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I was wondering about the speed records. I checked whether they are for real by 'extrapolating' the records of earlier trains. If we approximate the reduced power need from better aerodynamics with the 5% noise improvement, and train resistance with just the aerodynamic part, then some of the numbers add up:
  • a CRH2C with its original 7.2 MW power rating achieved a record of 370 km/h. The very same train, just by up-rating to 8.76 MW, should be capable of attaining 395.0 km/h – check: it achieved 394.2 km/h.
  • An also 8-car CRH380A is again up-rated to 9.6 MW. Assuming 5% less drag, 413. km/h should be possible – check: it achieved 416.6 km/h.

However, while the long trains should be faster, I get lower numbers:
  • A 16-car CRH380AL is more than twice as powerful (20.44 MW) while drag should be significantly less than twice as much: assuming 40-45% of the 8-car train's drag for the pantograph and front, the 16-car train should have about 50% more. However, I get only about 461 km/h.
  • A CRH3C had 8.8 MW and achieved 394.3 km/h. The 8-car CRH380B has a little less drag, say 2%, and more power (9.2 MW), but the relative increase is less than for the CRH380A. So, although there are no test results yet, it can be safely assumed that this will be a slower train, barely capable of passing 400 km/h.
  • The CRH380BL has exactly twice as much power, which, with the above figure for pantograph and front drag, wouldn't allow it to go faster than around 436 km/h!
  • After some trawling today, I discovered that the record run for the CRH380BL was conducted in a reduced 12-car formation (diary corrected accordingly). That means only about 25-30% more drag than the predecessor, and a 'predicted' maximum speed of around 466 km/h.

My extrapolations for the long trains are still around 20 km/h below the actual records. I am therefore guessing that the records were 'helped' by a downward slope or sustained tailwinds, or maybe even an 'overclocking' of the motors.

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Another editor's note: I added a picture for the Shanghai-Hangzhou line (messed up draft), and a sentence about the E5 Series Shinkansen's roof.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Jul 1st, 2011 at 05:27:33 AM EST
Done a great post, as you always do do, DoDo.  I wonder if you could measure the actual speed from the videos, perhaps timing against the overhead support posts?  There doesn't seem that much independent filming around though?
by njh on Sat Jul 2nd, 2011 at 06:05:52 AM EST
[ Parent ]
If post distance is the standard 75 m, then it should be a little under two posts per second. The clips are too short to say more than that it is around that.

But I'm not doubting that the measured speeds displayed on the monitor are sufficiently precise. Also, I should add a fourth possibility to tailwind, downward slope and motor overclocking: maybe the real outlier is the 8-car CRH380A record (i.e. it is 20 km/h less than it could be), and I am significantly underestimating the air resistance improvement for both types. It's a tall order, though: I estimate a 20% improvement for the CRH380A and a 13% one for the CRH380B would do the trick, but given that the improvement for the CRH380A front alone was just 10% and the pantograph wasn't replaced, underframe, sidewall and car joint improvements would have had to be very radical.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sat Jul 2nd, 2011 at 08:51:22 AM EST
[ Parent ]

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