While I didn't use the exact method Armstrong proposed, I did follow his general approach. In this post I'll cover the development of my iNdoor layout design from the start of design to the point where I transitioned to detailed design and decided to move to CAD (computer-aided design).
Rarely, if ever, do you start a layout design with a completely blank slate. Usually you have something in mind already, and ideally you already have a thorough list of the "givens and druthers" (to use Armstrong's term) of layout *musts* and layout preferences. For me I had my layout concept, the parameters of the layout room itself, a basic understanding of staging requirements (at first not quite as detailed as what is in the linked post, but pretty close), and a list of design standards:
- Minimum radii: 36" on the mainline, 24" for slow speed yards and station approaches, 18" for staging
- Aisle width minimum: of 3' (later expanded to 3'10")
- Track spacing: as close to 1" (13' 4" scale) as possible given spacing needed around curves
- Maximum freight train length: 12', with 16' for a few through trains
- Maximum passenger train length: 10' for distance trains, 5' (8 cars plus engine) for commuters
- Maximum grade: 1.5% (later reduced to 1%)
- Maximum reach: 2' from fascia to rear train track
- Maximum shelf width: 2' 2"
- Minimum switch size: #8 main layout, except a few #6 in industrial areas; #6 in staging
- No duckunders for normal operations and viewing (ok for occasional maintenance). If a duckunder situation appeared inevitable, use a liftout bridge or gate, but ideally not even that.
- Movability. I have no desire to move house ever again, but just in case we do move I wanted to build the layout in a manner that would allow it to be broken down to 4' sections for moving.
- Double deck with helix. If you have the room a single deck is nicer because the layout height can be optimal for your situation and the overall illusion of the model works better. But, the benefits in terms of railroad length made, for me, a double deck a given. For layouts featuring long, steep grades you can have multiple decks without a helix, but that isn't an option for this layout.
The first question was where to locate all the things that I wanted to include in the garage apartment: the layout, my home office, a gathering area (sometimes called an operator's lounge), and modeling workspace. I decided that the north room would be for trains, the smaller south room for everything else. The early goal was to avoid if possible extending the layout into the south room, but that wasn't a requirement -- I kept that as an option if needed (and of course that is where the main staging resides now).
The next question was what to do with the built-in desk in the north room. My first drawings tried to fit a layout in and around the desk, but very quickly I decided that the desk had to go. I would move it to the opposite corner in the south room.
Then came the main question: where to locate the layout benchwork itself. A common approach is to start with an around the walls design and then figure out where to put in peninsulas to use the middle space. I tried that with many designs, comparing the options, and also tried a number of designs which left one or two walls open. I tried variations with diagonals, curved benchwork, and a variety of other shapes. This wasn't so much that I didn't have a reasonable design in mind, I just wanted to make sure I'd explored all the options.
For this layout the biggest design challenge is the four-way, "X" junction of the two main lines. By this I mean a junction like one shown in this sketch:
Junctions in general are a complex topic in layout design, with three-way "T" junctions being simpler than "X" junctions and junctions to a branch of the same railroad often being simpler than junctions between railroads, as the latter usually needs some provision for interchange.
Junctions are fun to include in a layout because of the complex trackwork and the interesting operations that result from interchange possibilities (an interchange yard is often referred to as a "universal industry" because you can justify any kind of freight car via an interchange). In addition, if the junction is level you have additional operational interest in directing the traffic across the crossing. For my layout I wanted the junction mainly from the point of view of Union Station. To me one of the coolest things about large stations is the way that there are many trains departing at nearly the same time from different platforms, taking different track routes to different destinations. (As opposed to a station like in San Francisco, where trains leave roughly hourly in one direction -- toward San Jose. Much less interesting operationally.) In theory you don't have to have a junction to model multi-destination operation because you could have the trains departing from the station, go into staging, and you can pretend that there is a junction somewhere on the other side of staging. However, to me that wouldn't be really satisfying -- I wanted to include at least one major junction on the layout.
As part of the design process I skimmed all the model railroad magazines and books in my library looking at how others have modeled junctions. One common way is to have a "passive" junction. That is, the track for the crossing railroad is included on the model but it's not used and it doesn't go anywhere. Often the "passive" junction will include an active interchange yard that is fed from a staging yard.
Once you move into "active" crossings -- especially if you want all 4 legs of an "X" crossing to be active -- you run into a challenge trying to avoid creating a duckunder. To understand this, consider an "X" junction with tracks coming from 4 directions, which I'll call N, E, S, and W (see above sketch for an example). Suppose you are operating a model train from the N direction to the S direction, and walking along side it as is normal practice. There is no way you can accompany your train from the N side of the junction to the S side of the junction without somehow navigating around the track on either the E side or the W side.
