[HN Gopher] The Pneumatic Clocks of Paris
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The Pneumatic Clocks of Paris
Author : akpa1
Score : 102 points
Date : 2022-07-18 12:46 UTC (10 hours ago)
(HTM) web link (www.amusingplanet.com)
(TXT) w3m dump (www.amusingplanet.com)
| joezydeco wrote:
| Meanwhile, in the USA, Western Union used their telegraph network
| to build out a system of synchronized clocks. A long pulse on the
| line at the top of the hour engaged a solenoid in the clock that
| pulled the minute hand back to :00.
|
| https://hackaday.com/2019/09/25/100-year-old-atomic-clock/
|
| And, since this is HN, it's worth mentioning that this was a
| _subscription_ service.
| whatshisface wrote:
| Since the speed of sound is lower in tubes, I wonder how late
| the clocks were at the end of the network.
| hulitu wrote:
| As far as i understand the signal was transmitted through
| telegraph lines, not tubes.
| joezydeco wrote:
| If you're referring to the pneumatic network, one of the
| footnotes mentions a latency of 10 seconds, but the author
| does the math and says that's probably not accurate, more
| like 58 seconds at the 20km max distance.
|
| http://www.douglas-
| self.com/MUSEUM/COMMS/airclock/airclock.h...
| jbay808 wrote:
| The article doesn't seem to mention it, but the clocks were
| each offset to compensate for the propagation delay. It's a
| static correction, so easily done by just offsetting the
| minute hand position. (I can't seem to find the citation on
| this, though.)
| jonny_eh wrote:
| It's amazing that Western Union didn't lobby congress to ban
| free, government operated, time synchronization services.
| joezydeco wrote:
| Probably didn't need to. WU had the monopoly on cross-
| continent communication lines. The government didn't have the
| resources to compete.
| jonny_eh wrote:
| I was actually referencing: https://qz.com/1913544/telecom-
| lobbyists-stop-cities-from-bu...
| angryGhost wrote:
| do the clock still exist?
| t_mann wrote:
| My impression is that those trade/tech "expos" in the 19th
| century were really a massive acceleration force of innovation
| and industrialization. To the point that I could imagine that the
| lack of such expositions might be an explaining factor why the
| Roman empire never experienced an industrial revolution. Nowadays
| they're less important because they've been replaced by
| conferences (which are the same idea dialed up to 11, I'd argue,
| and no less important in driving innovation). Maybe I'm going
| completely off here, but would be interesting to read an
| analysis.
| foobarian wrote:
| Yeah why did the Roman empire not advance into
| electricity/steam power? All the precursor elements were there
| such as metalworking. Did they just not have a network of smart
| nobles with leisure time to tinker? Are universities required
| for that? Referring to likes of Newton, Leibniz, Faraday,
| Maxwell, etc.
| bufferout wrote:
| One theory is that the abundance of slave labour
| disincentivised any real push towards automation. That said,
| they did have massive water mill complexes for grinding
| grain.
| a-dub wrote:
| incidentally conedison still operates commercial steam delivery
| in manhattan to this day.
|
| https://www.coned.com/en/commercial-industrial/steam
|
| pneumatic signaling is cute. it makes me imagine the french mob,
| running around with black strap eyemasks, stripey shirts, bicycle
| pumps and hand-drills jacking into the system and running the
| clocks forward for nefarious purposes.
| gargs wrote:
| Apparently, they even had subscribers that paid half a penny a
| day for a timepiece.
|
| https://www.nature.com/articles/022226a0
| mhaye wrote:
| I wonder what the human side of maintaining the clock network was
| like. Did dedicated civic employees walk the clocks each day
| looking for telltale time differences that would indicate a break
| in the lines, and then debug with maps? I bet those maps would be
| interesting too. And how did they keep problems in one section
| from propagating through the whole system? Buffers and interlocks
| I suppose.
| ballenf wrote:
| Another interesting illustration of innovation displacing a
| successful and widespread infrastructure. It wasn't better pipes
| or a better gas in the pipes, it was technology from a different
| source that displaced these compressed air clocks and obsoleted
| the hundreds of miles of pipe needed to transport it.
