EMU 6.25kV to 25kV change-over switch mechanism

[Arun Sharma]

I am currently scratchbuilding a GE EMU and need some information - photographs/drawings ideally of one of the pieces of equipment underneath the GE class 305, 306, 309 EMUs. This equipment is the changeover switch that changed voltage from 6.25kV to 25kV. It looks to be very similar to the underframe PCM gear that was fitted to LT surface stock O & P stock from the late '30 onwards in that it was about 6feet long and was essentially an oil bath surrounding a pneumatic camshaft.

A [not very clear] pic of the equipment is shown in the att pic.

 

Does anyone know more about these equipments or have drawings/pics that I could see?

Edited March 31, 2018 by ted675

[stovepipe]

I think you may find some details in the proceedings of the 1960 BTC Electrification Conference, available here

 

http://www.railwaysarchive.co.uk/docsummary.php?docID=34

 

Page 221 might be a good place to start..

[Arun Sharma]

I think you may find some details in the proceedings of the 1960 BTC Electrification Conference, available here

 

http://www.railwaysarchive.co.uk/docsummary.php?docID=34

 

Page 221 might be a good place to start..

You are indeed correct Stovepipe - There is a mass of useful information in that reference.. 

I was directed towards that reference by those nice folk at the Barrowmore MRG whilst at Ally Pally. Indeed that is how they managed to identify for me what the large lump sitting under the MBSK/DMBSK cars was. However, what I could really do with are clear photographs/drawings of the equipment in situ so that I can create an accurate 3D model of it to stick underneath the 309/1 unit model.

As far as I know, there are no [accurate] model castings of that equipment in any scale.

Edited March 31, 2018 by ted675

[SRman]

I am currently scratchbuilding a GE EMU and need some information - photographs/drawings ideally of one of the pieces of equipment underneath the GE class 305, 306, 309 EMUs. This equipment is the changeover switch that changed voltage from 6.25kV to 25kV. It looks to be very similar to the underframe PCM gear that was fitted to LT surface stock O & P stock from the late '30 onwards in that it was about 6feet long and was essentially an oil bath surrounding a pneumatic camshaft.

A [not very clear] pic of the equipment is shown in the att pic.

 

Does anyone know more about these equipments or have drawings/pics that I could see?

 

While not wishing to divert anyone from the main topic, I feel I need to correct you on the PCM equipment as fitted to CO/CP Stock: that was only fitted to them from the late 1950s onwards (and was the reason for the 'C' prefix, standing for 'Converted'). Prior to that, they were O and P Stock and fitted with Metadyne control machines. PCM equipment was fitted to most other LT stocks, including the 1938 tube stock ... just not the O and P Stocks (until later).

 

P.s. I look forward to seeing the progress with your scratchbuilt stock.

Edited March 31, 2018 by SRman

[Arun Sharma]

Thank you SR Man - A mixture of brain failure and finger trouble.

 

This is where I am up to with the model so far - the second car of the two-car 309/1 unit is still in the flat at present.

 

This is an 0gauge model BTW

Edited March 31, 2018 by ted675

[Arun Sharma]

The next outing for this model - by which time I should also have rolled the etched sides for, and assembled-ish, the DMBSK, will be the Leigh 0gauge show on 28 April.

[Dagworth]

Does this help?

 

P1080821 by Ravensclyffe, on Flickr

 

P1080815 by Ravensclyffe, on Flickr

 

P1080814 by Ravensclyffe, on Flickr

 

Edit to add: there are a whole raft of underframe photos there taken at Coventry last year.

 

Andi

Edited April 1, 2018 by Dagworth

[Arun Sharma]

Thanks Andi - Seriously useful. I can see some serious 3D drawing sessions coming.

These also incidentally confirm the presence of the MBSK's main transformer in its expected position adjacent to the switch but inboard -i.e., in the midline of the vehicle underframe. Some of that visible [lateral] pipework will belong to the oil cooling system for the main transformer and some will be for the switch. They had separate radiators as it seems not a good thing for the two lots of coolant to mix.

 

PS - The prize winning cats are also rather impressive.

Edited April 1, 2018 by ted675

[Dagworth]

Thanks Andi - Seriously useful. These also incidentally confirm the presence of the MBSK's main transformer in its expected position adjacent to the switch but inboard -i.e., in the midline of the vehicle underframe. Some of that visible [lateral] pipework will belong to the oil cooling system for the main transformer and some will be for the switch. They had separate radiators as it seems not a good thing for the two lots of coolant to mix.

Watch out though, there are two designs of transformer on 309s!

 

Andi

[Arun Sharma]

Yes, Thanks for that Andi - I saw some of that on the Rail 80 photo website pics. It is surprising that even though by ?1964-5 the GE main line was no longer using 6.25kV, that these vehicles retained the switch capability. Indeed even the two units that survived to go into departmental stock at Old Dalby still retained that switch. I suspect that, since 6.25 divides quite neatly into 25, the switch was also part of the series-parallel switching system to increase/reduce power rather than just a system for accepting different OHLE source voltages.

[Dagworth]

Good thing is that of the two units that have survived one is fitted with one type, and the other has the other

 

Andi

[melmerby]

Slightly off topic:

Weren't the early AC locos (e.g. AL1) also dual voltage?

How did they change from 6.25kV to 25kV?

