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ANCIENT SIEGE ENGINES

Fig. 195 shows the large front cross-piece (IV, fig. 193, P. 280), between the sides of the catapult, as well as the three supports that hold the uprights and the cross-bar from movement when the latter is violently struck by, the released arm.¹

FIG. 195.-THE FRONT END OF THE CATAPULT. Scale ½ in. = 1 ft.

The winches are here omitted.

Fig. 196, Opposite page, shows the arm-the rope which pulls down the arm-the slip-hook for releasing the arm when it is wound down-the winding roller-the upper edge of the skein of cord-the winches-and the other parts of the engine previously described.

We also see in fig. 196 the padded cushion against which the arm strikes with terrific force when its upper end is checked by the cross-bar. The cushion is of the same depth as the cross bar. It is 16 in. long and about 6 in. thick.

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It is made of soft hide, doubled and packed with horsehair, and should be nailed to the cross-bar.

Without this protection the arm and cross-bar would soon be shattered.²

FIG. 196.-THE AFTER END OF THE CATAPULT. Scale ½ in. = 1 ft.

A spanner for turning the winches is shown in position on one of the pinion wheels.

The arm (of ash, straight grained and without a knot or shake) is 7 ft. long and 4½ in. thick, with rounded edges. It tapers from a width of 8 in. at its butt-end, to a width of 6½ in. at the part above the ring-bolt where it commences to enlarge into the cup that holds the stone.

The tendency of the arm of a catapult is always to draw out of the skein of cord, in which its butt-end is placed.

This is the result of the strain applied to the arm when it is being

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wound down by the roller. To prevent this slipping of the arm its butt-end should be slightly increased in bulk, as shown in fig. 193, p. 280.

The cup or circular hollow at the end of the arm-in which the stone is laid-is 5 in. wide and 2 in. deep at its centre.

The arm should be tightly bound at short intervals with lashings of quarter-inch cord, fig. 196, page 285. Sometimes an arm will endure the great strain applied to it from the first and show no sign of fracture, though it may bend not a little when it is wound down to its full extent.

It is, however, probable that the first arm or two tried in the catapult will way, especially if too much initial pressure is put upon them.

The arm should be tested by degrees and only pulled down its full distance after several trials at shorter ones.

For this reason their engineers constructed the arm of a catapult of three longitudinal pieces.

They first fastened three smooth and closely fitting planks together with glue and with small rivets ; then they shaped the planks, thus held together, into an arm of correct size and outline.

The arm except its enlarged head-end, was next wrapped tightly round its entire length with several layers, one above the other, of strong linen soaked in glue, the linen being cut in strips about 3 in. wide.

Finally strong cord, also soaked in glue, was closely lashed over the linen from the butt-end of the arm to the cup for the stone.

The arm was made on the same principle as a carriage spring, or a longbow of several pieces, and was infinitely stronger and more elastic than one formed of solid wood.

THE WINCHES OF THE CATAPULT, FIG. 197. FOR DIMENSIONS SEE NEXT PAGE

These are the most important parts of the catapult, and generate its projectile force.

However carefully a catapult may be constructed, its effectiveness chiefly depends upon the two winches that twist the skein of cord in which its arm works.

The plans in fig. 197 show a winch and its cross-bar in various positions.

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LARGE WHEEL.-14 in. diameter across its top surface.
Its bore (i.e. the aperture for the skein of cord), 8 in. diameter.
Total length of the wheel, 8 in.
Length of its flange that fits through the iron plate, 3 in.
Thickness of the flange, ¾ in.

PINION WHEEL.-6 in. diameter. Its length, 4 in.

The cross-bars fixed across the apertures of the large wheels, and over which the ends of the skein of cord pass, are each 10 in. in length, 4 in. deep and 1¼ in. wide across their tops.

They decrease to 1 in. in width at their lower edges and are, therefore, slightly sloped at their sides, as shown in IV, fig. 197, page 286. These cross-bars fit like wedges, into the slots cut to receive them inside the large wheels of the winches, fig. 197. They are rounded on their exposed edges so as not to fray the cord they hold and, of course, they equally divide the apertures of the wheels.

Though this was the method of fixing the cross-bars adopted by the ancients, I have had my winches cast with their cross-bars solid with their wheels and not as separate pieces.

The wrought-iron plates through which the flanges of the large wheels of the winches pass and on which the projecting rims of these wheels revolve, are each 1 in. thick. These plates are bolted to the sides of the catapult, fig. 202, page 298.

The round shanks of the spindles of the pinion wheels (secured at their ends by washers and nuts), also pass through these plates as well as through the sides of the framework of the catapult, II, fig. 197.

