Thread: Modern DC EMUs
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Old April 20th 04, 08:12 AM posted to uk.railway,
Chris Rogers Chris Rogers is offline
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Default Modern DC EMUs

(Dominic) wrote in message . com...
With an older DC EMU such as a 4-CEP I imagine that the driving motor
car can be uncoupled from the set and run independently under its own
power, and that 2 such cars could form a 2 car train.

This is not always the case with Mk1 EMUs - as I understand it, in
some units (like the 4-CIG IIRC) the driving cars are not the motor
cars - the units have separate driving trailers and a single motor
car. In this case, the 3rd Rail pickup shoes are on the
leading/trailing vehicles and not the motor car itself, so apart from
having no cab, an isolated motor car like this would have no power

However, in principle, I believe you are correct with some stock which
indeed has driving motor cars.

Are the driving motor cars of modern DC EMUs such as Networkers,
Junipers, Electrostars and Desiros independent multiple units in this
way? It seems that no set is ever run without a pantograph trailer car
- is this because the motor cars rely on the electronics or other
systems in this car, even when running from the DC 3rd rail? Or can
the motor cars run seperately from the rest of the set?

Modern stock introduces problems through a concept known as
'distributed systems'. The equipment required for the train to work is
not fitted exclusively on the driving or motor cars, but is
distributed along the length of the train. In this case, by removing
one or more cars from the set, some essential equipment would be
removed too.

In the case of Voyagers, you would expect that any formation of 2 or
more cars would be possible as each car has its own engine - in fact
because of distributed systems and other technical limitations, the
minimum consist of a unit is 4 cars.

I was told by a technician that in the case of Class 444/450 Desiros
that it is a very difficult procedure to separate cars in a set
anyway, because they are semi-permanently coupled and not designed to
be separated.

Hope this is of interest,


P.S. This is written from my own, perhaps limited, knowledge and
understanding of the technical aspects. I am not from a railway
technical background, but believe this information to be correct. I am
sure more knowlegeable contributors will confirm or refute what I have