Locomotives with two pantographs, one up at a time

 
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
There are some electric locomotives that each have two pantographs, one up at a time, can anyone explain this. Though I must say that modern pantographs are asymmetrical, quite a paradox given that older ones were symmetrical, the only asymmetrical current collectors (largely confined to trams) were trolley poles (which were either turned at each end or came in pairs with one up and the other down) and bow collectors (flipped over when changing direction).
When there are two pantographs, they are always set in opposite directions and maybe if you understand why this is, you can see what I mean if I tell you that symmetry is an advantage of diamond pantographs.

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  justapassenger Minister for Railways

There are some electric locomotives that each have two pantographs, one up at a time, can anyone explain this.
Myrtone
There are four reasons that this may occur, depending on the context.

1. Pantographs with different physical dimensions to run across different networks, e.g. Channel Tunnel and conventional networks or locos equipped to run between Switzerland and Germany or Austria.
2. Different pantographs for different electrical systems, more common on multi-system EMUs but not unknown on locomotives.
3. Redundancy.

Look closely at the pantographs on a TGV locomotive (TGV trains are not EMUs, they have locomotives at each end like a HST/XPT) and you'll see the two pantographs are physically different, because the high speed overhead system has different physical properties to the suburban overhead they use for the run between the terminus and the start the high speed system.

Though I must say that modern pantographs are asymmetrical, quite a paradox given that older ones were symmetrical … When there are two pantographs, they are always set in opposite directions and maybe if you understand why this is, you can see what I mean if I tell you that symmetry is an advantage of diamond pantographs.
Myrtone
The symmetry of a double arm pantograph is not an advantage and there is no paradox, because the modern single arm pantographs are superior in every meaningful measure. They are lighter, simpler, aerodynamically superior, safer, more responsive to the geometry of the overhead and less wearing on it.

That's why lots of locos and EMUs delivered before the 1980s with double arm pantographs have been upgraded to single arm pantographs in mid-life refurbishments.

The top reason to mount them 'back to back' if there are two on the same vehicle is simply that it's the most convenient layout. The mountings are close together allowing for a single feed to go into the vehicle, and the amount of roof space denied to other equipment is minimised.

The aesthetics of single arm vs double arm would be quite a subjective issue. You prefer the symmetry of a double arm design, I prefer the clean and sleek look of a single arm design.
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
The symmetry of a double arm pantograph is not an advantage and there is no paradox, because the modern single arm pantographs are superior in every meaningful measure. They are lighter, simpler, aerodynamically superior, safer, more responsive to the geometry of the overhead and less wearing on it.
justapassenger
Okay, so does that mean that a symmetrical pantograph that were as light, as simple, as aerodynamic, as safe, as responsive to the geometry of the wires with just as much wearing of it would have no advantage.

That's why lots of locos and EMUs delivered before the 1980s with double arm pantographs have been upgraded to single arm pantographs in mid-life refurbishments.
justapassenger
So does the single arm variety actually do a lot better, like many times better?

The top reason to mount them 'back to back' if there are two on the same vehicle is simply that it's the most convenient layout. The mountings are close together allowing for a single feed to go into the vehicle, and the amount of roof space denied to other equipment is minimised.
justapassenger
I didn't know there was any reason for that other than what I call geometrical correctness. Let me give other examples, bidirectional vehicles nearly always have two identical front ends. Also, all bidirectional passenger carrying vehicles (like carriages or motor coaches) seem to have longitudal seating, reversible seats or most commonly, half the seats facing each way. This is geometrically correct, having all seats fixed and most facing one end is not basically because they would all be facing forward when driven from one end and backward when driven from the other.

