O scale: Encyclopedia II - O scale - Standards

O scale - Standards

The differences in the various O gauge and O scale standards often confuse newcomers.

O scale - O gauge and O scale

O scale tends to imply an accurate scale model at 1:43, 1:45, or 1:48 scale. It may run on traditional three-rail track, but more likely, it runs on more realistic-looking two-rail track using direct current. However, the height and spacing of the rails is not true to scale. Often, hobbyists will use the phrases "two-rail" or "three-rail" to clarify which they mean.

To some O gauge usually implies a toy train running on three-rail track, scaled at approximately 1:48. To many it is a gauge which allows larger precision models to be made to. Using the odd scale of 7mm = 12 inches a scale of 1/43.5 is established. Especially in the UK many models are made to this scale for running on layouts, small and large, indoors and out.

When used as a narrow gauge track 0 gauge allows scales of 1/32 representing 40" or meter gauge track. 1/20 representing 24"/600mm narrow gauge railways.

However, the two phrases are often also used interchangeably, particularly on eBay.

O scale - O27 gauge

O27 gauge is a variant whose origins are slightly unclear. Some historians attribute its creation to A. C. Gilbert Company's American Flyer, but Ives used O27 track in its entry-level sets at least a decade before Gilbert bought Flyer.

The modern standard for O27, however, was formalized after 1938 by Gilbert, who scaled the locomotives and rolling stock at 3/16 inches to the foot, or 1:64. After World War II, this practice was continued by Louis Marx and Company, who used it throughout its product line, and Lionel, who used it for its entry-level trains. O27 track is spaced at the same width as regular O gauge track, but is slightly shorter in height and has thinner rails than traditional O gauge track. For these reasons, regular O and O27 track cannot be used together without difficulty.

The name comes from the size of the track's curves. A circle made of eight pieces of standard curved O gauge track will have a 31 inch (787 mm) radius. A circle made of 8 pieces of curved O27 track is smaller, with a 27 inch (686 mm) radius. Full-sized O cars sometimes have difficulty negotiating the tighter curves of an O27 layout. Although the smaller, tin lithographed cars by American Flyer, Marx, and others predate the formal O27 standard, they are also often called O27 because they also operate flawlessly on O27 track.

The O27 standard is still used today by Lionel, K-Line, and others for its least expensive O gauge trains. It is most popular with children and with people who have limited space, as it is the least realistic of the O scale standards.

O scale - Exact scale standards

Dissatisfaction with these standards led to a more accurate standard for wheels and track, called Proto:48. This duplicates to exact scale the AAR track and wheel standards.

The track gauge normally used for O is correct for British O but not American. The difference between the two also explains why HO is 1:87 - it is 3.5 mm to the foot, half of British O, but is not used in Britain.

Possibly because of the large size of American railroad systems, accurate scale modeling in standard gauge O scale is rare in the United States, though narrow gauge modeling is much more common.

Four common narrow gauge standards exist, and the difference between On3, On2, On30, and On18 is a frequent source of confusion. On3 is exact-scale 1:48 modeling of 3 foot (914 mm) gauge prototypes, while On30 is 1:48 modeling of 30 inch (762 mm) gauge prototypes, On2 is 1:48 modeling of 2 foot (610 mm) gauge prototypes, and On18 is 1:48 modeling of 18 inch (457 mm) gauge prototypes. On30 is also sometimes called On2½.

Because On30's gauge closely matches that of HO scale, On30 equipment typically runs on standard HO scale track. On30 is considered by many to be the fastest growing segment of the model railroad hobby in general, and while many On30 modelers scratchbuild their equipment, commercial offerings in On30 are fairly common and sometimes very inexpensive, with Bachmann Industries being the most commonly found manufacturer. Bachmann's On30 trains are sometimes sold side by side with the company's HO offerings.

Hobbyists who choose to model in any of these O scale standards nevertheless end up building most, if not all, of their equipment either from kits or from scratch.

Adapted from the Wikipedia article "Standards", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki