MKTALI,rU<'.Y OK CAST IKON.
made, and if the wheel is found cracked in the plates or through the thread the wheels represented by the test wheel will be rejected. Wheels that are wet or have been exposed to the frost may be wanned sufficiently to dry or remove frost before testing. At the option of the manufacturer, if the test wheel fails under this thermal test, n second wheel showing the next lower contraction size to the wheel which
. \ Dry £///</ >/a^
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FIG. 92.—METHOD OK POCKING FUR HEAT TKST, C. U. & Q. R. H.
failed, and cast on the same date as the rejected wheel, may be selected by the inspector and tested. If the second wheel stands the thermal test, all wheels of the* same, and all lower contraction sixes, may be accepted; while the wheels of the same and higher contraction as the first wheel must be rejectee I."
"The contraction allowed on a cast iron wheel is )4 inch-™ JLf inch above and ^ inch below the mean circumference, divided into four tape sizes of Jil inch, The tape No. i, or highest contraction, represents the." weaker wheels, conditions being normal. The inspector being1 uwarc of this, almost invariably selects tapelictf