The aesthetics of single arm vs double arm would be quite a subjective issue. You prefer the symmetry of a double arm design, I prefer the clean and sleek look of a single arm design.
justapassenger

I don't think of it as about aesthetics but about geometrical correctness. If only someone could combine the geometrical correctness of a diamond pantograph with the advantages of a single-arm one.
Oh, I am fine with clean and sleek looks too, how about wing-shaped pantographs once tried by the Japanese? These are even aerodynamically superior to the single-arm variety.
  route14 Chief Commissioner

Reason 4: When overhead catches ice or snow, both pantographs can be raised to ensure a consistent current conduction.  However on AC networks one of them has to be lowered before crossing phase insulators.
  bevans Site Admin

Location: Melbourne, Australia
I think the L Class ran with the second panto up in the direction of travel.
  route14 Chief Commissioner

The difference is minimal, but a lot of systems mandate or the drivers prefer to raise the rear pantograph, because in case the pantograph flips and brings down the overhead, the broken contact wire won't fall on the driver's cab.
  petan Chief Commissioner

Location: Waiting to see a zebra using a zebra crossing!
There were rules in NSW about when their electric locos had either one or two pantographs raised. There were several threads on Railpage about this including the following  
https://www.railpage.com.au/f-t11331231-previous.htm
  route14 Chief Commissioner

So panto bouncing was a concern even in fine weather.  Fortunately it's a DC network so there is no phase insulator to take into consideration.
  kitchgp Chief Commissioner

The SEC Latrobe Valley 900mm light railway locos operated with both pantographs. To quote Light Railways Number 84 April 1984, SEC locos “normally operate with both pantographs in contact with the overhead, to minimise arcing and loss of power”. SEC 122 had both types of pantograph.

Some photos by Andrew Cook on the Trams Down Under website:
https://tdu.to/204297.msg

The VR L & E-classes (except for single-panto 1100 & 1101 obviously) seem to have run most of the time with the leading pantograph up. The Ls apparently used both pantographs in winter.
  ngarner Deputy Commissioner

Location: Seville
The Ls apparently used both pantographs in winter.
kitchgp
That certainly ties in with my memories of working on them in winter

Neil
  skitz Chief Commissioner

The SEC Latrobe Valley 900mm light railway locos operated with both pantographs. To quote Light Railways Number 84 April 1984, SEC locos “normally operate with both pantographs in contact with the overhead, to minimise arcing and loss of power”. SEC 122 had both types of pantograph.

Some photos by Andrew Cook on the Trams Down Under website:
https://tdu.to/204297.msg

The VR L & E-classes (except for single-panto 1100 & 1101 obviously) seem to have run most of the time with the leading pantograph up. The Ls apparently used both pantographs in winter.
kitchgp
When there was frost (VR L).   One to knock to ice and the other for contact.

The light show apparently spectacular.
  Heihachi_73 Chief Commissioner

Location: Terminating at Ringwood
The symmetry of a double arm pantograph is not an advantage and there is no paradox, because the modern single arm pantographs are superior in every meaningful measure. They are lighter, simpler, aerodynamically superior, safer, more responsive to the geometry of the overhead and less wearing on it.

That's why lots of locos and EMUs delivered before the 1980s with double arm pantographs have been upgraded to single arm pantographs in mid-life refurbishments.
justapassenger
Ironically, the Melbourne Hitachis were all fitted with single-arm Faiveley pantos from new, but had to be fitted with double-arm MetroVick pantos (ripped straight of the roof of scrapped Taits, Harrises, and probably L classes too as a few of them had V/Line stickers on them) because the Faiveleys were getting tangled in our worn out overhead, to the point that it was seemingly more common to see a Hitachi with a MetroVick panto than a Faiveley.

At least one Comeng (395M) also suffered from our bad overhead and wore a MetroVick for a short time in the early 80s, although this was by far the exception rather than the rule; it may have even been the only Comeng to ever be fitted with one. Late in their lives, the L class locos also had a mix of MV (factory) or Comeng-style Brecknell Willis (aka Austbreck) pantos, depending on what was available at the time.
  kitchgp Chief Commissioner

Wasn’t the pantograph moved to the rear of the later Hitachi M cars to provide greater distance between the centre units when running in 6-car M-T-M-M-T-M configuration?
  YM-Mundrabilla Minister for Railways

Location: Mundrabilla but I'd rather be in Narvik
Wasn’t the pantograph moved to the rear of the later Hitachi M cars to provide greater distance between the centre units when running in 6-car M-T-M-M-T-M configuration?
kitchgp
I THINK that was the case but there was also a period when Taits were running as six car M-T-M+M-T-M with two centre pantographs together.
  Valvegear Oliver Bullied, CME

