T-TRAK Standards

T-TRAK standards are minimalistic by nature. The concept of T-TRAK is to be able to simple enough that anyone can participate. Over the years, a number of "best practices" have arisen, but the standard has remained the same.

Resources

T-TRAK Standards Document

T-TRAK Guidelines to Interfacing

T-TRAK Larger Corners RP

T-TRAK Track Clearances

T-TRAK In Other Scales

Mixed Units in the Standard?

One thing people find a bit confusing with the T-TRAK standard is that mix of imperial and metric units. The reason for this is because the T-TRAK standard is built around Kato UNITRACK, and UNITRACK is measured in metric. So any measurement dealing directly with the track (track length, radius, track spacing, etc) will all be in millimeters (mm), while all other measurements (module height, depth, etc) will be in inches (in).

Module Size

While the T-TRAK standards allow for many different modules, most can be grouped into one of 3 categories: Straight, Corner, and Junction.

Straight Modules - The track length will define the modules width. The module frame should be 2-4 mm shorter than the desired track length to ensure a secure connection at the module ends. The track length is in multiples of 310mm. Module depth is at the discretion of the modeler. However, recommended depths include 8¼” and 12” with a maximum depth of 14⅜”.
Corner Modules - (90-degree curve) The track radius will define the modules width & depth. The module should be 50mm larger than the larger radius. For example, A common corner use 315mm radius track, so the module is 365mm (or 14⅜") square.
Junction Modules - A junction module has straight track along the 'red line' and curve track along the 'yellow line'. The width & depth will be defined by the radius of the curved track. Please see the module page for full details.

No matter what type of module, the modules frame should have a nominal height of 2¾" and must be adjustable to 4".

Track

T-TRAK modules have two common mainline tracks. These are usually marked as 'red line' and 'yellow line', with red being the one closest to the 'front' edge.^† The standard requires Kato UNITRACK on the ends, but it is recommended that UNITRACK is used along the whole length. Spurs, passing siding, yards, etc. are allowed, and left to the discresion of the modeler.

The first track is to be set back 1½" from the 'front' edge of the module, measured to the edge of the of the Kato ballast track.

Track spacing is 33mm, measured from track centers. Kato doubletrack is set to 33mm, or one can use the notches along the side of a Kato Rerailer.

^† Because T-TRAK modulars are designed to be viewed from any angle, there is technically no 'front' or 'back'. And with no front, or back, which track is part of which line can change depending on layout setup. But an understanding among modelers has come to define that the 'front' is the side with the 1½" setback, the first track after that setback is labeled "red" and the second track is labeled "yellow".

Module Wiring vs Layout Wiring

While it may seem confusing at first, the wiring standard of "blue to the outside" (or B-W-W-B) has stood the test of time. It has proven to be the most flexibility with very minimal compromise when it comes to layout designs. One reason for the confusion is because "module wiring" is separate from "layout wiring". At the module level, it is important to follow the B-W-W-B standard, which gives that module the most flexibility in how it can be used in any layout. At the layout level, we look at the overall layout elements, and then we make any necessary adjustments for electrical polarity.

For an explanation of the benefits and flexibility of the BWWB standard, see the T-TRAK Wiring page.

Wiring

Not all modules are required to have power feeders^††, but those that do must use the Kato style connectors (or compatible). These white connectors are indexed so that you can not accidentally connect the ground wire to the hot wire.

All T-TRAK modules are required to be wired following the "blue to the outside" standard, and each line is required to be wired independently. (ie. you will need two Kato Terminal Unijoiners [part 24-818] per module) The front most rail, and the rear most rail of the double track mainline should be connected to the 'blue' wires of the Kato power feeders, and the two innermost rails should be connected to the 'white' wires.

^††There is no formal required standard for which modules should or shouldn't have power feeds, it is suggested that any straight module bigger than a single should have power feeders. In addition, since it is easier to add the power feeders at the time of building, it is generally better to add them when you can.

Kato Terminal Unijoiners [part no. 24-818]

[need photo of wires connected to track]

Summary Table

* This is just a sampling of common module types. A more comprehensive list can be found T-TRAK Modules page.

	Module Width	Module Depth	Module Height^†††	Track Length (Common Kato track pieces)
Single Straight	308mm 12⅛ in	125 - 365mm ~5 - 14⅜ in	70 - 101mm 2¾ - 4 in	310mm (2) 20-000 & (2) 20-040
Double Straight	618mm 24⅓ in	125 - 365mm ~5 - 14⅜ in	70 - 101mm 2¾ - 4 in	620mm (4) 20-000 & (2) 20-020
"Small" Corner	365mm 14⅜ in	365mm 14⅜ in	70 - 101mm 2¾ - 4 in	282R & 315R, 90-degree (2)20-110 & (2) 20-120
T-Junction "Jackson Junction"	595mm (23½") 20 ⅞ in	365mm (14⅜") 20 ⅞ in	70 - 101mm 2¾ - 4 in	597mm of straight, (2)90-degrees of radius 282

^††† Height is measured from table top to the bottom of the Kato UNITRACK

Track must be 33mm (centerline to centerline) apart. Kato double track pieces are 33mm apart, or you can use the notches on Kato re-railer to get the correct spacing. (Note: It is recommended to NOT use the Kato double track 62mm feeder track [20-043] since it does not provide BWWB wiring without some modifications)
Any module that has power feeders, must be wired with "blue to the outside" rail, or "BWWB". Electrical connectors from the module must be the Kato connectors. The easist way to get this right is to use two Kato Terminal Unijoiners [24-818]; one for each track.

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