In the first installment of this series, I mentioned a couple of times that the track geometry of Lego Trains is unique from most other model trains, and sometimes very limiting. Let's delve further into what the phrase "track geometry" means.
There are five pieces available directly from Lego for your train track needs: a 16-stud straight piece, a 16-stud curved piece with a radius of 40 studs (measured from the center of the track), a left and a right switch (~32 studs long each), and the 4-stud-long flex track piece. The rails are spaced six studs apart, with an extra stud on the ties, to make each track section 8 studs wide. Switches are of course, wider, but the dimensions of the individual routes are still 8 studs wide.
Other track pieces are available from third-party manufacturers, or one can modify the track themselves, but for the moment we'll focus on these five 'official' parts. You will find that the 16-stud straight can fit on a 16x16-stud baseplate, with a 4-stud margin on either side. In a similar vein, a quarter-turn of curved track will fit on a 48x48-stud baseplate. When you attach a curved track to the diverging route of a switch, you will see that the following straights create parallel tracks, spaced 8 studs apart. Now, remember from part 1 when our full circle of track equaled 30"x30" (76.2cm x76.2cm)? A 16-stud-square baseplate is 5 inches by 5 inches (12.7cm x 12.7cm)! Let's put all this information in a picture for a clearer understanding:
The point of all this is that Lego tracks adhere to a grid system, which can make planning a layout very easy. Now that we've established this grid, let's look at a few track arrangements that do not fit on the grid, and some space-saving techniques that DO fit on the grid.
New layout builders may find that their creative arrangements of curved track do not meet up properly when one is trying to close their loop (though the advent of flexible tracks can help alleviate this issue), and this is usually due to a funky arrangement of curves not aligning to the grid.
It is also worth pointing out at this time that model trains generally do not like opposite-direction curves back-to-back (these are defined as S curves, as they resemble the shape of the letter). Some of the Lego Train sets can handle it, but heavier pieces of rolling stock (read: most MOCs) will bind on the curves or possibly derail. If you're going to put curves in opposite directions in a row, it's best to put a piece of straight track in between them, or at least a couple of sections of flexible track.
Putting a piece of straight track in between opposite directions of curves brings us to a handy trick to save space and pieces in our layouts: one straight track can equal two curved tracks. Observe the following:
We've stated a couple of times that a curved track must be attached to the diverging route of a switch to align both routes to be parallel on the grid. Here's the info straight from Lego's mouth, taken from a leaflet that came with the World City line of trains in the early 2000s:
But let's suppose you want your diverging route to curve off in a different direction. Again, we can replace two curved tracks with one straight track and save on parts and space:
A good example of applying this information would be the turnaround loop. In the first section of this series, the return loop was built without using this curved-track shortcut. Here is the return loop in both fashions: once with the switches and curves set up in a standard fashion, and two arrangements with the one-straight-for-two-curves trick:
Let's look at one more example of the application of this track trick before we apply our knowledge to layout planning. In the first installment of this series, we only looked at single-track railroads, or track plans with only one main route. If one wants to run multiple trains at once without interference, it is advised to have two independent loops of track, or loops that do not share any portion of their route.
While having two independent loops for running trains is nice, one might wish to switch a train from the inner loop to the outer loop, or perhaps interchange some cars between the trains on each loop. This is where a "crossover" comes in. A crossover is a pair of switches linking two independent sections of track.
We COULD simply link the two diverging routes of our switches and connect our independent loops that way, but once again, our layout wouldn't perfectly conform to the grid. Better to use two curved tracks (one for each switch, so the diverging route becomes parallel to the main route) with a straight track in between, or just one straight track to link those two switches and conform our layout to the grid.
At this point, one might beg the question: "What's so important about lining up to the grid? Those two independent loops still fit together, even if they're not aligned perfectly to the 5"x 5" (12.7cm x 12.7cm) grid! What's stopping me from building something like that?" The short answer is: nothing! If you're able to make a track layout work without aligning your tracks to the grid, more power to you! If you're just building tracks all over the living room floor for an afternoon of fun, then the grid doesn't concern you all that much, and most of the information thus far is simply to inspire ideas and help troubleshoot derailments and other minor issues. The point of the grid is that it's an easy reference point to ensure all tracks will fit together, AND, as we will see in future installments of this layout planning series, aligning to the grid makes it easier to lay out streets and buildings alongside our tracks.
We will look at one more type of railroad track arrangement and how we can use our straight-track-for-two-curved-tracks space-saving technique to make it easier, but first, here are a few more examples of crossovers between tracks. We will drop the grid from the example images for the moment.
So far, the only method we've seen for turning a train around is the reversing loop. Novice train enthusiasts may be familiar with the turntable, but these are difficult to build in Lego, and are usually just for the locomotive; not practical for turning an entire train. This is where the Wye comes in. Named after the letter Y for its shape, this track arrangement requires three switches to work. A good prototype example can be found at the Tennessee Valley Railroad Museum in Chattanooga:
A wye can be used for turning trains, or to connect a branch line that is perpendicular to the main line. We can build a wye using three of our switch track pieces. Note that if you are using electrical track instead of the modern plastic track, a wye will cause a short-circuit. We'll look at how to prevent short-circuits in the future. Here are three examples of a wye in Lego, two of which use the one-straight-for-two-curves trick that has been a main feature of this installment of the track planning series: