Reconstruction of one carroballista from motives of the Trajan's- and Marc Aurel Column (Rome)  


Methodology

Based on means of analysis of the illustrations (menu option Analysis) on the Trajans- and Marc Aurel Column one won realizations, one can make a reconstruction of this type of bolt- firer. The reconstruction should be broadly in line with the past - through finds and written traditions - one gained knowledge about ancient arrow- firing catapults.

The reconstruction has only a proposal character. Example, the winch system for stretching the catapult isn't sawn in the illustrations. Therefore the system used with the reconstruction can deviate from the original execution. How constructional details in the reality looked, lets itself clarify only by finds, which can be assigned these catapults. Since construction units of ancient torsion cannons are found again and again, they are not to be excluded for the future. Also is it quite possible that in museum magazines relics such like catapults lie and those have not been even identified yet.

The reconstruction begins with individual components units then to the entire catapult.

Torsion stands

The torsion stands have the task to store the two washers and hold them in distance. In each case two locking collars with two vertically standing props are riveted. The front props have formations in which the catapult arms rest later in the front position. At each prop two eyes riveted in which the curved and lower bar strut of the clamping frame is to be mounted.

In the locking collars the counter drillings for the washers are placed, in which these are locked by means of locking pins.

The stands have a height of approx. 300 mm. The locking collars are held outside in the diameter of 145 mm and inside the clamping chucks are suitably, prepared.

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Illustration 1  
Left and right torsion stand. Reconstruction after findings from the  
French Lyon and Gornea (Romania)

The strives

The two torsion systems are positioned by two struts on distance. The lower frame bridge takes up later the stock with the slider and the tripod with the hinge for elevator adjustment. The strives are equipped from wrought steels and to the weight savings with reciprocally in-forged fillets. The forks of the strives have at their ends in-forged recesses in their width the riveted retaining eyes fit. For the assembly the forks by the eyes pushed to this into the forks to engage. The connection is then fixed by hit retaining wedges. These can be poured from bronze (as drawn), from wrought steels or wood. The immense advantage of this construction is those, if necessary the fast disassembly of the torsion stands.

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Illustration 2
Frame bridge with holding hooks. In the foreground as exploded view..


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Illustration 3
Upper, arched-strut and the frame bridge. 



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Illustration 4 and 5
Mountig of the strives. The hooking connections are fixed by bronze wedges.


Clamping frame

Illustration 6 shows the clamping frame without washers, chord bundles, catapult arms and protection sockets. The uncovered
torsion stands clarify the constructional structure.


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Illustration 6
Installed clamping frame. Those wahsers, chord bundles,
catapult arms and protection sockets are missing.


Washers
 

The washers are poured out of bronze. The inside diameter amounts to approx. 80 mm with an outside diameter of 145 mm. The height amounts to approx. 90 mm. An edge cast-on at the lower surface serves for the adjustment in the locking of collars of the torsion stands. A cast in transverse groove serves for the admission of the locking- bolt. Four trained drillings have the task to fix the washer by means of locking- pin in the drillings of the locking collars. The reconstruction is based on findings from the Italian Cremona, dated n on 69. A. C..

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Illustration 7
Washer Left: bird view.   Right: below view   
Reconstruction after a safe-keeping found. 


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Illustration 8
Washer with mounted locking bolt and holding pin.
   

Washer bar

Catapult construction units which are least likely to attract attention might be the washer bars. At first sight a simple construction unit. A right rectangular piece parallelepiped formed forging to entwine that torsion rope above is rounded. Regard in findings (e.g. Cremona) presents these construction units as quite complex things.

What makes these construction units reflect expected as complicated?

The washer bars rest in cast in (and/or sawed in or in-filed) slots of the clamping washers. Simple straight lines a pin used can these during stretching or shooting laterally shift. Around this to prevent the ancient technical designers formed out these chucking devices down in such a way that these were fixed in the washers positively. A further characteristic are two to the axle centre of the pins symmetrical projections at the top sides. Thus the different length stretch of the torsion bundles becomes balanced with stretching. The tensile stress of the chord bundles is kept from outside to inside alike in this way.

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Illustration 9 
Washer bar.
 
The washer bars serve a further purpose to one: To give at them the stretch key set around the torsion bundles the necessary pre loading. Construction ally conditionally from there the range of the pins must remain free of drillings for the locking pin. The stretch key seize positive over the washer bas and this - pull after the locking pin - including the washers are turned.


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Illustration 10
Torsions stands with mounted washers, washer bars
and holding pins.


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Illustration 11
In chord bundle installed catapult arm. The torsion bundle
is in the relaxed condition represented. 


