Do I understand correctly that trains must slow down in extremely hot weather, such as what we have been experiencing in Texas? If this is true, what are the reasons? Also, what would the top speed be for Amtrak's trains in Texas?
With continuous welded rail, the risk is sun kinks caused by the expansion of the rail. Rail anchors are used to combat this problem, but the risk still exists. Perhaps the mudchicken or some of the other engineering experts can explain better.
Trains had an article on this subject a while back. Each railroad has its own rules for both severe heat and extreme cold. This affects Amtrak, and might affect high speed rail passenger services as well; but I don't know how this is or can be handled.
The beauty of jointed rail was that every 39 feet there was a joint with space which (inadvertenly?) absorbed expansion and contraction of rail as temperatures change. But in ribbon or welded rail, there is not that joint space so the rail dispacles itself from a straight line when temperatures change. That's not an engineering, technical nor scientific explanation, but it is an explanation.
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It is also my understanding that welded rail if laid on concrete ties is less apt to have sun kink problems as concrete helps dispense the heat while wood does not. Also the weight of concrete ties compared to wood help with the problem, I did not read the article in trains will have to go back and look it up.
Al - in - Stockton
Example:
New York to New Haven,
"Rule 1177-Q Weather Restrictions During periods of extreme temperatures, speed restrictions will be in effect due to possibility of catenary damage and/or rail irregularities." "Permanently installed 60 mph speed signs, blue numerals on white background, installed on catenary poles at point of restriction."
A chart that shows in actual Mile Posts, not all track and curves:
Level 1, above 80 F and below 32 F, 60 mph in curves
Level 2, above 90 F below 15 F, 60mph curves 70mph in most other areas
Level 3 below 5 F, 60mph
Don U. TCA 73-5735
Today in Stockton the temperature will be 108 degrees and further south going to Bakersfield it will be even hotter. Temps in the high 90s are not all that unusual in the San Joaquin Valley during the summer months and we can expect 100 degrees on at least 23 days each summer.
Before we break ground in the valley on the HSR I think the heat alone alone would be a good argument to take another look at Maglev. Since Maglev does not actually touch anything along its guideway would it not make more sense than conventional HSR. The California system is supposed to travel at speeds between 200 and 220 mph does that mean only when temperatures are below 80 degrees. If that is going to be the case than HSR in California is only going to live up to its promised speeds for four months of the year. Shanghai has similar temps to the Central Valley and they have a very successful Maglev system that is not effected by the heat. It does consume more electrical power in extreme heat they do not say why, Is it more required for A/C or more for power it does not say.
DMUinCT Example: New York to New Haven, "Rule 1177-Q Weather Restrictions During periods of extreme temperatures, speed restrictions will be in effect due to possibility of catenary damage and/or rail irregularities." "Permanently installed 60 mph speed signs, blue numerals on white background, installed on catenary poles at point of restriction." A chart that shows in actual Mile Posts, not all track and curves: Level 1, above 80 F and below 32 F, 60 mph in curves Level 2, above 90 F below 15 F, 60mph curves 70mph in most other areas Level 3 below 5 F, 60mph
Is this old NYNH&H rules or MN rules. The CAT problem should be eliminated once all the constant tension CAT is installes. No more sags or snap intos.
I have been obsessed with sun kink every summer since VRE reports delays because of sun kink on CSX (but not Norfolk Southern) tracks.
Why can't there be an expansion joint? Is it hard to locate where the expansion joint would go? Is it just not feasible?
I still maintain that "sun kink" slow orders can and should be overcome by technology. CSX makes a big deal about it here in the Washington DC area. Curiously, NS does not.
passengerfan Before we break ground in the valley on the HSR I think the heat alone alone would be a good argument to take another look at Maglev. Since Maglev does not actually touch anything along its guideway would it not make more sense than conventional HSR. The California system is supposed to travel at speeds between 200 and 220 mph does that mean only when temperatures are below 80 degrees. If that is going to be the case than HSR in California is only going to live up to its promised speeds for four months of the year. Shanghai has similar temps to the Central Valley and they have a very successful Maglev system that is not effected by the heat. It does consume more electrical power in extreme heat they do not say why, Is it more required for A/C or more for power it does not say. Al - in - Stockton
Al, I don't think it's a problem for dedicated or new railway systems. The problem I believe arises with existing railway systems that are half upgraded / half not. As we have with the Amtrak Northeast Corridor and most of the Private Railway network in this country. Dallas Area Rapid Transit (DART) has no such speed restrictions in hot weather (70-75 mph top speed) nor does it have issues with sun kinks that I am aware of. Older roadbeds have the issues as they do also with failing subgrades, washouts, etc.
