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The Catapult
II. View of a winch (from above) as fitted into one of the sides of
the frame of the catapult. One end of the twisted skein may be seen
turned round the cross-bar of the large wheel.
III. Side view of the large wheel of a winch.
IV. The cross-bar of one of the large wheels. These pieces fit like
wedges into tapering slots cut down the barrels, or inside surfaces, of
their respective wheels.
V. Perspective view of the wheels of a winch.
The winches are vital parts of a catapult, as they generate its projectile
power.
They are employed to twist tightly the skein of the cord between which
the butt end of the arm of the engine is placed.
The cord composing the skein is stretched to and fro across and through
the sides of the catapult, and alternately through the insides of the large
wheels and over their crossbars; as shown in fig. 3, p. 14.
Fig. 5 - The Iron Slip Hook.
This simple contrivance not only pulled down the arm of a catapult but
was also the means of setting it free. However great the strain on the
slip hook, it will, if properly shaped, easily effect the release of the
arm.
The trajectory of a missile can be regulated by this form of release,
as the longer the distance the arm is pulled down the higher the angle
at which the projectile is throw. On the other hand, the shorter the distance
the arm is drawn back, the lower the trajectory of its missile.
The slip hook will release the arm of the engine at any moment, whether
it is fully or only partially wound down by the windlass.
The slip hook of the large catapult shown fig. 1, p. 10, has a handle,
i.e. lever, 10 inches long, the point of the hook, which passes through
the eye bolt secured to the arm, being 1. in. in diameter.
Fig. 6. The Skein of Cord, See Opposite Page
A. The skein as first wound over the cross bars of the large wheels
(shown in section) of the winches.
B. The skein of the butt end of the arm (shown in section) placed between
its halves. |
