Author Topic: High Speed Railways  (Read 432 times)

Leisured

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High Speed Railways
« on: November 29, 2018, 04:07:13 AM »

I have recently travelled by train over parts of Europe, and have been amazed at the smooth, stable ride at speeds of up to 300 km per hour. The track is rail on ballast, as it has been for 180 years.

How do the European railways keep the track so stable? I have looked at some rail forums but the contributors donít seem to have any technical knowledge. I have seen Youtube videos of ingenious rail maintenance equipment, but I am not much the wiser. One of the high speed trains I travelled on, between Lille and Charles de Gaulle airport, was double decker, at 300 km per hour! Any side to side rocking will be amplified by two decks.

There have been proposals for over a hundred years to have rail carriages stabilised by gyroscopes, spinning round a vertical axis. The original plans were to replace two rails with one, and have an active gyroscope using precessional forces to stabilise the carriages. I can see that a gyroscope stabilising a conventional two rail train could be passive, and rely on the inertia of the spinning gyros to dampen side to side movement. I have not heard that gyros are used to stabilise trains.

Any ideas?


Just Joe

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Re: High Speed Railways
« Reply #1 on: November 29, 2018, 08:50:01 AM »
Seems like I heard the European rails are welded together rather than bolted.

https://www.youtube.com/watch?v=5uxsFglz2ig

ncornilsen

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Re: High Speed Railways
« Reply #2 on: November 29, 2018, 11:36:12 AM »
I imagine someday, someone will bomb all of our existing infastructure into oblivion. Then we can completely rebuild it and make it as smooth as glass, instead of patching the existing stuff together.


cerat0n1a

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Re: High Speed Railways
« Reply #3 on: November 30, 2018, 06:13:06 AM »
Seems like I heard the European rails are welded together rather than bolted.

Not an expert, but I think rails have been continuous welded everywhere for last 60+ years?

I think speed limits on US trains have a whole host of factors. There are a variety of speed limits imposed due to signalling, track condition, curvature, the amount of grade crossings, the condition of the rolling stock etc.

In terms of avoiding oscillation, AFAIK it's mainly down to the design of the wheels and suspension. No need for any fancy gyroscopes. Plenty of technical details on the French TGV on the web if you look.

PDXTabs

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Re: High Speed Railways
« Reply #4 on: November 30, 2018, 09:24:33 AM »
I imagine someday, someone will bomb all of our existing infastructure into oblivion. Then we can completely rebuild it and make it as smooth as glass, instead of patching the existing stuff together.

This is wrong for so many reasons:
  • The big European rail push didn't come until the oil crisis in the 1970s.
  • Large parts of the Iberian peninsula were never bombed.
  • We completely rebuild infrastructure all the time. At least we used to, when we paid for infrastructure.

Just Joe

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Re: High Speed Railways
« Reply #5 on: November 30, 2018, 12:47:43 PM »
You mean do it right the next time it needs repair? Long term choices rather than short term choices which are the cheapest? The USA seems to have troubles with this. Fast and cheap seem to be our cultural specialty.