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'Firefly',  a faithful and powerful reconstruction of the Orşova ballista

The remains of a ballista were found in the Roman Fort in Orsova during rescue archaeology in the 1960s before the rising waters of the Danube behind a dam covered the site. The position indicates that it was probably one of four such weapons, one at each corner of the fort, used if necessary to shoot at attacking troops. The darts would have had no difficulty in passing through any armour. Only a few metal parts were found, the important iron kamarion, which fitted over the top of the launching ramp, and the right hand mechanism (kambestrion, or field frame) for holding the sinew rope which took the tension of the weapon and then released it, sending the bolt 800 metres or more, with tremendous force, sufficient to pass through a fully armoured soldier. The ladder frame, or kamakion, which fitted under the launching ramp was not found.

Nick Watts has made 'Firefly', a superb and accurate reconstruction of the Roman ballista found at Orsova. He has also treated it as a scientific endeavour, with careful and accurate measurements of velocity, energy, range and accuracy, something which has never been attempted in modern times. There is no other such data available anywhere in the world. The kind of performance level he presents in his blog at  http://wattsunique.com/blog/  has not been generated since ancient times. His ballista is far and away the best authentic ballista anywhere in the world.

Another attempt at the Orsova ballista, made as an outswinger in Britain in 2005, cast a bolt a maximum of 100 yards, as against his Firefly smacking out a heavy one pound bolt (467 grams) at an estimated 360 feet per second, with the sharp tipped bolt being found protruding from Mother Earth at an approx. 45 degree angle, 845 yards downrange.

Nick is one of the few people in the world who could possibly have built this machine, which requires not just technical expertise, research skills, creativity, the ability to troubleshoot and a big well equipped workshop, but the passion to follow the project through to completion, with precious little reward or encouragement.

I salute him. Such men do not pass this way often.


Text above: Don Hitchcock, with performance data of 'Firefly'  from Nick's blog.



orsova ballista







Reconstruction by Nick Watts of the Roman ballista found at Orsova, Romania.

Known as 'Firefly', it will reliably and accurately throw a bolt more than 800 metres.

Photo shows the rig set up on the back of a pickup on a firing range to test range and accuracy.

Photo: Nick Watts
Text: Don Hitchcock




orsova ballista
Ballista at the National History Museum of Transylvania, located in Cluj-Napoca.

This is an excellent display of the main parts of the Orsova ballista, with the original bar with an arch in the middle, or καμαριον, kamarion, and the right hand mechanism for holding the sinew rope which took the tension of the weapon and then released it, sending the bolt 800 metres or more, with tremendous force, sufficient to pass through a fully armoured soldier. The left hand mechanism has been recreated for the display, but unfortunately an exact copy of the curved vertical bar was made instead of the mirror image as should be the case.

The overall length of the original bar is 145 cm, but it would have been longer when originally made, since the forked ends were found corroded and truncated. The length of the rod itself to where the forks start is 125 cm.

Photo: Cristian Chirita
Permission: GNU Free Documentation License, Version 1.2 or any later version.
Text: Baatz (1978)


orsova ballista

This is one of the parts of the ballista found at the fort in Orsova. Catapult historians refer to this part in an iron frame ballista as the Kamerion.

It is a long iron spar forged to an arch in the middle. The two ends of the spar were forked. All four ends of the two forks were broken, but at one of the broken ends a single small rectangular hole was preserved intact and apparently the beginning of another. The object was considerably bent and twisted.

Photo: Baatz (1978)
Text: Nick Watts


orsova ballista



On either side of the arch in the Kamerion there is a pair of small round holes going through the spar. These two holes that straddle the arch were put to good use in 'Firefly'  by utilising them as anchor points for rigging a front sight.

Photo and text: Nick Watts


orsova ballista
This photo gives a good idea of the scale of kamerion. The main spar is in remarkably good condition.

Older styles of ancient ballistas were not as adept at throwing shorter style bolts as the later iron framed machines. The danger with the older wood framed machines was that if something went wrong, and the bolt turned sideways during the power stroke, it would likely smash into the supports in the middle of the box frame.

With an arched frame the whole mess would be cast out the front, avoiding unpleasant ricochets and perforated catapultiers.

Photo: Baatz (1978)
Text: Nick Watts


orsova ballista



The first mockup of the main components of the ballista, consisting of just the recreations of the elements found at Orsova, but including the missing left hand field frame.

