pethadine82
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Just a quick question, forget the signalling for a sec but can S7/s8 stock work on third rail 750v DC power?
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Can S7/S8 stock work on third rail only?
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Theoretically, if the centre-rail shoe was bonded to the wheels, to allow the negative return current via a running rail.
That is my understanding, anyway..
notadriver
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Just out if curiosity where would they go on third rail only ?
Dstock7080
Established Member
They could only work on one system at a time, conversion work would be require before using each system.
Easy transfers could be made at Wimbledon, East Putney, Richmond and Gunnersbury if the signalling was altered to accommodate this.
Easy transfers could be made at Wimbledon, East Putney, Richmond and Gunnersbury if the signalling was altered to accommodate this.
WinterChief
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They will already work on 750V DC But gearboxes, axle covers and axles were never designed for the return of current so extensive (and expensive!) mods would need to be carried out - For very little gain.
would it really be that much work? After all, various other LU stock has been converted in the past (admittedly older stock)- and I'm pretty sure some has been converted more than once- I'm sure I've not imagined seeing pictures of Met locomotive "Sarah Siddons" running on 3rd rail?
The benefits of doing so are the issue- you'd at the very least still have to have a bonded 4th rail between Acton Town and Hanger Lane junction (in Ealing) and Ruislip-Uxbridge- at the risk to operational flexibility traded off with maintenance simplification you could fully separate the District and Picadilly between Barons Court and Acton Town.
More radically, could you run S-Stock from Acton to Ruislip? This would then allow complete separation of the Picadilly and District (much like the separation of the Jubilee and and Metropolitan)
It would actually surprise me if the S-Stock hasn't been specified with the potential for 3rd rail running.
The benefits of doing so are the issue- you'd at the very least still have to have a bonded 4th rail between Acton Town and Hanger Lane junction (in Ealing) and Ruislip-Uxbridge- at the risk to operational flexibility traded off with maintenance simplification you could fully separate the District and Picadilly between Barons Court and Acton Town.
More radically, could you run S-Stock from Acton to Ruislip? This would then allow complete separation of the Picadilly and District (much like the separation of the Jubilee and and Metropolitan)
It would actually surprise me if the S-Stock hasn't been specified with the potential for 3rd rail running.
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Nym
Established Member
Remeber for a moment who owned Metronet SSL Ltd. when the S Stock was being 'specified' then you'll realise you may well be supprised...
Also, in practice, other stock uses the SSR quite a lot anyway, and there's already problems with interoperability of signalling systems, so why would you want to make a stock move even harder?
Also, in practice, other stock uses the SSR quite a lot anyway, and there's already problems with interoperability of signalling systems, so why would you want to make a stock move even harder?
edwin_m
Veteran Member
Both OLE and third rail units have bonding and brushes to take the return current. Bearings in particular probably wouldn't take kindly to it. I don't know if LU stock also has this bonding as it might be needed in certain fault situations.
As stated, running on third rail would require the fourth rail shoes to be bonded to the vehicle body and back to the wheels as described above. This would have to be disconnected before reaching LU fourth rail as the LU running rails need to be isolated from both traction rails. Also third rail units have (I think) a 750V bus cable linking all the shoes within a single unit, but on the fourth rail system each car is self-contained and runs from its own pickups. If this is essential for third rail operation then it would also need to be disconnected before reaching a LU fourth rail section.
Making a unit operate on both systems therefore needs quite a few circuit breakers which would have to work reliably each time and probably don't have a safe failure mode (failure either to open or to close could be a safety issue in certain circumstances). Not impossible but a bit tricky and potentially unreliable.
Other than engineering trains, and discounting the Picadilly sharing with the District and Met, what tube-gauge stock moves use the SSR? If you disconnected the Picadilly as I suggest, then the SSR could for stage one move to a similar system to the Watford DC/Richmond District and WLL/District to Wimbledon. This would then allow the stock modifications to pure 3rd rail operation to be carried out gradually, then convert the lines to the simpler 3rd rail system.
If you went really radical- how much of the SSR has super low roof clearance? Could track beds be lowered enough on the SSR for the eventual S-Stock replacement to be OHL powered?
Dstock7080
Established Member
'92, '09 and S Stock are all motored but do not have shoes on every car.
notadriver
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I thought 09 stock (Victoria line) was not 100% motored as this wasn't needed to meet the required specification?
edwin_m
Veteran Member
Are the shoes on different cars electrically interlinked or does each shoe-equipped car only supply a specific group of motors?
I'm aware that the transition between third and fourth rail on Putney Bridge a few years ago has a gap which is only just over one coach long. If the shoes were interlinked through a unit then this would cause a short circuit by bonding the third rail of the third rail system (at 750V above earth) to the third rail of the fourth rail system (at about 400V above earth). This was however a few years ago and may have been changed for some reason.
Nym
Established Member
It's not all bogies motored as there isn't space underneath...
You need space in two of the cars for compressors, and with the compressor there isn't space for the MITRAC invertors. It's sod all to do with the spec.
2009TS is formed;
A-B-C-D-D1-C-B-A
With shoegear on A, D and D1 cars.
Motors on bogies in A, C, D and D1 cars.
and Compressors in B Cars.
--- old post above --- --- new post below ---
Depends on the stock.
DC Electrical Systems on all LUL stock is isolated between shoegear cars.
The DC network is only to spesific motors on each car, traditionally, only supplying the motors where shoegear is provided (on conventionally controlled DC stock).
Modern stock still isolated the DC bus between cars, for example on the Victoria Line, the motors in the A car are fed from the A car, and the D and C or D1 and C cars from the respective D or D1 car.
The DC Control circuits are traditionally (mostly) bussed through all cars and units, but again, this is dependant on the stock.
On newer stock, a different system is provided from the PCMs that allows electrical auxillaries to function from a single set of shoes between cars, but not traction current supply.
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edwin_m
Veteran Member
Thanks Nym, that confirms my understanding in respect of the shoes on individual cars not being parallelled, though it seems logical to power the non-tractions systems from any car that has power available and this can be done without the risks at supply changes that I mentioned earlier.
Nym
Established Member
All of the shoes on each car are commoned though, if you'd like some more detail on a spesific stock then drop me a PM and I'll see what I can answer for you.
Also, it should be noted that it is only on 'modern' stock that there is a power busline throughout the train, rather than the older stock that only has control lines throughout (even emergency circuits are only local).
edwin_m
Veteran Member
Thanks, the commoning of shoes on each car was as I understood it. Just that my previous dealings with this arrangement didn't cover the more recent types of stock.
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