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RP-3.5 Hi-Rail - Track

RP-3.5

NMRA STANDARDS are the primary System for Interchange. For those modelers undergoing transition between Ready-to-Run and Scale Model Railroading according to NMRA STANDARDS these alternate Systems are provided. Wheels and Track made to these specifications will NOT Interchange with those made to conform to NMRA STANDARDS

.

See RP-3 for diagram illustrating dimensions, and see RP-4.5 for related WHEEL Systems.

Note that these Systems are not developed or controlled by NMRA. For scales where overseas manufacture predominates, applicable NEM/MOROP Standards, modified to agree with observed practice, are shown. For scales where domestic manufacture predominates, dimensions reflecting observed practice in the field are shown. While believed to be reasonably accurate, these dimensions must be followed with reservations, and NMRA cannot be responsible for their accuracy.

Name of Scale Scale to Foot G
Track Gauge
min/max		 C
Check Gauge
min		 S

max		 F
Flangeway
max		 H
Flange Clearance
min		 P
Point Spread
max
O 1/4" 1.250"*(31.75mm) 1.156" 1.090" .094" .094" 1.131"
1.278" (32.45mm) (29.35mm) (27.7mm) (2.4mm) (2.4mm) (28.7mm)
S 3/16" .865"* (22.0mm) .772" (1) .703" .096" (1) .094" .744"
.885" (22.5mm) (19.6mm) (17.85mm) (2.4mm) (2.4mm) (18.9mm)
HO .138" .650"* (16.5mm) .604" .562" .052" .047" .589"
.665" (16.9mm) (15.3mm) (14.25mm) (1.3mm) (1.2mm) (15.0mm)
N .075" .354"* (9.0mm) .320" .290" .041" .035" .305"
.372" (9.45mm) (8.1mm) (7.35mm) (1.05mm) (0.9mm) (7.75mm)
Z .055" .256"* (6.5mm) .230" .206" .029" .024" .220"
.263" (6.7mm) (5.85mm) (5.2mm) (0.75mm) (0.6mm) (5.6mm)

* Denotes Preferred Dimension

NOTES:

1. (In table above) These dimensions are waived for turnouts of closed frog design.

2. Outside third rail for O and S Scales is 1/8" above stock rails and spaced 11/16" out from gage line. Inside third rail should project 1/16" above the top of stock rails.

3. Tin Plate (Hi-Rail) track in 1/4" and 3/16" scales should have curves of radius in multiples of 4" and 3" respectively, should have insulated spacing clamps for these dimensions, and should have longer standard lengths and sub-multiples of 1/8L available. Minimum turnout should be designed for these center-to-center distances.

Erratum:
A typographical error was discovered in the O scale dimension "G". Max should have been 1.278", not 1.178" as was shown. The error was corrected February 08, 1997.