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Post by silenthunter on Jul 14, 2017 20:45:50 GMT
I bought from eBay this week a 1949 BR Eastern Region timetable that includes the early electric services from Liverpool Street using the Class. Shenfield (& Hutton) to Liverpool Street took 44 minutes stopping at all stations; with Crossrail it is due to take 40.
Mind you, the steam fast took 32 minutes.
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Post by nickf on Jul 16, 2017 11:04:53 GMT
I have a vague memory that the first incarnation of electrification on this line was at a lower voltage than what is usual now, as the engineers were worried about the clearance of the OHL at over bridges. Can better informed people confirm?
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Post by John Tuthill on Jul 16, 2017 12:23:32 GMT
I have a vague memory that the first incarnation of electrification on this line was at a lower voltage than what is usual now, as the engineers were worried about the clearance of the OHL at over bridges. Can better informed people confirm? Off the top of my head, it started at 1500V in '49, then whent up tp 6.25KV, then 25KV as now.Others with better knowledge will help? |
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Post by norbitonflyer on Jul 16, 2017 12:44:57 GMT
I have a vague memory that the first incarnation of electrification on this line was at a lower voltage than what is usual now, as the engineers were worried about the clearance of the OHL at over bridges. Can better informed people confirm? Off the top of my head, it started at 1500V in '49, then whent up tp 6.25KV, then 25KV as now.Others with better knowledge will help? That's right. The Shenfield and Southend Victoria liens were originally electrified at the then standard 1500V dc. When 25kV ac became the standard, there were concerns about clearances so some stretches were converted to a lower 6.25kV ac instead. Most Eastern Region units were fitted with extra switchgear to switch an extra 4-to-1 transformer in and out as required. |
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Post by silenthunter on Jul 16, 2017 12:53:38 GMT
I believe that on the line west of Shenfield, the change was straight from 1500V DC to 25kV AC. At any rate, the 1940s masts are only now being replaced.
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Post by westville13 on Jul 16, 2017 19:41:20 GMT
Didn't both the Shenfield re-electrification and the blue trains in Glasgow have 6.25KV sections where clearances were tight? And an initial series of fires when the switching did not work 100%?
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Post by phil on Jul 16, 2017 20:45:30 GMT
I have a vague memory that the first incarnation of electrification on this line was at a lower voltage than what is usual now, as the engineers were worried about the clearance of the OHL at over bridges. Can better informed people confirm? Off the top of my head, it started at 1500V in '49, then whent up tp 6.25KV, then 25KV as now.Others with better knowledge will help? Correct! The Liverpool to Shenfield electrification scheme was a pre-WW2 scheme (that along with the Sheffield Victoria / Wrath - Woodhead - Manchester route) had all the design work completed (the EMUs were ordered by the LNER in 1938), but very little physical work done on the ground before conflict erupted halting work. Post WW2 There was a desire to complete the work as soon as possible with the full Shefield scheme being completed by 1949 as per the pre-war designs. Thus the Shenfield scheme used initially 1500V DC - NOT AC! Like all DC electrification, this is far less efficient than any AC equivalent due to the laws of physics (though it is an improvement on 750V) This choice of 1500V DC is because:- (i) In the 1930s (when the scheme was designed) engineers and scientists were incapable of developing small yet powerful, not to mention robust) rectifier suitable for mounting inside a locomotive that would allow the use of high voltage AC at 'mains' frequency (50Hz) as the technology simply hadn't been invented yet. (ii) DC traction motors are ideal for train propulsion but can only be run off AC voltages when they have a very low frequency (hence the use of 15KV at 16.75Hz in Germany* and similar low frequency AC by the LBSCR back in the early 1900s). This requires all sorts of specialist electricity generating kit and introduces complications when the supply is taken from generators also supplying the national grid - far simpler to go for a DC system (even if the cables have to be thicker and the number of substations increased) In fact early plans for the WCML also envisaged this route using 1500V DC (as per several main lines in France / Netherlands done in the 1930s) - it was only because of the results of experiments in France with an improved generation of Mercury arc rectifiers suitable for mounting on board locos that UK policy changed and 25KV AC became the new standard - by which time the Shenfield electrification was already up and running. Thus the Shenfield line was converted to 25KV AC in November 1960* * en.wikipedia.org/wiki/15_kV_AC_railway_electrification** www.lner.info/locos/Electric/shenfield.php |
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Post by norbitonflyer on Jul 16, 2017 23:23:52 GMT
the full Shefield scheme being completed by 1949 as per the pre-war designs. Shenfield, I think you meant. Sheffield - Manchester was completed in 1954 - the new Woodhead Tunnel (necessary because overhead cables wouldn't fit in the old single-track bores) being the main cause of delay. One of the results of the change of supply system from ac to dc was the oversized white-elephant of Reddish depot in Manchester - built for a much larger dc loco fleet than ever materialised. |
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Post by spsmiler on Jul 20, 2017 23:43:56 GMT
So it is true, some of these units were built before the war and painted in LNER livery! Ironically this was blue/grey, a colour scheme that BR later used on InterCity stock, although BR only painted these trains in either plain green or plain blue.
On a related topic, I have a small photographic input on the page about the Co-Co (Class 77) locomotives and also I corrected some mistakes about which sections of Northern Heights did or did not eventually open on the Northern Line page. However Edgware is still spelt incorrectly.
Simon
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