stanley T
Member
- Joined
- 28 Jun 2011
- Messages
- 146
Alternative time lines are a bit of a waste of time, and in the case of the UK rail business, often a bit depressing. They can be quite fun and instructive, however.
In the general mess that was the post-1955 modernisation programme, one decision is generally regarded as far sighted: to go for 25kV a.c as the standard for future electrification. Globally, perhaps, but under British conditions, one wonders. With the insulators of the time, this involved major engineering works rebuilding bridges and lowering trackbeds with the restricted British loading gauge. The WCML, only as far as Weaver Junction, took an age to electrify and the early a.c locos, with mercury arc rectifiers, were none too hot either. Those problems lessened with d.c overhead (1.5 or 3kV) but all that heavy gantry, numerous substations, and heavy wiring to blow over in British gales.
There was an alternative. As far back as 1910 the South Eastern and Chatham planned to electrify its suburban lines at 1500V DC fourth rail- the latter more sensible with such a high voltage than third rail, to prevent earth leakage. Bottom contact, already proven in the USA, and safer (the top and sides of the live rail can be insulated) and far less prone to icing. That voltage is about as high as you can get with electrified rail, to avoid arcing, but its doable its used on the newly built Guangzhou metro. Manchester to Bury worked perfectly well on 1200v DC side contact for years. Unfortunately WW1 intervened, the SE&CR electrification never happened, and the Southern got the underpowered and far more hazardous 600-750v top contact system.
The point is that even today costs of electrifying on 750V third rail per mile are about the same as at 25kV and thats with better insulators for a.c not requiring such high headspans. The bridge and tunnel costs cancels out the numerous substations. With substations 3-4 times further apart, installation costs would have been substantially lower than for 25kV a.c in the 50s and 60s, structure more reliable (no dewirings) and the trains simpler and cheaper as well.
High speed? Well until the TGV came along 1.5kV held the world speed record, and even today TGVs speed along at up to 200km/hour between the end of the LGV at Tours to Bordeaux and beyond. Ah, but that is overhead: what about you cant get shoegear that works at over 100mph? Well a class 442 got to 108mph and was then limited by the lack of SR juice; nobody has really tried to make a 125mph pickup shoe and it should not be much harder than a high speed pantograph. Freight? Electro diesels as with class 73 and the more powerful class 74, with the added advantage of being able to use unelectrified sidings.
Today a.c delivers superior performance , but in this world the WCML, ECML and GWML would all have been electrified by 1970 as steam carried on for an additional 5 years or so. The zoo of unreliable diesel locos that emerged after 1955 would not have been built. The diesel HST would not have happened, but an electric one would, as would fourth rail Pendolinos; as for non-electrified main lines, a 16 or even 18 cylinder Paxman Valenta would have delivered a 3500-4000 hp loco with a lower axle load than a class 67.
In the general mess that was the post-1955 modernisation programme, one decision is generally regarded as far sighted: to go for 25kV a.c as the standard for future electrification. Globally, perhaps, but under British conditions, one wonders. With the insulators of the time, this involved major engineering works rebuilding bridges and lowering trackbeds with the restricted British loading gauge. The WCML, only as far as Weaver Junction, took an age to electrify and the early a.c locos, with mercury arc rectifiers, were none too hot either. Those problems lessened with d.c overhead (1.5 or 3kV) but all that heavy gantry, numerous substations, and heavy wiring to blow over in British gales.
There was an alternative. As far back as 1910 the South Eastern and Chatham planned to electrify its suburban lines at 1500V DC fourth rail- the latter more sensible with such a high voltage than third rail, to prevent earth leakage. Bottom contact, already proven in the USA, and safer (the top and sides of the live rail can be insulated) and far less prone to icing. That voltage is about as high as you can get with electrified rail, to avoid arcing, but its doable its used on the newly built Guangzhou metro. Manchester to Bury worked perfectly well on 1200v DC side contact for years. Unfortunately WW1 intervened, the SE&CR electrification never happened, and the Southern got the underpowered and far more hazardous 600-750v top contact system.
The point is that even today costs of electrifying on 750V third rail per mile are about the same as at 25kV and thats with better insulators for a.c not requiring such high headspans. The bridge and tunnel costs cancels out the numerous substations. With substations 3-4 times further apart, installation costs would have been substantially lower than for 25kV a.c in the 50s and 60s, structure more reliable (no dewirings) and the trains simpler and cheaper as well.
High speed? Well until the TGV came along 1.5kV held the world speed record, and even today TGVs speed along at up to 200km/hour between the end of the LGV at Tours to Bordeaux and beyond. Ah, but that is overhead: what about you cant get shoegear that works at over 100mph? Well a class 442 got to 108mph and was then limited by the lack of SR juice; nobody has really tried to make a 125mph pickup shoe and it should not be much harder than a high speed pantograph. Freight? Electro diesels as with class 73 and the more powerful class 74, with the added advantage of being able to use unelectrified sidings.
Today a.c delivers superior performance , but in this world the WCML, ECML and GWML would all have been electrified by 1970 as steam carried on for an additional 5 years or so. The zoo of unreliable diesel locos that emerged after 1955 would not have been built. The diesel HST would not have happened, but an electric one would, as would fourth rail Pendolinos; as for non-electrified main lines, a 16 or even 18 cylinder Paxman Valenta would have delivered a 3500-4000 hp loco with a lower axle load than a class 67.