What’s the difference between O gauge and O-27 gauge?
Before we explore different styles of track, a quick explanation of the difference between “O gauge” and “O-27 gauge”:
- First of all, O-27 gauge track is the same gauge – or rail width – as O gauge track. All O gauge equipment will fit on O-27 track.*
- Second, as you will see by the end of the next paragraph, “gauge” has nothing to do with “scale.”
Originally, O gauge track came in a minimum curve diameter of 31”, and O gauge trains were built (approximately) to a scale of 1/48 – that is, one inch of an O scale model was equal to 48 inches of the prototype of that model. Then along came the S gauge trains of American Flyer. Built to a smaller 1/64 scale that could negotiate tighter curves than O gauge trains, an S gauge layout took up less room than an O gauge layout, and marketers made much of this advantage.
In response, O gauge train manufacturers introduced O-27 gauge, which had the same rail width (gauge) as O gauge, but a minimum curve width of 27”. To make their O-27 trains able to negotiate these tight curves, they downsized the scale of the models (to about the same 1/64 used for S gauge models) to reduce their length.
The O-27 designation quickly became attached to Lionel’s “entry level” train sets, giving a status boost to their “standard” O gauge equipment.
Confused yet? Don’t worry too much, the difference between O gauge and O-27 is only important when it comes to old-school tubular track (we discuss track styles on our Choosing Track for an O Gauge Model Railroad Layout page), or if you have scale-length locomotives and train cars and try to use 27” curves. Nowadays, most manufacturers use the terms differentiate between scale of their models – referring to true 1/48 scale models as “O Gauge” and their smaller semi-scale models as “traditional” or “O-27 gauge.”
If you do opt for old-school Lionel tubular track, just remember, O-27 tubular track has a lower profile (rail height) than O gauge tubular track, and has brown metal “ties” while standard O gauge track is made with black “ties.” Old-timers will tell you that O gauge trains have deeper wheel flanges that don’t work on O-27 track, but I’ve never had a problem, and since all the newer track styles have rails the same or lower profile than O-27 tubular track, I doubt it’s an issue with any modern O gauge equipment.
*While “standard” O gauge trains will fit on O-27 track, because of their greater length, some may not be able to negotiate the tighter 27” curves.
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