Location: Richmond Vic
Yeah; but Taits were built by good tradesmen from quality materials. Hitachis were made of old sardine cans.Very Happy
  YM-Mundrabilla Minister for Railways

Location: Mundrabilla but I'd rather be in Narvik
Yeah; but Taits were built by good tradesmen from quality materials. Hitachis were made of old sardine cans.Very Happy
Valvegear
I was always happy to see a Hitachi turn up for my commute.
At least one could open the windows for some fresh hot or cold air rather than simply re-breathing your own and everyone else's dog germs.
  Valvegear Oliver Bullied, CME

Location: Richmond Vic
In Taits we not only rode with open windows; we had open doors as well. In my four years of commuting to school on Taits, I never saw anyone fall out of an open door.
  ngarner Deputy Commissioner

Location: Seville
Wasn’t the pantograph moved to the rear of the later Hitachi M cars to provide greater distance between the centre units when running in 6-car M-T-M-M-T-M configuration?
kitchgp
Yep, that was definitely the case.

Neil
  kitchgp Chief Commissioner

In Taits we not only rode with open windows; we had open doors as well. In my four years of commuting to school on Taits, I never saw anyone fall out of an open door.
Valvegear
A few seats would have 'fallen' out, say going over the Yarra on the Cremorne bridge. A few passengers would have been injured attempting to alight from (or board) moving trains.
  Valvegear Oliver Bullied, CME

Location: Richmond Vic
A few seats would have 'fallen' out, say going over the Yarra on the Cremorne bridge. A few passengers would have been injured attempting to alight from (or board) moving trains.
"kitchgp"
What's the source of your information?
  kitchgp Chief Commissioner

Observation.
  Valvegear Oliver Bullied, CME

Location: Richmond Vic
Your observations must be more intensive than mine. In four years (1954-57 inclusive), I did not see one incident of the type you mentioned.
(Come to think of it, I didn't experience "track faults", "train faults", "equipment failures" either. The 0748 Burwood to Flinders Street turned up as regularly as the sunrise.)
  kitchgp Chief Commissioner

Whilst obviously a lot harder to do these days, with sealed windows and closed doors, unfortunately, the ‘tradition’ continues:
https://www.9news.com.au/national/sydney-mum-turns-in-son-after-recognising-him-in-video-of-seat-being-thrown-off-moving-train/8db836be-2c40-4b6e-908d-bd54e815499b

It was always amusing to see the occasional passenger stumbling on the platform after alighting from a train that hadn’t quite stopped and was moving faster than they thought.

This bloke takes the cake (may be behind a paywall if you’ve used your quota):
https://www.theage.com.au/national/victoria/train-surfer-seriously-injured-after-jumping-from-train-into-yarra-river-20161118-gsssa1.html
(Perhaps he was a Good Samaritan jumping in to retrieve the seats his mates had thrown in.)
  YM-Mundrabilla Minister for Railways

Location: Mundrabilla but I'd rather be in Narvik
Whilst obviously a lot harder to do these days, with sealed windows and closed doors, unfortunately, the ‘tradition’ continues:
https://www.9news.com.au/national/sydney-mum-turns-in-son-after-recognising-him-in-video-of-seat-being-thrown-off-moving-train/8db836be-2c40-4b6e-908d-bd54e815499b

It was always amusing to see the occasional passenger stumbling on the platform after alighting from a train that hadn’t quite stopped and was moving faster than they thought.

This bloke takes the cake (may be behind a paywall if you’ve used your quota):
https://www.theage.com.au/national/victoria/train-surfer-seriously-injured-after-jumping-from-train-into-yarra-river-20161118-gsssa1.html
(Perhaps he was a Good Samaritan jumping in to retrieve the seats his mates had thrown in.)
kitchgp
Typical media.

Port Melbourne line rail bridge pictured for a 2016 rail incident.
Only problem is that trains had not run on this bridge since 1987 - 29 years prior to the incident.

'... Police are asking for anyone who might have seen the man jump on the train to call Crime Stoppers on 1800 333 000. ...'

Only problem is that he jumped OFF the train.

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