NOTE 3. - I propose here to enter into some detailed explanation regarding
the military engines that were in use in the Middle Ages.[2] None of these
depended for their motive force on torsion like the chief engines used
in classic times. However numerous the names applied to them, with
reference to minor variations in construction or differences in power,
they may all be reduced to two classes, viz. great slings and great
crossbows. And this is equally true of all the three great branches of
mediaeval civilisation - European, Saracenic, and Chinese. To the first
class belonged the Trebuchet and Mangonel; to the second, the
Winch-Arblast (Arbalete a Tour), Springold etc.
Whatever the ancient Balista may have been, the word in mediaeval Latin
seems always to mean some kind of crossbow. The heavier crossbows were
wound up by various aids, such as winches, ratchets, etc. They discharged
stone shot, leaden bullets, and short, square-shafted arrows called
quarrels, and these with such force we are told as to pierce a six-inch
post (?). But they were worked so slowly in the field that they were no
match for the long-bow, which shot five or six times to their once. The
great machines of this kind were made of wood, of steel, and very
frequently of horn;[3] and the bow was sometimes more than 30 feet in
length. Dufour calculates that such a machine could shoot an arrow of half
a kilogram in weight to a distance of about 860 yards.
The Trebuchet consisted of a long tapering shaft or beam, pivoted at a
short distance from the butt end on a pair of strong pyramidal trestles.
At the other end of the shaft a sling was applied, one cord of which was
firmly attached by a ring, whilst the other hung in a loop over an iron
hook which formed the extremity of the shaft. The power employed to
discharge the sling was either the strength of a number of men, applied to
ropes which were attached to the short end of the shaft or lever, or the
weight of a heavy counterpoise hung from the same, and suddenly released.
Supposing the latter force to be employed, the long end of the shaft was
drawn down by a windlass; the sling was laid forward in a wooden trough
provided for it, and charged with the shot. The counterpoise was, of
course, now aloft, and was so maintained by a detent provided with a
trigger. On pulling this, the counterpoise falls and the shaft flies
upwards drawing the sling. When a certain point is reached the loop end of
the sling releases itself from the hook, and the sling flies abroad whilst
the shot is projected in its parabolic flight.[4] To secure the most
favourable result the shot should have acquired its maximum velocity, and
should escape at an angle of about 45 deg.. The attainment of this required
certain proportions between the different dimensions of the machine and
the weight of the shot, for which, doubtless, traditional rules of thumb
existed among the mediaeval engineers.
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