Big Diesel Little Diesel

In the Modernisation plan BR ordered 'main line' loco's across the power range from 1000 to 3300hp.

Now, I can understand that in some places a big loco is too big or heavy, and I also realise that a larger loco will be more expensive to maintain simply because it has more wiggly bits and traction motors as well as a higher capital cost.

But, assuming locos of a similar era and including the capital costs, whats the extra cost of running a 'high power' loco compared with a low power one. Given that there has never been a 'Class 37' replacement I suggest that its not that favourable but can anyone comment?

 

I don't know the answer to the question, but it's noticeable how many trains are over-powered these days. We have pairs of 66s on the Rail Head Treatment train, pairs of 68s on a single nuclear flask, Class 37s top and tailing 3 coaches on the Cumbrian Coast, and now we are getting 2+4 HST formations. I suppose some of these formations are for operational reasons, but it seems very inefficient from a fuel consumption point of view.

 

To be honest the 33's and 37's were being outclassed by increasing trainloads by the 1970's and the 47's were being hammered into frequent failures on container trains by the mid 1990's. It made economic sense to purchase large batches of high horsepower locos with guaranteed better reliability. There were other economies such as fewer spares to be kept and less time type training drivers. Service reliability also improved with fewer loco failures.
Is it worth a different design, spares etc to save maybe 20%fuel consumption and then have a loco that is restricted from working full load trains?
Just a reminder that railfreight in the UK is balanced on a tightrope of very fine commercial margins. An extra 100tonnes payload per train or saving a drivers duty over a week can make the difference between profit and loss. DBC, FL, GBRf and DRS are in it for the money and nothing else......

Cheers, Neil

 

Some of these trains are not as light as you might think. Firstly a lot of the freight or departmental is running at speeds far greater than the old coal trains of yesteryear. Secondly the weight included a 100 tons of dead loco as run around facilities are rare. Put them together and you soon find you are hauling 200tons on the Cumbrian coast or a flask train might be more.

73/9s are the nearest replacement to 37s.


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While not answering the original question, another part of the background to this is the thinking around at the time of the BR Modernisation Plan. BR was still hoping to be able to hang on to a lot of old-style freight traffic (including short, slow trains; and single wagons being dropped off and collected from goods yards at every station). There were also a lot of very short, slow passenger trains on branch lines. BR Managers were unable or unwilling to recognise that the advent of the motorway system, mass car ownership and large lorries would wipe out rail's share of both those kinds of traffic.

So Modernisation Plan diesels included a lot of smaller types designed to directly replace the less powerful types of steam locomotive. Other reasons for having a range of smaller diesels might have beeen their suitability for lightly laid branch lines and goods sidings; and the manufacturers' lack of experience at that time in building more powerful diesels within the British loading gauge and axle loadings.

At the time of the first orders for mainline diesels, BR HQ did not see any need for power above 2000 hp. The 3300 hp Deltics only happened thanks to their enterprising manufacturer, and success in persuading East Coast management that the Deltics would be good to have on that route.

 

I suppose the 350hp shutters had been operated perfectly satisfactorily for quite a few years whereas IIRC the more powerful early diesel prototypes did suffer from electrical problems with the transmission, while the even more powerful WR gas turbines had serious electrical problems (contributing to Swindon's decision to go for hydraulic transmission).

So perhaps at that time there was an intuition that power might be inversely proportional to reliability?

 

AIUI a class 38 was proposed as a replacement for the 37s but it never happened.

 

Actually, this is a very good answer to the OP. On today's railway, where most passenger services are worked by multiple units, the main employment for locomotives is on heavy block workings. I would guess that Rail Head Treatment, nuclear flasks and engineering are only a tiny proportion of the revenue, and therefore do not justify investment in specialist traction. From a purely commercial point of view it makes more sense to spend a little more on fuel for a class 66 than to invest in a special purpose Type 1 diesel.