An almost inconceivable strain can be applied to the skein of cord by four or five men turning the winches of the catapult, a strain so immense that no arm of serviceable dimensions could be made to withstand the force that would have to be applied to wind it down.

Some mediæval writers describe the devices formerly employed for reducing the friction created between the rims of the large wheels of the winches and the iron plates on which they revolve.

In the catapults I have made, I have not however found anything of the kind-such as ball bearings-necessary, other than plenty of grease inserted between frictional surfaces.

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FIG. 198-A SIEGE CATAPULT.

Critism.- A catapult for discharging stones and javelins but in impossible engine in most respects.

In this case there is a grooved piece of wood (in the form of a shallow trough) on the top of the engine. This trough is intended to hold the javelin, the projecting butt-end of which is supposed to be struck by, the released arm of the catapult. I do not believe a catapult was ever employed to project a javlin. It certainly, could not do so in the manner here depicted, for the reason that the arm of the machine could never strike a true blow. Besides this, the arm of a catapult casts a stone with a motion and does not recoil with the quick snap of a spring, such as would be necessary to flip a javelin forward and as is the case with the engine shown in fig. 216, p. 316.

Again, the winches for winding the skein of cordage are put in the weakest part of its framework in this catapult, i.e. between the uprights instead of between the sides where they should be.

From Polybius. Edition of 1727.

THE SKEIN OF CORD

We will now conclude that our catapult is ready for its skein of cord, its winches being in position one on each side of the framework.

In the first catapult I made I fitted a skein of thick rope for the arm to work between, but I found it was impossible to put an even strain upon the rope when twisting it up with the winches.

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The result of this uneven strain was, that the lengths of rope which formed the skein-each 1½ in. thick-broke one by one like rotten thread, owing to the force applied by the winches affecting them in detail instead of collectively.

After a series of experiments with various kinds of cordage, I discovered that the finer the cord used within reason, the more elastic and compact was the skein and hence the less its liability to break.

The fracture of a few strands of a large skein of fine cord is of no consequence, but the breaking of one stout rope amid a skein of a dozen lengths of such rope, means a noticeable loss of power.

The ancients were well aware of this and made the skeins of their catapults of thin cords of twisted hair.⁴

If horse-hair were not available in sufficient quantity, sinews from the necks of horses or oxen were used ; ⁵ I do not find that ordinary rope was ever employed.

The elasticity of hair is so great, that however tight a large skein of it is twisted its extreme stretching or breaking limit cannot well be reached.

For this reason, there is always sufficient life or spring in the most tightly twisted skein of horse-hair to give the requisite velocity to the arm of the catapult.

It is evident that if the skein of a catapult were twisted up to its extreme limit, it would break under the further strain entailed on it by winding down the arm of the engine.

After testing every kind of material for the skein of a catapult I find that horse-hair rope ¼ in. thick-is far the best.

Failing horse-hair, pure flax in the form of sailmaker's sewing twine is a fairly good substitute.

If this twine is used for the skein of a catapult it should be spun into a cord ¼ in. thick.

1. The top cross-bar, against which the arm strikes, should be of ash, 6 ft. 6 in. long, 8 in. square. It should be reduced at its ends to 6 in. square and stepped into and bolted to the tops of the uprights
2. In my largest catapult, the sound made by the arm striking the cross-bar can be heard at a distance of over a mile !
3. I smashed six arms in succession in the first fairly large catapult I made before I could obtain one that lasted. The piece of selected ash used by a cart-builder for cutting a pair of shafts from can usually be made into the arm for a catapult.
4. In cases of emergency, woman's hair was made into skeins for catapults and balistas, and of all material nothing was so elastic or enduring for this purpose. When the inhabitants of Carthage commenced the heroic defence of their city (149-146 B.C.) they were forced to hurriedly manufacture weapons of all kinds to replace those which they had recently surrendered to the Roman general Censorinus (see footnote, p. 261). In various modern works we read of how 'the noble matrons of Carthage cut off their long tresses and twisted them into ropes for catapults.'
   I can find no authority for any such picturesque writing, as ancient authors simply record the fact 'that women's hair was used at Carthage.' For instance, Florus, in his Roman History, a chronicler who flourished early in the second century, writes 'and the women parted with their hair to make cordage for the catapults.' Again, Zonaras, Byzantine historian, Chronica, ix. 26, says 'for the ropes of the catapults they used the hair of the women.'
   At the siege of Salona by Marcus Octavius, one of Pompey's generals, the Roman women cut off their hair that it might be made into ropes for the engines of the besieged. -Cesar's Commentaries on the Civil War, Book iii. Chapter ix.
5. Ligamentum colli, also known as Ligamentum nuchae see note, p. 64.