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Old November 28th, 2009, 01:51 PM   #701
korund
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british pantographs

I was wondering why there is only one panthograph on the most of british electric locomotives? In Poland, which is where I come from, electric locos come with two pantographs and under normal circumstances only the rear one is up. The main reason for that being when it gets damaged the other can be used. Does it mean that british pantographs are foolproof?

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Old November 28th, 2009, 02:42 PM   #702
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Originally Posted by korund View Post
I was wondering why there is only one panthograph on the most of british electric locomotives? In Poland, which is where I come from, electric locos come with two pantographs and under normal circumstances only the rear one is up. The main reason for that being when it gets damaged the other can be used. Does it mean that british pantographs are foolproof?

Thanks
Up until the class 85 they were built with 2 pantographs. These first generation were subsequently rebuilt and one pantograph taken out, the space used for what seem to be gas jars, perhaps for compressed air or hydraulic pumps of some sort. From the class 86 onwards only one pantograph was fitted.

I am sure the British ones are not foolproof, but they are reliable, and operationally are not too much of a concern. It seems to be more economic to have a spare locomotive, rather than a spare pantograph on every loco.
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Old November 28th, 2009, 05:29 PM   #703
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As far as I know, the Class 92 is fitted with two pantographs. Since this is a dual-voltage locomotive running on 25 kV AC from overhead lines or 750 V DC from a third rail, both pantographs operate under the same power supply system (25 kV AC), don't they? If so, does the presence of two pantographs have anything to do with the fact that the Class 92 is designed to operate services through the Channel Tunnel, or are there any other reasons?
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Old November 30th, 2009, 04:10 PM   #704
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Yes you are correct. Its just speculation, but perhaps two pantographs are included to comply either with French/Belgian etc standards, or as you say in the channel tunnel.
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Old December 2nd, 2009, 03:08 AM   #705
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Yes you are correct. Its just speculation, but perhaps two pantographs are included to comply either with French/Belgian etc standards, or as you say in the channel tunnel.
I think this is the case, in the event of a problem on the train in the tunnel it can split in half and all passengers can move to whatever half can get out. So it would need a pantograph at either end.
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Old December 2nd, 2009, 03:29 AM   #706
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Originally Posted by korund View Post
As far as I know, the Class 92 is fitted with two pantographs. Since this is a dual-voltage locomotive running on 25 kV AC from overhead lines or 750 V DC from a third rail, both pantographs operate under the same power supply system (25 kV AC), don't they? If so, does the presence of two pantographs have anything to do with the fact that the Class 92 is designed to operate services through the Channel Tunnel, or are there any other reasons?
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Yes you are correct. Its just speculation, but perhaps two pantographs are included to comply either with French/Belgian etc standards, or as you say in the channel tunnel.
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Originally Posted by Stainless View Post
I think this is the case, in the event of a problem on the train in the tunnel it can split in half and all passengers can move to whatever half can get out. So it would need a pantograph at either end.
There is some confusion here.

The British Class 92 loco is NOT used for hauling passenger traffic through the channel tunnel. There is one loco at one end of the train.

Totally different to Eurostar and Eurotunnel car & wagon operations. These both have a locomotive at either end.
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Old December 2nd, 2009, 10:42 AM   #707
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Yes, the class 92 is only occasionally used for passenger traffic, and that is on charter trips for enthusiasts, and only on the mainland in Britain, a few times a year.
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Old December 2nd, 2009, 11:01 AM   #708
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The main reason for that being when it gets damaged the other can be used.
In case of a damage you can often not move any more even if you have a second pantograph. The reason for that is that you parts of the damaged pantograph are laying on the roof of the locomotive and would make a short circuit between the roof line and the roof itself as soon as you try you use the second pantograph. In earlier days the engineers grounded the catenary and walked up to the roof to clear the debris. Nowadays you are normally pulled to the nearest shed to clear up the roof.

The main reason for still having to pantographs is for maintenance reasons. Each pantograph is only used during 50% of the time the locomotive is running. Therefore you can double the maintenance interval for the pantograph strips.
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Old December 2nd, 2009, 12:25 PM   #709
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The main reason for that being when it gets damaged the other can be used.
In case of a damage you can not move any more even if you have a second pantograph. The reason for that is that you parts of the damaged pantograph are laying on the roof of the locomotive and would make a short circuit between the roof line and the roof itself as soon as you try you use the second pantograph. In earlier days the engineers grounded the catenary and walked up to the roof to clear the debris. Nowadays you are normally pulled to the nearest shed to clear up the roof.

The main reason for still having to pantographs is for maintenance reasons. Each pantograph is only used during 50% of the time the locomotive is running. Therefore you can double the maintenance interval for the pantograph strips.
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Old December 2nd, 2009, 12:30 PM   #710
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Quote:
Originally Posted by korund View Post
I was wondering why there is only one panthograph on the most of british electric locomotives? In Poland, which is where I come from, electric locos come with two pantographs and under normal circumstances only the rear one is up. The main reason for that being when it gets damaged the other can be used. Does it mean that british pantographs are foolproof?

