A query on BR GE EMU designations.

[AM9]

Having lurked on these forums (fora?), for over a year, this is my first posting with a question to anybody who remembers the GE EMUs in the '60s & early '70s.
In that period, I travelled on all the classes of stock from the LNER designed units through to the 'Clactons'. Until the '70s, they were not TOPS numbered but had sequential numbering with gaps that ran from 001 (Shenfield metro stock) to 627 (Clacton 4 car non-griddle).
When the London to Chelmsford and Southend 1500V DC lines were converted to AC and other GE & LTS lines were electrified to AC from scratch, the units were converted to the BR 1948 numbering system, e.g. AM6 etc. These AM designations rolled into the all-number TOPS system in the early '70s, i.e. making an AM6 a 306.
With the aid of a 1962 Ian Allan book and various online sources, I have identified all the sequential numbered stock into its respective 1948/TOPS desgnation except the 510-519 Outer Suburban 4-car units.
I would be grateful if anybody here could help with any information.

 

[Taunton]

except the 510-519 Outer Suburban 4-car units.
I would be grateful if anybody here could help with any information.

I believe you mean 501-519. These were AM5, and later class 305, the same as the 3-car inner suburban units numbered 401 upwards, but with an additional trailer composite.

http://www.therailwaycentre.com/Recognition Tech Data EMU/EMU_305.html

Among the identical-looking GE EMUs, AM5/305 was used for the GEC-equipped units and AM8/308 for the English Electric-equipped ones, regardless of whether they were second class-only 3-car or full 4-car sets (there were all four combinations of these). The GEC units were the ones which had the explosions in the 6.25/25Kv changeover equipment when they were first introduced.

 

[AM9]

Thanks for the response. Yes 510 is a typo. What confused me is that these units had flat fronts like the LTS units, (201-321) whereas the Enfield & Chingford unit, (401-452) had a raked cab front similar to the GE units, (133-165). In addition the 4xx units had low back 2nd class seating with large windows between the doors as there were no transverse luggage racks - only small high-level shelves above the windows.

I remember the transformer problems on some units and recall one journey on the way to work when we were delayed for about 30 mins at Brentwood. Eventually, we were released, to crawl past a smoking unit 518 on the up main. The solebars were decidedly sagging, and reportedly, the transformer went into meltdown. I also remember the 6.25kV to 25kV conversion - I think from the Mountnessing neutral section to Liverpool St.

Apart from the impact of Ray Buckton's work to rule, they were interesting times on the GE, 309s in particular.

 

[Taunton]

What confused me is that these units had flat fronts like the LTS units, (201-321) whereas the Enfield & Chingford unit, (401-452) had a raked cab front similar to the GE units, (133-165).

No, the 305s all had the raked type, as designed at Wolverton and fitted to a range of new units at the time around the country. You had to look at the interior layout, or for the extra car, to differentiate the variants.

The LTS flat-fronted units class 302 were 201-312. The last nine for the LTS scheme 313-321 were actually class 308, and had the raked front. Their motor car was initially fitted out as a full luggage vehicle, although later being converted to passenger accommodation in a rather amateurish way. They were used on the LTS line and formed a small exceptional group there, recognisable by their different fronts. Normally around the first 20 of the class 302, 201 to 220, were operated out of Liverpool Street on the Southend Victoria line, rather than on the LTS, and this applied for many years.

http://www.therailwaycentre.com/Pages EMU/Recognition EMU/IllusEMU_305.html

I also remember the 6.25kV to 25kV conversion - I think from the Mountnessing neutral section to Liverpool St.

The second voltage conversion on the GE lines in about 25 years. The 6.25/25 changeover points were quite a long way out, beyond Shenfield on the main line (Mountnessing, as you say), beyond Barking on the LTS, and Cheshunt on the Cambridge line. The whole of the Southend Victoria line was 6.25 Kv. This meant that many of the "GE 25 Kv" trains, particularly the inner suburban second class only ones, hardly ever ran on 25 Kv. Improvements in insulation allowed the final conversion to the single standard.

 

[AM9]

http://www.therailwaycentre.com/Pages EMU/Recognition EMU/IllusEMU_305.html

Thanks for the above, it's put something straight in my memory.

The second voltage conversion on the GE lines in about 25 years. The 6.25/25 changeover points were quite a long way out, beyond Shenfield on the main line (Mountnessing, as you say), beyond Barking on the LTS, and Cheshunt on the Cambridge line. The whole of the Southend Victoria line was 6.25 Kv. This meant that many of the "GE 25 Kv" trains, particularly the inner suburban second class only ones, hardly ever ran on 25 Kv. Improvements in insulation allowed the final conversion to the single standard.

Interestingly, the line was electrified at 1500VDC as the clearances were restricted on the GE, smaller than the GN and W8, W10 routes etc. weren't even a twinkle in BR's eye. The original insulators had a single saucer shaped disc construction. It seems that this was retained in 6.25kV days, whereas the LTS had slightly larger three section insulators. Both were replaced when it all went 25kV although the higher performance designs were smaller than the original 1960 scheme ones. It was BR reducing the required clearance of infrastructure from 13 inches to 8 1/2 inches that benefitted both the GE upgrade and the main LMR schemes. The heavy peak hour services out of Liverpool St stretched the capability of the low voltage sections, especially when a four-unit 309 turned on the power!