The Manchester journal. [volume] (Manchester, Vt.) 1861-current, 1888-04-26
Different types Of Car Wheels.

The different kinds OF car wheels in use
include those made entirely of cast iron,
cast iron bodies with steel tires, the 80.
called paper wheels made Of iron or steel
disks and hubs with steel tires, the inter
ior space between the disks being occupied
by the paper, wheels with spokes welded
to the hub aud tires, aud wheels made
from coil OF ribbon or comparatively
thin strips Of metal and then welded. BY
far the largest number Of car wheels 10
this country are cast iron, while abroad
wheels with tires are almost exclusively
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, comparatively hard
metal is employed, and cas.-iron wheels
without tires are made with chilled faces.
There is a liability in the process Of man.
uiucture that the metal may be left more
or less brittle, and therefore 10 condition
to finally erd In an unexpected failure.
just how and why brittleness is brought
about at these times is not positively
known. Investigators have not been able
to produce at ell times the conditions
which will cause results identical with
those met when the yare not wanted. 1t is
pretty certain, however, that some OF the
causes OF brittleness, which are only iden.
titled after their effects are produced, are
the initial strans 10 the metal, which tend
to warp it in various directions. Initial
strains may exist to such an extent, and
beyond our ability to ascertain without
destroying the metal. that slight addi'
tonal load is sufficient TO cause complete
rupture, and the processes Of manufacture,
particularly with cast-iron, are known to
introduce these initial strains and danger
Gus conditions. To avoid so far as posi-
BILE severe strains from cooling, curved sur.
faces in the webs are employed, which
allow them to spring instead OF fracture,
luesc iuay 10 IS'CuScu W
ing but that softens the metal and re.
moves the effects OF the chill; 10 steel, the
metal would still retain q degree OF hard
ness commensurate with its chemical com.
position. which is point 10 favor OF the
latter metal. When once . crack is start
ed in homogeneous mass it will, when
strained, extend readily, and IL probably
dosen't matter whether the straining IL
from external sources or within the meta
itself. This rather dry discussion is neces.
ssry TO explain in measure, sn intricate
feature Of these metals, which feature no
doubt, has played an important part in
many serious disaster.
The fact that the wheel was a compare.
lively new one which fractured at a recent
accident would give weight to the suppo-
siiion that It's Initial condition may have
contributed largely to its destruction, uD-
less conclusive evidence OF another kind is
shown. In some places initial strains are
not Objectionable, they are even valuable,
but they must be regular 10 their action
aud under control, and not scattered btre
aud there throughout the mass. WhereI
car wheels are slid, by excessive break
pressure stopping their revolutions. ID
tense heat is developed, as shown by th,
display OF sparks, and. As new rail surface
is constantly being presented, the effect OF
this sbrasive action is less on the rails
than on the wheels. On the tread OF the
wheel fat place is worn, which Ia ffe.
quently found TO be excessively hard, and
presents surface marked With foe cracks
Whatever danger might arise from the eI-
tension Of these cracks 10 avoided by the
prompt turning down Of the wheel to 8
smaller diameter. although done for the
purpose Of restoring It's cylindrical form