Thanks
I thought It was because a lot of them dnt run backwards. They would only need to change them when they change direction?
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Old December 2nd, 2009, 01:35 PM   #711
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I thought It was because a lot of them dnt run backwards. They would only need to change them when they change direction?
Do you mean the locomotive or the pantograph? I don't think there has ever been a loco that can't run backwards.
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Old December 2nd, 2009, 03:51 PM   #712
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Do you mean the locomotive or the pantograph? I don't think there has ever been a loco that can't run backwards.
They I don't mean reverse lol. I mean like running facing backwards...
Most english trains run in fixed sets. So pantograph would always face the same way, but they would just swap between which ever one is ar the 'front'.
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Old December 2nd, 2009, 04:45 PM   #713
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They I don't mean reverse lol. I mean like running facing backwards...
Most english trains run in fixed sets. So pantograph would always face the same way, but they would just swap between which ever one is ar the 'front'.
Yes they do run in fixed sets, but there are no units apart from classes 390 and 395 that have two pantographs. So apart from them, all pantographs must be able to go in both directions. All other EMUs, when working in multiple, must have all their pantographs up otherwise whatever unit doesn't, won't have any power. Besides, even on 390s the pans can go in both directions, because they are sometimes seen using whatever is the front one, instead of the normal rear. I can only assume 395s are the same though I haven't witnessed this yet.

There are no locomotive hauled electric trains that have 2 locos also, (apart from Eurostar) so the pans on these must also be able to work in both directions.
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Old December 2nd, 2009, 05:19 PM   #714
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makita09, the Class 390s in normal service run with the front pan up, although either can be used. Which pan do the 395s use?

poshbakerloo, do you know what you are talking about?!
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Old December 2nd, 2009, 06:39 PM   #715
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makita09, the Class 390s in normal service run with the front pan up, although either can be used. Which pan do the 395s use?

poshbakerloo, do you know what you are talking about?!
my mistake, I thought it was the rear, I got confused with TGVs. The 395s seem to use the country end, except when in 12car the first unit uses the front, the second uses the rear. I suppose this is so the vibrations in the contact wire have reduced by the time the second pan passes. But I don't think it really matters. I can't see how it would.

Last edited by makita09; December 2nd, 2009 at 08:13 PM.
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Old December 6th, 2009, 02:58 PM   #716
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Originally Posted by pcrail View Post
In case of a damage you can often not move any more even if you have a second pantograph. The reason for that is that you parts of the damaged pantograph are laying on the roof of the locomotive and would make a short circuit between the roof line and the roof itself as soon as you try you use the second pantograph. In earlier days the engineers grounded the catenary and walked up to the roof to clear the debris. Nowadays you are normally pulled to the nearest shed to clear up the roof.

The main reason for still having to pantographs is for maintenance reasons. Each pantograph is only used during 50% of the time the locomotive is running. Therefore you can double the maintenance interval for the pantograph strips.

I couldn't agree more, but I also think that it depends on how much damage to the pantograph there is. Of course, if it's serious you can't move your train as that would represent a safty hazard to other trains as well.

But, what if the damage is not that serious? Imagine a locomotive-hauled passenger train awaiting departure with a couple of minutes left. The driver lowers the pan (I don't quite know why but I've seen that many times) and then he tries to raise it up, but he can't because of the "raising/lowering mechanism" failure. Having a spare pantograph would, in this case, save time, since there is no need for a change of the locomotive, and, in the worst-case scenario when there are no other locos, it would save the whole service.

I realize that my example may seem very unlikely. Still, it's possible. And of course, that's not the only reason why the Polish railways use locomotives with two pantographs. We employ a 3kV DC power supply system and locos with series-wound DC motors, so high current from the catenary is needed to get the train moving, since those motors have a low resistance field and armature circuit. When voltage is applied to them, the current is high(current=voltage/resistance). One pantograph doesn't provide a good path for such high current and another one is needed. Drivers use both to start a train. Then, as the train accelertes and the drag of the train decreases, the front one is lowered and the train continues with only one pantograph up. This is even more appreciated in hostile weather conditions, especially in the winter.

Last edited by korund; December 7th, 2009 at 04:54 PM.
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Old December 15th, 2009, 08:47 PM   #717
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Why did hitachi make the trains only 225 kmh? The new shinkansens run at speads of 320 kmh with one line planned at 360 kmh.
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Old December 16th, 2009, 12:18 AM   #718
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Why did hitachi make the trains only 225 kmh? The new shinkansens run at speads of 320 kmh with one line planned at 360 kmh.
A higher speed needs a higher gearing, meaning acceleration is poorer - these are commuter trains. Also, the first 35km out of London has a 140mph (225 kph) line speed limit.
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Old December 17th, 2009, 05:20 AM   #719
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When the rail pickup s at 25Kv 50Hz one only needs 1 pantograph
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Old December 23rd, 2009, 10:58 PM   #720
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When the rail pickup s at 25Kv 50Hz one only needs 1 pantograph
I don't think anybody said anything different.

Virgin drivers have now been instructed to run with the rear pan up on Pendolinos instead of the front.
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