Sunday, December 27, 2009

Designing my train layout - 6 - Why it works for me

In my last posting, I explained the process that led to my final design. In this posting I'll try to explain why the design works for me.

The first aspect of this layout that I feel happy about is that of staging. Let me digress a bit and show you an old Marklin layout that I built back in 2003:

This layout was also essentially an oval but the key difference compared to the current design is that I had placed some bare staging tracks at the back of the layout separated by a view blocker (1/4" plywood). The intent was that viewers would stand at the front of the layout and watch trains stop at or pass through the station. While operating this layout, I realized that I could have made a second station instead of the bare staging tracks.

In the current layout, one possible style of operation would be to simulate time-table driven movements through a station. In this mode of operation, each station can act as the staging area for the other station.

In the diagram shown above, each green arrow represents a train. As you can see, it is possible to have as many as eight trains staged around station 1 in order to run a timetable sequence of trains passing through station 2. Of course, in a similar manner, I can use the station 2 as staging for running traffic through station 1. A word about the term "timetable": Unlike the US where most trains on freight railroads are extras, in India, Most trains are actually listed on the timetable.

In addition to timetable driven operations, I also plan to use the layout as two bidirectionally signaled single lines. This style of operation is often used in places where traffic density is higher than can be supported by dedicated double lines. This happens near big cities and on hill sections.

Finally, I have made provisions for four storage sidings for trains not used in the main sequence of operation. Since I tend to be very careful in my rolling stock purchases, I don't thing I will exceed this relatively modest amount of storage space for a while.

Since there is a considerable amount of available space in the center of the layout, I could add storage sidings there in the future if I need the space.

So this concludes the postings on the design of the layout. Next, I will cover the construction as well as some tips and tricks that I have learned in the process.

Saturday, December 19, 2009

Designing my train layout - 5 - double track

While leafing through the Armstrong track planning book, I came across this diagram that changed my thinking drastically. The thing that caught my eye was this text from one of the captions: "In model practice, where mainline length is severely limited, two and three track railroading may actually surpass single-track operation in variety"."

Most of the trunk lines in India are double track (with the Chennai-Mumbai section being the only important route with a lot of single track). Upon reflection, I realized that what I wanted was a lot of parallel action. Furthermore, the station configurations could be made more realistic. I then decided to give double track a try. I started by taking a fresh look at the "water wings" configuration from a double track perspective:

The results were surprisingly good. I was able to fit two stations that each had a single passing loop shared between the two tracks. I have, in fact, seen this layout in some small stations on double line sections in India:

Although promising, there were two issues:

  • Lack of visual separation between the stations. The two stations are physically close together even though there is a nice long run between them. The only obvious solution was an oval. Now, I had initially rejected ovals because I though they looked boring. However, it was clear that a good old oval is what would work best for me.

  • I came to the conclusion that I wanted the stations to have different configurations. Specifically, I wanted a conventional double station as shown in the next diagram. Although configuration B would be more prototypical and offer greater operational flexibility, I was willing to settle for configuration A. The point is - it looks like a regular double track station.

At this point, I showed the last design to my friend Dale Schultz who has built a large Marklin layout. Like myself, Dale is interested in using computers to automate train operations. He is a very sharp thinker whose judgement I greatly respect. He told me I was on the right track but suggested that I reduce the number of sharp curves. The next design I came up with was this:

This was now getting interesting. Notice that the lower station remains curved. This was intentional - I had come to feel that at least one of the stations ought to be curved for aesthetic reasons. The two problems were that the passing sidings in the upper station were too short and there was only one cross over and it was too far removed from the nearest station. The next step was to integrate the crossover with the upper station, thus:

This was definitely an improvement. There was a pleasing curve to the upper station and both stations had passing sidings of acceptable length. Dale suggested investigating curved turnouts. I looked through the Walthers catalog and found that the Shinohara #7 curved turnout would be perfect for my needs. This turnout has radii of 24 and 2.8.5 for the diverging and normal routes. This is the next design I did incorporating curved turnouts for the crossovers.

