Single straight module
The single straight is the unit that defines the standard. Every other length, every corner and every junction is derived from it. Build one of these correctly and you have a module that will couple to anything else in the country built to the same rules.
The footprint is rectangular and the track is parallel to the long edge. The numbers in the table are the ones that will be checked, by eye or by gauge, when you set up next to someone else's module. Treat them as hard targets; the optional flourish belongs above the deck, not in the dimensions.
| Length × depth × height | 308 × 300 × 70 mm | excludes skyboard & feet |
|---|---|---|
| Track length | 310 mm | protrudes 1 mm each end |
| Front track setback | 38 mm | front face → ballast edge |
| Track centres | 33 mm | 8 mm gap between Unitrack bases |
| Track grade | 0% | level only on all main line |
| Levelling range | 70 → 100 mm | M6 carriage bolt + tee nut |
| Vertical clearance | ≥ 45 mm | rail top → anything overhead |
| Side clearance, straight | ≥ 12 mm | rail outside edge → scenery |
| Side clearance, curve | ≥ 15 mm | inside & outside |
| Skyboard visible | 200 mm | above the deck |
| Skyboard total | 250 mm | includes the part inside the box |
| Skyboard top corner radius | ≤ 18 mm | ~20¢ coin works as a template |
The 38 mm front setback is what makes the front fascia readable from above — far enough back that the ballast edge isn't sliding off the front of the deck, near enough that a passing train is the visual subject and not a thin strip up the back. It also leaves a useable apron of scenery between the front rail and the world.
The 70 → 100 mm levelling range comes from a single carriage bolt and tee nut at each corner. 70 mm matches the deck height; the 100 mm ceiling is the height a long-suffering meet host can wind a bolt down to without anything dramatic happening. If the table you're on slopes more than that, the table is the problem, not your module.
Multi-length and corners
Once the single straight is settled, every other piece in the kit follows from it by addition. A double is two singles; a triple is three; corners and junctions are sized to drop into the same grid. Track length always overshoots module length by 2 mm.
| Single straight | 308 × 300 mm | track 310 mm |
|---|---|---|
| Double straight | 618 × 300 mm | track 620 mm |
| Triple straight | 928 × 300 mm | track 930 mm |
| Quad straight | 1238 × 300 mm | track 1240 mm |
| Outside corner | 365 × 365 mm | 90° turn |
| Corner radii | 282 / 315 mm | Kato #20-110 / #20-120 |
| Double corner | 365 × 732 mm | two 90° corners on one board |
| Junction module | 365 × 596 mm | paired opposite a double corner |
| U-turn footprint | ≥ 760 mm wide | end-of-loop reversal |
Module length is always exactly 2 mm shorter than a multiple of 310 mm. The track makes up the difference, protruding 1 mm at each end. This single rule is what makes the system work — module-to-module, the rails meet edge-to-edge with a hairline UniJoiner gap and no fettling on the day. Internalise it and every other dimension on this page falls out as a consequence.
A double-corner board carries two 90° turns on one piece of MDF and is the cheapest way to put a U-turn at the end of a layout. The junction module sits opposite it in many club layouts, providing the cross-over or the lead into a yard. The 760 mm width on a U-turn assumes the outer Kato radius (315 mm) plus a sensible apron and a fascia that doesn't overhang the trestle.
Quads are not a typo: they exist, they're allowed, and a long flat quad is one of the few places on a T-TRAK layout where a long Australian goods train can stretch out. The reason they're rare is mostly storage and transport. Two doubles fit in most car boots; one quad doesn't.
Track parts (Kato Unitrack)
The standard is built around Kato Unitrack. The list below is what you'll actually order to build a module and to electrify it. Kato part numbers are stable across decades; if you find a 1990s instruction sheet at a swap meet, the codes still mean what they say.
