Table of Contents
Standards Introduction
1. Summary
Within O Gauge there are three basic standards for wheelsets and track; Finescale, ScaleSeven and Coarse scale. These are all to 1:43.5 scale and share the same dimensions for structural clearances (Figure 1) and track spacing (Figure 2) as shown below.
Figure 1
Figure 2
Here the main line spacing should be at least 48mm, giving a track centre to centre of 80mm, but must be wider on curved sections where clashes due to overhanging coaches and locos must be prevented.
2. Determining standard dimensions
On plain track, the wheelsets are guided by the flanges fitting between the rails and the Wheelset Gauge needs to be sufficiently well matched to the Track Gauge to ensure that the wheelsets do not either bind or slop about between the rails.
However, wherever tracks diverge or cross, it is necessary to create gaps in the rails to let the flanges of the wheels on one route pass through the rails of the other route. This leaves the wheels momentarily unguided, with the risk that they may become derailed.
In this situation the relationship between the Wheelset Check Gauge and the Track Check Gauge (shown in red in Figure 3) is crucial.
Figure 3
If the Wheelset Check Gauge is too big relative to the Track Gauge the check rail will not guide the other wheel through the gap in the rail and it will tend to foul the crossing nose.
If the Wheelset Check Gauge is too small relative to the Track Gauge the wheels will bind on the check rails and poor running will result.
FineScale
FineScale is the most commonly used standard with strong trade support, most layouts and test tracks are built to this standard. The wheels and track do not represent an exact scaling of the prototype but are a compromise between accuracy and practicality.
FineScale Standard
There are two additional variants of FineScale, O-MF and O-SF, these are described in the Further Details Section.
ScaleSeven
ScaleSeven uses wheelset and track dimensions scaled directly from the prototype. As a consequence rolling stock built to this stand will only run on track built to the same standard.
For further information on modelling to this standard refer to the Scale7 Group
Coarse scale
Coarse scale dates back to the days when track was laid in sections on the floor and wheels had to have deep flanges just to stay on the track. It is also the area of O scale modelling that is the least standardised.