| Bayart wrote:
| In the instance, the piping can easily be repurposed to run
| other kinds of lines (for example electric, phone, fibre).
| Which it certainly was.
| Razengan wrote:
| I would have loved to see how the world's technology would be
| like if electricity was discovered much later and there had been
| no major wars. Probably closer to Steampunk/Gearpunk.
| whatever1 wrote:
| OMG I misread the title.
| steveBK123 wrote:
| I do wonder if there was an (unmentioned in article)
| synchronization system like a special midnight pulse to get the
| clocks all back in sync in case there was drift.. or it was all
| handled by periodic inspections
| _int3_ wrote:
| This was not just for clocks. There were pneumatic network in
| Paris "distributing compressed air at a relatively low pressure
| of 5-6 bar over a network of (eventually) more than 900 km of
| mains, serving more than 10,000 customers." That run the industry
| and lasted over 100 years until 1994.
| kweks wrote:
| These were two distinct networks, the other network was run by
| the PTT :
| https://fr.m.wikipedia.org/wiki/Poste_pneumatique_de_Paris
|
| It was kept in operation until 2004 for government services!
| _int3_ wrote:
| "Citywide compressed air energy systems have been built since
| 1870.[23] Cities such as Paris, France; Birmingham, England;
| Dresden, Rixdorf and Offenbach, Germany and Buenos Aires,
| Argentina installed such systems. Victor Popp constructed the
| first systems to power clocks by sending a pulse of air every
| minute to change their pointer arms. They quickly evolved to
| deliver power to homes and industries.[24] As of 1896, the
| Paris system had 2.2 MW of generation distributed at 550 kPa
| in 50 km of air pipes for motors in light and heavy industry.
| Usage was measured by cubic meters.[23] The systems were the
| main source of house-delivered energy in those days and also
| powered the machines of dentists, seamstresses, printing
| facilities and bakeries." [1]
|
| [1] https://en.wikipedia.org/wiki/Compressed-
| air_energy_storage
| rob74 wrote:
| Also interesting (especially that it lasted until 1994), but
| the system from this article _was_ just for clocks - I don 't
| think power tools could use power which was only delivered for
| 20 seconds and then off for 40 seconds. If you translate that
| to computing, one system supplied the Vcc, the other supplied
| the (very slow) clock. No data lines unfortunately :)
| gerikson wrote:
| > when the invention of accurate mechanical and electric clocks
| made the need for a central synchronization clock obsolete, and
| the service was discontinued
|
| Most accurate clocks in factories and railway stations are
| controlled by a central timekeeping source, so it's not quite
| correct that such a source is obsolete.
|
| (edit: wording)
| bombcar wrote:
| Yep, in many _many_ cases it 's more important to have all the
| clocks be the _same_ than it is for them to all be correct - it
| 's just with the rise of radio clock signals and NTP it's
| easiest to make them all be the same by making them all
| correct.
| technothrasher wrote:
| I also noticed that this statement was a bit weird. Accurate
| mechanical clocks were already pretty well invented at that
| point. By the mid-19th century the best regulators were good to
| about 0.5s/month, and any further development in anything but
| the most specialized mechanical clocks after that point were to
| make them cheaper, not more accurate.
|
| As for electrical clocks, indeed rather than replacing central
| synchronization, the incorporation of electricity spurred the
| wide adoption of master/slave systems which didn't really
| subside until the last quarter of the 20th century. And most
| often the master clocks in those systems were highly accurate
| mechanical weight driven pendulum clocks, with the slaves being
| electrically driven. (apologies for the deprecated master/slave
| terminology, that's how they were referred to at the time)
| nbernard wrote:
| > The pipes ran through the sewers of the city, and the tunnels
| of the Metro and the RER, a commuter rail network serving Paris
| and its suburbs.
|
| > However, the system was repaired and pneumatic clocks continued
| to work until 1927.
|
| Considering that the RER started to operate in 1977 [0], I find
| that hard to believe.
|
| [0]:
| https://en.wikipedia.org/wiki/R%C3%A9seau_Express_R%C3%A9gio...
