NASG S-MOD Standards

The NASG S-MOD Standards were developed so that S scale modelers could gather from anywhere and easily join their modules into functioning hassle-free layouts. These standards have been accepted by the NMRA Engineering Committee as the basis for the NMRA’s "S" standard gauge module standards. They accommodate scale standard gauge, narrow gauge, and/or hirail.

• The Basic NASG S-MOD standards packet: (pdf)
  • Physical Standards - dimensional standards for single - and double-track main line
  • Electrical Standards - wiring for cab and block control
  • Operational Standards - responsibilities of module owners before and at modular meets
• Concept Description of the S-MOD Layout Electrical System: (pdf)
  • control wiring description
  • diagrams
  • troubleshooting
• Handheld Throttle (pdf)
  • construction
  • use with the S-MOD system
• Recommended Track, Wheel, Turnout Dimensions, and Clearance Standards:
  • NASG Track and Wheel Standards
    • Track, Standard Gauge S 3
    • Track, Narrow Gauge S 3.5
    • Wheels, Standard Gauge S 4.5
    • Wheels, Narrow Gauge S 4.5
    • Track, Proto: 64 RP 3
    • Wheels, Proto: 64 RP 4
    • The NASG Clearinghouse offers track and wheel gauges for S standard gauge.
  • NMRA Standards
    • standard-gauge NMRA turnout dimensions (RP 12.3)
    • The NMRA recommended practice for car weight is 2 oz. plus another 1/2 oz. per inch of car length.
    • Sn3 track and wheel gauges are available from the NMRA.
  • Clearance Diagrams and Gauges
    • older (pre-stack car era) clearance template (PDF)
    • newer " Plate H" clearance template (PDF)
    • If you prefer to purchase a clearance gauge instead of making one, S clearance gauges are available from banta modelworks made of either wood or acrylic.
• Additional Resources
  • The S-MOD System of Module-Railroading" by Don Thompson and Don DeWitt, in four parts from The Herald, 15 pages:
    • Planning the Module, Volume 20, No. 4, March 1987 (PDF)
    • Building the Benchwork, Volume 20, No. 5, May 1987 (PDF)
    • Laying the Track, Volume 20, No. 6 (PDF)
    • Installing the Electrical System, Volume 21, No. 3 (PDF)
• More on wiring from the NASG DISPATCH
  • "The S-MOD System - Checking the Wiring in Your Module" by Don DeWitt, Vol. 12 No. 1, February 1989. This is a must have! (PDF)
  • "The S-MOD System - Building a Portable Control Panel for S-MOD Railcab Layout" by Don DeWitt, in two parts, Vol. 12 Nos 2 & 3, April-June 1989
    • Part 1 (PDF)
    • Part 2 PDF (PDF)
  • "Basic Turnout Wiring" by Stan Stokrocki, Vol. 10 No. 1, March 1987 (PDF)
• Corner Module construction from the NASG DISPATCH
  • "Corner Modules Part I - 48" Hexagonal Corners", Ted Larson, Vol. 20 No. 5, October 1995 (PDF)
  • "Corner Modules Part II - 60" curved corner, Houston S Gaugers", Ted Larson, Vol. 20 No. 6, December 1996 (PDF)
  • "Connecticut S Gaugers' 90-Degree Corner Module Design", Bill Krause, Vol. 21 No. 1, February 1996 (PDF)
  • "Corner Modules That Eliminate Spacer Modules", Bill Krause, Vol. 21 No. 3, June 1996 (PDF)
  • "The Split 59" corner (Enhancements to Connecticut S Gaugers' corner)", parts 1, 2, 3, Bill Krause, Vol. 20 Nos. 3, 5, 6, June, October, December 1997.
    • Part 1 (PDF)
    • Part 2 (PDF)
    • Part 3 (PDF)
• Other Module material from the NASG DISPATCH
  • "A Compact End Module Part I", Ted Larson, Vol 19, No. 6, December 1994 (PDF)
  • "A Compact End Module Part II", Ted Larson, Vol 20, No. 2, April 1995 (PDF)
  • "Joining Rails of Different Sizes", Bill Krause, Vol 21, No. 2, April 1996 (PDF)
  • "Turnout Actualing Mechnism for Houston S Gaugers Modular Layout", J. Troxell, Vol 21, No. 6, December 1996 (PDF)

More on S-MOD Standards

Send questions/comments about S-MOD to: Bob Sherwood, NASG Engineering.

For additional online information on the S-MOD Standards go to Paul Yorke's S-MOD web site.

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