Acela Speeds

[ApproachMedium]

There is nothing variable about fixed tension catenary. Its fixed. it sits one way and thats it. There are no adjustments. I dont know why i keep seeing it called variable here.

[EuroStar]

constant tension catenary does hold up much better in weather changes, but the stretch they did the work on almost never has downed wire because its straight and pretty simple. A place to have CT wire is down in maryland where its close to all of those rivers and high winds. Theres always problems with wire down there. Other than the signal upgrades i think a lot of this project was a waste and the concepts and money could have been better spent elsewhere

Yes, the money could have been used much better elsewhere, but accounting for the politics, this was probably the only option. It was a High Speed grant money, and if they used it on a stretch to lift the speeds from like 85 to 120, that would have not cut it with the purpose of advertising it as a "High Speed" grant. The reality though is that what this and pretty much every passenger line in the US needs is increases in the average speeds, not short segments of high speed running. Rising the lowest speeds is where most of the time gains are to be had.

[gokeefe]

There is nothing variable about fixed tension catenary. Its fixed. it sits one way and thats it. There are no adjustments. I dont know why i keep seeing it called variable here.

Likely misunderstanding in what "varies" on "constant tension" wire. Pullies with weights may go up and down but the tension remains the same. What is truly "variable tension" would be the old wire which could get tighter or looser depending on climate because of the "fixed" points of attachment.

Regardless, I'm happy to see the project in NJ wrapping up. Now on the the harder stuff.

[ApproachMedium]

I finally ran by the 2 track part of the high speed section. It looks no different than when i saw it 2 months ago. They really take forever to get any of this done. No new wire up yet at all.

[Ken W2KB]

There is nothing variable about fixed tension catenary. Its fixed. it sits one way and thats it. There are no adjustments. I dont know why i keep seeing it called variable here.

It is not intentionally variable in tension but in fact the tension varies. It's called that because the tension varies substantially with temperature of the metal - the contact wire and the suspension wires expand and contract with temperature thus changing the tension. Very hot weather compounded by electrical current resistance heating results in sagging and extremely cold weather can cause over tension to the point of separation failure. So since the tension varies, it is in that sense variable, not variable in the sense of capable of routinely being adjusted through some sort of control mechanism.

[gokeefe]

This may be an explanation accepted among the enthusiast community but the language is not accepted by the technicians. Hence the disagreement ...

[ApproachMedium]

There is nothing variable about fixed tension catenary. Its fixed. it sits one way and thats it. There are no adjustments. I dont know why i keep seeing it called variable here.

It is not intentionally variable in tension but in fact the tension varies. It's called that because the tension varies substantially with temperature of the metal - the contact wire and the suspension wires expand and contract with temperature thus changing the tension. Very hot weather compounded by electrical current resistance heating results in sagging and extremely cold weather can cause over tension to the point of separation failure. So since the tension varies, it is in that sense variable, not variable in the sense of capable of routinely being adjusted through some sort of control mechanism.

But, there is no "tension" the wire is hung, its HUNG from the insulators. There is no pulling on it, no tension. Thats why its called fixed tension. If you watch them take down the old wire between county and midway you can see this. As the temps rise the wire can sag more but the difference isnt much. Where it really matters is when a train goes by. If you see what the fixed tension wire does, it bounces because of it just hanging there. This bouncing effect can ripple in front of and behind the train. More so behind the train. Sometimes so bad that it causes contact issues on adjunct tracks. And if fast enough as well, can cause problems on trains with multiple pantographs.

[Ken W2KB]

I think we are talking past each other. I was speaking as an engineer, from both a physics and engineering standpoint, and having seen tension and sag studies by other engineers for electric utility transmission and distribution conductors which like railroad catenary messenger, hanger and contact wire systems are hung from insulators from overhead supports. The tension and sag does vary considerably with temperature. As an example, this whitepaper I found online describes among other things the methodology for calculations. http://home.eng.iastate.edu/~jdm/wind/T ... AndHTS.pdf I am reasonably certain that the original PRR engineers used the best methodology available at the time, which would have included these factors, in the design of the catenary system.

[ApproachMedium]

I am just telling everyone what the railroad calls it and how we differentiate the two things. Railroad terms dont always mesh with the nitty gritty engineering terms

[Ken W2KB]

I am just telling everyone what the railroad calls it and how we differentiate the two things. Railroad terms dont always mesh with the nitty gritty engineering terms

Thanks. There are odd or slang or seemingly confusing to outsiders terms in many if not most industries I suspect. For example the transportation of electric power via transmission lines is called "wheeling" in the electric utility industry. No wheels whatsoever involved.

[Ken W2KB]

I am just telling everyone what the railroad calls it and how we differentiate the two things. Railroad terms dont always mesh with the nitty gritty engineering terms

Thanks. There are odd or slang or seemingly confusing to outsiders terms in many if not most industries I suspect. For example the transportation of electric power via transmission lines is called "wheeling" in the electric utility industry. No wheels whatsoever involved.

[Arlington]

Speaking of Acela speeds, wasn't one of the limiting issues the operating speeds of other trains on the corridor?

are all the long-distance trains now operating at a hundred and twenty-five miles per hour now that they have new diners and baggage cars?

[STrRedWolf]

Speaking of Acela speeds, wasn't one of the limiting issues the operating speeds of other trains on the corridor?

are all the long-distance trains now operating at a hundred and twenty-five miles per hour now that they have new diners and baggage cars?

Limiting issues are speed of other trains over two-track sections, and the speed of some of those sections.

For instance: The B&P Tunnels. Max speed: 30 mph. Number of tracks? 2. Wouldn't be so bad... but MARC trains use it too. Oh, and the B&P Tunnels date back to the Civil War and are costly to keep in good repair. No word yet on the latest iteration of the Circle Tunnel which would up the speed to 79 mph AND have four tracks going through that shuffle outer track MARC locals to station tracks 4/5 and inner express/Amtrak trains to 6/7.

[ApproachMedium]

That B&P tunnel i barely trust doing 30mph in... Forget anything faster. The curves are 30 but i dont go over 25 because the forces will throw people around.

Adjunct tracks have nothing to do with the top speeds, but track spacing does a little bit. None of that is limiting the top speed to 135mph. The current trainsets are limited to 130mph around ANY curve with tilt enabled. The problem is that even if straight track is good for 160 or more, the cars get wheel climb in curves over 130mph. The newer trainsets will not have this issue so in areas where you can do 135, youll be able to stick to 135 even in the turns (for B speed regionals, they are 125 in the same curves usually)

The long hauls are still at 110 because the legacy viewliners are not overhauled yet to permit the 125mph operation. All of the new LDSL(View2) cars are good for 125.

[STrRedWolf]

Let me make it much clearer:

There are several sections of the NEC that are only two tracks, period. One in ether direction. They are shared between Amtrak and commuter trains. In Maryland, they're shared with diesel equipment on those commuters that can only do maybe 100 mph for the loads they have now (yes, the MP36's)... and they may be stopping because the station is right up ahead (WAS to NCR). So you got a slowdown there.

Add the section of the NEC called the B&P Tunnels which the curves are 30 mph (although going south I think the engineers go faster), plus you got ALL the trains going through it... and how many trains can you fit on one track through that section between West Baltimore and Baltimore Penn Station?

Now if you had four tracks from DC to New York, you put the outers to the commuter trains and the inners to Amtrak. Amtrak will go top speed for longer, because they don't have to muck with all those pesky commuter trains that are ahead of it -- they're on a separate track. They're no longer any concern for Amtrak trains.

In other words, <balmer>CAPACITY CAPACITY CAPACITY!!!</balmer>