A Brief Survey of Modular Model Railroading HO, OO, and O Scale Railroads
As with N scalers, HO scale rail modelers have a set of standards that should be employed when constructing modules for show display or home use. In fact, most standards for HO scale railroad modules have been directly adapted from the N-Trak standard. © Copyright http://www.modelbuildings.org All rights reserved.
The National Model Railroad Association has published standards for modular construction. These guidelines are usually included and expanded in the variations which apply to all scales when constructing modules. The complete NMRA Standards and Recommended Practices can be found at: https://www.nmra.org/index-nmra-standards-and-recommended-practices
While most model railroad modules adhere to the physical construction recommendations, there can be significant modifications of the wiring recommendations. One very popular variant is the use of Anderson Power- Pole electrical connectors rather than the Cinch-Jones connectors recommended by NMRA. The widespread use of Digital Command Control on model railroads has also led to variations of throttle control wiring. Most of the standards, when they specify DCC, opt for support for the Digitrax Loconet configuration. It is also fairly common for local groups or model railroad clubs to modify these standards in some fashion to allow for local variations in the supply of module raw materials or popular brands of equipment.
While most model railroad modules adhere to the physical construction recommendations, there can be significant modifications of the wiring recommendations. One very popular variant is the use of Anderson Power-Pole electrical connectors rather than the Cinch-Jones connectors recommended by NMRA. The widespread use of Digital Command Control on model railroads has also led to variations of throttle control wiring Most of the standards, when they specify DCC, opt for support for the Digitrax Loconet configuration. It is also fairly common for local groups or model railroad clubs to modify these standards in some fashion to allow for local variations in the supply of module raw materials or popular brands of equipment.
HO-Trak Modular Railroads
Modules must be 40 inches from the floor to the top of the rail, with leg adjustment range of 2 inches. Modules must be multiples of 2 feet in length and must be 2 feet in width. Corner and curved modules are permitted. Each railroad module must include a skyboard at the back of the module. The depth of the module frame ad the ends where joining another module must be between 4 and 4 1/2 inches. The dual main line tracks must end 3 inches from the end joint of the module and must have a tie-free length of 1 ½ inches to allow the insert of sectional track module join pieces. Curved module track radii must be 40 inches. https://drive.google.com/file/d/1B7z311uDnyl0LOhh79NL8kJetCzpp3AU/view
T-Trak Modular Railroads
The T-Trak standard uses Kato Unitrak as a standard rail. Since Kato also makes Unitrak in HO scale, the same standard can apply to HO scale railroad modules made to this specification, substituting HO Unitrak for N Unitrak. A great advantage of T-Trak modules is their small size and monetary investment. Modules can literally be built at a kitchen table, and the small area and diorama concept encourages a high level of detail.
Free-Mo Modular Railroads
Like the other modular standards, Free-Mo is based on a 24-inch width. Modules are taller than similar NTrak, HO-Trak, or One-Trak units at a standard height of 50 inches from the rail head to the floor. Modules are allowed to have elevation grades as well, in which case the module height to the rail head on the layout should not exceed 62 inches. When elevated, track height from end to end must be a multiple of ¾ inch. Like most of the other standards, there is a recommendation for the size of the track (code), and the dimension of the turnouts. There is, however, another component involving the philosophy of construction of the modules. Free-Mo attempts to create as much realism in the representation of the models and scenery as possible. Including such things as Lego structures, dinosaur toys, or other elements often found in “toy train” layouts are highly discouraged. Accuracy and authenticity to both the environment and era are paramount in the Free-Mo standard.
OO-Trak Modular Railroads
The great thing about standards is that there are so many to choose from! Of course, there is absolutely no reason you need to follow all, or even any, of the recommendations if you have reason not to. One such reason could be that your chosen railway club has some unique notion of how they want your modules to interface to other members’ units when setting up for a show. Another reason might be that you are only building modules for your own use and never anticipate interfacing them with units built by others.
One group in New Zealand has done just that. Called the Arun Valley Railway, their modules are built on a 1300 by 200-mm or 300-mm length/width standard, with corresponding sizes for end or corner modules.
Since OO scale model railways are very close to HO scale (1:76 vs 1:87) and run on HO scale track, any of the above HO scale standards would certainly apply and work well for the OO scale modeler. OO scale is fairly rare in the USA, but is found in some abundance in the British Commonwealth and Europe. There is an NMRA OO scale special interest group, and the modular standards outlined by the NMRA are applicable to OO modules as well as HO.
O Scale Modular Railroads
O scale modular railroading is not formalized with a recognizable standard as of this writing. However, as in the case of OO scale railroads and in addition to some HO and N scale implementations, there is nothing to stop individuals or clubs inventing their own “standard”. In fact, there are cases where the Free Mo concept has been applied to O-scale layout construction. The smaller size of T-Track modules probably doesn’t allow for very effective O-scale reproduction, but the use of sectionalized track with attached plastic roadbed in the standard is matched by the availability of such track in 3-rail O-scale products. An upscale T-Track based on O-scale products and equipment would certainly be possible. The non-trackwork construction, wiring, and interfacing techniques certainly scale well when going from HO Free-Mo or HO-Track. Some electrical issues might bear consideration, as DCC on O-scale is not widespread. Throttle control would certainly need some thought if a club is seeking to standardized O-scale modules.