I was reading the article in the July Trains, and when I looked at the map - The Twin Cities light rail was missing.. The original Mpls to Mall of America line was powered by Flexity Swift cars from Bombardier. The new purchase of cars will be the Siemens S70/Avanto cars. Expansion operation between Mpls and St Paul is scheduled to start on June 14th.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
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Charlotte has 20 of those S70s. They must be working out well because Cats just ordered 22 more of them.
Dave
Lackawanna Route of the Phoebe Snow
The differences between Light rail and street cars can be murky. Many cities that have both types. Often both can and do operate on the same tracks for at least some mileage.
The trains article does give one big distinction. Street car tracks often have tighter curves and use articulated cars to traverse those curves. Light rail cars many times cannot negotiate those curves due to their longer wheel base.. Mentioned was Atlanta that is building its street car tracks so that the under construction light rail can use those track when they are finally connected.
IMHO the idea of limited stops for light rail versus street car becomes an express / local type operation where they overlap.
Even the MUing of both types is murky.
There isn't really a clear dividing line between streetcars and light rail as the earlier postings suggest a lot of overlap, which goes back more years than many of us might think. As an example, consider the operations of Pacific Electric, Red Arrow Lines, Illinois Terminal near St. Louis, etc.
Not as murky but still not that sharp would be the dividing line between light rail and rapid transit.
Charlotte has a street car line actually under construction. The "street cars" they have been testing look very similar to the existing light rail, but the current plan is to use three replica trolleys that have been in inventory since before the light rail opened.
I have to agree that LRV many times is just new politco-speak for street car. The Twin City system uses articulated cars, runs in the streets, along-side the streets, and on private r-o-w(even a tunnel under the MSP International airport).
The S70s are articulated, and Siemens calls them a low floor tram.
Single car operation even during rush hours: streetcar
multple-unit, train operation frequent light rail
Mostly dedicated separate RoW: light rail
Mostly street operaton streetcar
Enroute to the train show in Timonium, my wife and I were waiting for the light rail in Baltimore. When I saw it I said "Here it comes". She looked and said "Where"? "Right there". "Behind that bus stopped at the traffic light"? "That's not a bus". "Are you serious? The train has to stop at traffic lights?"...
blue streak 1Dave: noticed that the CLT street cars use trolley poles. The overhead wire is single trolley. Are the street car and light rail not going to run on the same track ?
I did not take that picture. That was taken on the light rail line which was not yet in service. They did briefly run on the same line, but the replica trolleys are now in storage at the CATS light rail maintenance facility. They will not be running on the same tracks when the street car line is completed.
Charlotte had a private trolley museum that restored old trolleys and ran them with a generator on an abandoned NS rail line. The runs were discontinued when that section of ROW became part of the light rail Blue Line. They turned much of their inventory over to CATS. Those two in the picture are not restored, they are modern replicas. Number 85, on the other hand, is the last trolley that ran in Charlotte. It was located and restored by that private museum.
Overhead for use by both poles and pantographs is possible and was typical of Key System.
That is the light rail cat. that the replicas are running under. The restored #85, on the other hand is on the light rail track but is pulling a generator for power because the cat. was not yet electrified.
The green and yellow trolley cars are not operating under catenary but rather only under trolley wire, a single-conductor system. Catenary is a double-conductor construction which uses a hanging "messenger" wire from which "droppers" are attached to support the trolley wire, and keep it horizontal, thus aiding in keeping the current collector (trolley pole or pantograph) in continuous contact under high speeds.. The term "catenary" originally referred to a cable or chain hanging under its own weight. And yes, I do know that the trolley wire in the picture is sagging under its weight but nevertheless that type of construction is not properly termed catenary.
