I have often seen pictures of trolley cars with the single pole catenary connection. My question is how does it stay in contact with the overhead wire? It seems that the swaying of the car over the tracks and going through turns would cause it to disconnect.
Another thing that is amazing to me is the operation of the high speed electrics such as the Acela and the trains in Europe and Japan. They appear to have a wide shoe for wire contact but, how long does it last going at those speeds? To me it looks like it would quickly burn through.
The trolley pole’s base has springs on it that force the trolley pole up with a fair amount of pressure so that it will stay in contact with the wire, generally. I say “generally” because even with that upward pressure, the poles would find their way off the wire at specialwork, etc.
The contact wire zigzags back and forth to each side of the track centerline spreading out the wear on the Pantograph’s wearstrips. All countries that operate highspeed services use special hard carbon wearstrips paired on each pantograph. Likewise the contact wire is a harddrawn copper alloy for long wearing. The Pantograph wearstrips are replaced at regular intervals
…And of course along with the spring pressure of the trolley pole upward towards the trolley wire…the pickup wheel surely must have a rather deep grove {similar to v-belt pulley}, to keep contact with the trolley wire. And I would imagine the trolley pole must be an operation that swivels very easily to support it moving to follow the wire.
I too am amazed how a wear factor on the contact pad of a high speed electric train pantograph is not a constant maintenance factor…
Not sure what modern practice is, but graphite grease was worked into the contact shoes on the pantograph, this in turn created a mirror-like finish on the bottom of the contact wire which was just about as friction free as a surface could be.
Trolley poles have used shoes instead of wheels for current collection since around the 1920’s, mostly because lubrication of wheel bearings was an additional maintenance item and shoes maintained better contact with the wire. Poles have almost always been mounted on a swivel base, a necessity at street corners in street railway operation.
I have a video by Steve Neff that shows a night run on a commuter train from Stamford, Conn. into Penn. station. Its one of the cab ride videos. It does seem like the catenary wire zig-zags although its very hard to see as this was shot at night in snow. I had never realized they did this but it makes sense.
What do the systems using third rail do in snow storms and ice to keep the rail unobstructed?
Normally the contact rail is partially covered, for safety and weatherproofing, but Icing is a problem. They normally muddle through, these systems tend to use EMUs with multiple contact shoes, so that some are always making contact. The arcing from the other shoes over time melts the ice. Also if the operator expects icing conditions they will keep running trains as this will prevent the formation of ice on the 3rd rail.
On CTA (Chicago) they use a gravity type 3rd rail shoe, which runs on the top of the third rail. So its not possible to cover the top of the 3rd rail in this design. As one of the other respondents noted when icing conditions are expected they will tend to run longer consists or to run trains more frequently to keep ice from building up on the head of the rail. All cars are equipped with spring-applied sleet scraper blades as well which bear on the top of the 3rd rail to keep ice from building up.
In addition, they have several cars equipped to spread sleet paste on the head of the rail, again in the interest of keeping ice from accumulating. Finally, much of their third rail is equipped with heat-trace tape to warm the rail a bit. In areas where they have had a problem with ice buildup (sections of subway near portals, etc.) they have infra-red heat lamps mounted on the subway walls to keep ice from forming on the rail/in the trackbed, etc.\
CTA no longer has any sections where the trains are powered by overhead catenary, but when they did, there were special inserts that could be put on the pantagraphs to cut through any ice build-up on the contact wire.
QUESTION: Yes, the Skokie Swift was pantograph equipped from the get-go (1964), but what about the South Boulevard extension through Oak Park and the Evanston/Wilmette line north of Howard St.? I don’t ever recall seeing pantograph equipped passenger cars working these routes. When winter conditions required, did the CTA equip some of the trolley poles affixed to their “Green Hornets” and “Cincinnati Heavyweights” with special ice scrapers?
2nd QUESTION: Circa 1972, the CTA parked one or two yellow steeple cabs on a service track that was immediately north of the Howard St. station. This track was west of the southbound mains and nearly parallel to the Skokie Valley Route. The CTA used these locomotives to work the freight business between The Milwaukee Road connection near Wilson Ave. and the Lill Coal Company located further north. I seem to recall that these engines had pantographs, but I could be wrong. What say you?
Another possibility is to operate special engines (locomotives or EMUs) with two pantographs. The first - in running direction - is a special ice-scratcher. The second one takes electricity from the catenary.
