Here’s some of the skinny on O gauge:
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O gauge refers to the width between the rails, which, I’m guessing, is somewhere around 32 mm (don’t have my ruler/track with me).
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A humongous variety of scales and track is emcompassed in O-gauge.
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Types of track include:
a. 2 rail, such as code 148 (148/1000 of an inch high rails, which I use), code 155, code 125 (which toy flanges won’t work with), code 197 and 205 (Old Pullman makes these for G gauge but they work for O gauge too), code 215 and 250 (these too would work for 2-rail O but would unlikely be used by the "scale concious 2-rail O crowd).
BTW, I’m going to be carving up my 3-rail 027 into 2-rail track, which I’ll be using in a part of my outdoor layout where I’d like to have real rusty spurs using my R/C equippped toy trains.
b. 3-rail track includes a plethora of track types from the realistic looking Atlas and Gargrave (choice of wood or plastic ties), tubular O, tubular 027, RealTrax, ScaleTrax, Fasttrax etc etc etc. Huge choices of rails too, from steel and stainless steel to nickel-silver and “tin”. Curiously, brass appears to be missing from the lineup. 3-rail track usually codes out to 215, such as 027 rails and Atlas, and full O tubular, which I’m guessing is nearly 250.
- Choice of scales is equally daunting.
a. There’s O scale 1:48 which supposedly represents 4’ 81/2" real RR track but I think that 1:45 is actually more representative, and purists scratchbuild to this.
b. There’s semi-scale which is anything smaller than 1:48 up to almost 1:64 S scale (actually some pre-war stuff seems even smaller than that). There are no hard and fast rules on what constitutes semi-scale.
c. Then, there are the large-scale trains that operate on O-gauge track, very common among the garden RR crowd, esp. in UK… These represent narrow gauge or industrial railways. For example there’s 2 foot gauge trains operating on O gauge track