- Join the NMRA
- About the NMRA
- Education
- Resources
- Community
Search NMRA.org
S-7 Clearances
Note: For Help with
NMRA Gauge letter definitions and the AAR Plate diagrams on which
it's based see Standard S-7 Clearances and
the NMRA Gauge
This Clearance Diagram and its dimensions produce the Preferred "M" Track Centers shown in STANDARD S-8, which also shows the additional side clearance and Track Centers required for curved track.
BRIDGE AND STRUCTURE CLEARANCES - TANGENT TRACK
| Scale | A | B | C | D | E | F | G | H | P |
|---|---|---|---|---|---|---|---|---|---|
| 1" | 6-1/2" 165mm |
||||||||
| O(17) | 2" | 1-1/16" | 1-19/32" | 3-3/16" | 1-1/16" | 11/16" | 1-19/32" | 5-27/32" | 1-19/32" |
| 50.8mm | 27.0mm | 40.5mm | 81.0mm | 27.0mm | 17.5mm | 40.5mm | 148mm | 40.5mm | |
| O Scale | 1-7/8" | 1" | 1-1/2" | 3" | 1" | 5/8" | 1-1/2" | 5-1/2" | 1-1/2" |
| 47.6mm | 25.4mm | 38.1mm | 76.2mm | 25.4mm | 15.9mm | 38.1mm | 140mm | 38.1mm | |
| On3/On30 | 1-1/2" | 3/4" | 1" | 2-1/2" | 3/4" | 1/2" | 1-3/8" | 4-1/4" | 1-3/8" |
| 38.1mm | 19.0mm | 25.4mm | 63.5mm | 19.0mm | 12.7mm | 34.9mm | 108mm | 34.9mm | |
| On2 | 1-7/16" | 2-1/2" | 5/8" | 1-1/8" | 4-1/4" | ||||
| 36.5mm | 63.5mm | 15.9mm | 28.6mm | 108mm | |||||
| S Scale | 1-13/32" | 3/4" | 1-1/8" | 2-1/4" | 3/4" | 15/32" | 1-1/8" | 4-1/8" | 1-1/8" |
| 35.7mm | 19.0mm | 28.6mm | 57.2mm | 19.0mm | 11.9mm | 28.6mm | 105mm | 28.6mm | |
| Sn3 | 1-1/8" | 9/16" | 3/4" | 1-7/8" | 9/16" | 3/8" | 1-1/32" | 3-3/16" | 1-1/32" |
| 28.6mm | 14.3mm | 19.0mm | 47.6mm | 14.3mm | 9.5mm | 26.2mm | 81.0mm | 26.2mm | |
| OO Scale | 1-3/16" | 5/8" | 15/16" | 1-7/8" | 5/8" | 3/8" | 15/16" | 3-7/16" | 15/16" |
| 30.2mm | 15.9mm | 23.8mm | 47.6mm | 15.9mm | 9.5mm | 23.8mm | 87.3mm | 23.8mm | |
| HO Scale | 1-1/32" | 9/16" | 13/16" | 1-5/8" | 9/16" | 11/32" | 13/16" | 3" | 13/16" |
| 26.2mm | 14.3mm | 20.6mm | 41.3mm | 14.3mm | 8.7mm | 20.6mm | 76.2mm | 20.6mm | |
| HOn3 Scale | 27/32" | 13/32" | 9/16" | 1-3/8" | 13/32" | 9/32" | 3/4" | 2-11/32" | 3/4" |
| 21.4mm | 10.3mm | 14.3mm | 34.9mm | 10.3mm | 7.1mm | 19.0mm | 59.5mm | 19.0mm | |
| TT Scale | 3/4" | 13/32" | 19/32" | 1-3/16" | 13/32" | 1/4" | 19/32" | 2-3/16" | 19/32" |
| 19.0mm | 10.3mm | 15.1mm | 30.2mm | 10.3mm | 6.4mm | 15.1mm | 55.6mm | 15.1mm | |
| TTn3 Scale | 5/8" | 5/16" | 7/16" | 7/8" | 5/16" | 3/16" | 9/16" | 1-23/32" | 9/16" |
| 15.9mm | 7.9mm | 11.1mm | 22.2mm | 7.9mm | 4.8mm | 14.3mm | 43.7mm | 14.3mm | |
| N Scale | 19/32" | 5/16" | 7/16" | 29/32" | 5/16" | 3/16" | 15/32" | 1-21/32" | 15/32" |
| 15.1mm | 7.9mm | 11.1mm | 23.0mm | 7.9mm | 4.8mm | 11.9mm | 42.1mm | 11.9mm |
NOTES:
- Narrow Gauge locomotives with extra-wide cylinder spacing such as "K" types, require standard gauge dimensions for A, B, G and P.
- For increased clearances in curved track follow rules of STANDARD S-8.