Multiple working systems

[MrSir]

I'm trying to figure out how a multiple working system works. I originally only thought that a train with the same multiple working system as another train could only operate in multiple if they were right next to each other or if the coaches or wagons had a special modification to make it work but now I've watched a video of the Colas Class 67s with a Network Rail service and a video of the Wherry Lines Class 37s where in both situations the engine at the back revved up at the same time and with the same power when departing the station whilst having coaches between the 2 locomotives, I'm starting to have doubts about how I thought it originally worked.

 

[Towers]

Any system that involves either a "push-pull" arrangement, so a loco at one end and a driving trailer of some sort at the other (eg Class 91+MK4s+DVT), or a loco at either end (eg HST), essentially relies upon a jumper cable which runs the entire length of the train and relays relevant control inputs from the driving end to whatever is on the rear. In the case of locomotives, this tends to be via a separate jumper cable, whereas on a modern multiple unit (Sprinter etc onwards, pretty much) this will usually come through the coupler units.

To give an idea, HSTs use a '36-way' jumper cable; so there are 36 individual cables within the jumper, each of which can relay a different signal or command from one power car to the other. The Southern Region of BR developed its own variant with 27 wires, which was fitted to all of it's MK1-based 'Slammer' electric multiple units as well as several classes of locomotives, which meant that pretty much anything on the Southern could work in multiple with anything else. A very simple but well thought through idea, giving total flexibility. So clever was this system that there is now a preserved 'Slammer' somewhere on a heritage line, which can be attached to their resident Class 73 and then driven from within a cab of the electric unit, despite there being no third rail, the cab controls of the EMU driving the loco attached to it.

 

[MrSir]

Any system that involves either a "push-pull" arrangement, so a loco at one end and a driving trailer of some sort at the other (eg Class 91+MK4s+DVT), or a loco at either end (eg HST), essentially relies upon a jumper cable which runs the entire length of the train and relays relevant control inputs from the driving end to whatever is on the rear. In the case of locomotives, this tends to be via a separate jumper cable, whereas on a modern multiple unit (Sprinter etc onwards, pretty much) this will usually come through the coupler units.

To give an idea, HSTs use a '36-way' jumper cable; so there are 36 individual cables within the jumper, each of which can relay a different signal or command from one power car to the other. The Southern Region of BR developed its own variant with 27 wires, which was fitted to all of it's MK1-based 'Slammer' electric multiple units as well as several classes of locomotives, which meant that pretty much anything on the Southern could work in multiple with anything else!

But what about a consist like just some random Mk1 or Mk2s with something like a 37 at each end? With no special wiring, would the 2 Class 37s work in multiple?

 

[Towers]

But what about a consist like just some random Mk1 or Mk2s with something like a 37 at each end? With no special wiring, would the 2 Class 37s work in multiple?

They wouldn't, unless they were cabled. The only other way is to have them both being driven separately, as per banking locos for example.

 

[Ken H]

But what about a consist like just some random Mk1 or Mk2s with something like a 37 at each end? With no special wiring, would the 2 Class 37s work in multiple?

There is a system of using the RCH lighting control jumpers to do the job. Developed by the rail technical centre, it was first used with the cl47/7 -"DBSO Push pull trains in Scotland and later on the new DVTs on the WCML. It used time division multiplex to relay the control signals along the train. Glory was it could be used with any coaches with RCH jumpers. When every thing was!

 

[norbitonflyer]

There is a system of using the RCH lighting control jumpers to do the job. Developed by the rail technical centre, it was first used with the cl47/7 -"DBSO Push pull trains in Scotland and later on the new DVTs on the WCML. It used time division multiplex to relay the control signals along the train. Glory was it could be used with any coaches with RCH jumpers. When every thing was!

I assume the locos/DBSOs needed special modifications for this to work - hence the 47/7 subclass. Other types used on push-pull work presumably have to have the same mods fitted either from new (on the 67s?) or retro-fitted to the 37s - and the 86s and 90s on the Great Eastern and WCML?

I think the original ScR push-pull trains (top and tail 27s) did use specially adapted coaches, allowing "blue star" control signals to pass between the two locos

 

[43096]

There is a system of using the RCH lighting control jumpers to do the job. Developed by the rail technical centre, it was first used with the cl47/7 -"DBSO Push pull trains in Scotland and later on the new DVTs on the WCML. It used time division multiplex to relay the control signals along the train. Glory was it could be used with any coaches with RCH jumpers. When every thing was!

The system fitted on the Edinburgh-Glasgow Class 47/7 "Shove Duffs" and DBSOs was different to the later TDM system, although both used the RCH jumpers to transmit the signals. The DBSOs were converted to the later TDM system when they transferred to Anglia so that they were compatible with the Class 86s. TDM was fitted to all of Classes 86, 87, 89, 90 and 91.

 

[edwin_m]

All American diesel locomotives use a common system devised by the Association of American Railroads, and the American designs imported to the UK also have this (and none, as far as I know, have the old TDM system). Some passenger stock has been through cabled with this system too, and DVTs converted to use it.

 

[30907]

Fairly certain the 37s worked top-and-tail - that was definitely so on the Cumbrian Coast before the driving trailers were introduced.

I'd be surprised if the power of 2x37 was needed to/from Gt Yarmouth

 

[XAM2175]

It is also possible to transmit the multiple-working signals via a coded radio link between locomotives - General Electric call their system "Locotrol" - but I don't believe it's used in the UK.