Some years ago, in France, after a rainfall, the temperature dropped fastly in winter, and the water on the catenary of high-speed-lines froze, insulating the catenary. Some high-speed-trains had to be hauled by diesel-electrics at the “modest” speed of 80mph until temperature increased again. It made for some funny fotos.
What is the voltage that is used by electrified systems such as amtrak, metra, or Chicago Transit? Do they all take power off of the national grid or does any of them use their own generation systems?
This may be a trifle [#offtopic], but before the western (Skokie) half of CTA’s Skokie Swift was taken off caternary last year and put onto shoe like the eastern (Evanston) half, I had been told more than once prior, that the Swift was the only rapid-transit in the Americas to shift modes of electric reception “on the fly.”
It was fun: heading west toward Skokie a small road sign advised “pan up”; the other way the instruction was “pan down.” There would be a slight pause between modes of electrification, but it didn’t last any longer than the NYC subways’ blackouts between blocks.
Yes, keeping the third-rail and shoe in contact during icy weather is a chore, but then haven’t you seen what an ice storm can do to catenary?
It varies a lot, some of Amtrak’s comes from the grid, and some they generate. Amtrak owns the Safe Harbor Dam and Hydroelectric power station on the Susquehanna River south of Columbia, PA. Amtrak uses 25Kv/60 Hz AC north of New Haven, and 11 Kv/ 25 Hz AC south of there. Metra Electric and the South Shore use 1.5Kv DC. Most systems using electrified 3rd rail are 600 to 750V DC. The two coal mining electrified railroads in the western US use 50Kv/60 Hz AC.
In railway engineering, a catenary structure consists of overhead lines used to deliver electricity to a railwaylocomotive, multiple unit, railcar, tram or trolleybus through a pantograph or a trolleypole. These structures consist of an upper structural wire in the form of a shallow catenary, short suspender wires, which may or may not contain insulators, and a lower conductive contact wire. By adjusting the tension in various elements the conductive wire is kept parallel to the centerline of the track, reducing the tendency of the pantograph or trolley to bounce or sway, which could cause a disengagement at high speed.
The overhead power lines that are merely a single wire hanging on a cable suspended between two poles is usually refered to as the “trolley wire”. I believe this was used more often for fairly slow speed operations, but there might have been exceptions to that. I think the Chicago-Milwaukee North Shore interurban used trolley wire. I’ll stand corrected on this, but I don’t think pantographs could be used for pick-up with trolley wire, pe
Trolley (or single) wire is usually used with poles, which need to track relatively straight, and with what I call, “Bow poles,” which have a pantograph-like shoe. When bow poles or normal pantographs are used, the wire must zigzag from side to side to prevent wearing grooves in the shoes.
The tram station adjacent to the main JNR ststion in Hiroshima, Japan was equipped with single wire and supported both bow poles (city streetcars) and pantographs (interurban articulated cars.) The bow pole cars had a single pole centered on the car. Over the stub tracks where they terminated the wire was raised so high that the pole was close to vertical. When they started up, the pole would reverse - raising the wire about a foot as it did so. The process was completely hands off.
The wire above the streets was all single. Once on private right-of-way, the interurban ran under catenary.
The Hiroshima reversal was typical for many British trams and may be in use in Blackpool today.
Between New Haven and New Rochelle, Amtrak uses Metro North’s 12.500V 60 Hz power, and possibly uses this power down to Harold Tower near Sunnyside Yard, where the 11,000V 25Hz power begins, through to Washington and Harrisburg. Or perhaps they revert to 25,000V 60 Hz as in use east of New Haven to Boston. In any case Amtrak uses three types of AC power in the Corridor. The Metro North electrification was changed after they stopped using Cos Cob, and that is the reason a GG1, if restored, cannot be used east of NYC.
Boston’s East Boston Tunnel (“Blue”) line uses catenary overhead wire north of Airport Sation (or from Maverick since there is overlap) and third rail south and west of that point. This change is made during a station stop and not on the fly. Both systems were at 600V dc, but may have been moved to 750V dc. Of course, Metro North’s New Haven Line trains switch from 600V underunning third rail to 12,500V 60Hz while wizzing through Mount Vernon Station.
CTA’s Evanston line used direct suspension overhead with trolley pole current collection although I do remember riding a 51-series articulated coach (equipped with pan trolleys) on one Saturday about 1975 to see Northern Illinois play Northwestern at Dyche Stadium.
The North Shore Line used a mix of catenary and direct suspension overhead with trolley pole collection everywhere. The Skokie Valley line and part of the Shore Line had catenary.