Modelling Traffic Patterns

[rhobat bryn]

I have a number of unanswered questions on this for my own layout.  It stems from the fact that there are two companies sharing the station, one will use a platform with a runround and the other will use a platform without.  The Dyffryn Mynach will use the platform without.  When the train arrives, the second loco will draw up to it ready for departure.  When the train departs, the first loco will then proceed to the shed for coaling and watering; standard practice as I'm sure you already know.  The Cwm Pwyll will use the runround with a watering facility at the throat end of the platform.  So far so good.

However things are complicated by the fact that the Cwm Pwyll line is meant to be an hour's journey from Porth Illtud (the harbour) to Bryn Moel (the valley terminus).  My question is whether a loco conducting a 2 hour journey would be runround like that or would it be sent to the shed as will happen with the Dyffryn Mynach loco?

[tedp]

A loco will only be sent to the shed for overnight stabling. Coaling will take place from a coaling stage next to the shed, or sometimes alongside a headshunt (Portmadoc had a coaling stage at the end of the line at some time). Cleaning the fire would take place over an ashpit, and watering the engine takes place anywhere along the line. On my layout there are ashpits and coaling stages not only at Rae Bridge shed, but also on sidings elsewhere. Cleaning the fire is usual after a long run, to make sure the grate doesn't clog up with ashes. So ashpits would be positioned somewhere in any main station. Water cranes or tanks are spaced out anywhere a train is scheduled to stop (stations, halts and sidings on the main line).

[rhobat bryn]

How long would a loco be able to run for between coalings?  The Cwm Pwyll line will be using Campbeltown and Machrihanish 0-6-2Ts.

[tedp]

This depends on the load, the gradients, the air temperature and the skill of the crew. Generally, I think coaling up once every round trip would not be unusual. The late John Allen experimented with a timer on his trains that slowly ran out, cutting the power in the end. It was supposed to be re-set only when the loco was at a coaling stage or a water tank.

[rhobat bryn]

The late John Allen experimented with a timer on his trains that slowly ran out, cutting the power in the end. It was supposed to be re-set only when the loco was at a coaling stage or a water tank.

That's very sophisticated.  However I've decided, on the basis of what you say, that the Cwm Pwyll line has its shed and coaling stage at the Bryn Moel end of the line (offstage at present) which would enable a runround with a watering at Porth Illtud to credibly take place.

Many thanks for your comments, Ted; generous as always.

[Graeme Dunbar]

I guess there is also the matter of logisitics. The coal has to come from somewhere (adjoining standard gauge, sea port or canal?) so it would make sense to coal up at the corresponding end of the line and move as little of it as necessary to other locations along the line.

[tedp]

On the surface this seems to be correct. But loco coal is needed where the bunkers are low after a particular service pattern of the loco. Most railways ran wagons of loco coal from the source to the coaling stages. Some of them even coaled up from a wagon.

[rhobat bryn]

In my particular scenario, coal would be imported through the dock to the valleys being, as it was, the main domestic and industrial fuel of its time, not just for the railways.  This was actually the case at Aberdyfi and Abermaw (Barmouth).  I dare say the same was true at Porthmadog as well. 

[Tigger]

"...it would make sense to coal up at the corresponding end of the line and move as little of it as necessary to other locations along the line."

Valid point Graeme.  I recently realised that for 36 years the L&TR has had loco facilities at the top of the line but no coal wagons to get the loose coal up there!  As one loco is always out-shedded at Tawel-llety I think it's high time the railway had some!  Part of this winter's works programme I think...

[Graeme Dunbar]

On the surface this seems to be correct. But loco coal is needed where the bunkers are low after a particular service pattern of the loco. Most railways ran wagons of loco coal from the source to the coaling stages. Some of them even coaled up from a wagon.

Yes, I can see that this makes sense on a railway network or a long line that would have "supply dumps" along the route.

I don't suppose many 009 layouts (or the railways, real or imagined that they represent) are of this type. Many will go from the coast up to higher ground or from a centre of population and industry to the sources of goods or materials they were built to service.

I guess it depends on many things. I wonder for instance whether it might be more economic to send a "light engine" off by itself some distance to be refuelled than move resources to an awkward location, or whether engines might be swapped part way. In the case of goods other than perishables, fuel cost is going to be significant and delays less so, but passengers will be less patient.

It is all good fun and adds a lot to the operation and realism of the model. Similar logic can be applied to other aspects: for example, if there are extensive cattle or sheep pens, is there a market near by?