| bombcar wrote:
| None of the RER tunnels are shared/repurposed?
| rob74 wrote:
| The Wikipedia article https://en.wikipedia.org/wiki/R%C3%A9se
| au_Express_R%C3%A9gio... doesn't sound like it:
|
| > _The RER 's tunnels have unusually large cross-sections.
| This is due to a 1961 decision to build according to a
| standard set by the Union Internationale des Chemins de Fer,
| with space for overhead catenary power supply to trains.
| Single-track tunnels measure 6.30 m across and double-track
| tunnels up to 8.70 m, meaning a cross-sectional area of up to
| 50 square metres, larger than that of the stations on many
| comparable underground rail networks._
|
| Paris has basically three distinct stages in "urban rail"
| development:
|
| - first, the mainlines were built from stations on the then-
| outskirts of Paris (Gare du Nord, Gare de L'Est etc.)
|
| - then trams and later metros were built to link these train
| stations to the city and serve additional areas.
|
| - finally starting from the 1970s they started building rail
| tunnels so suburban trains could run directly from one train
| station through the city to another station - similar to the
| S-Bahn systems in Germany or Crossrail in London. The RER
| tunnels were all built in this phase.
| gregschlom wrote:
| No that's definitely a mistake in the article. Not only are
| the RER tunnels from the 70s, they also run much deeper than
| the metro tunnels. They didn't exist in any form at the time.
| The metro tunnels did, though
| bobthepanda wrote:
| It's possible that on construction of RER that previously
| separated pneumatic lines were then routed through the RER
| tunnels as well, no?
|
| I know in NYC that water pipes and electric tend to get
| routed through/around subway tunnels once constructed.
| kweks wrote:
| The RER integrates converted sections of existing tunnels,
| IE the RER B:
|
| The northern terminus of the Ligne de Sceaux opened at
| Luxembourg in 1895. Between 1973 and 1977 it was converted
| into RER B.
|
| (
| https://en.m.wikipedia.org/wiki/Luxembourg_station_(Paris)
| )
| baud147258 wrote:
| maybe when using RER, the author meant the short-distance train
| lines that already existed before the RER network was built up?
| supernova87a wrote:
| > "... _However, the system was repaired and pneumatic clocks
| continued to work until 1927, when the invention of accurate
| mechanical and electric clocks made the need for a central
| synchronization clock obsolete_... "
|
| This is not really true, in that you may remember from your
| elementary or high school days that many places _still_ have
| centrally synchronized clocks.
|
| When there are about 100 clocks distributed around a building,
| and not yet migrated to individually-kept radio/GPS/network time,
| the only staff-sanity preserving method of keeping them together
| is to use a central electronic pulse transmitted over the power
| lines (which the clocks are plugged into).
|
| If I recall right, there is an hourly pulse that tells the clocks
| to wait/speed up until the top of the hour is reached. Then
| there's a daily pulse that tells them to wait/speed up to reset
| to midnight!
| londons_explore wrote:
| I wonder what reliability was like... With just one pipe
| accidentally cut, the pressure across the pipe network might not
| rise high enough to 'tick' the other clocks.
|
| And if the clocks ever got out of sync for any reason, there
| doesn't seem to be any way to get them back in sync - for example
| they could have used a vacuum on the same pipes to 'suck' for a
| minute before midnight, and use a mechanical system which would
| fast-forward all clocks to midnight at that point.
| londons_explore wrote:
| An easy way to do 'syncing' is to have a pin stopping the clock
| passing midnight or passing the 'o'clock' position or
| something. That pin is only lifted by double the normal
| pressure.
|
| Then, in the minute before midnight, you tick the clock say 3
| minutes, with the final one being double the normal pressure
| allowing every clock to pass midnight.
|
| That should mean every clock on the network that is up to 3
| minutes slow will fastforward to being correct. And any clock
| that is fast will stop till the midnight sync signal. If a
| clock is way off (eg. 5 hours), then when it reaches midnight
| it will halt till it gets the signal to continue, and from
| tomorrow will be correct.
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