Photo: Nick Watts, spring 2008
Text: Don Hitchcock


orsova ballista
This 460 mm ash-wood ballista bolt from Dura Europos (Syria) tapers from a diameter of 30 mm at the rear to 14 mm where it enters the socketed iron head. The pyramidal point is 46 mm long.

The missile was designed for the new arrow-firing ballista, and has completely different proportions from earlier catapult arrows. Its tapering profile and armour-piercing tip make it a destructive weapon.

This artifact is the only intact specimen of a Roman ballista bolt ever discovered. It was excavated in Dura Europos, Syria, and is likely the type of projectile used by the Orsova ballista. Bolts of this type must have been made in the tens of thousands by the Romans. The wooden shaft is made from ash and the quadrobate iron tip is a four sided square, designed to punch through shields, armour, clothing, etc.

The thinner foreshaft of the Dura Europos bolt was designed to aid penetration, it also raised the ballistic coefficient to aid in a long flat trajectory. The swelling at the rear of the bolt not only helped absorb the powerful thrust of the bowstring, but also acted as a kind of aerodynamic counter weight to help keep it steady in flight.

This inherent stability was further aided by the short stubby fins. These fins were made from maple and glued into grooves cut in the ash body. Overall length is 18″, thickness at the rear end is 1 and 3/16″ and it tapers down to a bit over 1/2″ in the front. It was reported to be a good deal shorter than the type of bolt that came before it. Late style ballistas like the Orsova model did not have any kind of narrow opening around the bolt groove that the projectile would have to pass through.

Photo: © Yale University Art Gallery
Text: Campbell (2003) and Nick Watts.


orsova ballista bolts

Typical bolts fired from the reconstruction of the Orsova ballista by Nick Watts.

Starting from the top, the weights on these bolts are: 415 grams, 427 grams, 399 grams, 467 grams.

Photo and text: Nick Watts


orsova ballista orsova ballista

This is part of the ballista found at the fort in Orsova.

(left) Field-frame of the ballista (right) the bottom ring seen from the under side

Photo and text: Baatz (1978)


orsova ballista

This kambestrion or field frame was discovered at Lyon (France) and may well date from the battle between the Emperor Septimus Severus and the pretender Clodius Albinus in 197 AD. Apart from the associated washers and levers, no other catapult parts survived.

The upper and lower struts of the spring-frame would have slotted into the crudely made brackets projecting from either side of the kambestrion, and were perhaps wedged in place.

The Lyon kambestrion still has its original washers. The spring-hole is roughly 9 cm in diameter, but the inner diameter of the washers, and hence the spring diameter is only 7.5 cm. Furthermore, the washers are roughly 6 cm high, making the total spring height 44.5 cm, equivalent to almost six spring diameters.

Photo: © Musée de la civilisation gallo-romaine, Lyon
Text: Campbell (2003)


orsova ballista

Field frames are the repositories of the rope (sinew in the case of the Romans, man-made fibre in this reconstruction) which is used to store energy for the projection of the bolt.

This shows the reconstructed field-frames of the Orsova ballista after assembly but before realignment for symmetry. This sort of period piece construction requires many skills of layout, engineering and welding, and is far beyond the abilities of most amateurs.

Nick Watts has a blog which details the reconstruction of the Orsova ballista, 'Firefly' at http://wattsunique.com/blog/

Photo: Nick Watts
Text: Don Hitchcock


orsova ballista

An essential addendum to fabrication and engineering skills is a well-equipped workshop such as this.

This shot shows Nick engaged in the process of gently persuading one of the field frames back into alignment after some particularly high draw weights had caused a minor collapse in the curved stanchion.


Photo and text: Nick Watts


orsova ballista orsova ballista
The rope ready for insertion, left, and installed in the field frame right.

The first of our new magnum springs has been installed. 290' of waxed, 1/4" nylon rope, with about 7 000 lb of linear tension. Smells right to me. Tuning imminent. I’ll put the kettle on.

Following the theme of modularization implied by the loops found on the original Orsova field frame, every effort has been made to maximize all parts of the design in favor of simple, replaceable components. This is in keeping with our intent to make the machine on a "nothing spared" basis. It seems reasonable to assume that these weapons were well funded and had the benefit of multiple iterations to work out all the bugs. In the area of torsion engine maintenance, modular springs would surely be hard to beat. Sneaky old Romans must have done something along these lines.

It looks like an old man with a sore back, can disassemble Firefly and swap out one of her springs in about 30 minutes.

Photo and text: Nick Watts 5th February 2010


orsova ballista
This gives a very good picture of how the field frames actually are put together with the rope springs. The curved part of the field frames is there to accept the wooden limbs.