Streetcar systems used only trolley wire from their advent in the 1880s until high speed interurban transport developed in the early years of the 20th century and often employed catenary. In the 1950s I rode high-speed interurban trolley cars (capable of 90mph upwards) operating under (double-conductor) catenary installed circa 1912. SEPTA's Media and Sharon Hill lines in suburban Philadelphia now operate pantographs under trolley wire but classical trolley wire systems need to have the insulating hangers changed to accomodate pantographs. The picture shows the proper type used to allow pantographs, which as current collectors on RR lines here and abroad normally use catenary (e.g., Amtrak's NEC). Many new light rail lines unnecessarily use catenary (lacking high speeds) which ups the infrastructure capital cost considerably.
Hopefully the above will be informative (eliminating the confusion of terminology heretofore) and deter any need for a riposte.
The dictionary defintion of a catenary is the shape of wire or rope suspended between two points with the straight line distorted into a sag because of the weight of the wire or rope. Outside of railfan talk, professonals worldwide do use the terms single-wire catenary and messenger-and-contact-wire catenary. I have zero objection to railfans making up their own definitions, but you should be informed about what the profession states the term to mean.
I do agree the messenger catenary has been badly misused, and the worst case is Main Street downtown Buffalo. Absolutely inexcusable. Looks like they were going to run a Deutsches Budensbahn high-speed train under the stuff. Compare that with our beautiful and light single-wire catenary on Jaffa Road In Jerusalem. The North Shore had messenger catenary on the Skokie Valley line, but still ran 80mph north of North Chicago Junction to Milwaukee under simple wire, and with trolley poles and shoes yet! And now, with constant tensioning systems available for both single wire and messenger catenary, lighter construction is achievable with far fewer wire breaks and less pantograph or trolley shoe wear.
Guess I never expected to be accused of making up my own definitions, but maybe should have been aware it could happen given the adversarial nature of many posts. (Has the Goose been silenced?)
To support my position that a single trolley-wire system is not properly termed catenary, consider the following extract from Albert S. Richey's "Electric Railway handbook", McGraw-Hill, 1924 (2nd ed.), pg. 550: "Overhead trolley construction may be classed as (1) direct suspension, or (2) catenary suspension. Direct suspension comprises construction in which the trolley wires are attached, by suitable devices, to the main supporting system. Catenary suspension comprises construction in which the trolley wires are attached, by suitable devices, to one or more messenger cables which in turn are carried (a) in simple catenary by the main supporting system, or (b) in compound catenary, by secondary messengers which in turn are carried by the main supporting system."
Enough said.
You are correct, Richey is a good source and an excellent book. I am glad you have it. It has been a long time since I had the pocket ediiton in my pocket. He has one definition and the standard dictionary another. I should apologize. But he is not the only source, and the terms single-wire catenary and messenger catenary and compound-messenger catenary and triangular-messenger catenary (any left on the old New Haven?) all used. in the industry
Does Richey cover the case of pantograph and trollely-pole operation sharing the same wire? Not only Key System, but Sacramento Northern, and Central California Traction. I think New Jersey Transit's Newark Division, since the transition from trolley pole operation to pantographs during the PCC era did not happen overnight. A special type of hanger is required, but it should not be more expensive than a regular trolley-wire attachment "ear." And "messenger catenary" is no problem except for the required "frogs" which require gently ramped sides and are thus larger, to handle the pantographs at switches and diamonds.
I thought catenary was a line between 2 points with equally spaced weights. Zero is a weight, so trolley wire with no weights sounds like it can also be catenary.
Once upon a time an article said "Catamaran tower". I don't know if the reporter misquoted the railroad spokesperson.
Patrick Boylan
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gardendance I thought catenary was a line between 2 points with equally spaced weights. Zero is a weight, so trolley wire with no weights sounds like it can also be catenary.
Correct. A mathematical catenary hanging formula is any constant density wire, rope, etc between two points. A trolley wire does hang by that math formula. Wire has morphed by the electric traction business into being simple trolley when only one wire provides the only connection to power pickup.
