Heritage Line Loco Power Requirements

Ahh! PH's favourite livery of 'improved engine beige' rears its head!

 

Its interesting, perhaps, in this context that in his book Cook (head of Swindon works and later WR and NE region CME) records that the reason the GWR converted a number of the Star class to Castles was that "[we] made a case that on account of the larger boiler, which was working at a lower evaporation rate we could maintain Castles for one penny a mile less than Stars."

 

Two points that I don't think have been raised are the issue of daily diagram and yearly diagram.

On the daily point: we have a daytime duty that, in the summer, is typically 6 carriages (requiring a class 4 or above on our gradients). The same loco then hauls an evening dining service, which is typically 4 carriages. The class 4+ is obviously overpowered for the evening duty (which is just within the capability of a class 1P tank engine), but using the over-powered engine while it is in steam is clearly cheaper than steaming a smaller engine that is more closely matched to the duty, but would have to be steamed specially.

The other point is about yearly duties, especially for lines that have a markedly seasonal traffic. Suppose you have a line that operates for 10 months per year, and needs a class 2 for six of them, but a class 4 for three months in the summer and a month at Christmas. Which is cheaper - to have a class 4 in traffic working below capacity for six months, or have two locos (class 2 and class 4) when there is only work for one? The excess running cost of a class 4 doing a class 2 duty is actually very small, whereas the overhaul cost of having two locos in traffic when you only need one is considerable.

I think sometimes the excess cost of running a too-big loco is over-estimated. Far more gain to be had in coal consumption from efficient diagramming, particularly when there is a mix of duties that sometimes requires a large loco, and sometimes not. Clearly there are subtleties at work, but I think a more interesting question in the overall cost base is about what is the optimum number of locos vs. their optimum size (complex questions about annual mileages; target mileages between overhauls; resilience in event of failure; optimising locos to the traffic vs. optimising works throughput etc).

Tom

 

I don't think size is the only factor on the last point. Many large locos have relatively low axle loadings (due to lots of wheels) and some of them are rather kinder on the track than their smaller cousins (due to having 3 or 4 cylinders instead of 2).

 

How many can it take on the weekends?

 

Certainly on the GCR any tank engines are pretty much forced to take water on every round trip (16 miles, there and back). This means that a tank engine uses pretty much all of its allowance for running round at Loughborough, whereas a tender engine can often run straight round and be ready to go again in under 10 minutes*. This does make a difference in terms of clawing back time when delays occur. I imagine that adding the slightly longer run to Ruddington and back would pretty much force us to have regular loco swaps throughout the day if we ran a fleet of tank engines, at least unless and until we manage to put water facilities in at both ends. I can't see a scheduled 15 minute stop in the middle of the line in each direction on every through service being popular.

(*Incidentally the running round time on standard gauge railways always amazes me. I remember on a NG line in Germany once sitting on the train 2 minutes from departure time and wondering where the loco was (all I could see was some smoke coming out of the shed at the far end of the yard). We still left on time! But I digress.)

 

That's Tuetonic efficiency for you! Mind you, back in tbe early 70s, the intensive Talyllyn service of those days produced some pretty rapid rapid loco changes at Wharf, with the loco from the previous arrival scooting from it's berth on the watering road to couple up, and the train loco moving to same, pretty much the second the train with which it arrived cleared the shunt signal, just past the overbridge. Some very busy summers back then!

 

Some very busy summers back then!

And now come to that, which is something else PaulH seems to fail to acknowledge in his dislike of larger engines. Most railways have heavier trains to cope with demand and can therefore need larger engines to cope. He would surely not advocate spending lots of money on the loops and other infrastructure necessary to run an intensive service with smaller engines and lighter stock together with all the additional loads that implies for those who maintain them?

 

Depends on what has been done to it, and by whom, in theory 5 , but it could just as well be sat on top of a sleeper pile hiding

 

Not "forcing" them on anybody.

PH

 

That,alas, is rather the case as it is.

PH

 

Exactly so!

PH

 

Good grief! He was talking about machines to haul 300 plus tons at 50 plus mph averages, not tourist railway use at 25mph maximum.

PH

 

You should try being a buffet steward with a 14in Barclay 0-4-0ST on the front of 4 carriages. Interesting!

 

Not being very lateral there Paul. You mentioned earlier that there are few railways over 10 miles long which is true. But the number is increasing and many of them are finding that class 4 motive power is necessary and haul trains of the length now demanded by passenger loadings. That is being pragmatic for the reasons discussed in this thread.

I note your comment about watering at both ends of a line, but on the SVR (for example) they are already having to do just that with such engines, because they are running 16 miles hauling (often) 8 carriages. Maybe they should cut the line to 6 miles and run everything with 3 carriages max?

 

Everyone has a right to hold the views they have, i can understand why some people will look at a 5 car mk1 rake half empty half way through the day, and say, why are you running with 5 on, take two off , but what they don't understand is that later on, that train could be full and to run an shorter rake will mean disgruntled passengers, Same with saying why run a large engine, when you could use something smaller, again, its a simplistic question , the answer is complicated, for instance , something like a u class to some lines would be a large engine, but to others its a small un, when 31806 visited the NYMR she was at her limit of boiler ability to keep steam, yet she is a very free steaming engine, a BB, or WC, once lit up uses little more coal or water, because you can work it at a more economical cut off, and a skilled fireman doesnt waste coal or water, by controlled boiler management, compared to a smaller engine, that will be working harder to lift the same load, now there is the crew to think of, most these days will have at least 3 on the footplate, on a tender engine its not so bad, you are not in anyones way, but on a small tank, its hard to fit 3 in the cab and not be in each others way, if you are training a third man, a tender loco is by far easier as you can observe and correct where as on a cramped footplate it a lot harder , then there is the weight of the train, not every railway has the luxury of a lighter pre grouping rake, so Mk 1's it has to be, so a 2mt may not have the power , heritage railways are not in the business of wasting money, if anything,, they are very good at controlling expenditure so no railway will put up with a heavy coal and workshop bill if they are using engines that are not economical .

 

Intresting Martin specifically mentions BB/WC.... my understanding was always that they're hungry beasties, but I'd imagine 200 tons behind the drawbar at 25mph is a tad different from 450tons at 80mph.

 

What is interesting is the comments regarding the public perception of their experience, the fact that the carriages are more important than the loco is something I have noticed time and again. The colour and mechanical condition of the loco is of little consequence as long as it is relatively clean and goes chuff in most of the right places. What is more important is that the coaches are clean and well presented. In fact the more colourful loco liveries are far more interesting to JP than good old BR black.

 

A Star or a Castle is somewhat bigger than the Class 4 types used on the Dartmouth Steam railway which has sustained heavy gradients but only runs at 25 mph.

What's the problem with watering at each end of a 10 mile run? The passengers will be having their own watering stop whilst this goes on.

PH

 

because thats what i have experience of, a standard 5 is about the same , mogols i found after a days firing i was nearly emptying the tender of coal , A WC once you covered the grate , you could run an quite a thin fire where as the smaller engines you had to put more in , but the steam used would be less with the larger engines.