Pre-tensioning of the rope springs is done once these are installed on the machine. The leather covers are there just to hold everything in place until the unit is installed.

Note the bronze hardstops between the field frames and the limbs. These were thought at the time to be important to bring the limbs to a stop at the correct point, and to protect the bowstring from the awful snap of the limbs coming to a halt, but were later found to be unnecessary and were removed.

Nick's policy of 'first do no harm' when redesigning parts of the ballista was vital in this case. All that he had to do to return to the original specifications was to take a few seconds to cut the cords attaching the hardstops, remove them, and he was done.

Photo: Nick Watts 25th January 2010
Text: Don Hitchcock


orsova ballista

This 'exploded' view shows a 'vernier' plate with its four sturdy pins that lock it into position on the end cap of the field frame.

The washers that hold the rope spring can then be rotated to the desired level and locked in place with pegs that go through the rim of each washer, and into the vernier plate beneath.

Photo and text: Nick Watts 17th April 2009


orsova ballista
This shows the starboard field frame assembly as fitted.

This is the powerhouse of the whole machine, and much understanding of how the ballista works and is made can be gleaned from this one photo.

The field frame itself is the inner section, and bears loops at the top that allows it to connect to the Kamerion. This last item is made from spring steel and has a large horseshoe shaped arch in its center. The ends of the Kamerion terminate in a pair of forks. Each of the four ends to the two forks, is formed into a notched flange and these are designed to fit into the four loops presented at the top of the field frames. Carefully shaped bronze wedges, with split pins holding them in place, lock the flanges on the Kamerion into the loops on the field frames with great rigidity. The distinctively shaped Kamerion was the essential piece identifying the unique nature of what had been found at Orsova.

Larger sockets of unequal size on the bottom of the field frames are there to accept the ends of the flanges projecting from the ladder, so called because of the cross pieces which anchor and strengthen the whole assembly. The ladder is what keeps the whole machine dimensionally stable and connects the field frames to the walnut stock. These flanges on the ladder are outboard the socket and inboard it (as fitted) and are each held in place by one wedge on the left, and two on the right.

Above and below the field frame are the vernier plates. These have multiple holes unequally spaced with small increments in a vernier pattern so that the rotating washers that control the rope spring can be tensioned down to increments as small as 7 1/2 degrees. This narrow level of rotational discrimination in the locking positions for the washers, ensure that it is possible to effectively tune the machine so that both torsion springs are equally powerful.

Above and below the vernier plate are the washers, each with two big lugs to carry the crossbars which are thrust through the center of the rope springs. These washers also carry multiple holes which are positioned in a symmetrical pattern, so that when used in conjunction with the vernier plates, the rope spring can be tensioned by the very small increments mentioned above. Two hardened steel pegs, one on each side of each washer are inserted through the appropriate holes and into the vernier plates. In this manner the washers, and the springs that they control, can lock-in the correct tension.

Passing through the middle of the rope bundle is the metal end of the limb, which has a steel finger crooked around the rope, with the rope itself protected to some extent from the tender embrace of the steel finger by a leather sleeve.

This photo shows the ballista at rest. When the ballista is fired, the limbs are kept from hitting the curved stanchion in each of the field frames by the bowstring itself, leaving the clearance shown. The pocket on the curved stanchion is included in the design to provide the maximum arc of travel, and thus maximum power, to the limbs.

The four diagonal struts are slotted into holes in lugs on the vernier plates, and located with split pins, and are there to lead back to the spine of the ballista, and thus provide essential dimensional stability to the assembly by triangulation, as may be seen by reference to the main photo at the top of this page.

Photo and text: Nick Watts


orsova ballista
The spacers in this photo are important components when it comes to getting the most out of the torsion springs. In practice there are actually eight of them, one at either end of the four crossbars.

These spacers are used in the all important linear tensioning procedure that stretches the spring out in a straight line before the rotational torque is applied. Slipping them under the crossbars when the crossbars are pulled apart by a chain hoist accomplishes this operation. Interestingly, problems were encountered with these spacers wanting to migrate outboard when the machine was fired.

The solution was to cut angled bottoms on the spacers, and then heat treat them so they were harder than the receiving surfaces in the lugs on the washers, and this mechanically locked them in place quite reliably. The arched cutouts were included as a backup measure in case bindings were needed to further lock the spacers in place.

In practice these bindings have been omitted because they were deemed unnecessary.

