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Old September 3rd, 2014, 09:07 PM   #8441
Sunfuns
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The limiting factor is a cost not physics. At least at speeds we are talking about.
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Old September 3rd, 2014, 11:05 PM   #8442
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And Alstom AGV was built for same energy use and cost at 360 km/h as TGV at 300 km/h...
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Old September 4th, 2014, 12:14 AM   #8443
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Originally Posted by China Hand View Post
This is why Japan has HSR of 320kph and is developing MagLev to travel at 505kph. Get rid of the wheels and rails.
Chuo Shinkansen should be 286 km long between Shinagawa and Nagoya, cutting a detour of Tokaido Shinkansen that is 335 km between these stations. Chuo Shinkansen shall cover that distance in 40 minutes, with average speed 429 km/h.

There are plans to build a shortcut railway between Shanghai and Beijing via Lianyungang, that would be 1080 km long.

At the 429 km/h average speed of Chuo Shinkansen, the trip time should be 2:32.
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Old September 5th, 2014, 09:13 AM   #8444
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Originally Posted by chornedsnorkack View Post
Yes, but note that planes fly at 900 km/h!

..
Plane are governed by slight different (and vastly more complex) set of physics compared to just simple drag friction in trains. However, generally it's cheaper more energy efficient to run trains than planes. And that is reflected on AVERAGE cost of a plane ticket. However, precisely because planes are so costly to run, they have developed a very advanced system of dynamic pricing on plane seating to sure it's filled all the time and all price levels are presented to the consumer.


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Originally Posted by foxmulder View Post
More than three years, trains run at 350km/h in China. Physics didn't mind much. People used to say "300km/h is maximum" back then. Now, some other countries, other than China, is running at 320km/h and the limit physics let us increased to 320km/h. LOL.

The limit of physics isn't it can't be increased to 320km, it is that while speed (the utility presented to the consumer) increases linearly; energy and drag (the cost presented to the operator) increase exponentially.

Since in optimal point is where marginal utility meets marginal cost, the speed those systems choose to operate which depend on how much the consumer value speed and willing to pay for it, how efficiency the technology is, energy cost and how much government subsidy exist to support the transportation system running at negative economic profit. (One caveat though, higher operating speed can mean fewer trains needed to achieve the same throughout and tempo. Assuming throughout demand and tempo is high enough for this effect to kick in. So under some very specific circumstances, higher speed might have negative marginal cost)



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Originally Posted by 33Hz View Post
And Alstom AGV was built for same energy use and cost at 360 km/h as TGV at 300 km/h...
The non-fallacious comparison would be AGV running at 360 km/h vs AGV running at 300 km/h or TGV running at 360 km/h vs TGV running at 300 km/h.

Last edited by luhai; September 5th, 2014 at 09:46 AM.
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Old September 5th, 2014, 11:51 AM   #8445
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However, generally it's cheaper more energy efficient to run trains than planes. And that is reflected on AVERAGE cost of a plane ticket.
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Originally Posted by luhai View Post
The limit of physics isn't it can't be increased to 320km, it is that while speed (the utility presented to the consumer) increases linearly; energy and drag (the cost presented to the operator) increase exponentially.
No, the drag part of cost does not increase exponentially. It only increases with square of the speed, as long as the speed is not transonic.
And the utility presented to the consumer is not quite linear function of speed either.
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Originally Posted by luhai View Post
Since in optimal point is where marginal utility meets marginal cost, the speed those systems choose to operate which depend on how much the consumer value speed and willing to pay for it, how efficiency the technology is, energy cost and how much government subsidy exist to support the transportation system running at negative economic profit. (One caveat though, higher operating speed can mean fewer trains needed to achieve the same throughout and tempo. Assuming throughout demand and tempo is high enough for this effect to kick in. So under some very specific circumstances, higher speed might have negative marginal cost)
Compare a railway 100 km long running at 100 km/h with a railway of same length but running at 50 km/h. Both have 1 departure per hour.
The 100 km/h railway has 1 train running at a time (not counting the trains on return trip and in depot). The 50 km/h railway has 2 trains running (and also has trains on return and in depot).

Each train running at half the speed has one quarter the air drag and energy cost of one train at full speed. So the two slow trains combined have half the energy cost of one fast train. Yet the cost of owning and crewing the two slow trains is double the cost of owning and crewing one fast train. So, if the total operating cost is dominated by air drag, then higher speed costs; if air drag is the smaller component compared to owning and crewing the trains then higher speed saves costs.

And either way, higher speed has higher utility for the passenger (with the limited exception of overnight trains shorter than proper night´s sleep).

That´s an example of utility decreasing with shorter trip time. But there are other parts where utility depends nonlinearly on trip time.

