This U arm is attached to the long arm we have just
mentioned. A flat ring of heavy sheet brass is shaped to represent a
short transverse section of a cylinder. This segment is mounted on a
yoke which turns on pivots. In making such a model we can employ all the
proportions and exact forms of the larger drawings made on a ten-inch
radius. Such a model becomes of great service in learning the
importance of properly shaping the lips of the cylinder. And right here
we beg to call attention to the fact that in the ordinary repair shop
the proper shape of cylinder lips is entirely neglected.
PROPER SHAPE OF CYLINDER LIPS.
The workman buys a cylinder and whether the proper amount is cut away
from the half shell, or the lips, the correct form is entirely ignored,
and still careful attention to the form of the cylinder lips adds full
ten per cent. to the efficiency of the motive force as applied to the
cylinder. In making study drawings of the cylinder escapement it is not
necessary to employ paper so large that we can establish upon it the
center of the arc which represents the periphery of our escape wheel, as
we have at our disposal two plans by which this can be obviated.
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