Maglev is very, very expensive to build and maintain.
blue streak 1 DMUinCT Example: New York to New Haven, "Rule 1177-Q Weather Restrictions During periods of extreme temperatures, speed restrictions will be in effect due to possibility of catenary damage and/or rail irregularities." "Permanently installed 60 mph speed signs, blue numerals on white background, installed on catenary poles at point of restriction." A chart that shows in actual Mile Posts, not all track and curves: Level 1, above 80 F and below 32 F, 60 mph in curves Level 2, above 90 F below 15 F, 60mph curves 70mph in most other areas Level 3 below 5 F, 60mph Is this old NYNH&H rules or MN rules. The CAT problem should be eliminated once all the constant tension CAT is installes. No more sags or snap intos.
It's the Metro North General Orders (not latest printing).
Most track speed is up to 90mph but with restrictions for type of locomotive and if freight or passenger. Metro North runs the commuter trains, Amtrak the through service (including Acela), and P&W freight.
Metro North is replacing the old New Haven catenary (1904 - 1914) but NOT with Constant Tension Catenary. No money in Connecticut.
henry6 The beauty of jointed rail was that every 39 feet there was a joint with space which (inadvertenly?) absorbed expansion and contraction of rail as temperatures change. But in ribbon or welded rail, there is not that joint space so the rail dispacles itself from a straight line when temperatures change. That's not an engineering, technical nor scientific explanation, but it is an explanation.
Sun kinks were also a problem in the days of jointed rail. That type movement within a joint would require the joint bars to be somewhat loose, not a good situation, especially as train speeds increase.
Yes, they were a problem, but not as common today. Plus you used to have a section gang for every 5 to 10 miles of railroad.
passengerfanToday in Stockton the temperature will be 108 degrees and further south going to Bakersfield it will be even hotter. Temps in the high 90s are not all that unusual in the San Joaquin Valley during the summer months and we can expect 100 degrees on at least 23 days each summer. ..... The California system is supposed to travel at speeds between 200 and 220 mph does that mean only when temperatures are below 80 degrees. If that is going to be the case than HSR in California is only going to live up to its promised speeds for four months of the year. ..... Al - in - Stockton
..... The California system is supposed to travel at speeds between 200 and 220 mph does that mean only when temperatures are below 80 degrees. If that is going to be the case than HSR in California is only going to live up to its promised speeds for four months of the year. .....
There is nothing universal about the temperature of 80 degrees. More important is the variance from the neutral temperature of the rail, which will depend on the local climate. The neutral temperature is chosen to be the best compromise between tension forces on the coldest day and the compressive forces on the hottest day for the region. I assume the Central Valley does not often get -40 degree winter days so the neutral temperature will be rather higher than the Alaska Railroad probably uses.
Sun kinks, also known as track buckles and thermal misalignments, are usually the result of weak track structures. The ballast should be up to nearly the top of the tie, and extend a foot or more beyond the tie end before sloping down to the roadbed. The ballast stones should be irregular (fractured faces) so that they create an interlocking bed. And of course the rail must be solidly anchored against enough ties so that stresses do not build up in any one spot.
Many roads also have restrictions on performing certain types of track maintenance during high heat, since even minor disturbance of the ballast can trigger a sun kink.
Branch lines with jointed rail also experience sun kinks since they typically have weak track structures. Ballast is usually poor quality, and rather narrow in section. Years of rail creep due to minimal rail anchors has closed up joints. On a number of prairie branchlines here in Canada, in summer the railways avoid running trains during the middle of the day because of this risk.
John
jjtrainsMy wife and I just de-trained from Amtrak #1, the Sunset Limited, at Palm Springs, CA this morning a few minutes early. Yesterday, the run across southwest Texas, New Mexico and Arizona was made in 99 to 106 degree F temperatures with no speed reduction. Top speed was 82.6 mph with a lot of 79 mph running. Was wondering how the U.P. handles the "speed kink" problem on the ex-S.P. mainline so as to not require speed reductions. Amtrak #1 ran ahead of schedule the entire way. (We were actually in the #421 sleeper from Chicago, switched at San Antonio from the Texas Eagle to the Sunset Ltd.)
The quick answer is that as long as your track structure is designed, built and maintained to a high standard, sunkinks are unlikely to occur and there is no need to issue slow orders in hot weather. But of course this requires that management allocate the necessary resources to the track department, which the stock analysts may not like. And, there must be enough traffic on the line to justify such expenditures, which is why these "heat slows" are more often found on secondary mains and branch lines.
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