7 ms·

Its sister tunnel - the Semmering Base Tunnel [0] - is scheduled to be completed in 2030. These two combined greatly reduce the travel time from Vienna to Graz

by dachris 9mo ago

Its sister tunnel - the Semmering Base Tunnel [0] - is scheduled to be completed in 2030. These two combined greatly reduce the travel time from Vienna to Graz and Klagenfurt (combined 1h 15m time saving). You don't hear that much about great engineering projects today, yet it's still an incredible feat to build those. [0] https://en.wikipedia.org/wiki/Semmering_Base_Tunnel https://en.wikipedia.org/wiki/Semmering_Base_Tunnel

ekjhgkejhgk 9mo ago
> You don't hear that much about great engineering projects today Here's a great engineering project: https://en.wikipedia.org/wiki/Hawthorne_test_tunnel https://en.wikipedia.org/wiki/Hawthorne_test_tunnel
- MattRix 9mo ago
  is it though?
  - groestl 9mo ago
    I guess sarcasm.
    - ekjhgkejhgk 9mo ago
      ;-)
- jimnotgym 9mo ago
  Serious question about hyperloop trains running in a vacuum. How do you cool the carriages?
  - sawjet 9mo ago
    The tunnels aren't perfect vacuums
    - jimnotgym 9mo ago
      That doesn't help me, I'm afraid. It must be low enough pressure to allow lower air resistance on the train, so must be a significant vacuum. Even if not a perfect vacuum, the carriage can presumably not exchange air with it, since the carriage is at a higher pressure. If you used aircon in the train the lower pressure air in the tunnel would be very poor at convecting heat away?
mikewarot 9mo ago
Holy cow... 16.7 Hertz[1] power? At first that's a really odd sounding choice to this Hoosier. Turns out it's 1/3 of standard 50 Hz in Europe. [1] https://en.wikipedia.org/wiki/15_kV_AC_railway_electrification https://en.wikipedia.org/wiki/15_kV_AC_railway_electrificati...
- ErroneousBosh 9mo ago
  They actually used that in the US as well for railways. I remember a post years ago on the Classic Computer Mailing List from someone who said that their father had worked on the railways and pointed out that the "high bay" station lighting all ran off 3-phase 16.7Hz power. Apparently it looked okay at ground level but was quite disconcerting when you looked up and saw the lights flickering in patterns of three.
  - MrFlynn 9mo ago
    Early AC electrification systems in the US were typically 25Hz, not 16.7Hz. Parts of the northeast corridor still use 25Hz electrification.
    - ErroneousBosh 9mo ago
      I'm trying to find the post, but it was definitely 16.7Hz. I don't know that it was particularly "early" as such, probably the 1950s or so.
- usr1106 9mo ago
  It used to be exactly one third, i.e 16 2/3 so you can have generators on the same axle. However, being exactly one third caused unwanted resonance effects. So with the advent of power electronics it has been slightly shifted to 16.7 Hz. Within tolerance for the motors, but no unwanted resonance anymore. My high school physics is not sufficient to really understand it.

by dachris 9mo ago

ekjhgkejhgk 9mo ago

> You don't hear that much about great engineering projects today Here's a great engineering project: https://en.wikipedia.org/wiki/Hawthorne_test_tunnel https://en.wikipedia.org/wiki/Hawthorne_test_tunnel

MattRix 9mo ago
is it though?
- groestl 9mo ago
  I guess sarcasm.
  - ekjhgkejhgk 9mo ago
    ;-)
jimnotgym 9mo ago
Serious question about hyperloop trains running in a vacuum. How do you cool the carriages?
- sawjet 9mo ago
  The tunnels aren't perfect vacuums
  - jimnotgym 9mo ago
    That doesn't help me, I'm afraid. It must be low enough pressure to allow lower air resistance on the train, so must be a significant vacuum. Even if not a perfect vacuum, the carriage can presumably not exchange air with it, since the carriage is at a higher pressure. If you used aircon in the train the lower pressure air in the tunnel would be very poor at convecting heat away?

mikewarot 9mo ago

Holy cow... 16.7 Hertz[1] power? At first that's a really odd sounding choice to this Hoosier. Turns out it's 1/3 of standard 50 Hz in Europe. [1] https://en.wikipedia.org/wiki/15_kV_AC_railway_electrification https://en.wikipedia.org/wiki/15_kV_AC_railway_electrificati...

ErroneousBosh 9mo ago
They actually used that in the US as well for railways. I remember a post years ago on the Classic Computer Mailing List from someone who said that their father had worked on the railways and pointed out that the "high bay" station lighting all ran off 3-phase 16.7Hz power. Apparently it looked okay at ground level but was quite disconcerting when you looked up and saw the lights flickering in patterns of three.
- MrFlynn 9mo ago
  Early AC electrification systems in the US were typically 25Hz, not 16.7Hz. Parts of the northeast corridor still use 25Hz electrification.
  - ErroneousBosh 9mo ago
    I'm trying to find the post, but it was definitely 16.7Hz. I don't know that it was particularly "early" as such, probably the 1950s or so.
usr1106 9mo ago
It used to be exactly one third, i.e 16 2/3 so you can have generators on the same axle. However, being exactly one third caused unwanted resonance effects. So with the advent of power electronics it has been slightly shifted to 16.7 Hz. Within tolerance for the motors, but no unwanted resonance anymore. My high school physics is not sufficient to really understand it.