Pete,
Many thanks for your comments -- all apposite. Your third paragraph
particularly interests me. I take the point that an outer-tube
pneumatic railway might not be able to deliver very high speeds
because of the high requirements for the physical integrity of the
tube. As far as commuter traffic is concerned, one answer could be to
reduce the cross-sectional size of the vehicle. The present track
width and carriage size of the railways was largely established by
the stage coach, and something similar was automatically assumed by
the Lockheed engineers and the Swiss in their proposals. However, if
commuters sat one behind another in a much slimmer tube then less
powerful pumping stations and less exacting strength requirements
would be necessary.
However, a pneumatic railway system (considering only the transport
of goods) makes a great deal more sense if it's part of a very much
larger scheme involving factories and warehouses. The cost of
cut-and-cover for extensive schemes would be substantial, of course,
but, with the beneficial restoration of the countryside above
(ecological or agricultural), there would be a double income stream,
as it were. What I find rather intriguing also is what would be the
economic effect of laying out warehousing horizontally -- as such a
scheme would entail. Multi-storey factories of the 19th century have
long given way to horizontal layouts (despite the higher cost of the
land). Would the same apply to what is now the normal high-stacked
warehouse (at least for food and most consumer goods)? Although items
can be presently stored at high density the items themselves they are
slow to store, retrieve, load on lorries and sent out of the gate.
Delivery of goods from almost start (manufacturing, importing) to
finish (sales outlets, exports) could be achieved as rapidly as
required and without much by way of intermediate re-handling. This
could more than make up for the higher initial land costs.
Keith
At 18:08 26/12/2011, Pete Vincent wrote:
Most curious, the resender seems to have applied a random rearrangement
to my line lengths. Let's see if I can straighten them out...
On Mon, 26 Dec 2011, pete wrote:
An odd synchronicity, I stumbled upon this story just this summer,
and had an entertaining time reading about the whole adventure. The
invention was not initially Brunel's, but rather had been proposed
as early as 1799, and developed by a group of engineers who built
the first example in Dublin. It is thought Brunel's attention was
drawn to this example after an unintended incident during an early
demonstration of the new line, when the steam pump built up the
pressure to drive a full line of cars up the hill on which the line
was constructed, but only one car had been placed on the line, with
a single passenger, a young worker who volunteered. The
over-pressure drove the car up the hill at something over 65 mph,
an unheard of speed for 1844, and I expect that the young man held
the land speed record for a couple of decades, though no one was
keeping track of such things in those days.
The main advantage of the remote pressure driven line is that you
don't have to move the engine nor the fuel, so the cars can be much
lighter, and everything is much more efficient. That was a big
concern in the 19th century, when power came from heavy cast iron
steam engines burning mountains of coal. The development of the
electric locomotive engine freed the vehicles from the need to
transport fuel, though some still do (all locomotives are electric
driven - the diesels are diesel-electric, with the diesel engine
powering an electric generator which then powers an electric motor
which drives the wheels, for the same reasons of efficiency that
hybrid cars use a gasoline engine to drive an electric motor), so
the strong impetus for the use of remote power is considerably
reduced. In north america, the distances make electric power lines
less economical than carrying the diesel fuel, but tht is not the
case in europe, so electric lines are common there.
Another problem with the remote power pneumatic system is the
limitations on the power which can be delivered, being constrained
by the strength of the pneumatic pipe. The problem is also present
with electric rail lines, though not in such severe form, as you
can put a large amount of electric power down a fairly inexpensive
line by just using a higher voltage. With diesel electrics, more
power is just a matter of inserting more engines in the line of
cars. Typical freight trains in western Canada can have many
engines, and an immense load, being as much as 4km long and
weighing 18kt, with seven or more engines distributed along the length.
-Pete
On Mon, 26 Dec 2011, Keith Hudson wrote:
One of the greatest inventions of the 19th century, and of all
man's time, has yet to be developed. It failed initially for a
trivial reason which, today, could be easily overcome. When it is
finally embarked upon, it will change the physical infrastructure
of many countries to such an enormous extent that we can't
possibly imagine all its ramifications. Its development may still
lie a century in the future, though there's no reason why a
particularly enterprising culture such as Singapore or Switzerland
or Israel shouldn't start planning it tomorrow.
I'm reminded of the invention every day as I sit at my keyboard
and look out of the window. Yet, to my complete surprise this
morning, I realize that I have never written about it before now.
