T-TRAK-Z - Tabletop Modular Z scale Railroading - Standards and recommendations

Created by Josh Murrah and Vic McTee, Revision 1.7 by Josh Murrah, 5/19/2019

Interactive group area: https://www.facebook.com/groups/ttrakz

What changed in 2018, and why?

T-TRAK-Z, as of mid-2018 had never taken off, and the feeling is that it's largely due to the previous specifications. The track system choice was out of date, and the layout geometries were never considered beyond a basic rectangular shape. This document details a system that enables geometry that allows for larger, more interesting layout designs.


Track system - Rokuhan

Rokuhan has a robust mix of modern molded roadbed design, with Marklin's long-established sectional geometery. It also has the replaceable plastic/metal joiner combo that this type of modular system requires. This enables Z, for the first time, to duplicate the variety of modules that can be built in the larger N scale. Rokuhan track is imported to the US by Ztrack, who is also the distributor for AZL. Modeltrainstuff.com carries the full line as well as all Z scale online/local dealers.


Track set back - 3 inches / 76mm From Fascia Edge to Track Center Line

The three inch setback is perhaps overly generous, but we have the room for it in Z scale (all the below curves still allow a layout to fit on a single table width), and it will allow for two sidings on the front line plus a "train wreck" easement, or will instead allow some nice scene/scenery options. There's also lack of rearward scenery area on the module, so the front area helps.


Corner radii - three options - 195mm/220mm, 220mm/245mm, 245mm/270mm - minimum mainline radius 195mm

Rokuhan provides a wide number of radii, spaced 25mm / 1" apart. The two core/key radii are 195mm & 220mm. That is what is provided in the starter kit, and they are the two radii available in both 45 degree and 30 degree sections, along with being the radius pair the curved turnouts are designed for. Any radii smaller than 195mm on main lines are not allowed for mainline. Designs have been created for inside/outside corner geometry, T-Junctions, star junctions, various yards and working single and double line balloon loops, in all three radius combos all without cutting any track sections. When planning a layout, there needs to a single radius combo choice, as the three size options are generally not interchangable. Local clubs should determine their own optimal radius, and build corners and junctions to work with their choice.

  • 195/220 corner module (most common): 295mm (approx. 11 5/8") depth/width
  • 220/245 corner module: 320mm (approx. 12 19/32") depth/width
  • 245/270 corner module: 345mm (approx. 13 9/16") depth/width

Module dimensions

Rokuhan has a geometry of 220mm. That's the multiplier that makes all the various radii work, and is also the length of a double crossover, much as the width of T-TRAK-N modules and Unitrack crossovers are both 310mm. That means all modules need to be a multiple of 220mm.

The module max depth is one inch less than a 195/220 corner, which makes it 270mm (approx. 10 5/8"), which allows for a small central trench for bus cables and backdrops. Regardless of what radius corners your club uses, don't break this critical max depth. To state this another way, if you build the modules any deeper, the modules won't fit into a smallest-radius layout, as are most common currently, so you won't be able to combine with other players at a show. Don't risk being turned away.

The module height is the same as T-TRAK-N, 70mm / 2.75" with a additional foot adjustment of 32mm / 1.25". There was some research into scaling down the module height and it would be more pleasing looking, however the hard fact is that the electrical accessories don't actually scale down, good examples are the Digitrax UP5 front panel mount or the Anderson Powerpole electrical outlet in the back.


Dimension summary:

  • width: multiple of 220mm with 1mm setback on each side
    • single is 218mm (approx. 8 9/16")
    • double is 438mm (approx. 17 1/4")
    • triple is 658mm (approx. 25 15/16")
    • quad is 878mm (approx. 34 9/16")
  • max depth: 270mm (approx. 10 5/8")
  • height: 70mm / 2.75" with a additional foot adjustment of 32mm / 1.25".

Backdrops - optional but highly recommended - 178mm / 7" recommended height

There will be a central trench in almost all cases. Since there is a trench, there is an optional, but highly recommended practice of using backdrops to help hide it for beautification purposes and general use as a backdrop/view block. A lot of research was done and the listed height is ideal for shows.

Electrical - Powerpole plugs

The electrical distribution will utliize T-TRAK's electrical bus recommended practices, we're just extending them to the feeders and back of the module. See pages 8 and 9 of this document: http://ttrak.org/T-TRAK%20Standards.pdf

The module plug is Anderson Powerpoles, in a 2x2 configuration reaching to the back of the module. A knockout hole and Powerpole outlet on the back of the module is recommended to avoid hanging wires. All manufacturers of N and Z modules already include the hole for the socket.

The track shall be be fed as follows, from front edge to rear edge of the tracks… black-red, yellow-black. The goal electrically is to have consistently fed, opposing polarities on the two rails, to allow for opposing travel directions with DC and to allow use of junctions and figure eights.

The track feeder mechanism is left to the modeler, the options known to work are: Rokuhan feeders, Atlas N code 55 terminal joiners, and soldering.

Accessory power is optional, and is 12VDC, via Anderson Powerpoles, in a 1x2 horizontal configuration, per the above T-TRAK specification. These also need to reach to the rear of the module, preferably mounted in a 2x2 outlet or the 1x2 clamping mount on the back.

The bus itself can simply be a powerpole-to-Rokuhan pigtail for the smallest setups using one or two Rokuhan DC controllers, larger setups should adhere to the T-TRAK recommended practices and construct a 2, 4 or 6 conductor bus set per that document, with power pole feeders.

Here are four pictures for N scale T-TRAK as samples, I'll update these later with T-TRAK-Z specific photos. Where you see the white Kato plugs in these pics, envision this as the connection to the bus or as Rokuhan plugs if your layout isn't large enough for a bus.
electrical1.jpg electrical2.jpg electrical3.jpg electrical4.jpg
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