Acela Speeds

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Acela Speeds

Postby quadrock » Mon Nov 21, 2005 12:54 am

Hey all...I seem to remember that the Acela's were taken out of service because of cracks found in the brakes during testing for higher speeds in New Jersey between Newark and Trenton. Anyone know if these tests were completed and what came/will come out of them??
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Higher Acela Speeds in NJ???

Postby NellieBly » Mon Nov 21, 2005 2:48 pm

I'm not aware of any plan or testing having to do with increased speeds for AE in New Jersey or anywhere else. Current top speed is limited to 135 south of NYP by the old, variable-tension catenary. New constant-tension catenary will be needed for higher speeds.

As for curve speeds, AE was designed to run at nine inches of unbalance. Due to tracking problems on curves, Amtrak has never requested, and FRA has never permitted, operation at more than seven inches of unbalance. This has nothing to do with the tilting feature, which is only for passenger comfort, but rather to truck hunting problems. Also, FRA has restricted AE to a max of 130 MPH on *any* curve.

I don't think any of this will change in the near future.
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Postby hsr_fan » Mon Nov 21, 2005 3:38 pm

Actually, the brake rotor problem was reportedly discovered on an Acela Express trainset following a test run in NJ intended to lead to increased speeds. I don't think they plan to raise the top speed from 135 to 150 until the catenary is replaced, but I'm guessing that there might be some curves where they're currently not even operating at seven inches of unbalance, and they would like to.
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Postby quadrock » Mon Nov 21, 2005 7:39 pm

What exactly is the difference between constant and variable tension catenary and how expensive is it to replace? Also, does NJ Transit's lines (Montclair-Boonton, Morris & Essex, North Jersey Coast Line) use constant or variable tension wire?
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Postby hsr_fan » Mon Nov 21, 2005 8:43 pm

Constant tension catenary uses pulleys and weights every so many feet to maintain the tension of the wire. Not sure exactly how the catenary wire is connected, and insulated from the pulley and weight portion. The only NJT line that I know has constant tension catenary is the Coast Line from Matawan to Long Branch.
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Postby Nasadowsk » Mon Nov 21, 2005 9:26 pm

I can ask, but I think parts of the M&E are in fact constant tension.

Basically, constant tension means that the system is weighted at one end, so that the wire never really dips, sags, or moves out of alignment. As long as you hold the tension on the wire at a more or less constant, it will stay where you put it, and do so very easily. Also, the wire behaves the same at every temperature.

Normal catenary holds the wire at a fixed tension - that is, they set it when it's put up, and it stays at that tension. But only at that temperature. The tension drops in the heat, rises in the cold. Extremes either way can break the wire or cause too much sag. It's fine for some applications, like slow speeds or terminals, where you can ditch the weight system, though any new construction uses constant tension because it's pretty much standard - the parts for a 600VDC system are catalog items, even in the US (all that LRT adds up!)

IMHO, the bigger limiting factor is the signal system - no ACSES below New Haven. IIRC, 135mph only happens under certain cases.

As for 9 inches? Not going to happen.
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Postby hsr_fan » Mon Nov 21, 2005 9:40 pm

Nasadowsk wrote:IMHO, the bigger limiting factor is the signal system - no ACSES below New Haven. IIRC, 135mph only happens under certain cases.


You sure about that? I was pretty sure they have it on the 135 mph stretch through NJ.
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Postby Nasadowsk » Mon Nov 21, 2005 10:49 pm

Yes, but it's not a given. I've read it only happens when certain traffic conditions are met. i.e., your train may/may not run 135. For the few miles it's going to, it makes no difference in running time, just like going 150 in Mass makes almost no difference - Amtrak could achive the same results with tighter scheduling and 125mph operation, and at less cost.
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Postby quadrock » Mon Nov 21, 2005 11:49 pm

How expensive would it be to change out the catenary to constant tension? I'm assuming that north of New Haven to Boston is already constant, and that everything south of New Haven - New York - Washington would need to be upgraded, am I right? And does Amtrak currently have any plans/cost estimates of what this would cost?
I'm also assuming that new catenary would also get the newer voltage that the Morris & Essex have, negating the need for phase changes.
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Postby Jersey_Mike » Tue Nov 22, 2005 1:51 am

How expensive would it be to change out the catenary to constant tension? I'm assuming that north of New Haven to Boston is already constant, and that everything south of New Haven - New York - Washington would need to be upgraded, am I right? And does Amtrak currently have any plans/cost estimates of what this would cost?