 

[hexagon789]

There is a system of using the RCH lighting control jumpers to do the job. Developed by the rail technical centre, it was first used with the cl47/7 -"DBSO Push pull trains in Scotland and later on the new DVTs on the WCML. It used time division multiplex to relay the control signals along the train. Glory was it could be used with any coaches with RCH jumpers. When every thing was!

Developed by Brush, hence the official name of "Brush two-wire system".

It used Time Division Multiplexing and Frequency Modulation but was much simpler than the later TDM systems.

I assume the locos/DBSOs needed special modifications for this to work - hence the 47/7 subclass.

Yes, theres quite a number of chunky electrical cabinets (technology of the day) in a /7.

I think the original ScR push-pull trains (top and tail 27s) did use specially adapted coaches, allowing "blue star" control signals to pass between the two locos

Blue Star cables AND crucially a through control air pipe. Control air is what 27s use to control the engine governor.

The system fitted on the Edinburgh-Glasgow Class 47/7 "Shove Duffs" and DBSOs was different to the later TDM system, although both used the RCH jumpers to transmit the signals.

Basically control inputs from the DBSO (4 notch power controller) went into an Input Module where relays converted these control inputs to low voltage and low current signals. These signals were then converted into a series of pulses 640 microseconds long, this being the TDM part of the process.

These pulses were checked by the
Parity Checking System before then being fed into the Transmit Module where they were converted into a Frequency Modulation wave (155 kHz) sent via the RCH lighting cables to the loco where the FM Module, Control Module, Receive Module and Output Module converted the signal to 110v DC On or Off via a bank of remote control relays that interfaced with the loco auxiliary power system.

== Doublepost prevention - post automatically merged: 17 Oct 2021 ==

Fairly certain the 37s worked top-and-tail - that was definitely so on the Cumbrian Coast before the driving trailers were introduced.

I'd be surprised if the power of 2x37 was needed to/from Gt Yarmouth

They did use double power on the Wherry Lines.

The 37s used by DRS, and coaches, are all Blue Star fitted.

 

[SuspectUsual]

how does multiple working work with locos with the same system (eg blue star I guess as the most common) but different engines etc? For example a 20 and a 37. Totally different power outputs, presumably different rpm etc for the engines themselves

 

[hexagon789]

how does multiple working work with locos with the same system (eg blue star I guess as the most common) but different engines etc? For example a 20 and a 37. Totally different power outputs, presumably different rpm etc for the engines themselves

I presume it gives the same air pressure in the engine governor.

 

[James James]

All American diesel locomotives use a common system devised by the Association of American Railroads, and the American designs imported to the UK also have this (and none, as far as I know, have the old TDM system). Some passenger stock has been through cabled with this system too, and DVTs converted to use it.

Similarly, most new locos on the continent* support ZWS/ZDS/ZMS (these are all time-based multiplexing systems, so in some way similar to TDM in terms of the technology being used - the ZWS variant seemingly only supported remote-control of a single loco, ZDS is for combined use of 2 locos, and ZMS allows for remote-control of 1-4 locos). For newer passenger trains however - and many EMUS - WTB is the standard of choice** - but usually that requires retrofitting WTB into the appropriate locos (and/or specifying it as an option when ordering your locos - it certainly doesn't appear to be fitted by default) - the ZWS/ZDS/ZMS combo this seems to be the current standard for most locos.

* At least this covers Bombardier and Siemens locos, i.e. Traxx and Vectron and Eurosprinter - and those happen to cover freight and some passenger duties for a huge proportion of the continent. That leaves out France and Spain where I have no idea what's going on, and a few small series such as Skoda/Newag/Pesa but those would be the exception to prove the rule.

** At least the OBB seem to use WTB for various push-pull trains including the Railjet, DB are using it for their IC2 and at one point retrofitted the IC1, and SBB have a pre-standardisation variant of WTB too apparently. It's speculated but unproven that the DB ECx will use WTB to allow use with the existing Diesel locos


Interestingly, the class 68's claim to support WTB (some are fitted with AAR, but that was presumably done to allow use with the Mk3 DVT's which had already been fitted with AAR to allow use with the 67s) - and perhaps that's being used for the TPE Mk5's?

 

[Richard Scott]

I presume it gives the same air pressure in the engine governor.

Yes it does. The different power output makes no difference. The load regulator on each loco will ensure the output from the engine matches the road speed so the engine will always be correctly loaded. Only thing driver needed to ensure was that they didn't exceed maximum speed of the lowest speed loco.

 

[Ashley Hill]

A red triangle DMU could work with a blue square DMU but if driven from the red triangle set you had to remember to keep changing gear!

 

[Taunton]

how does multiple working work with locos with the same system (eg blue star I guess as the most common) but different engines etc? For example a 20 and a 37. Totally different power outputs, presumably different rpm etc for the engines themselves

The American AAR (Association of American Railroads) system is brilliant for this. You can multiple a brand-new all-electronic GE unit with a 1950s Fairbanks-Morse one and they work fine together, with all other combinations in the typical North American multi-unit "lash up". I don't think US railroads would have anything else. It's been a significant part of keeping out any foreign manufactured locomotives - the Krauss-Maffei hydraulics shipped over in the 1960s were really a lost cause because of this.

== Doublepost prevention - post automatically merged: 17 Oct 2021 ==

A red triangle DMU could work with a blue square DMU but if driven from the red triangle set you had to remember to keep changing gear!

That was actually banned after at least one unit was destroyed by fire after the driver forgot, oversped the transmission of the trailing unit, the shaft broke and punctured the fuel line.