Catapult arms

The two catapult arms transform the energy stored in the rotated rope bundles over their lever force into a straight-line forward movement of the chord including projectile pins. Beside the chord there are the most highly stressed parts.

The catapult frameworks consist of wood with an iron reinforcing. The iron reinforcing serve the reinforcement of the felling trees hurry and prevented with their break an uncontrolled fly away from wooden fragments.

With a traditional catapult system if the arms are pressed with stretching into the chord bundles, another effect comes to carry with the internal system. The forces work in reverse and „draw “the parts from the chords. When shooting the catapult arms are accelerated forward in addition and to fly - without suitable retaining measures - from the torsion bundles. Solution is a hook at the end of the iron reinforcement. A further hook on the opposite side causes an effective centring in the chord bundles.

For the admission serves the bow- string to the reinforcement border of a fastened hook. The bow- string hook is firmly installed and directly mounted in the wood. An adjustable bow- string hook for adjustment to the makes with one internal catapult system little sense, since the arms stand in a state of rest almost parallel. In addition comes the enormous forces, which would bend from the wooden mounting out-standing hook.


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Illustration 12
Catapult arm with  iron reinforcing.

The catapult arm is through pushed by the relaxed chord bundle, turned over 90° and centred by means of the two hooks. Recognizable now is (illustration 11) the functions of the recess in the front prop.

There the catapult arm in its front relaxed position finds its counter bearing. Thus after the shot the situation of the catapult arm is corrected also each time into seeing.

Caps and protective sleeves 

On campaigns the catapults of the weather were exposed and in the combat mission to also opposing weapon effect. In order to protect the sensitive chord material of the clamping bundles against outside effects, a cover took place by means of covers and cylindrical cases.

As materials iron or bronze was available. As manufacturing process for the covers bronze casting presents itself. Bronze or iron sheet metal also driven would be possible.

For the cylindrical sockets driven sheet metal cases are most probable.



Illustration 13
Mounted cap. The selection shows the asembling situation
  

The covers could have been simply attached to the clamping chucks - depending upon attainable passport measure they could also be wedged . Unproblematic ally for the upper covers. The lower covers could have been mounted the same way. There was then, however always the danger that these could replace themselves by vibrations in case of transport. Indeed the representation during the transportation situation on the Trajan's Column the lower covers the lower covers were removed.

(See menu option analysis)

Those cylindrical protection sockets are manufactured dividedly. On the torsion stands they are pushed at with the fork ends of the strives in the stands fastened. The squares recesses above and below are the passage for the retaining eyes of the torsion stands were the bend and lowest vine is to be fixed then.

The opening for the catapult arm is at the edges outward floated around a damage of the felling trees hurry catapult arms through creates edge to avoid.


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Illustration 14
Protection sleeves made out of bronze. Representation on
average for classification the assembly situation.

Before torsion stand completely assembled now in curved and lower tie bar to be used the protective sleeves must be put on. These consist of two parts and have recesses for the retaining eyes at the stand and naturally area for the tension and firing movement of the catapult arm. By the circular execution of the locking collars at the torsion stand the cases can be set positively. The two protection sockets receive their actual stop by the fork arms of the props with the torsion stand to be wedged.

 
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Illustration 15
Assembling of the protectiong sleeves.

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Illustration 16
Assembling of the caps.

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Illustration 17
Almost complete installed framework. All protecting sleeves and
caps are mounted, the bow string is hung up.

Illustration 17 shows the advantage of this type of construction of a clamping frame. Construction units of this kind - in each case a on the right of and a link rushing guidance - could be provided with stock covered. If a chord set was damaged with the employment, a fast exchange was possible against a made available intact system. The catapult arm had to be pulled out and afterwards the iron wedges to the under and arched- strut to be solved. In addition it was to be given possible a worn or defective torsion system to the arsenal, without having to remove the actual catapult from the place of work.

This possibility was not given with the traditional weapons in wood post and beam construction way. If the covering was damaged, this had to be replaced in a complex procedure.

Possible it was to be brought even necessarily the entire catapult for the repair in the arsenal.


The stock 

The stock takes up the slider including catch and the stretching winch. For the guidance of the slider a dove- tail formed groove is trained. At the rear end the camps for the clamping hoist are installed. Furthermore the two stop angles are fastened in front with those, the stock is riveted  to the clamping frame down.

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Illustration 18
Stock with guidance for the slider and the clamps for the winch.

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Illustration 19
Stock as exploded representaion.