- #20-000248 mm straightworkhorse
- #20-04062 mm straightinfill
- #20-04162 mm feeder trackpower feed
- #20-020124 mm straighthalf-stick
- #20-110282 mm radius cornerinner
- #20-120315 mm radius cornerouter
- #20-04562 mm adapterPeco/Atlas at module ends
- #20-05078–108 mm expansion trackslack-taker
- #20-091short-track pack (29 + 29 + 45.5 mm)infill
- #24-000re-railergauges 33 mm spacing
- #24-815UniJoiner — standardconductive
- #24-816UniJoiner — insulatedblock break
- #24-830connector switchsiding isolation
- #24-831selector switchpassing-loop control
The re-railer (#24-000) earns its keep twice over: once as the part you drop on the rails to put a wagon back on the track, and once at the bench, where its moulded base is the simplest way to confirm your two tracks really are at 33 mm centres. Set the re-railer across the pair, and if anything binds, rework the module before the glue cures.
The insulated UniJoiner (#24-816) is how you make a siding electrically dead, or how you split a long rake of modules into manageable power districts. They look identical to the standard joiner from above; mark them on the underside with a dot of paint or a paint pen so the next person to dismantle the layout knows what they're holding.
Clearances
The clearance figures in §1 — ≥ 45 mm overhead, ≥ 12 mm straight side, ≥ 15 mm on curves — describe the shape of the empty space a passing train needs. The Australian envelope is taller and a touch wider than the loading-gauge most off-the-shelf N-scale scenery is designed against, and that gap is the single most common reason a module fouls a guest's loco.
Before you commit to a tunnel portal, an overbridge or an awning, make a cardboard clearance gauge. Cut a rectangle to the inside dimensions of the envelope, mount it on a sliver of stripwood, and run it down the rails by hand. If it scrapes, you have a problem at the bench, not at the meet — and the bench is the cheap place to find it.
Most off-the-shelf N-scale tunnel portals and bridges are sized for the European or US envelope and are too tight against the Australian one. Plan to either modify the casting (file the inside of the arch), scratch-build the portal to clearance, or — if you can't — alert the meet coordinator before setup so the layout can be planned with your module on a branch instead of the main line.
If a published model demands a slightly larger envelope than the standard allows, the convention is a 3 → 6 mm rise across the affected stretch — enough to clear a stubborn portal without breaking running. It must be flagged in advance so the rest of the layout knows to taper into and out of it. Showing up on the day with an unannounced rise is what gets your module quietly skipped over for the next meet.
Side scenery within roughly 3 mm of the joining face should be assumed to clash with whatever your neighbour has built. Trees, signal masts, telegraph poles and platform canopies are the usual offenders. Either keep the last 3 mm of the deck deliberately bare, or make those features removable so they can be lifted aside while the layout is set up.
Materials
The standard does not mandate a specific timber — it mandates dimensions and behaviour. In practice, two materials dominate.
6 mm MDF is the preferred deck for most builders. It's cheap, it's flat, it stays flat in a normal house, it takes paint and ground cover without fuss, and it's plenty strong at the sizes T-TRAK uses. Its one weakness is moisture: an unsealed MDF cut edge will swell if it gets wet. Seal every cut edge with thinned PVA or a coat of acrylic primer before you put scenery near it.
Plywood is the alternative. 6 mm or 9 mm B-bond exterior ply is acceptable; A-bond marine ply is ideal if you're prepared to pay for it. What you must avoid is construction-grade C/D ply — the cheap interior stuff with voids and a knotty face — because it delaminates, warps and chips the moment it's stressed at the corners.
For the substructure, glue blocks are 32 × 32 × 300 mm stock timber, cut from a single dressed length and glued and screwed into the inside corners. The levelling feet are M6 tee nuts driven into the underside of the deck, paired with M6 × 50 mm full-thread carriage bolts threaded up from below. Carriage bolts (the ones with a domed head and a square neck) sit flat on the table, don't snag the carpet, and don't need a separate foot pad to work.
Whether you've built in MDF or ply, paint the four cut edges of the deck before you do anything else. A spilt drink or a damp scenic mat will otherwise wick into the panel and lift it from underneath. Two thin coats of acrylic primer is enough; you don't need to make it pretty, you need to make it sealed.
Mini-T cross-reference
If you've come here looking for Mini-T, you want a different page. Mini-T is a separate sub-system at the same scale: 150 mm deep instead of 300 mm, sized in 62 mm length steps rather than 310 mm, and built only in 12 mm hardwood ply because the narrower deck needs the stiffness. Mini-T modules are not interchangeable with the standard described on this page — they couple to other Mini-T modules, not to the main N-scale fleet. See mini-t.html for the full spec.