It would cost a * and its not even necessary. The Metroliners went 150 IN SERVICE before the speeds were dropped due to unsafe track conditions. The wonderfully engineered PRR catenary is not to blame.

any new construction uses constant tension because it's pretty much standard - the parts for a 600VDC system are catalog items, even in the US (all that LRT adds up!)


LRT systems really need to behave more like the trolley lines that came before them. That CT cat is a waste of money, pure and simple. If drooping is really a problem just send out the wire-gangs twice a year to re-tension the wire just like they did in the old days. Except for the curves many light rail lines could probably support high speed trainsets. Its insane.

Anyway, back to the ACELA, I don't know what ACSES has to do with anything as that is just for curves and the like. The additional cab signal aspects have already been implemented on the NEC, so Amtrak would just need to re-do the block logic for CLEAR 150.
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Postby quadrock » Tue Nov 22, 2005 2:56 am

So Amtrak could theoretically go 150 in this section, or are there new FRA rules in place since then that forbid it with non-constant tension catenary. Also, what exactly are the advantages of the newer electric phase of catenary that were installed in the New Haven-Boston project, and NJ Transit property?
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Postby Ken W2KB » Tue Nov 22, 2005 9:02 am

quadrock wrote:How expensive would it be to change out the catenary to constant tension? I'm assuming that north of New Haven to Boston is already constant, and that everything south of New Haven - New York - Washington would need to be upgraded, am I right? And does Amtrak currently have any plans/cost estimates of what this would cost?
I'm also assuming that new catenary would also get the newer voltage that the Morris & Essex have, negating the need for phase changes.


I attended an IEEE local meeting a few years ago, with the main agenda item a presentation by Amtrak engineering (professional, not locomotive) management on the electrification project from New Haven to Boston. They mentioned the plans that existed to upgrade the rest of the NEC to 25kV, 60Hz, constant tension. They also mentioned that the PRR catenary and supporting structures were nearing the end of their useful life and would eventually need replacement.

The project would be very expensive, on the order of magnitude of a billion dollars, and because of the need to keep the very busy corridor trains running, actual construction would take about 10 years to accomplish.
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Postby Ken W2KB » Tue Nov 22, 2005 9:10 am

Jersey_Mike wrote: The wonderfully engineered PRR catenary is not to blame.


Certainly well engineered, but 70 plus years of use, and decades of less than optimim maintenance have taken their toll. It will need to be replaced sooner rather than later. A lot of the supports and infrastructure are in relatively poor condition, far worse than an electric utility would tolerate for its transmission assets.

Even the well engineered PRR stuff, in prime shape, would sag on very hot days, worse with heavy electric loading, thereby limiting speeds from time to time. Replacing it all with constant tension is probably not significantly different in cost than replacing it all in the old design. It would be done in conjunction with conversion to 25kV and 60Hz, both distinct advantages.

I belive that while the PRR design works well, the constant tension design is superior.
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Postby pgengler » Tue Nov 22, 2005 9:46 am

Would a move to 25kV affect operation in some of the tighter spaces, like the Hudson River tunnels? I seem to recall hearing/reading somewhere that the high voltage requires roughly twice as much clearance between the locomotive/car roofs and the catenary as 11kV/12.5kV, and it's close in the tunnels (perhaps also in Baltimore).
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Postby Ken W2KB » Tue Nov 22, 2005 12:29 pm

pgengler wrote:Would a move to 25kV affect operation in some of the tighter spaces, like the Hudson River tunnels? I seem to recall hearing/reading somewhere that the high voltage requires roughly twice as much clearance between the locomotive/car roofs and the catenary as 11kV/12.5kV, and it's close in the tunnels (perhaps also in Baltimore).


It requires greater clearance, but the relationship is such that it is not close to doubling. It is in the range of 20 to 25 percent greater clearance to go from 12.5 to 25kV. (e.g., a 12 inch insulator would have to be changed to about 15 inch). Whether that is problematic in either tunnel, I don't know. However, if the equipment can change voltage on the fly, as does Acela and others, it would not be costly to have a transformer at the tunnels to reduce the voltage to 12.5 kV therein. For the Baltimore tunnels it would be possible to increase the height; for the North River, no, but the two additional tunnels proposed could be sized accordingly.
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