This topic was addressed in two articles in Model Railroad Planning 2000. Paul Dolkos covered the topic in detail in one article and suggested that if the crossing angles were sufficiently acute you could avoid a duckunder by keeping two legs of the crossing (say, N and E) together on one side of the shelf and the other two on the other. This approach was used in the Hutchinson, KS layout I linked to earlier, and a sketch of this approach is shown here:
You can see that the junction can be fit into a single 2 foot wide shelf using this method. I seriously considered using this method but ultimately rejected it. One problem is that I wanted passenger trains to be able to go in all 4 directions, which would not be possible given an acute angle and my minimum radius. But the real problem is that the acute angle would not look right. Granted, there have to be things on your layout which don't look exactly like they would in real life, such as curving a freight yard around a room corner, but to the degree possible I wanted to minimize those visual "giveaways" which spoil the illusion.
So, I tried different designs using a 90˚ crossing (or at least reasonably close to 90˚), including putting the crossing in the middle of the room and at various diagonals. Eventually I came to the same conclusion a lot of other modelers did, based on the layouts that I saw in the books, which is that the optimal way to model a real-looking, active, 4-way junction is to put it along a wall. Here is an example of this in sketch form:
In this method two adjacent legs of the junction (let's call them N and E for this example) are positioned along the wall facing each other. As they near each other they curve toward the (approximately) 90˚ intersection. The other two legs, S and W, then go out towards the middle of the room.
The reason this can work is that the S and W legs won't go very far before they transition into staging. Practically speaking, unless you have a warehouse-sized space for your model layout you're not going to be able to model a long stretch of all 4 legs of the junction, so we pick the two which go into the center of the room as the legs to keep short. Going with this approach I came up with this concept:
To be honest I wasn't initially 100% thrilled with this approach either, but it seemed to be the best compromise. In the first draft of this concept (not shown) I located the peninsula along the bottom wall in the drawing and was troubled by the way the N and E legs left the crossing then both curve around about about 135˚ to get to the next wall. The 36" minimum radius (and given the space, probably a wider radius for both curves) helps somewhat, but 135˚ curves are still iffy. I addressed that in the above sketch by locating the crossing on the west (right) wall. This way one of the legs had to manage only a gentler 45˚ curve to then head towards the end of the layout, and staging or a helix. For the other leg, by moving the junction as far as possible toward the south end of the West wall (the top end of the drawing) I could break the 135˚ curve into two lesser curves and improve the appearance.
At this point there were still a few big design issues to take care of. 1) Locating the helix. 2) Width of the peninsula, and what to do with the remaining interior space. 3) Where to locate the branch line. 4) Desire to get maximum use of the layout space, and thus to extend the double deck over the peninsula. 5) Where to locate staging.
Locating the helix (item 1) was just too obvious -- the west alcove. I had briefly considered that as a potential dispatchers office, but a) a dispatcher would be much more comfortable in my home office in the south room rather than in this cramped space and b) this was a perfect spot for an oval helix between the two levels.
In terms of item (2) I tried minimizing the width of the peninsula in an effort to somehow cram in yet another peninsula, then realized that a simpler approach would be much cleaner. I'd use a wide peninsula, one that took up the available space in the middle up to the limits of the minimum aisle width. This would result in a very wide space, almost 9', for the peninsula, which is too wide normally. However, I'd create a walled-in "box" in the interior which would also serve as the support for a second deck on the peninsula (addressing item 3) and the upper deck peninsula would then be the obvious place for the branch line (item 4). Voila! I had figured out a workable high level design. The sketch now looked like this for the lower level:
Note that at this point I am not identifying any of the layout design elements (LDEs -- using Tony Koester's term from Model Railroad Planning) except Union Station on the sketch -- those will be located during the detailed design phase. Also note that there are two main lines identified, the N-S (north-south) which runs for most of the lower level, and the E-W (east-west), which is part of the lower level, but via the helix moves to the upper level where it is the only main line:
The last question was what to do about the one remaining issue, the location of staging?. My initial thought was that the tracks which terminated on the lower peninsula would have staging under the peninsula itself. The two tracks which terminated on the lower south wall would have hidden U-turns and then have staging underneath the lower deck. My plans for the upper deck staging were vague -- maybe thinking of trying to squeeze staging in immediately under the upper deck. The helix area was an obvious spot for a staging entrance, but I wanted to avoid any sort of bridge from the south wall tracks to the helix.
Realizing that a workable staging solution was essential that would be the first topic I tackled when I started the detailed design.
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