Dominic wrote:
(Chris Rogers) wrote in message
. com...
(Dominic) wrote in message
. com...
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.
That's interesting. I didn't know this inflexibility applied to
Voyagers. I thought distributed systems were less common on DMUs.
Maybe it's because of their 3-phase electric transmission?
Modern MU's have many systems that if placed in close proximity to each
other can affect performance, ie it is not a good idea to put OTMR
computers close to other stuff pumping out high levels of electrical
energy. The systems are distributed along the train in the same way that
the drive, be it hydraulic or electric is. Cross feeding between cars is
possible so that if one engine cuts out the coach is powered from the
others for ETS/HVAC purposes. It actually is not that inflexible. Modern
depots lifting equipment capable of lifting 5-10 cars at the same time.
By treating it as a unit and not a set of vehicles maintenance is easier
to plan.
The TMS systems in operation are only really effective over a maximum of
5 cars, so when coupling two sets the TMS on both must be able to talk
to the other one and gain information on all the systems by way of data
transfer, with this, the cross feeding etc, a lot of cables run between
the vehicles.
The TMS is usually in one of the outer vehicles behind the cab. Couple
two with the TMS at opposite ends to each other and there can be a few
seconds delay whilst the messages between computers match up and talk to
each other. In the early days of Voyagers 175s, and 180s drivers and
crews would be seen pushing buttons repeatedly after 5-6 seconds thereby
starting the system diagnostic over and over again. Mods to reduce the
complexity and display only the information the driver needs to see have
reduced this problem considerably. To test the viability of the TMS
several very long MU test trains have been run with up to 4 TMS's all
communicating along 20 vehicles. It worked.