Class 306 AC Conversion

[john prytherch]

They were, but the Hadfield/Glossop units were not designated Class 506 until the introduction of TOPS either, several years after the conversion. TOPS did use an entirely logical numbering system at first with similar units or different unit types operating in the same area e.g. 306/506 were the LNER units and 104/304/504 running most of the other Manchester services.

There's an excellent article "DC to AC" by Eric Stuart in the September 2021 issue of British Railways Illustrated (Vol 30 No 12) at pp.520-527. It covers much of the ground in this thread including the GE and LT&S changeover dates. As well as some general electrification history. Its only tiny error is in saying that Metrolink is now 1500 v dc (It's 750 v isn't it?)

If anybody would like the magazine, please let me know and I can post it on. I'm always trying to declutter!

 

[76020]

I'm suspicious of "according to Wikipedia" where no source is given. In this Wikipedia entry I can't see what the source is for the rebuilding being done at Eastleigh.

OK fair enough, the reason I posted this thread in the first place is to find out some more information, so thank you again to everybody that has responded and also Wikipedia is not 100% accurate!

 

[AM9]

There was no space for a transformer and rectifier on the motor car, but there was on the trailer car, so the pantograph was moved to create a centre pantograph trailer. I believe this involved swapping the low and high roof sections between the cars.

Adding to that, the space required for the original DC traction equipment required the motor car to be about 5ft longer than the two trailers. Whilst running as DC units - like the 506s, the guards area took up the space beneath pantograph and behind the driving cab so the layout in the passenger area was fairly well matched to the door spacing as it was on the trailers. After modification to ac, the extended passenger space meant that the doors were offset, with there being almost double the passenger space in the front 'cul-de-sac'. See side view of the motor car here. Conversely, moving the guards area to the centre trailer meant that it intruded into the area between the first set of doors so there was an angled end wall where the lowered roof was. The combined effect of these two changes impacted on the dwell times of the trains in busy times, especially when stopping at stations with exits at the country end of the line, (e.g. Forest Gate, Ilford and Chadwell Heath).
I suspect that the considerably lower crash resistance requirements of the '60s meant that the roof did not form a primary stressed component in the body structure, allowing the pantograph bay to be moved.

 

[Snow1964]

They wouldn’t have been AM6 as DC units would they? 306 is of course the TOPS numbering but 3xx replaced AM as the designation for AC multiple units. Others e.g. 502s or 506s have the designation for DC outside the SR and must have been called something else originally. Would 306s and 506s not have been part of the same class?

The DC units in the 5xx series were in a more random order than the numbering of the AC units 3xx which were simply a change from AM (ac multiple unit), thus AM6 became class 306

From memory AM1 was the experimental conversions, then they basically went AM2, AM3 etc in date order. The conversions to AM6 and AM7 were simply allocated before next class, AM8 (later 308), the AM series got to AM12 (later class 312)

From memory (haven’t got a book handy), 501s were Broad Street units, 502 and 503 Merseyrail, 504 were the Manchester-Bury, 505 was Manchester-Altringham, and 506 the other 8 units of the 100 the LNER ordered in 1938. They were not in age order.

 

[507020]

Adding to that, the space required for the original DC traction equipment required the motor car to be about 5ft longer than the two trailers. Whilst running as DC units - like the 506s, the guards area took up the space beneath pantograph and behind the driving cab so the layout in the passenger area was fairly well matched to the door spacing as it was on the trailers. After modification to ac, the extended passenger space meant that the doors were offset, with there being almost double the passenger space in the front 'cul-de-sac'. See side view of the motor car here. Conversely, moving the guards area to the centre trailer meant that it intruded into the area between the first set of doors so there was an angled end wall where the lowered roof was. The combined effect of these two changes impacted on the dwell times of the trains in busy times, especially when stopping at stations with exits at the country end of the line, (e.g. Forest Gate, Ilford and Chadwell Heath).
I suspect that the considerably lower crash resistance requirements of the '60s meant that the roof did not form a primary stressed component in the body structure, allowing the pantograph bay to be moved.

I had noticed the door spacing had ceased to be even but not that the motor car was longer than the trailers. Why didn’t they just make them all the same length as the motor car? You say 1960s, but they were actually a pre-war LNER design, just not built until after nationalisation.

The DC units in the 5xx series were in a more random order than the numbering of the AC units 3xx which were simply a change from AM (ac multiple unit), thus AM6 became class 306

From memory AM1 was the experimental conversions, then they basically went AM2, AM3 etc in date order. The conversions to AM6 and AM7 were simply allocated before next class, AM8 (later 308), the AM series got to AM12 (later class 312)

From memory (haven’t got a book handy), 501s were Broad Street units, 502 and 503 Merseyrail, 504 were the Manchester-Bury, 505 was Manchester-Altringham, and 506 the other 8 units of the 100 the LNER ordered in 1938. They were not in age order.

The AM/30x units weren’t all conversions were they? Some were built as AC from new, e.g. the AM3s were the Glasgow ‘Blue Trains’ BR’s only sliding door EMU until the 313 and the AM9s were the ‘Clacton Express’ neither of these ever used DC.

I thought the 501s were Euston - Watford DC units, but rather than ‘Merseyrail’ the 502s were the Southport, Ormskirk and Crossens units and the 503s were the Wirral units, which were only later used for Merseyrail. Following 506s, the 507s and 508s of course still run. It says on Wikipedia that the LMS classified the 502s and 503s as AM2 and AM3 units using a different numbering system than was later used by BR, but they must had had a class designation other than simply ‘Southport’ etc.