[Tigger]

However things are complicated by the fact that the Cwm Pwyll line is meant to be an hour's journey from Porth Illtud (the harbour) to Bryn Moel (the valley terminus).  My question is whether a loco conducting a 2 hour journey would be runround like that or would it be sent to the shed as will happen with the Dyffryn Mynach loco?

The timetabled time between Llanmynach and Tawel-Llety is an hour each way and the train lays over for half an hour, which is plenty of time to coal up, oil round, water, oil etc for a single loco so in fact the three passenger trains and one goods train normally in service only need five locos.  I actually use seven, with one loco laying over at Tawel-Llety and two at Llanmynach.  Not actually necessary but it keeps all my models running and gives plenty of variety.  It also means that I can introduce an extra train at any time without the panic of suddenly needing to find an extra loco!

[tedp]

As I wrote in the Cliffhanger thread, I think modelling railway operation is as much part of railway modelling as scenery and rolling stock. I feel many of us have a similar opinion.

There are several ways of representing traffic flows. Card systems have been in use for many decades and they can even be used to designate actual wagon loads going from one place to another: so many tons of coal, so many head of sheep or cattle. This is the most realistic approach as it directly makes you think of loads rather than wagons to transport them, but the down side of this is the amount of arithmetic needed to calculate the number of wagons needed. It is a bit indirect.

About 30 years ago I read of the goods circulation system devised by the late John Allen, who built the Gorre & Daphetid RR. I decided to implement that myself, as it is rolling stock oriented instead of load oriented. Rather than re-writing all this on the forum I would like to point you towards the web pages I wrote on the subject. I hope these are a useful contribution to this thread:

General operation approach: http://www.009dutch.nl/cdr/main/pages/eoperation.htm
Goods traffic simulation (John Allen system): http://www.009dutch.nl/cdr/main/pages/eoperation1.htm

[rhobat bryn]

Yes, I can see that this makes sense on a railway network or a long line that would have "supply dumps" along the route.

I wonder for instance whether it might be more economic to send a "light engine" off by itself some distance to be refuelled than move resources to an awkward location, or whether engines might be swapped part way.

I'm not sure I understand the point fully.  In the case of a valley where coal is imported via the harbour, coal trains would have to be marshalled to deliver coal to every town and village on the line for the benefit of domestic and commercial users alike.  Adding another truck's worth for the railway would involve a very low marginal cost in terms of fuel resources.  Perhaps I'm missing something here.    ???

[tedp]

It might pay to investigate how the coal trade by rail was organised 80-odd years ago. Perhaps there were local peculiarities in the Welsh valleys but I think there was a general pattern to this kind of traffic. Loco coal may have been subject to the same rules but remember a steam loco is fired with a different quality coal from what you use for heating a house. So they won't be transported in the same ship's hold or necessarily in the same coal train.

One thing to remember is that in those days they didn't use 'just in time' delivery, using a single wagonload to an individual coaling stage right from the delivery source, as storage costs weren't as much in the picture as today. The logistics were therefore much simpler.

I think a railway company would order a batch of steam coal, transport it from the harbour in a number of wagons, store it at a central depot and forward it to various locations. A local coal merchant would order a batch of household grade coal (think of several wagon loads), store it on his own premises, bag it and distribute it by horse and cart. The traffic pattern is similar but the end distribution is different as the railway will use its own wagons to forward the loads.

[rhobat bryn]

As I understand it, coal was delivered to the West Wales ports serving the West Wales Valleys from Cardiff with coal produced in the South Wales Valleys.  However I take your point that different coal would be used for different purposes though both types would be delivered to the port for distribution.  When I spoke to a guide on a 19th century sailing schooner, his view was that coal would have been carried on board in sacks and manhandled off the ship by the crew.  What I haven't been able to establish is whether bulk coal was ever delivered at this time (late 19th/early 20th century) and if so in what vessel.

I also take your point about distribution of steam coal.  In my scenario therefore, the coal would be delivered to the shed at the valley terminus and distributed, if necessary, to other points of the line.  With regards the domestic coal, my plans include a coal merchant's line in the goods yard where it is distributed locally.  However a coal merchant's office would also be found at every goods yard on the line, which in those days would be at every significant station.

In addition to investigating the existence of bulk coal carrying sailing ships, I shall need to investigate the frequency of these deliveries to the ports.