I felt that I was closing on the final design. The last tweak to the design was to confine all the curved turnouts to one side of the layout - mainly for aesthetic reasons.

And that did the trick. I was now fully satisfied with this design - The full process had taken about seven weeks but it was time well spent. A 3D view is shown below that includes the benchwork. I am deliberately not using the space in the center of the layout for the time being. I may eventually come up with some use for the space but it will be left vacant for the time being.

In my next posting, I will explain the operational possibilities of this layout.

Thursday, December 17, 2009

Designing my train layout - 4 - more single track designs

With the "folded dogbone" eliminated from consideration, I took a look at some alternatives, starting with the "water wing" configuration. The following is an initial sketch to explore this configuration and it seemed promising:

After some thought, I was able to come up with the following design. As you can see, I was actually able to fit three stations into this design. I should note that the third station (on the straight section at the top of the layout) was really more in the nature of a what-if exploration. I was still thinking in terms of two stations, the main ones being on the ends of the two lobes. The two main stations are well separated and the passing loops are surprisingly long.

The problem with this design was that the stations could simply not accommodate more than one passing loop due to the curves involved. also, there were no good locations for storage sidings of reasonable length. My other concern was the S-curves at the entrance to the passing loops. In hindsight, I realize that I ought to have looked into the possibilities of using curved turnouts. In any case, this configuration just did not look right to me.

At this point, I decided to relax some of my requirements and explore more exotic configurations. I present a few of these below

None of them seemed to be very appealing. At this point, I decided to take a few days off from 3rd Planit and re-read John Armstrong's classic treatise on layout design.

As I shall explain in my next posting, this break turned out to be a good idea. and I was able to break my mental log jam.

Thursday, December 10, 2009

Designing my train layout - 3 - Folded dog bone

Building on my experience with my previous layout, I decided to start by investigating single track main line designs. Basically, what I wanted was not much more than this schematic:

In other words, an oval with two stations. I wanted a reasonable amount of separation between the two stations. I wanted the train to have at least a short run between the stations. This schematic may seem very simple but it should be noted that complex behavior can arise from deceptively simple systems. Consider for example the difference between a simple and double pendulum. While a simple pendulum can be fully described by equations for simple harmonic motion, the tip of a double pendulum can move chaotically. In an analogous manner, even with just two stations, it is possible to create complex patterns of train movements. Having decided on a two station configuration, the next step was to see how long a main line I could fit within the space available available.

I prefer to do my design work directly on the computer using the 3rd PlanIt layout CAD software from I have been using this package for many years, initially using to design sectional Märklin layouts. I think that 3rd PlanIt is a very powerful package and there is indeed quite a bit of a learning curve. However, once you get the hang of it, 3rd PlanIt just seems to get out of the way and lets you explore designs very quickly.

The first general shape I investigated was a folded dog-bone. I have seen this shape used in many track plans and tried to get it to fit in the space available.

The nice thing about this shape is that there are good locations for locating the stations allowing decent separation between them. However, the main problem is that the curves at the end of the "bulbs" necessarily have to be very tight. Nothing more than 20 inch radius curves can fit in the space available. another problem is that access to the interior of the layout would be problematic.

In order to use curves of minimum 24 inches radius, I discovered that there were two options, neither of which were attractive.

1. Overlap the bulbs: This allows two large radius bulbs to be accommodated. However, as previously mentioned, I was not keen on a multi-layer layout. A second problem is that by having the bulbs on different levels, the main line and the stations must necessarily be on an incline.

2. Widen the layout: Widening the layout allowed the use of 24 inch radius curves but the increased width unacceptably cut into walkway around the layout. One more problem that I discovered was that the station passing loops could not be made very long. I don't really want very long trains but this seemed a bit ridiculous - barely 41 inches for the station on the top.

Clearly a folded dogbone was not going to work for me. In my next posting, I will describe some exotic variants of the folded dogbone that I tried.