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

Created by Josh Murrah and Vic McTee, Revision 1.6 by Josh Murrah, 10/6/2018

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

What recently changed, and why?

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 The track system choice was out of date, and the lengths and geometries were never considered beyond a basic rectangular shape.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


Track system - Rokuhan

Rokuhan has a robust mix of the old spec'd MTL track geometery with very similar joiners, but has the larger radii, wider variety of track lengths and a capability of types of super elevation & concrete ties that exceeds what Unitrack provides. I have been able to recreate all of my T-TRAK-N designs in this smaller scale using this system. Rokohan track is imported to the US by Ztrack, who is also the distributor for AZL. Modeltrainstuff.com carries the full line as well as any local dealer who can order AZL.


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

The three inches 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 one table), 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 will generally not work together. Local clubs should determine their own optimal radius, and build corners and junctions to work with their choice.

  • 195/220 corner module: 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

Rokohan 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"). This does allow for a small central trench for bus cables and backdrops. Regardless of what radius your club uses, the max depth has to conform to the smallest radius. To state this another way, if you build the modules deeper, the modules will not fit into a smallest-radius layout. To make interoperability easier this standard will not include support for modules deeper than this maximum, but they are allowed as long as properly planned. Some examples of planning for very deep modules include such things as a 2" bottom-facing pass through channel for tabletop bus cable, and running sets of modules back to back in a specific area of the layout for geometric or aesthetic reasons.

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, a good example is the Digitrax UP5 front panel mount which needs the full 2.75".


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. Due to the module not being as deep and the track being set quite a bit farther back (the backdrop height is limited by the need to see your train on the opposite side), the backdrop needs to be 7" total, with only 4.25" visible above the back of the module.


Electrical - Powerpole plugs

The electrical distribution will follow 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, that can be reached at the back of the module, preferably in a outlet on the back of the module. 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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