took 50 seconds, thus averaging about 25 mph. Another,
smaller demonstration line was built at a fair in the US in 1867
by Alfred Ely Beach.
Beach then formed the Beach Pneumatic Transit Company, which
obtained permission to build a freight-carrying pneumatic line
under Broadway in New York. But what he actually opened in 1870
was a passenger-carrying pneumatic subway, the only one to
actually operate under a city street. It was only 312 feet long,
from Warren Street to Murray Street. The tunnel was 9 feet in
diameter, and was worked by a single car with a capacity of
Beach tried but failed to get permission to extend the line.
It closed after a few months, and New York did not get a subway
again until 1904, when the first Interborough Rapid Transit route
was opened (from City Hall station along the present Lexington
Avenue, 42nd Street shuttle, and 7th Avenue lines to, um, initially
somewhere around 120th Street). This route was electric and so
have been all its successors.
Beach's tunnel had been almost forgotten when the crews
constructing the new subway broke into it in 1912.
In London, a pneumatic underground line was started *with* permission,
but construction was never completed. This was the Waterloo and
Whitehall Railway, which planned to connect Waterloo station to Great
Scotland Yard, 1/2 mile away, with a 12'9" diameter tunnel passing
under the Thames. Considering that the Thames Tunnel project of
Sir Marc Brunel and Isambard Kingdom Brunel -- now now part of
the Underground's East London Line -- had faced massive technical
and financial difficulties before its long-delayed completion only
about 20 years previously, this was no mean undertaking.
The Waterloo & Whitehall was halted by the financial crisis of 1866;
and it was never revived. The tunnel had been started from the
Great Scotland Yard end, and had just reached the river; work on
the underwater section was beginning. There were other proposals
for passenger-carrying pneumatic lines, but none saw construction
in that form. (At least one, under the Mersey at Liverpool, England,
was eventually opened as an ordinary railway.)
The next type of underground line to open in London was the Tower
Subway, which also passed under the Thames. It was a short route,
just under the river, worked by a small cable car. It opened in
1870 and was short-lived. (The tunnel served as a footway for a
while after that, then was taken over for pipes. The Thames Tunnel,
conversely, had been used first as a footway, then converted to
After this time, electric railways began to become practical.
The next underground line to open was the City & South London,
now part of the Underground's Northern Line. Its first section
(from Stockwell to a now disused terminus at King William Street,
replaced by the present Bank station) opened in 1890. It used
the new deep-level tube tunnels, with more limited ventilation
than on the Metropolitan Railway, so steam was out of the question
in any case. The original plan was for cable haulage, but instead
the new electric locomotives were tried and the line has always
been operated electrically. The line was first built with 10'2"
diameter tunnels, forcing use of rather small cars. (The cars
also had only tiny windows, on the grounds that there was nothing
to see -- so they got the nickname of "padded cells".)
All of the later lines in London, opened from 1900 onwards, were
built on the same general pattern as the C&SL, with deep-level
tubes and electric traction -- first by locomotives and then by
multiple-unit trains. The other tube lines vary from 11'6" to
12-foot diameter tunnels, and the C&SL was enlarged in the 1920's
to match. This is still rather small compared to most other
subways in the world, and is the reason for the distinctive
shape of the tube trains.
With the success of the electric lines, the Metropolitan and
District faced the loss of traffic, and they too were converted
to elecricity -- at least for the underground sections in central
London in 1905. The first line of the present New York subway
system opened in 1904 and this, too, has always used electricity.
(This was the original Interborough Rapid Transit route, from City
Hall station along the present Lexington Avenue, 42nd Street shuttle,
and 7th Avenue lines to, um, somewhere around 120th Street). Beach's
tunnel had been almost forgotten when the crews constructing the
new subway broke into it in 1912.
Meanwhile, the humble original concept of the pneumatic dispatch tube
continued to develop. The first of them, 1.5 inches in diameter,
had been built in 1853 by J. Latimer Clark; it connected the
Electrical and [sic] International Telegraph Company's office in
Telegraph Street, London, with their branch 675 feet away at the
The key invention was J. W. Willmott's double sluice valve of 1870,
which allowed rapid dispatching of successive capsules. It was also
possible, as had been done on the pneumatic railways, to use both
positive pressure (on the order of 1 atmosphere) and vacuum, to
drive the capsules both ways from a single pumping station. The
tubes became quite common; many miles were built in various European
and North American cities. By 1886 London had over 34 miles of them
for the Post Office's telegraph service alone. In the Paris system
a person could pay a fee for a message to be sent specifically by
They were also used within large buildings, and some survive in
use to this day.
Finally, in 1990, the Brazilian company Sur Coester stunned the
world by opening at a fair in Djakarta, Indonesia, a demonstration
line of their Aeromovel system. This is nothing more nor less
than an elevated atmospheric railway. The structure is concrete,
with steel rails and a rectangular concrete air pipe larger than
those on the 19th century lines. The longitudinal valve is made
of heavy cloth-reinforced rubber. Computerized remote control
Pneumatic dispatch tubes were depicted in the 1985 movie "Brazil";
Beach's tunnel was depicted, in rather distorted form, in the 1989
movie "Ghostbusters II"; the modern form of the New York subway
has been depicted in many movies, notably the 1974 one "The Taking
of Pelham One Two Three"; but I don't believe the atmospheric or
pneumatic systems have ever been depicted at work in any movie.
Clearly this needs to be rectified! :-)
Almost all the information in this posting about the pneumatic
and atmospheric systems comes from one book... "Atmospheric
Railways: A Victorian Venture in Silent Speed" by Charles Hadfield,
1967, reprinted 1985 by Alan Sutton Publishing, Gloucester; ISBN
For other topics, I principally consulted "The Pictorial
Encyclopedia of Railways", 1976 edition, by (C.) Hamilton Ellis,
Hamlyn Publishing; ISBN 0-600-37585-4; some details came from other
books or my memory.
The information about the Djakarta line comes from two postings in
rec.railroad, one last November by Andrew Waugh quoting the November 24
issue of "New Scientist" magazine, and the recent one by Russell Day
citing "Towards 2000".
Mark Brader "Great things are not done by those
SoftQuad Inc., Toronto who sit down and count the cost
utzoo!sq!msb, email@example.com of every thought and act." -- Daniel Gooch
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