Trackwork Standards

The new layout will be constructed using ballasted flex track, and possibly some hand-assembled track as well. I’m particularly considering use of the Fast Tracks jigs for switches, as well as possibly some track soldered to squares of circuit board to simulate concrete-slab construction used in some stations and for newer Shinkansen track.

My goal here is to have multiple double-track lines, but avoid the “too much track, too little scenery” problem. As those are conflicting requirements, I’m not setting myself an easy task. I also want to have visually appealing track for long passenger trains. This will include some elevated viaduct track to raise trains above the scenery (very prototypical for Tōkyō). And it will include some sweeping wide-radius curves as well as track that winds through urban areas with a more congested feel. Level changes will also be required, as the prototype does this in a number of places, although this will be done more for scenic impact than anything else.

All of this leads to a few basic guidelines. I’d previously written about some of these issues (here and here), but I’ve been thinking about them more since then.

Physical Standards

1. As on the prototype, switches and crossings-at-grade will be minimized, but I do expect to include some where they make sense prototypically, to provide for some more operational variety and to break up the “everything looks the same” aspect of unbroken parallel tracks.

2. Although Japanese model trains can handle fairly tight radii, they don’t look good doing so, with sharp angles between passenger cars. For that reason alone, my typical minimum radius outside of yards and tram lines will be around 30” (75 cm). I may use wider radii for some scenic curves. I could reduce this to about 55 cm without impairing the look significantly, and I might use that in some tighter urban areas, as a way to imply lack of space for the railroad. For more about how I’m determining my minimum radius, see the discussion on this page.

3. Curves will be superelevated, with easements (transition curves) used where appropriate (mainline tracks with curves longer than 40 cm need easements, and superelevation will likely look good on any mainline curve, but moreso on ones long enough to use easements)

4. Track will use a mix of wood and concrete ties (as does the prototype), potentially along with the slab track mentioned above. My intent is to use code 55 rail, although I may use code 70 for Shinkansen, just to emphasize the difference.

5. I haven’t yet standardized my parallel-track spacing. I’d originally planned to use the NMRA-standard 26 mm (~1 1/32”), but for compatibility with the Fast Tracks crossover jig, I’m considering 28 mm (~1 3/32”), at least for commuter lines where I’d use that.

- Prototype Shinkansen lines are wider-spaced than narrow gauge. An exact conversion would work out to around 27 mm, but I may use a wide spacing than is used for the narrow gauge lines, again to visually emphasize the difference between them. Using 32 mm may be sufficient to create that look, but I should probably do some mock-ups before I lock this down.
- Fast Tracks double-crossover #8 needs 27.7 mm, but a normal crossover from two switches needs more, and on the prototype spacing appears to vary at some crossovers anyway. I may use 26 mm as standard mainline paired track spacing, and vary for others. When more than two tracks are parallel, pairs often are separated from adjacent pairs (to provide room for workers, overhead poles, and other things). I need to consider inter-pair spacing.

6. Turnout sizes will be #8 minimum for mainline track outside of stations, and #6 minimum for stations and most yard tracks. Where possible, broader switches (such as #12) will be used on mainlines.

7. Flex track (or similar long stock rails) will be used to minimize rail gaps. Rail will not be gapped in or near transition curves or curve ends (this includes vertical transitions). Gaps within curved rail will be minimized.

8. A minimum of 16 cm of tangent track is required between reversing curves, 20 cm is preferable.

9. Clearance for trains must allow for raised pantographs. The NMRA (S-7) clearance gauge requires 42mm above the rail, but Kato’s clearance gauge requires 48mm at the peak (but with a narrower and rounded profile). Clearance requirements are discussed on my Track Standards for Straight Flex Track page. To allow for thicker roadbed material in some places (doubled 3mm cork layers, for example), clearance from the subroadbed will be 60 mm to the overhead. When track is supported on 3/4” plywood subroadbed, this implies an inter-layer spacing of ~80 mm (8 cm, or 3 7/8”).

As noted there, with roadbed and track I need around 56mm (2.2”) above the subroadbed, or about 75mm assuming 3/4” (19mm) plywood subroadbed. I may increase this by another 3mm to allow for a second layer of cork roadbed, for noise deadening.

Note: yes, clearance will be 60 mm from subroadbed or 80 mm from support, whichever is easiest to work with at the time. Better safe now than sorry later.

10. My goal is to keep grades under 3%. Most Japanese model trains seem to operate reasonably up to 4%, although I haven’t done much testing of this and want a safety margin (I do need to do some testing for really long trains with one motor car). With that, trains should be able to operate well. However, given my current track-level spacing, this means that moving between levels will take about eight feet of track (2.4m), somewhat over one train length. I think that will be acceptable, as any such changes will typically be hidden (I know of one exception, but there the grade change is part of the scene).

