Pantograph vs. Trolley poles

[Ian Blenk]

Hi All,  a question, is it possible for pantographs/trolley poles to operate on the same wire, or were the wires different? Any examples of them both on a railroad/interurban?

As always many thanks

 

Ian B

[John Wass]

Trolley wires are positive and negative, fine for trolley poles but a pantograph would span  across these and course a short. They use earth return through the running rails. Pantograph don't need as much extra cable work to hold them in place were as the trolley pole type certainly does.

Edited October 8, 2021 by John Wass

[Titan]

It depends - it was possible for them to run on the same wire,  but there might be some issues - pantographs might be too wide in narrow streets, and junctions could be interesting as trolleys require some kind of switch or "points" to guide them the right way, which could interfere with pantograph operation if not designed to accommodate them also .  pretty sure there is/was a mix of trolleys/bow collectors/pantographs on blackpool trams.

[Jeremy Cumberland]

Blackpool Tramway had (and probably still has - I haven't been there since the refurb) both pantographs and trolley poles on different vehicles, and I don't think this was unique.

23 minutes ago, John Wass said:

Trolley wires are positive and negative

Only for trolleybuses and three-phase AC. (Were any three-phase trolley systems actually built, I wonder. The only one I know of was the Portmadoc Beddgelert and South Snowdon Railway, but when this eventually opened as the Welsh Highland Railway, they used steam). Most railway/tramway systems were DC, with current return through the running rails, the same as most electric railways.

 

Edit: Of course, three phase wires aren't "positive and negative". The third phase was provided by the running rails.

 

23 minutes ago, John Wass said:

Pantograph don't need as much extra cable work to hold them in place were as the trolley pole type certainly does.

I don't understand. Trolley wires generally have less support than pantograph wires. I imagine this is more because of the low speeds associated with trolley systems rather than trolley poles being able to accomodate greater and more sudden variation in height, but trolley poles can certainly accommodate a great deal of variation.

Edited October 8, 2021 by Jeremy C

[Regularity]

Trolley poles on tramcars (UK) and streetcars and interurbans (USA) are not the same as those used on trolley buses.

 

I think the OP is asking about single-wire supply, ground-return systems.

 

There are usually major differences between trolley and pantograph supplies, especially around how the power line is suspended (some designs of hanger would drop the power line below the level of the support wire, enabling pantograph use, others would lead to pans snagging the support wire) and how turnouts are dealt with: trolleys need some form of frog: sometimes switchable, sometimes simply to allow the polly to be dragged onto the correct route. Usually 3 wires connect to the frog. With pans, the usual arrangement is to have two wires in parallel, with one diverging.

 

Trolley poles swing about to accommodate curvature, and act in a trailing manner e.g. through frogs and automatic trolley reversers, but pans are placed above a bogie/truck pivot, or if used one a fixed axle loco, above one of the axles, and the contact wire usually moves from side to side either side of the centreline of the track, to even put wear on the contact surface.

 

Put another way, whilst it is possible to run one on the other, there are difficulties to overcome.

 

Usually there would be pantographs and trolleys fitted to vehicles where different forms of knitting are used. I have seen interurbans with third rail pickups, a pantograph and a trolley pole, where different systems were combined into one. 
 

 

[Nearholmer]

40 minutes ago, John Wass said:

Trolley wires are positive and negative, fine for trolley poles but a pantograph would span  across these

Terminological trouble here.

 

“Trolley pole” usually means the pole, singular. Trolley bus electrification uses two wires, and two poles. Tram/streetcar electrification uses one wire, one pole, and running rail return.

[Regularity]

If you are looking for a system with all three (technically, four, as two different types of 3rd rail were used) then the Sacramento Northern is your thing.

 

[Nearholmer]

2 hours ago, Jeremy C said:

Were any three-phase trolley systems actually built, I wonder.

Yes, but not in the U.K. so far as I know ( there might have been oddities in industrial applications).

 

The Lugano tramway was I think the first paying application of three phase traction, and it had trolley-pole current collection, as did several other very early three phase railways. But, the arrangement was a variety of electrical accidents waiting to happen, and was quickly superseded by various forms of two-phase bow-collector, where at least a fixed relationship was maintained between the two limbs, rather than they being free to whip about independently.

 

 

Edited October 8, 2021 by Nearholmer

[Nearholmer]

7 minutes ago, Regularity said:

If you are looking for a system with all three (technically, four, as two different types of 3rd rail were used) then the Sacramento Northern is your thing.

