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Ballista  - Build a Ballista  - Ballista Design Plans - Roman Ballista Catapult
Roman  stone throwing and arrow throwing torsion ballista
Ballista
THE BALLISTA
FIG.13. - BALLISTA FOR DISCHARGING HEAVY ARROWS OR JAVELINS.
Approximate scale : ½in. = 1 foot.

This engine is here shown ready for discharge with its bow-string drawn to its full extent by the windlass. The heavy iron-tipped arrow rests in the shallow wooden trough or groove which travels along the stock.

The trough has a strip of wood, in the form of a keel, fixed beneath it. This keel travels to or fro in a dove-tailed slot cut along the upper surface of the stock for the greater part of its length. ( F, fig. 14.)

The arrow is laid in the trough before the bow-string is stretched. (A, B, fig. 14.)

The ballista is made ready for use by turning the windlass. The windlass pulls back the sliding trough, and the arrow resting in it, along the stock of the engine, till the bow-string is at its proper tension for discharging the projectile.
( Fig.13.)

As the trough and the arrow are drawn back together, the arrow can be safely laid in position before the engine is prepared for action. The catch for holding the bow-string, and the trigger for releasing it, are fixed to the solid after end of the wooden trough. ( Fig. 14. )

The two ratchets at the sides of the after end of the trough travel over and engage, as they pass along, the metal cogs fixed on either side of the stock. ( Fig.14.)1

By this arrangement the trough can be securely retained, in transit, at any point between the one it started from and the one it attains when drawn back to its full extent by the windlass. As the lock and trigger of the ballista are fixed to the after end of the sliding trough ( fig. 14. ), it will be realized that the arrow could be discharged at any moment required in warfare, whether the bow-string was fully or only partially stretched.

In this respect the ballista differed from the crossbow, which it somewhat resembled, as in a crossbow the bow-string cannot be set free by the trigger at an intermediate point, but only when it is drawn to the lock of the weapon. It will be seen that the ballista derives its power from two arms ; each with its separate skein of cord and pair of winches. These parts of the ballista are the same in their action and mechanism as those of the catapult.

Ballista

FIG. 14.- THE MECHANISM OF THE STOCK OF AN ARROW THROWING BALLISTA.

A. Side view of the stock, with the arrow in the sliding trough before the bow-string is stretched.

B. Surface view of the stock, with the arrow in the sliding trough before the bow-string is stretched.

C. Section of the fore-end of the stock, and of the trough which slides in and along it.

1 When the bow-string has been released and the arrow discharged, the ratchets are lifted clear of the cogs on the stock of the engine. This allows the trough to be slid forward to its first position as shown in A, B, Fig. 14. It is then ready to be drawn back again for the next shot.

D. Surface view of the trough, with the trigger and catch for the bowstring.

E. Side view, showing the keel (F) which slides along the slot cut in the surface of the stock as the trough is drawn back by the windlass.

G. Enlarged view of the solid end of the trough. This sketch shows the catch for the bow-string, the trigger which sets it free, the ratchets which engage the cogs on the sides of the stock, and the slot cut in the stock for the dove-tailed
keel of the trough to travel in.

Ballistas were constructed of different sizes for the various purposes of siege and field warfare. The smallest of these engines was not much larger than a heavy crossbow, though it more than equalled the latter in power and range.

The small ballistas were chiefly used for shooting through loopholes and from battlemented walls at an enemy assaulting with scaling ladders and movable towers.

The largest had arms of 3 ft. to 4 ft. in length, and skeins of twisted sinew of 6 in. to 8 in. in diameter.

Judging from models I have made and carefully experimented with, it is certain that the more powerful ballistas of the ancients could cast arrows, or rather feathered javelins, of from 5 to 6 lbs. weight, to a range of from 450 to 500 yards.

Ballista
Fig.15. - BALlISTA FOR THROWING STONE BALLS. Approximate scale : ½in.=1 foot.
This engine is here shown with its bow-string only slightly drawn along its stock by the windlass.

It will be seen that this engine is almost identical in construction with the one last described. (Fig.13.)

The difference is that it propelled a stone ball instead of a large arrow. The ball was driven along a square wooden trough, one-third of the diameter of the ball being enclosed by the sides of the trough so as to keep the missile in true direction after the bow-string was released.

The bow-string was in the form of a broad band, with an enlargement at its center against which the ball rested.

The description given of the mechanism and management of the engine for throwing arrows can be applied to the construction and manipulation of this form of ballista, which was also made of large and small dimensions.

Small engines with arms about 2 ft. in length and skeins of cord about 4 in. in diameter, such as those I have built for experiment, will send a stone ball, 1 lbs. in weight, from 300 to 350 yards. There is little doubt that the large stone throwing ballista of the Greeks and Romans was able to project a circular stone, of 6 to 8 lbs. weight, to a distance of from 450 to 500 yards.1

Ballista
FIG. 16. - THE SLIDING TROUGH OF THE STONE THROWING BALLISTA.

A. Surface view, with the stone in position.

B. Side view, with stone in position.

C. Front view of the stone as it rests in the trough against the enlarged center of the bow-string.

D. Enlarged view of the solid end of the sliding trough. This sketch shows the ball in position against the bow-string ; the catch bolding the loop of the bowstring, and the pivoted trigger which, when pulled, releases the catch. One of the
pair of ratchets which engage the cogs on the sides of the stock, as the trough is drawn back by the windlass to make ready the engine, is also shown. The trough has a keel to it, and slides to or fro along the stock in the same manner as in the arrow throwing ballista. (Fig.13.)

Compare with figs. 13 and 14, for further explanation of details.

1 The balls used by the ancients in their catapults and ballistas were often formed of heavy pebbles enclosed in baked clay, the reason being that balls made in this way shattered on falling and hence could not be shot back by the engines of the enemy. The ballistas for throwing arrows, and those employed for casting stones, were fitted with axles and wheels when constructed for use in field warfare.

Leonardo da Vinci Stonebow
FIG 17. - A SIEGE BALLISTA IN THE FORM OF AN IMMENSE STONEBOW
From ‘Il Codice Atlantico,’ Leonardo da Vinci, 1445 – 1520

Criticism. – A stonebow of vast size. A and B represent two kinds of lock. In A, the catch of the lock over which the loop of the bow-string was hitched, was released by striking down the knob to be seen below the mallet. In B, the catch was set free by means of a lever. C shows the manner of pulling back the bow-string. By turning the spoked wheels, the screw worm revolved the screwed bar on which the lock A traveled. The lock, as may be seen, worked to or fro in a slot along the stock of the engine. In the illustration the bow is fully bent and the man indicated is about to discharge the engine. After this was done, the lock was wound back along the scrubber and the bow-string was hitched over the catch of the lock preparatory to bending the bow again. Besides being a famous painter, Leonardo was distinguished as an inventor and exact writer on mechanics and hydraulics.

‘No artist before his time ever had such comprehensive talents, such profound skill or so discerning a judgment to explore the depths of every art or science to which he applied himself.’ – JOHN GOULD, Dictionary of painters, 1839.

From the above eulogy we may conclude that the drawings of ancient siege engines by Leonardo da Vinci are fairly correct.

Ballista  - Build a Ballista  - Ballista Design Plans - Roman Ballista Catapult
Roman  stone throwing and arrow throwing torsion ballista


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