Photo and text: Nick Watts


orsova ballista

This is a pair of the locking pegs that prevent the washer from unspooling when it is under load.

That is to say, the pegs lock in as much pre-load torsion as the experimenter deems wise. The pegs are fabricated from the shanks of 3/8" Allen bolts. These are made from grade 8, carbon steel, nice tough stuff, and are a suitable analog for the type of item that could be produced with ancient forgework.

Photo and text: Nick Watts


orsova ballista

Two of Firefly’s old washer locking pins have been reassigned to locking the limbs into their forward taper.

This is a photo of one of the locking pins and some of the handy-dandy ferrule cement that holds it in place.

The 1″ deep hole for this 3/8″ pin should pick up enough ash to form an effective lock. The hole in the limb is only .002″ larger than the pin, and when installed that gap is filled with the marvellously sticky ferrule cement. Application of a hot iron to the flattened tip of the pin will allow for its removal.

Photo and text: Nick Watts


orsova ballista



While the sum of all the forces in the firing cycle always seems to propel the limb aggressively forward into the taper of the limb iron, it is well to guard against any backward forces that might be encountered when applying the old heave-ho to the tension strap. It is imperative that the tension strap remain unbudgeably anchored at either end of a non-compressible limb.

Photo and text: Nick Watts


orsova ballista
These are the limbs. Note the pre-tensioned dacron cable epoxied to the leading edge to provide strength to the edge of the limb under tension.

The whipping on the end of the limb provides a nock for the bowstring, locates the end of the dacron cable, and provides a couple of high tension compression rings to protect the end-grain of the ash limb from splitting.

These Mk IX limbs are all finished, save for a bit of rasp work and some sanding. They weigh exactly 8 pounds each, and are 3" longer than the previous Mk VIII’s. Those previous limbs were a chunky 10 1/2 pounds each and are the ones responsible for all the data generated in the last year or so. We are hopeful that this new design of limb will develop much higher velocities.

Photo and text: Nick Watts, 19th May 2012


orsova ballista

Close up of the ratchet assembly for cocking the bolt. These details were not preserved in the remains of the original ballista, so they have to be designed on the basis of similar sub-assemblies of the times, and so that they would have been within the capabilities of the Roman blacksmiths who made the original.

Photo: Nick Watts
Text: Don Hitchcock


orsova ballista







The first time that 'Firefly' was ready for inspection in all her glory on a proper stand. Preliminary testing of the mechanism had been done, and there was still a lot of fine tuning and rigging to be done before being battle ready, but the ballista was starting to look very good indeed.

Photo: Nick Watts, Wednesday, 23rd March 2011
Text: Don Hitchcock







The Beginnings of the Orsova Ballista

Gallwey ballista

In the beginning was the Gallwey ballista, and it was good.

Nick had the advantage with this machine of a reasonable pen and ink sketch of the entire machine. Certainly, many details had to be worked out, but the basics were there. It provided valuable experience for the very much more difficult and demanding task of recreating the Orsova ballista, for which there was almost no information apart from the dimensions of the Kamerion and the field frames which hold the bundles of ropes which provide tension.

Photo: Nick Watts 1997
Text: Don Hitchcock



Gallwey ballista
The Gallwey ballista was inspired by this pen and ink drawing found in Sir Ralph Payne-Gallwey’s book, The Crossbow.

I had seen the Gallwey pen and ink drawing in a dictionary when I was ten years old. The desire to make one like it was baked into my subconscious at an early age.

Field testing of this first ballista continued from 1998 through 2001. After that the whole thing was pretty much mothballed, until now. At the time I put it away the machine had fired 358 shots and other than a broken limb (very exciting) showed no sign of damage. In retrospect I see that my documentation of this first round of testing never really did justice to the amount of labor involved performing it.

What records I have from ten years ago show that the muzzle velocity for this first machine averaged 310 feet per second when using 3/4 pound bolts. That puts the muzzle energy at 1150 foot pounds, about the same as a high end load for a .44 magnum. After the 5" diameter, 32" long torsion springs were tuned, it would put ten shots into a 3 inch circle at 50 yards.

I never got around to making a perfectly matched set of bolts, so this level of performance was only achieved by shooting the same bolt over and over again. However, considering the variation caused by having to resight for each shot, (it proved impossible to cock the machine without disturbing its aim) I was fairly ecstatic about its accuracy.

The 1″ diameter steel tip used on the bolts for accuracy testing had a flat end to help reduce penetration and thus ease removal from the plywood backstop. Even at that, the 1" flat tips would punch a hole through four sheets of 3/4" exterior plywood and leave a healthy dent in the fifth.