The NER had a bash at variety too, although not all at once, and bow-collector OLE is pretty much like OLE designed for pantographs. https://www.lner.info/locos/Electric/es1.php

Edited October 8, 2021 by Nearholmer

[Nearholmer]

As a slightly random aside, the reason trolley poles/cars/buses are called that is because the earliest current-collection systems consisted of a trolley, running on rigid bars fixed to poles at the roadside, the trolley being towed by the vehicle using a rope, and connected to it electrically by a cable.

 

There multiple other weird and wonderful arrangements were tried before “trolley wire” and “trolley poles” as became standard equipment were settled upon.

[uax6]

1 hour ago, Nearholmer said:

As a slightly random aside, the reason trolley poles/cars/buses are called that is because the earliest current-collection systems consisted of a trolley, running on rigid bars fixed to poles at the roadside, the trolley being towed by the vehicle using a rope, and connected to it electrically by a cable.

 

There multiple other weird and wonderful arrangements were tried before “trolley wire” and “trolley poles” as became standard equipment were settled upon.

 

I don't think that the rigid bars lasted very long, the practically installed systems used wires, and must have been fascinating to watch... 

 

Andy G

[Nearholmer]

There were all sorts of variants in the US and Europe, and the Siemens rigid slotted-tube (as opposed to bar) system, which used a sort of sled, rather than a wheeled trolley, did have a fair lifespan on some lines. The most bonkers sytem, an earlier Siemens iteration IIRC, and similar US ones, used a trolley that ran on the wire, and had nothing but a counterweight to keep it from falling off; my surmise is that it did indeed fall off pretty often, and possibly bonked people on the head as it descended, which given that it must have weighed maybe 5 to 10kg must have been ruddy dangerous.

[BR60103]

Toronto is currently transitioning from poles to pantographs.  They are converting one route at a time. But, as there are only two or three carhouses, some lines have to take both pickups. The cars for now have both forms of pickup.

The worst consideration is frogs. I think they put wire loops both sides of the wire to push down the pantograph. I don't know how they work at the right angle crossings. Eventually, the frogs will be eliminated.

The contact wire path has to be changed for pantographs. Pole wire is kept centered (except for certain purposes) while pantograph wire shifts from side to side to avoid wearing a groove. (Trolley bus poles have a swivelling shoe so that they can move to the side of the street.) 

Toronto bought used PCCs from Cincinatti (inter alia) which had two poles. Cinci ruled that they couldn't use the rails for the return current. I think the wire spacing was different than trolley buses by a few inches. 

 

Our local streetcar museum has at least one car with a pantograph. I'll see what they do when the lockdown eases. 

 

When the Edmonton system was new, we rode it. The pantograph rail cars crossed the trolley bus system at an acute angle. The streetcar wire came up to the TB wire and turned parallel to it for a few feet. In between was a wire that was parallel to the TB, went across aligned with the streetcar, then parallel to the TB. On the far side it was like the first. I think the pantograph wire was enough lower than the TB wire that it didn't touch and short.

 

[SRman]

During the changeover period from trolley poles to pantographs on Melbourne's trams, there were some routes and areas where both could be used, and some which were no-go areas for one or the other. Nowadays the system is only geared to pantographs but there may still be some wiring capable of accepting both, particularly in depots and their approaches.

There are still a couple of railway level crossings where trams cross, and those had to be differently set up for pantograph usage on the trams, compared to before when all the trams had trolley poles (the trains had pantos from way back). We still have some Z3 and A1 class trams, like 247 in the third photo) running around that used to have trolley poles: the solution when pantographs were fitted was to crudely cut off the trolley poles and leave the stub sticking up.

The Melbourne W class in the first pic is actually in Denmark in their tramway museum, but still has its trolley poles (picture taken in late 2018). The W class retained for use on Melbourne's streets all have rather inelegant pantographs fitted - they are so oversized they remind me of Heljan's first attempts at the class 86 locomotives. The City Circle tram in the second photo, though, was still fitted with trolley poles at the time of the photo - it is an old photo.

B2 class trams (fourth photo) had pantographs fitted from new.








 

Edited October 9, 2021 by SRman
Additional info added.

[Johann Marsbar]

7 hours ago, Nearholmer said:

There were all sorts of variants in the US and Europe, and the Siemens rigid slotted-tube (as opposed to bar) system, which used a sort of sled, rather than a wheeled trolley, did have a fair lifespan on some lines. The most bonkers sytem, an earlier Siemens iteration IIRC, and similar US ones, used a trolley that ran on the wire, and had nothing but a counterweight to keep it from falling off; my surmise is that it did indeed fall off pretty often, and possibly bonked people on the head as it descended, which given that it must have weighed maybe 5 to 10kg must have been ruddy dangerous.

 

On the trolleybus front, in the past couple of years a replica vehicle working on the Cedes-Stoll system (with an overrunning trolley), based on one tried out in West Ham and thereafter in normal service in Keighley has been constructed in the Czech Republic and lives at Sandtoft museum. The plan is to construct its own operating circuit there, but a short section of dummy overhead was installed for its ofiicial launch back in 2019....

 

 

 

 

At the moment the replica is fitted with batteries, so is capable of movement under its own power.

 

Edited October 9, 2021 by Johann Marsbar
added text

[Johann Marsbar]

Pantograph equipped LRVs have several interfaces with the trolley pole wires of trolleybuses in San Francisco.  The increased size of the insulated sections at points where the two systems cross can be seen in this photo...

 

[298]

Most Interurbans would have either closed or dieselised instead of converting to pantographs so actual older examples are rare, examples being the Sacramento Northern and Visalia Electric. Some locomotives give the appearance of having both a pantograph and trolley poles, but if the latter was only on one end it would have only been used to connect to the overhead to make the loco live to run the compressor needed for the air motor to raise the pantograph.

 

In both prototype and modelling realms you need comparable frogs to run pantograph equipped cars under trolley wire, as done with open topped Brush Balloon cars in Blackpool and San Francisco which retain trolley poles to avoid showering passengers with crud from the overhead. Also, prototype trolley poles can run on cruder wire than pantographs where the bottom of the contact wire has to be the lowest surface and allow sufficient clearance for the pan head. Conversely, once you've followed this rule pantograph operation in model form is easier to deal with than trolley poles, whose operation and authentic dewirements are tutted at by punters...

[45655]

5 hours ago, Johann Marsbar said:

 

On the trolleybus front, in the past couple of years a replica vehicle working on the Cedes-Stoll system (with an overrunning trolley), based on one tried out in West Ham and thereafter in normal service in Keighley has been constructed in the Czech Republic and lives at Sandtoft museum. The plan is to construct its own operating circuit there, but a short section of dummy overhead was installed for its ofiicial launch back in 2019....

 

 

 

 

At the moment the replica is fitted with batteries, so is capable of movement under its own power.

 

As I recall, the Keighley authorities were too tight to provide two pairs of wires, so when two trolleybuses passed one another the conductors had to unplug the flying leads (carrying 500 volts) and pass them over to their opposite number.  For some unaccountable reason this feature doesn't seem to have been reproduced on the replica.

 

However the real downfall of the Cedes-Stoll system was the patent motors, which were incorporated into the wheel hubs and used to burn out regularly. I don't think this weakness was ever overcome.

 

A bizarre system, with hindsight, although it's nice to see the replica.  At least the Keighley trolleybus routes were semi-rural.  (They were introduced to extend the reach of the tramways.) The mind boggles at the thought of the system being adopted in West Ham!

 

Keith.

[Nearholmer]

There’s an interesting discussion of the problems suffered by the motors here http://www.sfu.ca/person/dearmond/phono/Notes.early.collection.htm

 

The design had a phenomenally good pedigree, coming out of the Porsche-Loehner school of design, but I get the impression that Porsche particularly could see further than practically achievable engineering at the time could reach - that’s what being young and brilliant is all about, I suppose!

[Michael Hodgson]

The tramway museum at Crich mear Matlock has examples of just about every system going. Historic vehicles from systems all over the country and a number of foreign ones too.  They'd be the best people to ask. 

I think they've wired up their pole routes to support as many as possible.

 

With a single wire tram system they often had a reverse loop at the end so the trams could turn.  

Trolley buses must have faced the polarity problems that DC modellers are familiar with.

 

There are arrangements which enable trams and trolley buses to cross railways with OHLE on the level, which even with a double pole supply tends to require insulation between two power supplies at different voltages..

[Nearholmer]

1 hour ago, Michael Hodgson said:

Trolley buses must have faced the polarity problems that DC modellers are familiar with.

Not quite so severe, because the reverser is on the vehicle, rather than at the line-side as in a MR, and because the situation at a balloon loop would be more analogous to a MR “dog bone” on double track than a return loop on single track, but it would be interesting to hear how they dealt with it - my working assumption is that positive (say) was always on the left in the normal direction of travel, to give consistent outcomes when F or R was selected.

