PART II
_THE CATAPULT (WITH A SLING)_
[Illustration: FIG. 5.--A SIEGE CATAPULT (WITHOUT A SLING).
_Criticism._--This engine was moved into position on rollers and then props were placed under its sides to adjust the range of the projectile.
The end of the arm was secured by the notch of the large iron catch and was released by striking down the handle of the catch with a heavy mallet.
The arm is, however, too long for the height of the cross-bar against which it strikes and would probably break off at its centre.
The hollow for the stone is much too large, as a stone big enough to fit it could not be cast by a weapon of the dimensions shown in the picture.
_From an Illustrated Manuscript, Fifteenth Century (No. 7239), Bibl. Nat. Paris._]
The mediæval catapult was usually fitted with an arm that had a hollow or cup at its upper end in which was placed the stone it projected, as shown above in fig. 5.[4] I find, however, that the original and more perfect form of this engine, as employed by the Greeks and ancient Romans, had a sling, made of rope and leather, attached to its arm.[5] (Fig. 6, following page.)
[4] See also _The Crossbow_, _etc._, Chapters LV., LVI., illustrations 193 to 202.
[5] In mediæval times catapults which had not slings cast great stones, but only to a short distance in comparison with the earlier weapons of the same kind that were equipped with slings. I can find no allusions or pictures to show that during this period any engine was used with a sling except the trebuchet, a post-Roman invention. All evidence goes to prove that the secret of making the skein and other important parts of a catapult was in a great measure lost within a couple of centuries after the Romans copied the weapon from their conquered enemies the Greeks, with the result that the trebuchet was introduced for throwing stones.
The catapult was gradually superseded as the art of its construction was neglected, and its efficiency in sieges was therefrom decreased.
The catapults of the fifth and sixth centuries were very inferior to those described by Josephus as being used at the sieges of Jerusalem and Jotapata (A.D. 70, A.D. 67), p. 37.
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[Illustration: FIG. 6.--SKETCH PLAN OF A CATAPULT FOR SLINGING STONES ITS ARM BEING PARTLY WOUND DOWN.
Approximate scale: ¼ in. = 1 ft.]
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The addition of a sling to the arm of a catapult increases its power by at least a third. For example, the catapult described in Chapters LV., LVI., of my book,[6] will throw a round stone 8 lbs. in weight, from 350 to 360 yards, but the same engine with the advantage of a sling to its arm will cast the 8-lb. stone from 450 to 460 yards, and when its skein is twisted to its limit of tension to nearly 500 yards.
[6] _The Crossbow_, _etc._
If the upper end of the arm of a catapult is shaped into a cup to receive the stone, as shown in fig. 5, p. 11, the arm is, of necessity, large and heavy at this part.
If, on the other hand, the arm is equipped with a sling, as shown in fig. 6, opposite page, it can be tapered from its butt-end upwards, and is then much lighter and recoils with far more speed than an arm that has an enlarged extremity for holding its missile.
When the arm is fitted with a sling, it is practically lengthened by as much as the length of the sling attached to it, and this, too, without any appreciable increase in its weight.
The longer the arm of a catapult, the longer is its sweep through the air, and thus the farther will it cast its projectile, provided it is not of undue weight.
The difference in this respect is as between the range of a short sling and that of a long one, when both are used by a school-boy for slinging pebbles.
The increase of power conferred by the addition of a sling to the arm of a catapult is surprising.
A small model I constructed for throwing a stone ball, one pound in weight, will attain a distance of 200 yards when used with an arm that has a cup for holding the ball, though when a sling is fitted to the arm the range of the engine is at once increased to 300 yards.
The only historian who distinctly tells us that the catapult of the Greeks and Romans had a sling to its arm, is Ammianus Marcellinus. This author flourished about 380 A.D., and a closer study of his writings, and of those of his contemporaries, led me to carry out experiments with catapults and balistas which I had not contemplated when my work dealing with the projectile engines of the Ancients was published.
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[Illustration: FIG. 7.--CATAPULT (WITH A SLING). Side view of frame and mechanism.
Scale: ½ in. = 1 ft.]
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Ammianus writes of the catapult[7]:
‘In the middle of the ropes[8] rises a wooden arm like a chariot pole ... to the top of the arm hangs a sling ... when battle is commenced a round stone is set in the sling ... four soldiers on each side of the engine wind the arm down till it is almost level with the ground ... when the arm is set free it springs up and hurls forth from its sling the stone, which is certain to crush whatever it strikes. This engine was formerly called the “scorpion,” because it has its sting erect,[9] but later ages have given it the name of Onager, or wild ass, for when wild asses are chased they kick the stones behind them.’
