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Ancient Siege Engines
(II) The catch (D, B), being then free to swing, the end (F) of the
arm of the catapult is instantly released from the projection B, as seen
in II, fig. 201.
This figure may also be taken to represent the arm being wound down
by the rope and roller.
When the arm is a little lower than shown in II (taking it as coming
slowly down and not as flying up), then by lifting the handle (D) of the
catch its projection (B) drops over the end (F) of the arm. The leg of
the catch at the same time snaps into the notch of the lever A, at E.
In this way the catch is re-set and the arm again secured, as in I fig.
201.
(III) Surface view of the catch holding clown the arm.
(IV) Perspective view of the catch.
The iron framework of the catch was bolted to a cross-piece of wood
which connected the after-ends of the sides of the catapult.
The roller that wound down the arm was fitted on the front side of this
cross-piece, as shown in fig. 198, p. 289.
The rope attached to the roller was hitched by a hook to a ring lashed
to the arm, fig. 198, p. 289. When the arm was safely secured by the catch,
the rope that pulled it down was unhooked and the catapult was ready for
action.
In some catapults, one end of the rope which pulled down the arm was
spliced to a cross-bar of metal fixed in the framework of the engine; its
other end being fastened to the winding roller, fig. 198, p. 289.
This arrangement halved the exertion required to pull down the arm and
also halved the strain upon the roller, but it doubled the time occupied
in winding back the arm.
By using longer levers for turning the roller, the same effect is produced
as in the above method and without the loss of time it entailed.
Range of the Catapult
W hen its skein of cord is tightly twisted, the catapult I have described
will pitch a round stone weighing 10 lbs. to a distance of about 350 yards.1
Though this is a trivial range when compared with the result obtainable
1 This catapult might easily be fitted with
a pair of winches each larger by half than I have given in the plans. This
would entail a stronger and slightly longer arm, and also heavier sides
to the framework of the engine. With these alterations, the catapult would
cast a stone weighing 20 lbs.
The stones thrown by catapults do not increase in weight
in proportion to the increase in diameter of the skeins of the engines.
For example, a catapult with a skein 1 ft. thick will throw a stone three
times as heavy as will a catapult with a skein half the size, or 6 in.
A skein of 1 ft. in thickness would, however, be double the length of the
skein, which was only 6 in. in diameter, as in the former case the framework
of the catapult would be much wider than in the latter one. |