Note: I need to do some visual tests to see how 2% looks vs 3%. I have two scenic grades (both on the Chuo line section), and both are fairly steep (one is 1.66% in the real world), so 3% may be okay for them.

Electrical Standards

These standards derive from a lot of existing standards that have been developed over the years by model railroaders, particularly for modular layouts where simplicity and reliability are important. Some of these I used on the previous layout (the original Sumida Crossing) and a couple I’ve used even longer. I don’t claim any of these are original to me, but this is the set I’ve selected for use on the new layout.

The requirements for track wiring are covered in more detail in the Power Wiring section, which lays out both the original “want list” of features and the details needed to achieve them. That section also goes into more detail regarding track power systems themselves.

1. Rail will be nickel-silver, with non-soldered rail joiners or plastic insulating joiners where sections meet. All gapped rails not using insulating joiners will have plastic spacers superglued in the gap to prevent closure. Rail will be cleaned only with non-abrasive cleaners, to reduce pitting and subsequent dirt collection.

2. Track feeders will connect approximately every meter, and also to any separate length of rail. Rail joiners will not be assumed to be adequate conductors for train power.

3. Track feeders will be soldered to the rail, on the underside where possible, with a goal of carrying less than 3A in any feeder. Wire used in feeders will be at least 22 ga, which allows for up to 5A in enclosed spaces, with a voltage loss of about 0.5V/m at full load. Preferably 18ga feeders will be used, reducing voltage loss to 0.24V/m at 5A and 0.14V/m at 3A. Feeders will normally be limited to about 1m, with heavier wire used if longer feeders are required. Wire of at least 18ga will be used to connect feeders to any electrical components and to the track bus. If pre-tinned “hook up” wire is used (and it probably will be in some places), oversize by one gauge to handle increased resistance due to the tinning.

Note: feeders from track may be connected to “close” terminal strips, to allow short lengths of 22 ga to/from track, and longer lengths of 18 ga to electronics below the table. This also makes it easier to wire multiple feeders to one detector output.

4. Switch frogs will be powered. This may require DCC-compatible reversers, or be an A/B switch tied to the switch motor.

5. Electrical blocks will be established to meet track occupancy detection needs for signaling and grade crossings. Electrical blocks will gap both rails. As electrical blocks may have multiple feeders, current-based occupancy detectors must be placed before the feeders split.

6. Turnouts will have all rails gapped at clearance points or closer to the frog (but beyond the movable points by at least two attached ties). This includes both the straight and diverging route.

7. Separate tracks (e.g., parallel tracks) fed from the same booster will be isolated from each other by circuit breakers. Additional circuit breakers may be required for turnouts (space will be left to allow their addition, although they will likely not be installed initially). The goal here is to prevent one train from disabling power to another, except on the same linear track.

8. Storage tracks will have cut-out switches to allow depowering individual sidings. DPST On-Off toggle or mini-toggle switches will be used. Provision should be made (i.e., space reserved) for replacing these with relays in the future, to allow more sophisticated electrical control from a computer-based panel.

9. Where reasonable, the track bus and distribution wiring may have inline plug/socket joints to allow a section to be isolated. These will use Anderson Powerpole PP-15/30/45 connectors, which are available for AWG wire gauges 20 - 16 (accessory and feeder wiring), and 16 - 12 (track bus wiring) among others. Tin-plated open-barrel contacts and standard (vs finger-proof) housings will be used by preference. Colors will be coded to match wiring codes. These are low-resistance connectors designed for low voltage loss at high currents (much higher than we use).

These come in colors (many) so wiring can be color-coded, and they snap together, so they can be physically arranged to ensure proper polarity. This type of connector is increasingly being used in modular railroads, although the type of contact may vary. The metal contacts come in versions rated for various wire sizes (sometimes described by maximum amperage), by open or closed form (most are open) and by plating material (copper plated with either tin or silver). The metal contacts are also available in high mating force and low mating force forms, and the “high” version is probably preferable for the lowest-resistance joints.

10. Wires will be color-coded to clearly distinguish polarity or phase in grouped wires. As there may be several sets of bus wires (booster bus, track #1 bus, track #2 bus, etc) multiple colors will be required (e.g,, red/black, yellow/blue, orange/white). Green is reserved for grounds (but there may be more than one kind of ground). Due to the limited number of colors, other types of wiring (e.g., lighting, accessories) may use the same colors as bus wires, and will need to be distinguished by physical placement, size, and labeling. Where Anderson plugs are used, orientation (vertical, horizontal, or two-dimensional array), may be used to ensure proper connections.

11. Wires will be stranded, with two exceptions. Short lengths of solid wire may be used for track feeders, to simplify soldering. Magnet wire (which is not stranded) may be used in signals and structure lighting, or other places short lengths of low-current wire must be fit into a constrained space, but may not be used in track wiring. In general stranded wire is preferable for its flexibility and resistance to breakage from flexing.