of standard gage, the gages used in various parts of the world, and the necessity for varying the
standard gage.
a. "Sides" of a rail. Gage is measured from the "gage side" of a rail. The opposite
side is called the "field side." Before a rail is placed in track, it has no gage or field side. Once it
is laid, the side facing the centerline of the track becomes the gage side; the side facing away
from the centerline becomes the field side, as illustrated in figure 1.6.
b. Development of standard gage. Some rail lines within our borders have a
different gage; for instance, the 36-inch gage Rlio Grande Line in the Rocky Mountains. Such
lines are rare now, but at the end of the nineteenth century they were common. Until 1886, the
railroads in the South were predominantly 60 inches in gage, but such important lines as the Erie
and the Missouri Pacific were originally laid with gages of 72 and 66 inches, respectively.
The preciseness of 56 1/2 inches implies that there is a technical justification. In
studying railroading, you find cases where odd dimensions have such a justification. But so far
no one has been able to provide a reason for the modern standard gage. We know that the 56
1/2-inch gage was used in England before most U. S. railroads were built, and that the Baltimore
and Ohio and many railroads in Pennsylvania adopted it at the outset, apparently following the
British tradition. The question is, Where did the British get the 56 1/2-inch gage? One plausible
answer is that it corresponded to the ruts the Roman chariots cut in their roads. But probably
we should say that the 56 1/2-inch gage just happened and that in the United States it was the
one to survive the adoption of a common gage.
c. Other gages. Elsewhere in the world, other gages have survived. In Russia, the
60-inch gage is standard. In Ireland, trains run over 63-inch gage tracks, and in Spain and
Portugal, a 66-inch gage is in use. The rest of Europe generally use the 56 1/2-inch gage. In
some countries, the gage has not been standardized: India and South American countries have
considerable mileage with various gages.
d. Necessary gage variations. You know that standard gage in the United States and
certain other countries is 56 1/2 inches. Now you are going to learn that this gage doesn't always
measure 56 1/2 inches between rails. To prevent binding, it has been found necessary to
broaden the gage around sharp curves, as shown in figure 1.7. In some cases, the gage becomes
57 inches or greater. Of course, odd gages--those other than 56 1/2 inches--also increase on
sharp curves for the same reason. The gage is always widened on the inside, or low, rail.
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