 

[Snow1964]

The AM/30x units weren’t all conversions were they? Some were built as AC from new, e.g. the AM3s were the Glasgow ‘Blue Trains’ BR’s only sliding door EMU until the 313 and the AM9s were the ‘Clacton Express’ neither of these ever used DC.

Only AM1, AM6 and AM7 were conversions from DC stock, the rest were built as AC units from new.

AM1s were conversion on L&NWR 4th rail (Watford line) stock used to test ac system on Lancaster-Morecombe line in early 1950s.

In addition to AM3 for Glasgow, AM11 was also sliding door, and a top up batch of class 503 (Wirral) units was built by BR in mid 1950s, there were also the PEP prototype units, so class 313 wasn’t second BR sliding door EMUs

 

[AM9]

I had noticed the door spacing had ceased to be even but not that the motor car was longer than the trailers. Why didn’t they just make them all the same length as the motor car? You say 1960s, but they were actually a pre-war LNER design, just not built until after nationalisation.

My reference to different crash resistance was in relation to the structural modifications undertaken in the early '60s. The original construction defined by their late '30s design would have survived under grandfather rights (as the 506s did well into the MKIII construction era), but modifications to older vehicles which impacted on the strength of passenger vehicles would probably have ruled out simply swapping the roof, especially at the end of a multiple unit where collision performance is most important.

 

[The exile]

That’s not true. What is true is that the weight of stuff that came out was three times that of what went in. But the scrap value certainly didn’t pay for the job (Although it did reduce the total bill).

It was also circulating (as an urban myth?) when the Hadfield conversion was done in the 1980s.

 

[507020]

Only AM1, AM6 and AM7 were conversions from DC stock, the rest were built as AC units from new.

AM1s were conversion on L&NWR 4th rail (Watford line) stock used to test ac system on Lancaster-Morecombe line in early 1950s.

In addition to AM3 for Glasgow, AM11 was also sliding door, and a top up batch of class 503 (Wirral) units was built by BR in mid 1950s, there were also the PEP prototype units, so class 313 wasn’t second BR sliding door EMUs

I remember what it was now. The 313s were the first production BR sliding door EMUs outside the Scottish Region, with all others being pre-nationalisation designs, such as the 1956 503s.

My reference to different crash resistance was in relation to the structural modifications undertaken in the early '60s. The original construction defined by their late '30s design would have survived under grandfather rights (as the 506s did well into the MKIII construction era), but modifications to older vehicles which impacted on the strength of passenger vehicles would probably have ruled out simply swapping the roof, especially at the end of a multiple unit where collision performance is most important.

But did the modifications affect the vehicle strength much relatively? If you were to attempt such changes to a modern unit it would likely be severely compromised.

It was also circulating (as an urban myth?) when the Hadfield conversion was done in the 1980s.

It might be true that the scrap value of the DC kit all the way over Woodhead paid just for Piccadilly - Hadfield/Glossop section to be converted to AC.

 

[AM9]

But did the modifications affect the vehicle strength much relatively? If you were to attempt such changes to a modern unit it would likely be severely compromised.

Who's to say, the cars had a steel undercarriage and a steel 'coachbuilt' steel body, so changing the roofline might have affected the collision strength, - something that wasn't considered an issue in MKI days, (the MKI had a steel chassis and a coachbuilt body where collision resistance was felt to be sufficiently provided by the chassis and end panels, I can remember a description of the design talking about it being capable of sustaining a "200 ton end load"). That was before serious loss of life was experienced through collisions where coaches were overriding buffers and couplings. Without the longitudinal stiffness of a curved roof constructed at one time to prevent the end panels moving, the unist might have fallen apart. AFAIK, there weren't any serious collisions with the 92 class 306 EMUs in their ac life, so the railway got lucky.

It might be true that the scrap value of the DC kit all the way over Woodhead paid just for Piccadilly - Hadfield/Glossop section to be converted to AC.

I doubt that BR managed it's budgets that way. The scrap material probably went into a common disposal system and it's value was lost in the noise. It's not as if the rusty steelwork, catenary cables and even the cadmium/berillium copper conductor wire could be re-purposed within the organisation. Indeed, by the '80s both of the copper alloying metals were considered hazardous materials.

 

[Beebman]

It was also circulating (as an urban myth?) when the Hadfield conversion was done in the 1980s.

As I understand it the only major change to the OHLE infrastructure was to swap out the DC insulators for AC ones, otherwise the catenary remained in place as before. A few years ago I travelled from Piccadilly to Guide Bridge and AFAICS from Ardwick onwards the wiring appeared to be still the original 1950s compound type.

 

[colchesterken]

Memory jog please, were the class 315 fitted with a guards compartment I have not been able to find an original photo to confirm it
I have an idea they were converted a few years after they came into use?

 

[Snow1964]

Memory jog please, were the class 315 fitted with a guards compartment I have not been able to find an original photo to confirm it
I have an idea they were converted a few years after they came into use?

Not an actual separate compartment, but guards used the cab area

As built, when coupled the unused cabs of coupled units could be used as extra standing room by passengers, and had standard passenger door buttons, and the connecting door into adjacent saloon would be usable. Just the drivers side was closed off with a door.

 

[colchesterken]

Now that brings back a memory of the good old days. in the mid 60s commuting into Liv St when the Class 306 trains were full, sometimes they forgot to lock the middle drivers doors and people could get in the cab and stand. The best bit was the speed o worked in all cabs, so could get the idea of the speed the trains ran at particular points in the journey