A few questions!

[QPRfella]

Hi there, I've got quite into trains but there are still some things that confuse me! I live in South London so travel up to London Victoria using Electrostars quite a lot, but one thing that's always struck me as odd - those guys that walk around the platform injecting some sort of fuel into the trains that are yet to depart. I always thought the Class 377s were Electric Multiple Units so I don't quite understand what they're doing? Another thing was a question about Locomotive's coaches - with the HST and the Class 91, I see they use Mark 3 & Mark 4 coaching stock respectively, which are obviously just trailer cars because the power cars are enough to pull the train along. I was just wondering why they are so cluttered at the bottom then? I mean what is that big great thing at the base of the coaches?

I have a few more questions about the Class 91 and the Driving Van Trailer (which I still don't understand the concept behind) but if you guys could try and clear these ones up for now, I'd be really grateful! Sorry about my lack of knowledge

 

[O L Leigh]

I suspect you've been seeing the chap on the bowser topping up the water tanks for the toilets between trips.

As for what's below the solebar on Mk3's and Mk4's, it comprises mostly the air-conditioning, CET (toilet) tanks, brake gear and other gubbins. BR just decided to box it all in when they built them to make things neater and a little bit more aerodynamic.

O L Leigh

 

[tubeprune]

Regarding push-pull, you might find the following articles useful:

http://www.railway-technical.com/tr-ops.shtml#PushPullOperation

http://www.railway-technical.com/pu-pl.shtml

 

[P156KWJ]

other stuff used similarly to DVTs are DBSOs (Driving brake standard open) if you split that up...
Driving: power handle used to pick up power from the loco at the back (will not work without external power)
Brake: normal service braking available
Standard: standard class - easy
Open: i.e. not compartments as used in the majority of earlier mk1s

Gatwick express also used to use class 489 GLVs. Not sure what that stands for though

 

[heart-of-wessex]

GLV:

Gatwick Luggage Van (IIRC)


The DVTs and DBSOs I believe use something called TDM (Time Multiplex Division)?

 

[O L Leigh]

You can look at a push-pull set in much the same way as an MU. Both types of train have control circuits that run the entire length of the train and electrically control all of the train's traction and braking functions from the front cab. Precisely what form these control circuits take and the principle on which they operate will vary according to the type and class of the train in question.

The only real difference between an MU and a push-pull set is that the MU has it's control circuits carried in seperate cables, where the push-pull set uses a digital protocol that it sends along cables that already pre-exist in the coaching stock for lighting, PA and other functions.

O L Leigh