A group of trees about 100 yards ahead of me is the prompt. This
at is the beginning of one of the first tunnels of the Great
Western Railway built by the engineering genius, Isambard Kingdom
Brunel in 1833. It's still in use today. If I listen carefully at
various times in the day I can hear the low rumble of a
London-destined train approaching along a deep tree-lined cutting.
The sound then vanishes. If I walk to my back garden quickly I can
hear the sound again as the train emerges from the tunnel about
200 yards away to the east. (My house doesn't actually sit over
the tunnel, thank goodness!)
Brunel's first idea was that his Great Western Railway should be
pneumatic -- that is, driven by air pressure. It would be so much
more efficient than the locomotive system than was then being used
to pull carriages and freight trucks along. Instead, in Brunel's
experimental version, the leading carriage or truck had a short
downward extension on which there was a circular piston which
snugly fitted inside a 12 inch wide tube with a slit along the top
to allow forward motion. A steam-driven pumping engine a mile or
two ahead pumped out the air ahead of the train. The air pressure
behind the train would then push the piston forward -- and at very
high speed, too. The slit in the tube was was covered by a
continuous leather strap which slid aside briefly as the
piston-arm moved along the tube and then sealed over again when
the train was past. Brunel tried it out. He demonstrated
conclusively that a pneumatic railway was, indeed, much more
efficient than a locomotive driven railway (in which heavy steam
engines) have to travel almong as well as the freight.
The problem with this experimental model -- which Brunel hadn't
foreseen -- emerged within weeks. This was that countryside rats
took a liking to the leather valve, nibbled away at it and thus
rendered the tube less than air-tight. This dashed the whole
project. There were no rubber-like or plastic materials available
in those days which were rat-proof and could have been used
instead of leather. Thus, Brunel had to revert to the conventional
method of mobile steam-engines pulling the train for his Great
Western Railway. Another way of overcoming the problem was
theoretically possible. This was to construct a much larger tube
so that it fitted snugly around the whole front of the leading
carriage or truck. This would be even more efficient. But the cost
of building a tunnel for the whole distance of 110 miles between
Bristol and London was far beyond the pockets of the GWR Board of Directors.
However, to show that this method was feasible, a full-tunnel
short-length fun version was built in the grounds of Crystal
Palace in 1864 to the delight of hundreds of people who tried it.
Also a short-length passenger railway (with serious intent this
time!) was constructed under Broadway in New York. Once again,
however, this proved to be unfeasible because of lack of suitable
sealing materials. In the 1960s, some Lockheed engineers designed
a pneumatic system for a Boston-Washington commuter route. At the
same time, the Swiss were considering a pneumatic metro system
between their major cities. But in both cases it was cost, not
method, that stopped further consideration.
However, the cost could be much further reduced by a cut-and-cover
method of construction whereby, for most of its length, the top
soil is replaced over the top of the tube and the normal amenity
or agricultural value of the countryside is resumed. The overall
cost would also be reduced substantially if large factories and
warehouses (both increasingly automated with smaller numbers of
personnel) were integrated with pneumatic railways with
countryside above them all. Freight containers could be rolled on
and off vessels at the ports and imports delivered at regional
warehouses within an hour or two even in large countries. The cost
of land-freight could be reduced to levels scarcely more than
those of sea transport today. Countries without coastlines would
not be as disbenefited as they are now. As for commuters, the time
spent every day could be reduced to a fraction of that by car or
existing railways.
I gave a talk about this to the Bath Royal Literary and Scientific
Society about 20 years ago. A friend told me afterwards that I'd
given the talk in a flat, unexciting way. That surprised me but
perhaps I did. If so, the reason was probably due to the fact that
I then still considered Brunel's invention to be premature. If the
Swiss had decided against it for cost reasons in the 1960s then it
was still probably not the time for it to be taken up in the
1990s. But there is a difference today which is beginning to be
discernible as part of our credit-crunch problem and forthcoming
recession. This is that there is no great chain of new consumer
products ahead of us which existed all through the past 300 years
and served stimuli for economic growth. If there is to be
economic development (measure in conventional terms) then it's
going to come via new efficiencies on the production side and not
new consumer gew-gaws. Also, if we add in the desirable
restoration of a great deal of our countryside, then Brunel's
invention is surely going to be one of the answers one day.
Keith
Keith Hudson, Saltford, England http://allisstatus.wordpress.com
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Keith Hudson, Saltford, England http://allisstatus.wordpress.com
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