 

Cheers

 

Keith

[Dagworth]

Slightly off topic:

Weren't the early AC locos (e.g. AL1) also dual voltage?

How did they change from 6.25kV to 25kV?

 

Cheers

 

Keith

See full explanation in the PDF linked to earlier in the thread.

 

Andi

[keefer]

On the railwaysarchive site there are also the Interim and Final Reports into the transformer explosions that affected the Glasgow and GE EMUs. They go into a massive amount of detail about the eqpt and circuits (no photos though).

I'll post a link when I can get on my PC.

 

EDIT: Final Report here (80 pages) http://www.railwaysarchive.co.uk/documents/MoT_EMUFailures1962.pdf

Edited April 2, 2018 by keefer

[Titan]

Yes, Thanks for that Andi - I saw some of that on the Rail 80 photo website pics. It is surprising that even though by ?1964-5 the GE main line was no longer using 6.25kV, that these vehicles retained the switch capability. Indeed even the two units that survived to go into departmental stock at Old Dalby still retained that switch. I suspect that, since 6.25 divides quite neatly into 25, the switch was also part of the series-parallel switching system to increase/reduce power rather than just a system for accepting different OHLE source voltages.

 

The Great Eastern was largely 6.25kV until almost 1980. This is why the 312s were built with 6.25kV capability, albeit just the 312/1's allocated to the Great Eastern. It was only completely eliminated just before the introduction of the class 315, which was 25kV only, so it had to be!

 

The unit was not part of the tap changing equipment, that was done on the secondary side of the transformer. This unit switched the four coils of the primary - all series for 25kV, all parallel for 6.25kV. 

 

Knowing that BR was expert at minimising expenditure - I would imagine that when 6.25kV was eventually done away with, that the switch was disconnected from the voltage sensing apparatus and left in the 25kV position. Without having to do any switching the maintenance requirements for it would have been almost zero, and probably less hassle/expense leaving it where it is rather than removing it and modifying the wiring to the primary side, which would be all 25kV rated cabling so not an insignificant job!

Edited April 2, 2018 by Titan

[Arun Sharma]

Thank you Titan - An informative and useful post [#15] which explains why the equipment survives to this day.

Edited April 2, 2018 by ted675

[keefer]

Paragraph 258 of the report I linked to above mentions that there had only been one incidence of faulty APC changeover on the LMR AC locos (due to a slow-raising pantograph drawing an arc).

Shortly after, the APC equipment was locked to the 25kV setting, as the LMR did not have any 6.25kV.

[Arun Sharma]

I had the opportunity to measure one of these switches and a 3D drawing [to be followed idc by a 7mm scale print] is attached. Some bits still need to be added of course.

Edited April 19, 2018 by ted675

[Titan]

I had the opportunity to measure one of these switches and a 3D drawing [to be followed idc by a 7mm scale print] is attached. Some bits still need to be added of course.

 

Looks good - if I ever get around to completing my 4mm scale 309s I may be interested in a scaled down version - and I bet Clive would not mind a few too!

[Arun Sharma]

Looks good - if I ever get around to completing my 4mm scale 309s I may be interested in a scaled down version - and I bet Clive would not mind a few too!

I now have close up pics and measurements of all the bits under the solebars of the class 309 BDTC, MBSK and DTC so in a week or so, I should have them all drawn in 3D.

What I found especially interesting are the subtle [but visible] differences between the 8ft6WB trailer Commonwealth bogie and the 8ft9in WB Commonwealth power bogie under the MBSK [and presumably DMBSK on the 309/1]. I think I'm going to have to produce my own 7mm versions of these cosmetic bogie frames.

[Clive Mortimore]

I now have close up pics and measurements of all the bits under the solebars of the class 309 BDTC, MBSK and DTC so in a week or so, I should have them all drawn in 3D.

What I found especially interesting are the subtle [but visible] differences between the 8ft6WB trailer Commonwealth bogie and the 8ft9in WB Commonwealth power bogie under the MBSK [and presumably DMBSK on the 309/1]. I think I'm going to have to produce my own 7mm versions of these cosmetic bogie frames.

Hi Arun

 

The power bogie has 3ft 3ins wheels and is a lot heavier looking. I have started to bash some 4mm ones from the class 29 bogie as that is closer than the bogies under the trailers and hauled Mk1 stock.

You can see the difference in this photo of a ex buffet set running as a 3 car unit, circa 1983.

[Arun Sharma]

Thanks Clive - The motor bogies also have these rather interesting devices tacked onto the four corners as well as having different cross members.

 

[Arun Sharma]

Clive  - Attached are side views of the 8ft9in power bogie from MBSK and an ordinary trailer 8ft 6in bogie from a DTC.

Note the lack of ribbing on the compensation beam on the 8ft9in bogie.

Edited April 20, 2018 by ted675

[Clive Mortimore]

power bogie.jpgnon-power bogie.jpgClive  - Attached are side views of the 8ft9in power bogie from MBSK and an ordinary trailer 8ft 6in bogie from a DTC.

Note the lack of ribbing on the compensation beam on the 8ft9in bogie.

Hi Arun

 

Thankfully for me using the Hornby class 29 bogie that too has no rib on the compensation beam.

 

http://www.rmweb.co.uk/community/index.php?/topic/93301-dmu-conversions-for-sheffield-exchange/?p=2918232