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The Catapult
I concluded that the mediaeval drawings which depicted the arm of the
engine in a perpendicular position, as in A, fig. 194, were incorrect.
My surmise was that a catapult with a perpendicular arm would merely
bowl its stone along the ground, on the principle that the stone was retained
in the cup of the arm till the latter was checked by the cross-bar.
Carrying out this idea, I placed the winches of the first catapult I
made in front of the uprights and not behind them as in the weapon here
described.
By this arrangement the arm when released had of course an upward inclination
when checked by its cross-bar. Such a position for example as half-way
between C and A, fig. 194.
The result of this intended improvement on the ancients was,
With a Sloped Arm
1. The cross-bar which checked the arm of the catapult was soon knocked
loose through being struck in an upward direction.
2. The range of the projectile was unsatisfactory through the arm being
wound down only a short distance from its state of rest.
3. The projectile - as in the case of a perpendicular arm - left its
cup a considerable time before the arm encountered the cross-bar.
On the other hand I found that:
With a Perpendicular Arm (A, Fig. 194)
1. The cross-bar was struck a level blow, or one that was taken by the
three supports which lean against its centre and ends.
2. The range of the projectile was much increased owing to the additional
distance the arm was wound down, and which caused the skein of cord to
be far more tightly twisted than it was when the arm rested against the
cross-bar in a sloping position before it was pulled back.
3. The projectile left the cup of the arm as shown at C, fig. 194; and
as it did with a sloped arm. |