Catch and slider  

For stretching the string a device for locking the string is necessary  (catch). This must be arranged mobile toward the firing axle around to make possible the  stretching the chord by a course movement to the rear . As it comes even during pre loading of the torsion bundles to small irregularities, the catch must be laterally led. If this would not be the case  it comes to lateral emigrating of the catch. In addition something that leads over the slider standing chord to a pull-out torque in the catch of which by a suitable construction must be caught. For this reason this construction unit - is usually mounted ancient defaults - is usually mounted on a slider which is dove-tail formed and led into the stock.

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Illustration 20
Catch with fork arm for the string.


The chord is fixed in a fork-shaped piece, which are stores as a seesaw. The retaining piece is held in position by a deduction lever.
If the deduction can be pulled to the rear the chord owner evade upward and the chord can be release.

At the end plate another handle is still riveted. This can be lifted upward and is used for the pre-pressure of the slider.


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Illustration 21
Catch as exploded representation.

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Illustration 22
Slider with mounted catch.

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Illustration 23
Slider from below. The rivets carried out place by means of a counter plate.


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Illustration 24
Slider mounted, with winch and crank

 
Linear bolting device system

During the linear bolting device the locking action takes place through length wise at the stock arranged check elements (slots) in these the slider arranged pawls intervenes. The slots can be trained theoretically into the wood of the shank. Rest borders made of metal, wrought steel or made of bronze would be more favourably poured (Illustration. 25).


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Illustration 25
Linear bolting device system with pawls and at the stock
the rest border (side view)..

Alernative, radial bolting device system

The handle prevents a forward moving of the slider by the stress of the chord. The ratchet wheels are attached and fastened to the role of the winch. As model for the reconstruction a find from in the Greek Ephyra was used. After the shot the pawl will forward and the slider can - with  now freely turning ratchet wheels -  be pushed forward.

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Illustration 26
Radial bolting system with two ratchet wheels
and a double pawl.

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lllustration 27 
Ratchet wheel with locking lever.  

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Illustration 28
Radial bolting system as explosion representation

 
Winch with crank

 For the drive of a double armed crank the winch is used. To the transmission of the torque a square is used which is put into a role.
 Advantage is,  that the crank can be changed and the tightener thereby can be used of on the right or on the left.


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Illustration 29  
Crank with square and roll with ratchet wheels.

Illustration 29 clarifies the function of the rope winch. The bow-string is fastened to the catch of the slider and to these can now - in the stock sliding - be withdrawn.


The tripod

There are for two variants possible for the stand: Variant 1, execution for ground list, Illustration 30.

Variant 2, landing execution for list in a catapult bank (Illustration 31).
For variant 1, which can be set up the catapult without any problem on a wagon or unloaded. Actually  this is the more probable execution.

Variant 2 correspond to the representations on the Trajan's Column, whereby it cannot be surely clarified whether these representations do not show the false reality.


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Illustration 30
Tripod stand for ground list, with a hinge for the clamping frame.

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llustration 31
Tripod with short stand. These execution needs a base, for example a wooden bass.
(See Analyssis, the representations on the Trajan's Column).

Illustration. 31 shows a variant of the representations which corresponds to the Trajan's Column. Under the premise that these illustrations are not distorted - it is in this version -  remote from the stand in operation a substructure.

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Illustration 32
Stock, clamping frame and the hinge

 
By removing the bolt at the retaining hinge the entire catapult lets itself decrease from the tripod. Entire catapult with the stand for ground list
Illustration 35 show the arrow- thrower in the finished condition. Recognizable is the adjustable support of the stock for adjustment of  the
angle of departure.

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Illustration. 33
Catapult completely mounted in the view from behind. The  catapult arms
in front, relaxed position.

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Illustration. 34
Catapult completely mounted in the view from the front right.

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Illustration. 35
The slider stands in its front position. The catch is open to grisp the string.

Illustration 35 shows as far the slider - with an internally working catapult system - has to be put forward must around the chord latch.

Note:
In practice it has been shown that the string lets itself withdraw and latch without any problems with both hands approx. 15-20 cm, since the torsion bars are still relatively „soft the first 5-10° of the clamping angle “. Thus the problem of the slider with is outstanding is somewhat moderated.

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llustration. 36a
Slider in strained position with loaded projectile.

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Illustration 36b
Ballista in side view

Carriage (carrus)

The torsion catapults were used of campaigns, this means they were transportable. Two wheel cars with two course animals were used. The cars had a box like structure and wheels with spokes. The reconstruction is strongly related an illustration on the Marc Aurel Column. As track width the usual Roman measure was used of approx. 1,2m.