[7] _Roman History_, Book XXIII., Chapter IV.
[8] _i.e._ in the middle of the twisted skein formed of ropes of sinew or hair.
[9] The upright and tapering arm of a catapult, with the iron pin on its top for the loop of the sling, is here fancifully likened to the erected tail of an angry scorpion with its sting protruding.
FIG. 7.--CATAPULT (WITH A SLING), SEE OPPOSITE PAGE.
A. The arm at rest, ready to be wound down by the rope attached to it and also to the wooden roller of the windlass. The stone may be seen in the sling.
The upper end of the pulley rope is hitched by a metal slip-hook (fig. 6, p. 12) to a ring-bolt secured to the arm just below the sling.
B. The position of the arm when fully wound down by means of the windlass and rope. See also EE, fig. 8, page 16.
C. The position of the arm at the moment the stone D leaves the sling, which it does at an angle of about 45 degrees.
E. By pulling the cord E the arm B is at once released from the slip-hook and, taking an upward sweep of 90 degrees, returns to its original position at A.
[Illustration: THE SLING (OPEN).]
[F. Its fixed end which passes through a hole near the top of the arm.
G. The leather pocket for the stone.
H. The loop which is hitched over the iron pin at the top of the arm when the stone is in position in the sling, as shown at A and B, fig. 7.]
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[Illustration: FIG. 8.--CATAPULT (WITH A SLING). Surface view of frame and mechanism. Scale: ½ in. = 1 foot. The arm EE is here shown wound down to its full extent. (Compare with B, fig. 7, page 14.)]
I. I. } The side-pieces. II. II. } III. IV. The large cross-pieces. V. The small cross-piece.
The ends of the cross-piece beams are stepped into the side-pieces.
AA. The skein of twisted cord.
BB. The large winding wheels. The skein is stretched between these wheels, its ends passing through the sides of the frame, and then through the wheels and over their cross-bars. (Fig. 12, p. 19.)
By turning with a long spanner (fig. 6, p. 12) the squared ends of the spindles DD, the pinion wheels CC rotate the large wheels BB and cause the latter to twist the skein AA, between the halves of which the arm EE is placed.
FF. The wooden roller which winds down the arm EE. (Fig. 6, p. 12.)
The roller is revolved by four men (two on each side of the engine) who fit long spanners on the squared ends of the iron spindle GG.
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This spindle passes through the centre of the roller and through the sides of the frame.
The small cogged wheels, with their checks, which are fitted to the ends of the spindle GG, prevent the roller from reversing as the arm is being wound down. (Fig. 6, p. 12.)
HH. The hollows in the sides of the frame which receive the lower tenons 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. (Fig. 6, p. 12.)
KK. The hollows for the lower tenons of the two sloping supports which prevent the uprights, and the cross-beam between them, from giving way when the arm recoils. (Fig. 6, p. 12.)
[Illustration: 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 in which 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 respective wheels.
V. Perspective view of the wheels of a winch.
The winches are the vital parts of the catapult as they generate its projectile power.
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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 the sides of the catapult, and alternately through the insides of the large wheels and over their cross-bars; as shown in fig. 8, p. 16.
FIG. 10. THE IRON SLIP-HOOK.
[Illustration: FIG. 10.]
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 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 in fig. 6, p. 12, 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 one inch in diameter.
[Illustration: FIG. 11.--A SPRING ENGINE WITH A SLING ATTACHED TO ITS ARM, WHICH CAST TWO STONES AT THE SAME TIME.
_From ‘Il Codice Atlantico,’ Leonardo da Vinci._ 1445–1520.]
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[Illustration: 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, p. 16.
Cord of Italian hemp, about ¼ in. thick, is excellent for small catapults. For large ones, horsehair rope, ½ 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 many years.
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 be untwisted when the engine is not in use.
Previous to using the catapult its winches should be turned with the long spanner, fig. 6, p. 12, 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.
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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 rotation can be easily arranged to correspond.
As the skein of cord is being twisted by the very powerful winches, the arm 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 inch from 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 the ring-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 slip-hook.
The least delay in doing this, and the resulting continuation of the immense strain on the arm, may cause it to fracture when it would not otherwise have done so.
The plans I have given are those of my largest engine, which, ponderous as 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 in weight.
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 third the length of the arm, as shown in fig. 7, p. 14.
If the sling is shortened, the ball will be thrown at a high elevation. If the sling is lengthened, the ball will travel at a lower angle and with much more velocity.
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