Trolley Pole v. Pantograph

As a matter of fact, I know some London Tube lines used dual-third (4th?) rail systems, and I think a few systems used dual-overhead wires as well. It eliminated the issue of galvanic corrosion in water pipes, from current leakage along the rails. No reason a dual-line system couldn't be used in a modern trolley pole-equipped system, and even a pantograph-equipped car could use dual overhead lines, with either a large neutral zone at a junction or some sort of current-switching system as cars passed.

The dual third-rail system is still used today on the London underground. Condiut current collection in London and Washington was like this too and how unfortunate is it that there is not one tramway still uning the system. Would Washington have retained conduit curret collection had it survived, or would it have been replaced by something else, such as the Bordeaux ground level power supply?

Pantograph equipped rail-vehicles could use dual overhead lines, but the air-gap (between the wires) would need to be wider. This was used on some polyphase electric railways, in this case there were two wires for two of the phases and the rails for the third.

EDIT:A minor hazard associated with rail return is that if sand builds up on the rails the rail vehicle can become insulated, causing the whole body to become live at the line voltage. I believe that on the most modern trams and LRVs, the procedure would be to lower the pantograph before opening the doors.

I knew a motorman on SEPTA's Red Arrow division broad guage rail, routes 101 and 102, who, upon the changeover to pantograph operation, said he missed the health benefits of getting fresh air at the end of the line while changing poles.

http://health.yahoo.net/experts/menshea ... do-all-day

Similar research actually dates back to 1953, when British researchers found that (sitting) bus drivers were twice as likely to die of heart attacks as (standing) trolley operators.

Patrick Boylan wrote:I knew a motorman on SEPTA's Red Arrow division broad guage rail, routes 101 and 102, who, upon the changeover to pantograph operation, said he missed the health benefits of getting fresh air at the end of the line while changing poles.

http://health.yahoo.net/experts/menshea ... do-all-day

Similar research actually dates back to 1953, when British researchers found that (sitting) bus drivers were twice as likely to die of heart attacks as (standing) trolley operators.

That was also a more interesting procedure to watch--- besides leaving the car to change the poles, and most motormen would raise the front pole before lowering the rear pole so that the car's interior lights would remain lit, they also had to walk through the interior to "walk over" the seat backs--this was interesting to watch, even when you weren't about to actually ride in the car.

It was particularly interesting to watch on Pacific Electric's Hollywood cars and PCCs, which had one-piece, comfortably upholstered double seats which swiveled in the center. The conductor would grab the handholds of a pair of opposite seats, one in each hand, and give a mighty yank to dislodge each seat from the notch which held it in position and spin it 180 degrees until it slammed into the notch holding it in position facing the opposite way. Then he did the same thing with the next row, and the next row, and the next row, etc. Those seats took a lot of punishment.

Trolley poles are always and have always been asymmetrical but on a bidirectional vehicle either it is rotated at each end or they are in pairs and are changed when changing ends.
Pantographs are not generally like this and always used to be symmetrical, yet modern ones are not symmetrical and I actually don't get this. The thing is that I've heard that symmetrical (diamond) ones are usually heavier and take more power to raise and lower.
Single arm ones may be lighter and take less power to raise and lower but they have a geometry problem, you'll understand what I mean when you think about the symmetry of bidirectional vehicles. Trainsets with two single arm pantographs always have them set in opposite ways. If a rail vehicle has only one collector for both directions and it is asymmetrical, then there is that geometry problem, it raises the question of which way to set it.
It puzzles me that no one seems to have combined the symmetry of a diamond pantograph with the lighter weight and greater responsiveness of the single arm variety.

If a trolley pole or bow collector is operated in the wrong direction and the wheel or shoe should hit an irregularity in the overhead, then there is the tendency of the wheel or shoe to be pressed upward, and also no "give" at the pole base on the car roof, further increasing the chances of a snag.

If a single arm pantograph is operating with the upper half angled forward and upward and the shoe should hit an irregularity in the overhead then the upward pressure on the overhead is decreased. Also there is some push back "give," at the pantograph elbow. This would in turn decrease the chances of a snag. If the irregularity is large enough the pantograph shoe will get hooked and will snag regardless of direction of travel or whether the pantograph is a full diamond.

At any rate, single arm pantographs have evolved to the point of being very reliable in either direction. Incidentally, at least on the Boston MBTA multiple unit light rail trains have their pantographs oriented the same way or in opposite directions randomly.

Even TTC's new streetcar fleet still uses legacy trolley poles. When SEPTA finally replaces the 1981 Kawasaki cars,
will the subway-surface switch to pantographs like modern LRVs?

R36 Combine Coach wrote: ↑Tue May 04, 2021 9:11 pm Even TTC's new streetcar fleet still uses legacy trolley poles. When SEPTA finally replaces the 1981 Kawasaki cars,
will the subway-surface switch to pantographs like modern LRVs?

They might not, it all really depends on what they want to do.
Wires hung for Trolley poles and wheels are hung differently than for Trams or light rail pantographs.
To change to pantographs, they will probably have to rehang all the wires.

Frogs in the overhead over switches and crossings pose different issues to poles and pans. Systems designed for poles may also have hangers and pull-offs that don't allow pantograph operation. Where both are used, frogs must be protected by placing "gliders" on either side of the contact wire. San Francisco has quite a bit of pan/pole wire, as does Boston. For higher speed operation, wire for poles should be centered, while wire set for pans is often set to move from side to side to prevent wearing a groove in the contacts. Contacts in the overhead for electric switches would ideally be set differently as well, but most systems either use contactors designed for both or place gliders around the pole contactor and use a separate pan-only contactor closer to the switch.

Is the Boston pan/pole wire just left from when the PCCs were still running (25 and a half years ago), or has it been replaced with the same system for some reason?

I think, this picture

shows best, what to do, when Pans and Poles have to interact.
It's the intersection Church/Duboce in San Francisco.
https://www.google.de/maps/@37.7693968, ... 384!8i8192
I showed this picture to one of our overhead-specialists (here in Germany, where I live) he just sighed and said.. "Thank god, I don't have to deal with such a mess."

Boston's overhead wire has long been switched over to pantograph only, except of course on the isolated Mattapan Line.

Toronto's is in process; the Flexity cars on some lines still run with poles merely because the overhead conversion isn't complete yet. Last I was there (2018) about half of the lines had been converted.

The photo posted by Motorman is part of a very complex junction between light rail overhead and electric trolleybus overhead. That's a pretty rare case indeed!

Of course that example was hugely complicated by having trackless trolley overhead cutting through the crossing frog area. For those of you not familiar with the area, Duboce (east-west) serves as the exit from the Market Street subway. Church Street (north-south) is where the J Muni line heads south, using pantograph equipped LRVs, and also has a TT line. A couple of blocks south Church crosses Market, where dual-use (pole trolley and TT) crosses with the F line, which uses historic pole-equipped cars, mostly PCCs, running on the positive wire shares with TTs (so no pan use there, hence no gliders on the connecting track between Church and Market). The F lines pull-in/out route to the San Jose barn is via Church, so the entire Church line is usable for poles and pans. The frogs for poles at Church and Duboce are for access to the Duboce yard, used by the Market Street Railway for historic car storage at one time.

Boston has one pole-only line, the Mattapan line, which uses PCCs on private ROW. Boston did have a lot of pole-equipped work equipment until fairly recently, and may still have some. The T has been known to borrow work equipment back from museums in the past.