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Concord Model Railroad Club - Standards

Concord Model Railroad Club

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The Club's first modules were built following an NMRA-like standard.  This is the same standard used by the CVMRRC club.

Many members became displeased with the parallel, racetrack-like mainline, and started to consider other options, like the emerging FreeMo standards. It was thought that the NMRA standard was holding the Club back from designing and building a layout focused on operations.

The standards to left were written with the goals of combining the NMRA specs with the FreeMo standards, along with the numerous lessons that Club members have learned. The results are lighter modules, less track joints, more design flexibility, yet retaining the ability to connect to a "legacy" module.
HO Scale Standard Gauge Modular Standards
Adopted on September 8, 2003
Edited on October 29, 2006
Edited on June 29, 2013
Edited on April 18, 2015
Last Edited on April 24, 2016

Module Construction


Modules shall be constructed with light weight materials, with a foam core, furnature grade plywood ends, and luan facia and backdrops. Modules ended up being built with 3/8" plywood, instead of luan. Using luan, and building up T and I beams added complexity to the construction process, without removing significant weight.

The important concept is that the modules should be sturdy enough to be moved for shows, and light enough that they can be easily managed.

Straight Modules

Straight modules shall be no longer than 6 feet, and no wider than 3 feet.

Corner Modules

For ease of constructions, two of our corners are built from two 2x6 modules, connected as an "L".  Another two corners are built from two 2x4 modules, and two corners are built as a 4x4 "L".  The latter corners fit together "tetris-style" into a 4x6 footprint for shipping.  One additional corner is a 5x4 "L"


The backdrop shall be 18 inches high. To date, we have not built backdrops on most of the new modules. Backdrops will be built later, and designed to be attached after the layout is assembled. Since the new modules are designed so they can be flipped around, we don't want a permanment backdrop obscuring the view during a show. When setup at the Clubhouse, backdrops separate Franklin from Lebanon.


The top of roadbed shall be 40 inches, with adjustable supports that allow the modules to be lowered to 38.5 or raised to 41.5 inches.

Mainline Track


All track measurements are made from the front, or viewing side of the module, to the centerline of the track. All mainline track shall be code 100 nickel silver. Mainline tracks shall be set back three inches from the end of the modules. The first 6 inches of track shall be straight, creating a twelve inch straight transition between posible reverse curves. Rail joints, except at turnouts, shall be soldered.
All track clearances shall conform to NMRA Modern Clearanc standards.


Mainline turnouts shall be no smaller than #6#8.  Smaller sized turnouts may be installed to serve industry sidings, provided that mainline trains do not travel through the diverging route.

Mainline Turnouts shall be powered with slow-motion, stall type switch motors, or hand-thrown with Caboose Industries hand throws.


A single mainline track shall interface between modules, and be laid 7 inches (centerline) from the front of the module.  Modules that are expected to interface with standard NMRA modules shall have a second track, laid 5 inches (centerline) from the front of the module.  Multiple modules that connect together to make a scene, need only comply at the ends that connect to other modules.


See our newly written Evolution of Wiring document for an historical perspective, plus up to date wiring guides.


The track power bus shall be constructed with 12gauge wire, terminal strips, and spade connectors.  Short 24gauge wire shall be used for track feeders.  Two-pin connectors shall be used for each mainline between modules. Heat-shrink tubing, or paint on electrical insulation shall be used to cover solder joints.


Gaps, or insulated rail joiners, shall be installed across both rails within the module; solid rail jointers shall be used between modules.  A "gap-switch" shall be installed, which when in the closed position shall allow power to flow through the module. This may sound like a good idea, but in practice it adds complexity to the design, and could result in failures if the switch was changed during layout operations. We'll continue to use insolated rail joints at the end of the module, and unplug the track bus. Section houses have been installed on the layout to indicate where the gaps are located.


Circuit protection shall be installed in such a manner to prevent a single short from shutting down the entire layout. We're still relying on the multiple booster outputs for short circuit protection.

Special Purpose Modules


Two 6 x 6 foot corners to be used at joint CVMRRC/CMRC meets

Four 4 x 4 foot corners to be used at small shows, similar to the NH History Museum, and Pemi Valley Shows.

NMRA Compliant

The Concord Yard is  made up of NMRA compliant modules to be used for interfacing with the Bedford Boomers, or similar group. Both track and wiring!


We've never done this...

Two six foot modules that contain two feet of single track, and four feet of double-track, meeting the NMRA spec at the interface.  When placed so that the two NMRA ends join, the modules will form an eight-foot passing siding. Optionally, we could build the NMRA ends with all four tracks, forming a four track "yard" when connected. We have decided to use the four-track yard configuration, and model that to be the northern terminus of our Concord to White River Junction sectional layout. The yard will roughly be the Westboro frieght yards.


Jon Miner's two loops, each taking up 7x10 foot floor space are DCC compliant, with built in reversing units.  The loops can be used by themselves, or with any number of modules inbtween.  The loops support both single and double-track reversing.

Other Accesories

The module owner is responsible for providing two clamps and two joiner sections per module.
All track clearances shall conform to NMRA standards.