
Atmospheric railway - xiaq
https://en.wikipedia.org/wiki/Atmospheric_railway
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gmjoe
At the very end, about a current implementation:

> _The free piston is magnetically coupled to the passenger modules above;
> this arrangement allows the power tube to be closed, avoiding leakage. The
> transportation unit operates above the power tube on a pair of parallel
> steel rails. The company currently has a 1 /6 scale pilot model operating on
> an outdoor test guideway... The Corporation claims that a full-scale
> implementation would be capable of speeds in excess of 200 mph (322 km/h)._

It sounds like magnetic coupling is the solution to the maintenance issues.

But it also seems like you can only have one train on a track at any given
time.

Or, at least a track would have to be divided into sections, each with its own
pumps and own piston, which could only support one train at a time... and then
the piston would have to be sent backwards to the beginning of the section to
be ready for the next train. (And you'd need electromagnets to let go of one
piston and grab the one on the next section.)

So I can see why this might not be viable for something like a city's subway
system.

But at the end of the day... what advantages would this ever have over
electric trains that get their power from a third rail?

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bo0tzz
> But at the end of the day... what advantages would this ever have over
> electric trains that get their power from a third rail?

No heavy electric motors and other equipment in the vehicle, for starters

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Gravityloss
From the article:

> Fully loaded vehicles have a ratio of payload to dead-weight of about 1:1,
> which is up to three times better than conventional alternatives

Might make sense for a small system.

But electric machines have made huge advances in the last decades. Frequency
converters, DC-DC converters, high torque permanent magnet motors etc are now
very commonplace.

For example in the workshop, electric tools have supplanted pressurized air
ones.

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lawlessone
[https://en.wikipedia.org/wiki/Dalkey_Atmospheric_Railway](https://en.wikipedia.org/wiki/Dalkey_Atmospheric_Railway)

"The journey to Dalkey could be completed in just over 3 minutes with the
speed being limited by the need to brake for curves on the"

That's faster than the train gets there today.

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ungzd
Related technology:
[https://en.wikipedia.org/wiki/Fireless_locomotive](https://en.wikipedia.org/wiki/Fireless_locomotive)

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andygates
I did not know that a modern version of the system was in use. Spent a few
years living along the South Devon route, and Brunel's seals eaten by rats
were a definite thing.

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swah
I'm from Porto Alegre. The aeromovel works fine, but I guess an electric train
could fit the same constraints.

AFAIK the aeromovel is a matter of "regional pride" since a local engineer
invented/designed them in the 70s.