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Illustration 37
Reconstructed, two- wheel trolley.

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Illustration 38

Illustration 38. The catapult is simply put in to the wagon. For transportation there are on that edge of the structure stowing rings attached (Trajan's Column), to these can do that Weapon system by means of ropes can be fastened.

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Illustration 39
Wagon with catapult bank and holding pegs for the stand of the catapult. 

Illustration 39 shows the wagon with a catapult bank, for the admission of the version with a short stand. Into the catapult bank a wood tap is let in. The stand orders at the bottom over an appropriate drilling in to the foot. However the bolt firer lets itself surely is fixed,  the possibility orders to the side direction.


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Illustration 40a
Catapult mounted on wagon. This execution comes the illustrations
on that Trajan's Column very close (representation without course animals).


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Illustration 40b
Catapult mounted on wagon. Side view.


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lllustration 41
Side direction possibility on the pivot mounted catapult.

By means of pivots in the catapult bank the stand is surely held. The rough adjustment on the target takes place with wagons including course animals (course animals are not represented). The possible misalignment of the firing axle from the pole direction permits more than sufficient corrections.

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lllustration 42
Catapult in covered position. The tripod stands on a wooden landing.

The catapult decreasing from the wagon is necessary an under body (landing). With weir structures a bricked catapult bank made of stone would have been possible.

Projectile pin

With a torsion catapult a weapon system is meant. Over the winch manual energy is supplied to the system. This is stored in the torsion bundles and transferred with the shot over the catapult arms and over chord to the projectile. This flies then in a parabola flight path to the target. The effect in the target depends of the speed and the mass of the missile. The projectile arrow should be thus as fast and heavy as possible. If a hand sheet arrow of approx. 50 gram comes the weight of the pin for torsion catapult lies at approx. 350 gram. Since the speeds are approximately alike, by the mass enlargement a sevenfold effect in the target is produced.

The reconstructed projectile pin has a length of approx. 50 cm. The largest diameter amounts  up to 35 mm. The iron tip is approx. 80 mm long and weighs 120 gram. The square point goes into a conical, slit sleeve over with that the ogive of shell on the wood shank of the arrow is touched down. Stabilization in the flight takes place via a surface tail unit with 3 wings shifted by 90°. Quadruple a tail unit is technically not feasible, since the arrow with its lower surface in the guidance gutter rests upon.





Illustration 43
Projectile pin with wood shaft and iron square point. Reconstruction showing
findings of Dura Europos (3rd Century a. C.)

Illustration. 44
Arrow head with rod
or hollow socket for the wooden shank.


 Illustration. 45  
Projectile in inserted position.

Illustration 45 shows the pin inserted, catapult in maximum clamping position. In this position the chord angle is very small, the bow-string barley touches the wings.

Note: After a change of a reconstructed catapult on an internally working catapult system existing projectile pins had to be adapted regarding the wings. The wings became  flattened at the ends. Again arrows received an extended shaft end and the wings became approx. 15mm further in front set. The flight behaviour remained uninfluenced thereby.

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Illustration 46
Projectile pin with cone tail unit from a find from Vindonissa (Windisch).

Illustration 46 shows a projectile pin with a cone tail unit. The original has a length of approx. 12 cm and might be a projectile for a hand arm chest. The reconstruction was increased on approx. 32 cm, shank diameter in the back approx. 28 mm. With this projectile form there would be no problems with the wings also with small chord angle. Disadvantage it's smaller flight stability (easy oscillating), under the less favourable tail unit in cone form.

 
Fire projectiles

If the energetic effect is the centre of attention in the target with the standard bolt, it concerns with the fire arrow the release of a harming fire. Inflammable material - e.g. with oil or pitch soaked rags - in the fire baskets of the heads of the arrow were fastened and fired on suitable, inflammable targets. To avoid during the flight to avoid the incendiary compounds with additives from iron splinters, lime, saltpetre and sulphur were supplemented.

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Illustration 47
Fire projectile with one as " fire basket" out-forged point.


Conclusion

The accomplished graphic reconstruction points out how the catapults of the Trajan's Column could have been designed. Variants regarding the clamping system are conceivable. Both radial working locking systems  with a ratchet wheel and handle and linear working systems (see also menu option 4 building of catapults) could have been in use. Also regarding the binding of the torsion stands to the props for the torsion systems, variations in type would have been possible. Eventually also without a possibility to change for the torsion systems one did (see also menu option building of catapults). Regarding the structure of stand two possibilities could be derived by the analysis of the representations to the Trajan's Column . Both variants were presented here.


Designs and text:  Author

Source: see references