The Manitowoc pilot. [volume] (Manitowoc, Wis.) 1859-1932, 1888-03-22
Different Types of Car Wheels.

The different types OF wheels in use
include those made entirely of cast
iron, cast-iron bodies with steel tires,
the so-called paper wheels made OF iron
or steel disks and hubs with steel tires,
the interior space between the disks
being occupied by the paper, wheels
with spokes welded to the hub and
tires, and wheels made from coil of
ribbon or comparatively thin strips of
metal and then welded. By far the
largest numbeS of car wheels in this
country are cast iron, willie abroad
wheels with tires are almost exclusive
ly used. To give durability to the
wheels as regards wearing qualities
and avoid rolling down on account of
its softness, when steel tires are used,
a comparatively hard metal is en-
ployed, and cast-iron wheels without
tires are made with chilled faces.
There is liability in the processes of
manufacture that the metal may be
left more or less brittle, and therefore in
a condition to finally end in an unex-
pected failure.
Just how and why brittleness is
brought about at these times is not
positively known. Investigators have
not been able to reproduce at all times
the conditions which will cause results
identical with those met when they are
not wanted. 1t is pretty certain, how
ever, that some of the causes of
brittleness, which are only identified
after their effects are produced, are the
initial strains in the metal, which tend
to warp it in various directions.
Initial strains may exist to such an ex-
tent, and beyond our ability to ascer-
tain without destroying the metal, that
a slight additional load is sufficient to
cause complete rupture, and the pro-
cesses of manufacture, particularly
with cast-iron, are known to intro
duce these initial strains and danger
Gus conditions. To avoid so far as
possible severe strains from cooling,
curved surfaces in the webs are en-
pIoyed, which allow them to spring in
stead of fracture. These strains may
be released by annealing, but that
softens the metal and removes the
effects of the chill; in steel, the metal
would still retain degree of hardness
commensurate with its chemical COM
position, which is a point in favor of
the latter metal. When once a crack
is started in 4 homogeneous mass it
will, when strained, extend readily,
and it probably doesn't matter whether
the strainIng is from external sources
or within the metal itself. This rather
dry discussion is necessary to explain
in a measure, an intricate feature of
these metals, which feature no doubt,
has played an important part in many
a serious disaster.
The fact that the wheel was a COM
paratively new one which fractured at
a recent accident would give weight to
the supposition that its initial condition
may have contributed largely to its de-
struction, unless conclusive evidence of
another kind is shown. In some
places initial strains are not objection
able, they are even valuable, but they
must be regular III their action and
under control, and not scattered here
and there throughout the mass. Where
car wheels are slid, by excessive brake
pressure stopping their revolutions,
intense heat is developed, as shown by
the display of sparks, and, as new rail
surface is constantly being presented,
the effect of this abrasive action is less
on the rails than on the wheels. On
the tread of the wheel fiat place is
worn, which is frequently found to be
excessively hard, and presents a sur
face marked with fine cracks. What
ever danger might arise from the ex-
tension of these cracks is avoided by
the prompt turning down of the wheel
to a smaller diameter, although done
for the purpose of restoring its cylin-
drical form boston Herald.