Next we have PRR and New Haven RR type CAT. There is a powered " messenger " wire above the contact wire. The messenger is connected to each cross arm but does not hang as a catenary because: There are hangers from the messenger to the contact wire which holds the contact wire as a catenary between each hanger. That allows for much less distance between hangers but the sag between hangers is still a catenary formula. Since the messenger is attached at each cross arm the term is variable tension since the tension changes with temperature changes with much more sag in summer time. The messenger helps provide power to contact wire by the hangers.
Then we have constant tension CAT. A section of approximately 1200 - 1500 feet is built. The center of the section is attached to the cross arm for both messenger, contact, and sometimes another wire ( traveler ) . All other connections of the wires go thru rollers. Then at each end of a section the 2 or 3 wires are connected to a weight system that keeps the section in constant tension. To further keep the contact wire level the traveler if installed will attach to the messenger and the traveler will have connectors that may only be 1 - 3 feet apart connecting to the contact wire. That way contact wire is almost level but still hangs between connectors by the catenary formula.
Note: each section overlaps the next section by slowly rising above the next section.
The New Haven - BOS is constant tension CAT but South station in BOS terminates as a simple trolley since that is not high speed location
I can find nothing in Richey re trolley wire shared by pole and pantograph equipped cars. As you mentioned, the classical "ear" (and Z-leg pulloffs) cannot be used (because the span wire needs to be well above the pantograph to avoid entanglement). Don't know whether an old Ohio Brass catalog would show the more versatile hanger or whether it's a modern (post-Richey and now for new LRT equipment) development.
There was a contract in the last decade or so to replace the 100-year-old "gas-pipe" triangular catenary on the old NYC to New Haven trackage. I believe that the upgrade has been completed, since I saw no evidence of the old configuration on Acela trips from DC to Boston in December 2012 and January 2014. What is interesting is that many of the century-old steel-lattice towers are in still place, a lot with the lower part encased in new concrete, obviously to strengthen a rusted-out base. There are plenty of new towers too., don't remember if they're lattice or just H-columns, or both.
P.S. to Dave - - apology accepted.
LehighLad I can find nothing in Richey re trolley wire shared by pole and pantograph equipped cars.
I can find nothing in Richey re trolley wire shared by pole and pantograph equipped cars.
You are correct as far as it goes. A pan can work on trolley wire as long as the wire holders are all of the design that has the trolley wire below the holders. The cross support wires of the trolley wire must be a certain distance above the plane of the trolley wire(s).
Trolley poles with either graphite sliders or rollers can only work on CAT if all contact wire is connected together for contact poles to maintain their staying on contact wire. Usually there are short (6" ? ) insulation sections to separate different power sources
How that could be done with constant tension CAT is unknown since each section is separate ?
I have to stand corrected. The following you tube of the NEC somewhere between New Brunswick and Trenton shows a traveler wire on the PRR style CAT. Note you can view the messenger connected to the traveler connected to the contact wire.
https://www.youtube.com/watch?v=c4gOHCq3geg
Couple more points
On installations where there is only a trolley wire the trolley wire will have a larger diameter to carry the current since there is no messenger or traveler to share supply to short sections of contact wire. So the contact trolley wire at Boston South station will be thicker than the CAT contact wire in the country. Also contact wire can be smaller when the voltage is higher with the 25 Kv system able to carry 4 times the power that 12.5 Kv can It would be interesting to know MNRR contact wire diameter compared to the New Haven - Boston section.
Do not have any information as to various messenger wire compositions. Copper contact wire and some other conducting material for messenger would have different co-efficients of expansion, Have noted that constant tension section ends sometimes have a bar at the end which is attached top and bottom to the messenger and contact wires. Attachment to the weights is at the middle of the bar. That would keep both in the same tension. Interesting engineering problem.
Slidning gentel and long frogs joining the two wires at the pull-off weigiht or spring-for-tension point. The frog slides on one wire and is fixed to the other. I confess I do not know of any operating example, but it can be done.
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