[298]

3 hours ago, Michael Hodgson said:

The tramway museum at Crich mear Matlock has examples of just about every system going. Historic vehicles from systems all over the country and a number of foreign ones too.  They'd be the best people to ask. 

I think they've wired up their pole routes to support as many as possible.

 

 

They have previously run trolleybuses, with a small rail-borne trolley towed behind for current return.

 

The last time I went they had the main running line wired with parallel contact wires (one for the up direction, one for the down) to avoid having frogs in the overhead at passing loops.

[Philou]

This is a really interesting topic - love it!

 

I am a fan of trolleybuses as I lived in Cardiff until my thirties and the system was in use until January 1971 - can you believe already 50 years ago!

 

Insofar as Cardiff trams were concerned (gone before I was born) most had reversers at their terminals (I don't know if the frog was operated by the conductor or sprung) whereby the tram would reverse and the pole would follow a diverging route pass a sprung point and the tram continuing in reverse would then draw the pole forward and through the now correctly returned frog. The tram and pole would then continue in the 'right' direction. Insofar as I can tell, at junctions the frog was operated by the tram itself. The tram would take a diverging route through the pointwork with the pole continuing a short distance along the straight ahead line. The pole now at an angle to the tram would arrive at the frog that had a lever hanging down with which the pole would push and operate the frog. I think there was only one balloon terminus for trams at Roath Park.

 

On the other hand, all the trolleybus routes had balloon terminii (though a few reversers were provided until the routes arrived at their definitive ends) save one route at the Docks terminus in Bute Street (Tiger Bay) (Route 16 originally became Route 14). It was always a reverser until the abandonment of the route. There is a film of it in use on Youtube. Oh, it was also the only single decker trolleybus route in Cardiff (possibly the only one in the UK?). I was intrigued that the reverser existed as it ran parallel to the balloon terminus of the Nos 6 and 9 routes. It was the same electricky as the routes reconnected at the Monument terminus at a standard balloon terminus!

 

I have a question relating to both tram and trolleybus overhead: How were the bronze hangers that were attached to the span wire (similar to those shown in the photo above) insulated? The blade holding the contact wire was fixed inside but if there was no insulation there would have been a direct short between live and neutral in the case of the trolleybus system as there was no other form of external insulation on the span wire prior to its attachment to the traction pole - but what at the actual interface between the contact wire hanger (?) and the span wire itself?

 

In response to the OP's original question, that I took to mean tram - tram overhead, I have never seen pantograph and trolley pole using the same contact wire. What I did see in Montreux (possibly Vevey) was a trolley bus (pole) - tram (pantograph) contact wire along the same route. In this instance though the two were interlaced over a short distance BUT the trolley pole was deliberately dewired by a built-in deformation of the trolley-bus overhead (the pole being attached to an auto-rewinder) so the the pole never came into contact with the tram overhead. IIRC, it was to allow the tram to pass at a pre-determined point on the route. Once passed, the conductor had to reconnect the trolley pole to its contact wire. Didn't have a camera and as I was driving I couldn't stop and take in any other details.

 

Cheers,

 

Philip

[stewartingram]

Just a quick reminder - it was stated earlier in the thread - that Blackpool today uses both pantographs (on the current modern fleet, and some heritage cars), and trolley poles on other heritage cars. I'm not aware of any probelms that heep certain sections only for one type of collection.

 

Stewart

[Derekl]

3 hours ago, Nearholmer said:

Not quite so severe, because the reverser is on the vehicle, rather than at the line-side as in a MR, and because the situation at a balloon loop would be more analogous to a MR “dog bone” on double track than a return loop on single track, but it would be interesting to hear how they dealt with it - my working assumption is that positive (say) was always on the left in the normal direction of travel, to give consistent outcomes when F or R was selected.

I drove trolley buses in Johannesburg, South Africa in the early 1970s. The overhead was set up so that you could not get that conflict. If the road was too narrow for two vehicles to pass (rare in Johannesburg, but there was a route in Berea which had this difficulty), the wires were duplicated for direction. Similarly there were no return loops on a single track - there were balloon return loops but there was no question of "reversing loop" point work.

We rarely had to use reverse, but at a few triangular terminals you went forward to the right (usually) and then reversed back towards the left, the poles passing over a sprung frog to bring you back and ready to set off again. The reversing movement was fussy - I think the reversers had a limitation on speed (although I am not sure) and would preclude you running forward in reverse on an opposite pole track.

Although I never had a problem it was drilled into us on training that we make sure the poles had cleared the frogs before attempting to reverse, or go forward after the reversing move, suggesting to me that there may just have been the occasional problem.