BR diesel locomotive insignia

[SRman]

14 hours ago, jim.snowdon said:

The conventional definition of a multiple unit, diesel, electric or multi-mode, is a formation of one or more vehicles capable of operating as a train in its own right and (critically) being coupled to others of a compatible type in order to make up a train of two or more units, all under the control of one driver. An HST is not a multiple unit as you cannot couple two HSTs together as a train under the control of one driver. Nor, in their original form, were the Blue Pullman sets; it was only later after they were fitted with the necessary jumper capes each end that the 6-car sets qualified as diesel multiple units. 

 

Multiple Unit control is a different term that simply defines motive power units, whether locomotives or motor coaches, that are capable of being coupled together electrically so as to be controlled by a single driver. It doesn't matter how many non-powered vehicles are in between the powered ones. An HST is two locomotives coupled in multiple either end of eight carriages. Similarly, two, or three, blocks of locomotives coupled in multiple and controlled by wireless means from the lead set, as in very heavy freight trains in the US and other parts of the world, are operating in multiple, under MU control.

 

Jim

 

 

Being super-pedantic here: the Blue Pullmans were technically made up of half-sets, so could be argued to be multiple units, in that they could have different half-sets MU'd together. 

In fairness, while I agree with your definition, HSTs are sort of halfway houses between loco-hauled stock being top and tailed, and a true DEMU. Their power cars could, in theory, be used for hauling other passenger stock, or freight stock, but in practice would have been wasted on freight, and incapable of running the incompatible electrical systems of normal loco-hauled coaches.

Edited December 31, 2019 by SRman

[Zomboid]

6 hours ago, rodent279 said:

Interesting that the TC's were classified in the EMU number series, when really they are hauled stock, and should be numbered as such. Edinburgh-Glasgow push-pull sets were very similar in principle, except they could only be driven from one end, yet they were not numbered out of the hauled stock range, nor, as far as I am aware, were they treated as "units."

Probably a mentality thing. The Southern was (and had been for a while) pretty much entirely a multiple unit railway, so it suited them to think of the TCs as MUs.

 

Something similar happened with the Gatwick express mk2s; they were grouped into sets much like the old SR fixed sets, which had 4xx class numbers. At least according to SEMG they were...

 

Meanwhile Scotland had plenty of MUs, but also plenty of LHCS, so the MU mentality wasn't there.

[rodent279]

Though one question I have is could any coach, with suitable brakes and heating, be coupled in an E-G set, as long as it had RCH jumpers?

 

Edited December 31, 2019 by rodent279

[EddieK]

On 31/12/2019 at 08:57, rodent279 said:

Though one question I have is could any coach, with suitable brakes and heating, be coupled in an E-G set, as long as it had RCH jumpers?

 

Yes any coach could, provided that it had air brakes, electric train heat and RCH jumpers.  From the depths of my memory, in Spring 1987 I travelled in a push-pull set that had a Mark 1 RMB added at the non DBSO end.

RCH jumpers were, of course, fitted to stock for through lighting control. BR was then able to add public address to its trains by sending the messages down the RCH cables. (Hence the click from the speakers when the lighting was turned on or off). Then the high frequency TDM signals were also sent down the RCH cables.

Same principle applied to WCML push-pull operation, though with a more advanced TDM system.

[EddieK]

On 31/12/2019 at 08:02, Zomboid said:

Probably a mentality thing. The Southern was (and had been for a while) pretty much entirely a multiple unit railway, so it suited them to think of the TCs as MUs.

 

Something similar happened with the Gatwick express mk2s; they were grouped into sets much like the old SR fixed sets, which had 4xx class numbers. At least according to SEMG they were...

 

Meanwhile Scotland had plenty of MUs, but also plenty of LHCS, so the MU mentality wasn't there.

By the mid 1980s, BR was using set numbers for its coaching stock, so no doubt the push pull sets had "EC" set numbers. Don't know to what extent the individual vehicles were assigned to particular sets on the push-pulls, though. 

In 1989, when I started work on WCML coaching stock, the establishment of fixed set formations was just getting underway. Prior to this, the sets were formed with the correct number of vehicles of each type, but when an individual vehicle needed heavy maintenance or works overhaul, it was taken out of the set and a replacement was put in, that had just been maintained or overhauled. When Wembley Depot had a new maintenance shed provided, it was possible to stop an entire train for heavy exam, so no need to shunt odd coaches out. The next phase was to work out when each coach was due overhaul, then put together sets of coaches with the required formation and with overhaul due dates that sort of aligned. Then we would send a complete set of coaches for overhaul. Each set had a "WB" set number.

When I worked on the ECML, the Mark 4 coaches went through the "Mallard" overhaul, and in theory you could identify the set number from the First Class portion: if the set had 11305 and 11405 in it then it was BN05.

[rodent279]

On 31/12/2019 at 06:32, SRman said:

Being super-pedantic here: the Blue Pullmans were technically made up of half-sets, so could be argued to be multiple units, in that they could have different half-sets MU'd together. 

In fairness, while I agree with your definition, HSTs are sort of halfway houses between loco-hauled stock being top and tailed, and a true DEMU. Their power cars could, in theory, be used for hauling other passenger stock, or freight stock, but in practice would have been wasted on freight, and incapable of running the incompatible electrical systems of normal loco-hauled coaches.

Have just realised that Pendolinos aren't EMU's, as they can't run in multiple with each other. I guess they are simply electric units, EU's.