Sn2 has existed for some time.   A few modelers have made models, and published articles.  To ensure compatibility of models the there was a call for standard.  Those standards (recomended practices) were put forth back in early 2000’s,  to ensure compatibility between models.  Manufacturers benefit from standards because their models will be compatible with other Sn2 models. I am not suggesting that this page actually be standards, but guidelines. The concepts presented here are the result of discussions on Sn2_Trains yahoogroups list.

Sn2 Gauge is modeled using HOn3 (10.5mm):

  • 24″ in S scale is 3/8″. However, most modelers do not choose 3/8″ as the track gauge.
  • HOn3 gauge, 10.5mm, is the gauge adopted by most modelers. It works out to be 26.5″ in S scale. At roughly 10% too large, it is a compromise.

  • N gauge, 9mm, is roughly 23″ gauge and closer to 24″ than HOn3. However, most Sn2 modelers prefer HOn3 gauge, because the components (trucks, wheels, couplers, locos, ….) are closer to the size of S narrow gauge than N scale components.

As of 3/2/15, the brass locomotives and trucks manufactured for Maine 2-Foot modeling have been to the HOn3 track gauge.

Maine 2-foot couplers and height:

The following standard only applies to Maine 2-foot prototypes. The Maine railroads all used the same size coupler and had a common coupler height of 16″ rail head to center and car underbody heights of 18″ above the rail.

Based on the size of the HOn3 coupler, which is about the same size as true Sn2 couplers, the height of the car underbody, and the height of the coupler, we had to make a choice. Not all three dimensions could be accomplished. The member of the Sn2 e-mail list choose to compromise coupler height, and maintain body height. We felt that body height defines the look of Maine 2-foot cars more so than the coupler height.

Maine Sn2 Coupler Standard:

Coupler Style: HOn3 (714) Kadee or HO Old Time (711) coupler. The trip pins are snipped off.  More recently some have started using Sergent Couplers and others HO Kadee #163 short shank couplers.  Follow the links to see how they were done.
Car Body Height: 18″ in S scale = 9/32″ actual. For cars, this is the distance from the rails to the underbody sills.
Coupler Height: 14.5″ in S scale = .226″ actual

This coupler centerline height is derived from mounting the 714 couplers at the required body height. So, if one makes the body 18″ (9/32″), then the coupler height is automatically set.

This standard should hold for Passenger cars and Engines too.

The Sn2 Coupler FAQ provides inquiring minds the details behind the Sn2 coupler standard. Click to make a make coupler height gauge or buy a coupler height gauge.


The Sn2 Free-mo standard is a page on this site.  Several modelers have build modules to this standard an display them as the Sn2 Crew (see catagory links at right)

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