"European" catenary on the North-East Corridor (USA)

About 10 years or so ago, the catenary on at least
some parts of the North-East Corridor were replaced
with what was touted as "Eurpean-style" catenary.
It was never explained exactly what was meant by that,
but it was claimed that the "European" catenary was
much better than the old.
I recall from my years in Europe that one of the most
distinctive things about the catenary there was that
the wire was tensioned using weights -- the wire
would be run out to a pulley, with weights hanging off
the larger diameter wheel to apply torque and thus tension.
This meant that the tension would remain constant
as the wire expanded and contracted.
By contrast, in the Northeast (USA), the contact wire is
just tied off to posts at either end. As far as I have
been able to tell in my occasional trips around here,
that's still the case.
Am I just not seeing the weights? If they're not there,
what exactly is "European" about the new catenary?
And, given the number of reports of catenary problems
when it's too cold or too hot, why aren't weights used
in the USA?
Reply to
Alan McKenney
Loading thread data ...
I'm somewhat curious about the electric circuitry feeding the catenary. The "new" section has, in addition to the catenary and contact wires, two insulated feed lines (one on each side) plus grounded returns. Nice and simple. In contrast, between NYC and New Haven, there are (old) pylons carrying multiple conductors for the catenaries plus some higher voltage circuits. For example, at the New Rochelle station there seem to be 15 12 kV conductors for track power (plus the catenaries for 4 tracks) there. Why so many?
Also, since the trains are large single phase loads, how do they try to balance the railroad as a whole over the three phase supply?
Where is the switchover between the 25 Hz power to the south and 60 Hz power? Right at Penn Station?
Reply to
Robert Hubbard
Portland Oregon has the variable weight system for it's Max Train catenaries. Not surprisingly, these were originally designed by a European contractor, I believe.
At certain pylons, there are tensioning weights that can be added or subtracted, as necessary. The system is very similar to the systems I recall seeing in France.
Reply to
Beachcomber
All of the new LRT systems in the US I've seen have constant-tension catenary in sections where they have exclusive ROW. Many use simple trolley wire (variable tension with just a contact wire, no catenary wire) for street-running sections, though.
S
Reply to
Stephen Sprunk
Some of the pylons I've seen in Portland have multiple weights that are semi-enclosed in a metal box. There is a sort of cotter pin arrangement that selects how many weights are actually providing tension.
My guess would be that the tension on the long spans might vary over time (as the wire is stretched). Also there might be seasonal variations throughout the year due to temperature (and conductor sag?).
I'm no expert though. Perhaps someone with specific knowlege of this setup can provide more insight.
Reply to
Beachcomber
... Also, It could be that once a specific weight is set for a particular span... It pretty much stays that way...
The multiple weights could just be for ease in setting a specific level of tension during construction.
Reply to
Beachcomber
Adam H. Kerman schrieb:
In theory, a fixed weight works nicely, but in the real world, track has all kind of curves and obstacles, so that you might not have the same length, or the same resistance to the pull, whatever.
In order to get done with the job (of setting up catenary) until the end of the day, you'll simply measure tension, and put up weights as needed. It's done this way since almost 100 years.
Hans-Joachim
Reply to
Hans-Joachim Zierke
Now I'm particularly confused. Of course I expected that the weights hung would be chosen based on observation of conditions, but once the observations are made, the counterweight is chosen.
When is a variable amount of weight used under daily operating conditions? I still don't know what the OP was talking about.
Reply to
Adam H. Kerman
Yes, but typically it will not be one solid weight. For practical reasons, the total weight is divided among smaller more easily handled weight. Just because you observe a number of weight blocks pulling the tension, does not mean that, once set, the tension is varied.
I don't think the weights are varied once set. I have never heard of a specifically designed "variable tension" system (other than the ordinary system where tension is uncontrolled and varies with temperature). The only reason the tension would change would be if gravity varied, not a likely occurrence.
Merritt
Reply to
Merritt Mullen
Adam H. Kerman schrieb:
If you have 10 standardized concrete blocks already hanging there, why do you want to produce a special one and replace them? Lots of specially produced weights are certainly more expensive than standard weights.
Never.
Hans-Joachim
Reply to
Hans-Joachim Zierke
Ok; that makes sense.
That's what I thought. So there's no such thing as a "variable weight system" for catenary tensioning. You choose the appropriate amount of counterweight and hang it up.
Reply to
Adam H. Kerman
Adam H. Kerman schrieb:
It's not a technology, but a practical question.
But nonetheless, it might come handy later: If you are the SNCF, and want to run a high-speed record to impress the world, you'll first send some guys with additional weights.
Hans-Joachim
Reply to
Hans-Joachim Zierke
----------------------------
----------- I could see seasonally variable weights being of use because temperature changes do have a considerable effect on a catenary -it's "sag" as well as tension. Cold weather reduces the sag and increases the tension appreciably due to the change in direction of the forces involved as the conductor shortens. In hot weather the span may be too loose.
Reply to
Don Kelly
The wire changes length with temperature. The whole point of the weight & pulley scheme is to absorb that change; so you won't care about the temperature..
Reply to
David Lesher

Site Timeline

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.