The Saint Paul globe. (St. Paul, Minn.) 1896-1905, 1899-08-25
DEPENDS ON THE KIND.
Some Makes of Engine Wheels Slim
and Some Do Not.
To the Editor of the Globe:

To the Editor of the Globe:
II Is claimed that the wheels of an en-
to accommodate themselves to the cIrva-
luTe or the track 1 claim that this is
not so. Which is right? James Breen.
Inc foregoing query was submitted to
j. y Pattee, superintendent of motive
power OF the Great Northern railway
last night, and the following interesting
explanation received:
Owing to the construction of the ouerv
neither is wrong. The kind of wheel
used on the engine in question Is not
stated. There are two patterns of loco,
motive wheels in general use, in describ,
Ing which it is necessary to understand
that the wheel Of an engine Is made In
TWO parts, steel casting which COM
pr1ses the center, spokes and inside rim
ana Forged steel rim which is shrunk
on the casting and forms the part which
meets the track. These rims are made
In two different patterns. In one the
outside edge is turned on a lathe, giving
a surface which meets the rail on which
1t runs with a face which lies parallel
to line drawn through the axle. In
the other pattern the rim is turned down
to a tapering construction, the ffange
side Of the surface being larger than the
outer edge.
Locomotive wheels are always fixed
solid on the axle, and in those of the
trst pattern there is no question but
there Is lost motion in turning a curve
as both are the same size and the wheel
to the inside of the curve has less dis
lance to pass over. The outside rail
of the curve would Of necessity be the
longer, as it has a greater distance to
traverse than that which lies on the
inside.
But with locomotive drive wheels Of the
latter design, where the rims are turned
to tapering pattern, the conditions are
different. Letting A and B represent
wheels fixed on the same axle, the rim
on A tapers in the opposite direction
from that on B. Suppose an engine pass.
ing around curve, the wheel A being
on the outer side. The surface Of the
rim is somewhat less than six inches
wide For this reason the diameter of
either wheel is greater on a line drawn
at right angles with the axle, passing
through points near the fange, which,
it should be borne in mind, is on the in
side of the track, than on similar line
drawn through points on the outer edge
of the rim. When an engine passes
around curve. the wheel A on the out
side is always thrown in such a position
that the rail bears on points of the rim
nearest the edge. Therefore consider
ing that the diameter near the edge of
the rim is smaller, wheel A bears on the
track with it's diameter for the time be-
ing greater than that of the wheel B.
which is running on the edge of the
tapering rim. For this reason the inside
wheel accommodates itself to the track
and does not slip. Track on a curve is
always laid wider than on a straight
line in order to give wheels with a taper
ing rim a chance to meet the conditions
imposed by the curvature.
Wheels for locomotives, passenger and
freight cars are made in both patterns,
but the output of cast car wheels Of every
description is made with the tapering
rims. Locomotive wheels are made in
both patterns.