There are several major origin/destination pairs in China where current HSR times are in the region of 4...5 hours:
Beijing-Shanghai G1 and G3 4:48
Beijing-Shenyang G2583 4:05 (but at odd hours!)
Beijing-Hangzhou G31 5:07
Beijing-Wuhan G79 4:17
Beijing-Xian G87 4:30
Shanghai-Wuhan G576 4:56
Longhua-Fuzhou D2282 5:09

I have a suspicion that on these routes, where being major routes competing flights also exist, the utility of a train is comparable to utility of plane taking into account airport delays. For that reason, I suspect that modest improvements of speed from 300 km/h to 320, 350 or 380 km/h might bring nonlinear improvements of passenger utility, making train preferrable to plane which it now is not.

Are there any definite plans to make these improvements?
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Old September 5th, 2014, 12:25 PM   #8446
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The limiting factor is a cost not physics. At least at speeds we are talking about.
More money won't fix it, this not an issue of government lack of spending, the physics will force the trainsets into the shop for an overhaul after every run if you increase the velocity enough.

Think of Formula one racecars. They are completely rebuilt after one race.

The time involved to maintain a trainset at higher velocities just runs into practical issues of not enough hands and not enough time, even with unlimited funds.
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Old September 5th, 2014, 12:34 PM   #8447
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But if you compare a plane with train, the plane has a lot of drag caused by wings and tail, which the plane needs to remain in air. A train containing the same size passenger cabin does not need and does not have wings nor tail. It follows that a train travelling at 450 km/h on ground should have less drag, spend less energy and be cheaper to operate than a plane flying at 450 km/h near ground or at 900 km/h at a cruise level.
Zero lift drag coefficient of an A380 is 0.032.
Cd drag coefficient of HSR is ~ 0.064

Aircraft are 3D tubes, trains are flat on many surfaces by necessity.

More drag is from wheels, pantograph, catenary and the length of the carriages. The nose has little to do with it, and is that shape to merge the airstreams at the rear of the trainset.
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Old September 5th, 2014, 06:49 PM   #8448
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Zero lift drag coefficient of an A380 is 0.032.
Cd drag coefficient of HSR is ~ 0.064

Aircraft are 3D tubes, trains are flat on many surfaces by necessity.

More drag is from wheels, pantograph, catenary and the length of the carriages. The nose has little to do with it, and is that shape to merge the airstreams at the rear of the trainset.
First of all, comparing high speed trains to planes is unnecessary but if we are going to do it, we can be a little bit better than this.

First, area/cross section is a critical parameter to figure our total drag. When you think the huge cross section of A380 it is very easy to tell that A380 has much more drag than a CHR380A.

Second, it is not fair to include everything for train (wheels, pantograph, catenary) and exclude the wings ("Zero lift drag coefficient") from the plane.

And it is humorous to think what speed a CRH380A can reach if 4 TRENT-900 stuck to it even at sea level!!!

Last edited by foxmulder; September 5th, 2014 at 06:54 PM.
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Old September 5th, 2014, 06:52 PM   #8449
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Quote:
Originally Posted by China Hand View Post
More money won't fix it, this not an issue of government lack of spending, the physics will force the trainsets into the shop for an overhaul after every run if you increase the velocity enough.

Think of Formula one racecars. They are completely rebuilt after one race.

The time involved to maintain a trainset at higher velocities just runs into practical issues of not enough hands and not enough time, even with unlimited funds.
Yeah, you think material science, train design is stuck in 90s. There will be always developments.

And as I wrote, it is very ironic now people start to think the limit is 320km/h. It used to be 300km/h 2-3 years ago.
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Old September 5th, 2014, 08:48 PM   #8450
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Originally Posted by China Hand View Post
More money won't fix it, this not an issue of government lack of spending, the physics will force the trainsets into the shop for an overhaul after every run if you increase the velocity enough.

Think of Formula one racecars. They are completely rebuilt after one race.

The time involved to maintain a trainset at higher velocities just runs into practical issues of not enough hands and not enough time, even with unlimited funds.
You misunderstood. I was agreeing with you - possible to run at 400 km/h but costs too high due to energy costs as well as wear and tear.
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Old September 5th, 2014, 08:51 PM   #8451
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Originally Posted by foxmulder View Post
Yeah, you think material science, train design is stuck in 90s. There will be always developments.

And as I wrote, it is very ironic now people start to think the limit is 320km/h. It used to be 300km/h 2-3 years ago.
Airplanes fly exactly as fast now as 30-40 years ago. It is technically feasible to go faster, but then tickets will be only for Arabian sheikhs. Trains are no different only numbers are different. Maybe the limit is 352 instead of 320 with some superior materials, but those are just details.
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Old September 6th, 2014, 09:02 AM   #8452
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Very High Speed

Hi!

In China it is commercially circulated to 350 km/h between 01/08/2008 (Beijing-Tianjin) and at least 28/08/2011 (Wuhan-Guangzhou), to my knowledge. From 01/07/2011 was reduced line-to-line speed. CRH2C-2 and CRH3C circulated at that speed were.
Previous plans were that the Jinghu PDL (Beijing-Shanghai) had a top speed of 380 km/h. After many problems with the line and trains was opened to 300 km/h on 30/06/2011 and was announced to be circulated to 350 by the end of the year and 380 in 2012. After the policy change those plans were abandoned .
Currently cruising at 320 in some French lines (North, East and R-R) and the Tohoku Shinkansen in Japan. There is also a short distance to 310 in Spain (Madrid-Lleida: km: 64,400 to 124,400) and circulated to 305 in Korea.

JR East announced that it will reach 360 km/h on the Tohoku Shinkansen in 2020 with the E5 series.
SNCF in France announced that the GPSO line (Bordeaux-Toulouse, in 2024) will be achieved 360.
In Italy announced the 330 to 2011 in Milano-Torino and Rome-Naples, but not fulfilled. Now they want to standardize to 360 km/h both ETR 575 (Alstom AGV of NTV) as ETR 1000 (Bombardier-AnsaldoBreda V300Zefiro of FdS).

In China, Italy and Japan are ballastless track, in France is circulated on ballast. The V150 test in France, where reached 574 km/h was performed in a specially prepared section, but also had ballast (I can not explain how!!!).
There is a korean prototype called HEMU 430X intended reach 430 km/h.

A greeting, and sorry for my bad english
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Old September 6th, 2014, 01:27 PM   #8453
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Originally Posted by Sunfuns View Post
Airplanes fly exactly as fast now as 30-40 years ago. It is technically feasible to go faster, but then tickets will be only for Arabian sheikhs. Trains are no different only numbers are different. Maybe the limit is 352 instead of 320 with some superior materials, but those are just details.
Some think that if we could only get a high tech syfy wheel, or rail, or train, and that it was made of something new, that the speeds could continue to increase without bound.

That's not what will happen.

What is needed is a new mode of transport.

Maglev has been in development for 45 years, and look where it is now.
Solving these issues is non-trivial.

HSR as it is today will be improved in small amounts.
320 will rise to 350 or 360, but for the most part 80% or more of what we can do has been done.
To go much faster will require a new way of transport - the step beyond maglev.

The air is still there, aircraft are limited to 825 kph for commercial subsonic, economical flight.

If commercial trains (not one off tests) ever get to 80% of that - 660kph on a maglev - it will be a major accomplishment. I do not expect commercial maglev service at 660 kph in the next 40 years.

To go faster will require the next type of transport, something not invented yet.
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Old September 6th, 2014, 06:25 PM   #8454
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lets talk about economic feasibility, not technological one, we know that barriers are already broken, the problem is if people will pay to arrive few minutes earlier than they already do now and if maintenance and investment worth it.
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Old September 7th, 2014, 05:54 AM   #8455
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Nanchang-Changsha HSR to open on Sep 16

Nanchang-Changsha HSR is part of Shanghai-Kunming HSR
342km, 7 stations
Speed: 350km/h

(@央视新闻)
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Old September 7th, 2014, 08:55 AM   #8456
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Nanchang-Changsha HSR to open on Sep 16

Nanchang-Changsha HSR is part of Shanghai-Kunming HSR
342km, 7 stations
Speed: 350km/h

(@央视新闻)
For comparison, Wuhan-Changsha HSR, open since December 2009, is 348 km long.

It has arguably up to 7 stations, too:
arguably Wuhan
arguably Wulongquan East
  1. Xianning North
  2. Chibi North
  3. Yueyang East
  4. Miluo East
arguably Changsha South

On 16th September, shall trains travel at 350 km/h Nanchang to Changsha, and then slow down to 300 km/h on the Wuhan-Guangzhou high speed railway?
What shall be the best travel time Nanchang-Guangzhou on 16th September? Wuhan-Guangzhou is now 3:39.
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Old September 7th, 2014, 09:58 AM   #8457
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Most likely 350 km/h refers to the design characteristics of the line not the actual speed of comercial service.
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Old September 7th, 2014, 12:05 PM   #8458
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Most likely 350 km/h refers to the design characteristics of the line not the actual speed of comercial service.
The way chorned put it it sounded as if he took 350km/h as a service speed. I would understand that 350km/h mentioned by big dog referred to the design speed like most other 350km/h lines that actualy run at 300-310km/h.
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Old September 7th, 2014, 12:32 PM   #8459
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of course 350 is design speed, there's no Chinese HSR trains run at 350 as of now.
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Old September 7th, 2014, 01:11 PM   #8460
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Why are trains running at 305/308 km/h?
¿Delays?
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