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This spindle passes through the center of the roller and through the
The small cogged wheels, with their checks, which are fitted to the
the spindle GG, prevent the roller from reversing as the arm is being
HH. The hollows in the sides of the frame which receive the lower
of the two uprights. Between the
tops of these uprights the cross-beam is
fixed against which the arm of the catapult strikes when it is released.
KK. The hollows for the lower tenons of the two sloping supports
prevent the uprights, and the cross-beam between them, from giving
way when the
arm recoils. (Fig. 6.)
FIG. 9.—ONE OF THE PAIR OF WINCHES OF A CATAPULT.
Scale : 1/16 in. = 1 in
I. Surface view of one of the winches and of the thick iron plate
the socket of the large winding wheel of the winch revolves.
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
V. Perspective view of the wheels of a winch. The winches
are the vital parts of the catapult
as they generate its projectile power.
They are employed to twist tightly
the skein of 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
sides of the catapult, and alternately
through the insides of the large wheels
and over their cross-bars ; as show in fig. 8.
FIG. 10. 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 the 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 thrown.
On the other hand, the shorter the distance the arm is drawn back, the
the trajectory of its missile.
The slip-hook will release the arm of the engine at any moment, whether
is fully or only partially wound down by the windlass.
The slip-hook of the large catapult shown in fig. 6. , has a handle,
lever, 10 inches long, the point of
the hook, which passes through the
eye-bolt secured to the arm, being one inch in diameter.
FIG. II. – A SPRING ENGINE WITH A SLING ATTACHED TO ITS ARM, WHICH
TWO STONES AT THE SAME TIME.
From ‘ II Codice Atlantico, ‘ Leonardo
da Vinci. 1445-1520.
Fig. 12.-- THE SKEIN OF CORD
A. The skein as first wound over
the cross-bars of the large wheels
(shown in section) of the winches.
B. The skein with the butt-end of
the arm (shown in section) placed
between its halves.
C. The skein as it appears when
tightly twisted up by the winches.
Compare with AA, fig. 8.
Cord of Italian hemp, about . in. thick, is excellent for small catapults.
large ones, horsehair rope, . in. thick,
is the best and most elastic. Whatever
is used, the material of the skein
must be thoroughly soaked in neats-foot
oil for some days previously, or it is sure to fray and cut under
the friction of being very
tightly twisted. Oil will also preserve
the skein from damp and decay for
HOW TO WORK THE CATAPULT
There is little to write under this
heading ; as the plans, details of
construction and illustrations will, I trust, elucidate its management.
The skein should never remain in a tightly twisted condition, but should
untwisted when the engine is not in use.
Previous to using the catapult its
winches should be turned with the long
spanner, fig. 6, first the winch on one side of the engine and then
the one on
the other side of it, and each to exactly the same amount.
Small numerals painted on the surfaces
of the large wheels near their
edges, will show how much they have been revolved ; in this way their
can be easily arranged to correspond.
As the skein of cord is being twisted by the very powerful winches,
will gradually press with increasing
force against the cross-beam between the
uprights. The arm should be so tightly pressed against the fender,
or cushion of
straw, attached to the centre of this beam, that, whether large or
small, it cannot be
pulled back the least distance by hand.
If the skein of my largest catapult
is fully tightened up by the winches,
three strong men are unable to draw the arm back with a rope even an
the cross-beam, though the windlass has
to pull it down from six to seven
feet when the engine is made ready for action.
When the skein is as tight as it should be, attach the slip-hook to
bolt in the arm and place the stone in the sling suspended from the
top of the arm.
The arm can now be drawn down by means of long spanners fitted to the
windlass. Directly the arm is as low as it should be, or as is
desired, it should be
instantly released by pulling the cord fastened to the lever of the
The least delay in doing this, and the resulting continuation of the
strain on the arm, may cause it to fracture when it would not otherwise
The plans I have given are those of my largest engine, which, ponderous
it seems—(it weighs two tons)—is, however, less than half the size
of the catapult
used by the ancients for throwing stones of from forty to fifty pounds
As the plans are accurately drawn
to scale, the engine can easily be
reproduced in a smaller size.
An interesting model can be constructed
that has an arm 3 feet in length,
and a skein of cord about 4 inches in diameter. It can be worked
by one man and
will throw a stone, the size of an orange, to a range of 300 yards.
The sling, when suspended with the stone in position, should be one
the length of the arm, as shown in fig. 7
If the sling is shortened, the ball will be thrown at a high elevation.
sling is lengthened, the ball will
travel at a lower angle and with
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