Trains.

[Dave Plowman (News]

Seen a couple of articles where Chiltern Railways are converting some of their diesel electric trains to hybrid.

Of course the reporting poor in detail. Most say 'by Rolls-Royce adding a battery'

But the claims are intersting. A 20% fuel saving. But more interestingly

70% less NOX emissions.

Do they really spend that much time with the engine idling? The idea is they will enter and leave a station, engine stopped. Which will make a difference to local emissions. But overall?

Be nice to see just what has been done. I'd guess mods to the diesel engine and exhaust too.

[Andy Burns]

Couldn't find much detail

[Theo]

There are quite a number of conversion projects ongoing, including adding diesels to old electric trains (meaning they can be used on routes that are only partially electrified, eg the South Wales valleys, Reading to Gatwick), and old District Line trains reincarnated as battery, diesel-electric or hybrids.

This is a class 168 which is a diesel-mechanical multiple unit. That means the diesel has to rev hard when accelerating, and then it falls back to near idle when the train is on level ground, or slowing down. With a battery-electric hybrid system the diesel can instead run at the optimal revs to charge the battery, and acceleration is all electric. It can also regenerate when braking, something diesel trains can't do.

The 168s are about 25 years old so I wouldn't be surprised if there's a new engine as part of the refit (as the article suggests).

Theo

[Theo]

Ah, so that's 'Rolls Royce' because RR bought MTU Friedrichshafen, who make diesel engines which are already used in a variety of UK railway traction, including the 1990s diesel engines fitted to this class 168 stock. Not much to do with other parts of RR.

Theo

(Correction to my other post: the class 168s being converted here are diesel-hydraulic, not diesel-mechanical. The same inefficiencies apply though)

[Brian Gaff (Sofa]

If you have ever been in Kings Cross just before some of the 125s have been boarding and gone you would know how smelly and filthy those were and why its probably been done. These engines are efficient at speed but absolute crap when you have to slow or stop. I can almost taste them. Brian

[Brian Gaff (Sofa]

Well they are into everything of course, since they are now a big multinational. Some rocket parts are made by them as well mostly used in missiles though. Brian

[charles]

Paddington station was even worse

[newshound]

A toss-up whether it was better or worse that the days of steam, though, when I went on holiday to Wales in the 1950's and early 60's.

[jon]

I really liked the smell of steam trains, introduced to the smells when on Bedford station in 1943.

[Dave Plowman (News]

Yes. But made a great deal worse by the engines running all the time the train is waiting to depart. And, I'd guess, diesels well below today's standards as regards emissions.

[Max Demian]

I used to love the smoky smell of steam engines.

[Theo]

They need to run the engine for heating and cooling. Lighting, toilets, etc can run off batteries for a limited time, but HVAC can't.

On the HSTs such 'hotel' power was usually provided by the rear power car, ie the one closest to the buffers. So that's what made the most noticeable station smoke. In the late 90s/early 2000s the Great Western HSTs were reengined with MTU 16V4000 diesels - much cleaner than the original 1970s Paxman Valenta, but not as good as a modern car engine.

Nobody has managed to build a loco to modern Euro 5/6 standards that will fit inside the restricted UK loading gauge - instead various retrofits are underway because reengined locos don't need to pass modern regs.

Theo

[Max Demian]

Is the rear power car used for propulsion on HSTs at all, or would that mess up the couplings?

I notice that the new electric trains on the line from Reading to Paddington only have one pantograph extended at a time, either on the front power car or the next car to it. Isn't that rather wasteful as the rear one won't be doing anything?

[newshound]

I remember the rush to close the carriage windows coming up to the Severn Tunnel, though.

[charles]

The rear one will become the front one on the return journey

[Theo]

I believe so - there's only 2250hp per power car, so they need two to keep time. I'm not sure what the current shorter (GWR, Scotrail) versions do, since they have 4 or 5 coaches rather than the original 8 or 9.

I think there is something to do with overhead line dynamics: at speed the pantograph sets up oscillations in the contact wire. If you contact the wire from a wrongly angled pantograph (facing rather than trailing), or have too many pantographs within a certain separation, there's a limit to the speed the train can travel at before it disturbs the overhead line. To avoid that there's one pantograph facing each way and the right one is selected for the direction of travel. I think you can use the other pantograph under a suitable speed limit, or with suitable spacing (eg opposite ends of two 5 car units coupled together).

I'm not sure what the electrical load of a class 800 is, but to note a heavy electric freight train can be powered by a locomotive with a single pantograph, so I assume they aren't the limiting factor in current collection.

Theo

[Just Jim Dandy]

who cares

[Max Demian]

They didn't do that with steam trains. They had an elaborate turntable big enough for the engine plus tender.

(The problem of what you do to reverse a train at the terminus is an interesting one, with several solutions, that have only occurred to me in recent years. Also what holds the train on the track: it's not the flanges as I thought with model trains.)

[Tim+]

I think you?ll find that they did do that, very frequently in fact.

Tim

[charles]

They stripped that out at Mallaig which has a daily steamy in thesummer. I have a card showing theloco going backwards over the bridge across the River Morar/

At Waterloo all trains reverse out, driver changes ends.