Sharp tipped points would make it through six or seven sheets. Maximum range (shot at a 45 degree angle) with the 3/4 pound bolt was 480 yards. Lighter, 1/2 pound bolts made it out to 540 yards, while 1/4 pound flight style bolts averaged 760 yards.

The maximum pull weight at full draw was 4012 lbs.

Photo: Payne-Gallwey (1903)
Text: Nick Watts


Gallwey ballista Gallwey ballista



Field testing the Gallwey outswinger.

Photo and text: Nick Watts






Readers may be interested in this more general treatment of the Orsova ballista, and its various incarnations in the artillery of Rome:

http://www.torsionsfire.de/Analysis2.html



orsova




Map from 1940 of the area around Orsova, with the 2nd - 3rd century fort or castrum at Dierna shown circled in orange.

Photo: http://diernaorsova.blogspot.com.au/


orsova
Constructii Antice - ancient buildings
Monumente Romane - Roman Monuments
Necropole Romane - Roman Necropolis
Aria de întindere a Diernei sec II - III - Maximum extent of the Roman Settlement of Dierna, 2nd to 3rd Century AD.
A-P Cercetari Arheologice efectuate intre anii 1966-1969 - A-P archaeological discoveries made between 1966 and 1969
(A) Fortificatie Romana Tîrzie - (A) Late Roman Fortification

a) Zernes-Dierna Roman Castrum

The castrum is located west of the river Cerna. Due to its small size, the layout was originally considered to be the medieval fortress of Orsova.

The dimensions of the fortification, identified in the field, are 64 x 54 metres and the time is late Roman, during the reigns of the Emperor Diocletian, 284 to 305 AD and Constantine the Great, 306 to 337 AD. North of the fortress late Roman bricks and tiles bearing stamps were discovered.

In the barrows of the NE and SE of the late Roman fortification level are ceramics from the 5th to 8th centuries AD. (studied groups are between the 7th and 8th, 8th - 10th, and 10th - 13th centuries).

b) Roman City

It seems that Dierna developed as a civilian city, without a military garrison. It did not exceed the rank of municipium. A late Roman fortification civil settlement partly overlaps the ancient Roman city. Other constructions were investigated on different occasions (Danube Avenue Alley, 23 August Street, Decebal, Graţca Valley were on the site of the first cemetery, with the second cemetery near the Cerna Bridge).

We know that Roman habitation concentrated in two areas: the first stretching along the river, and the second between the two cemeteries. Bricks in the town were found only for the 3rd and 4th centuries AD. A double pattern representing the goddess Minerva shows the existence of official local military forces.

Photo and text: Descoperiri Arheologice din Banatul Romanesc
- Reportoriu -
Cu contribuţii de: Cosmin Suciu şi Silviu Istrate Purece
Editor: Sabin Adrian Luca
Dedic acest volum memoriei profesorului Florin Medelet.
Sibiu, 2006.


orsova fort

Position where the remains of a ballista were found in the Fort in Orsova during rescue archaeology in the 1960s before the rising waters of the Danube behind a dam covered the site. This position indicates that it was probably one of four such weapons, one at each corner of the fort, used if necessary to shoot at attacking troops. The darts would have had no difficulty in passing through any armour.

Photo: Descoperiri Arheologice din Banatul Romanesc
- Reportoriu -
Cu contribuţii de: Cosmin Suciu şi Silviu Istrate Purece
Editor: Sabin Adrian Luca
Dedic acest volum memoriei profesorului Florin Medelet.
Sibiu, 2006.


orsova




Topographical map of the Orsova area before the flooding of the old town.

Photo: http://diernaorsova.blogspot.com.au/


References

  1. Baatz, D., 1978: Recent Finds of Ancient ArtilleryBritannia, Vol. 9. (1978), pp. 1-17.
  2. Campbell, D., 2003:Greek and Roman Artillery 399BC-AD 363, New Vanguard (Book 89)
  3. Gudea, N., Baatz D., 1974:Teile spätrömischer Ballisten aus Gornea und Orsova (Rumänien) Saalburg Jahrbuch 31 (1974), 50-72 reprinted in: Mavors 11, 246-268, i.e. Baatz D., Bauten und Katapulte des römischen Heeres Steiner: Stuttgart, 1994
  4. Payne-Gallwey, R., 1903:The Crossbow, Mediaeval and Modern, Military and Sporting, Longmans, Green, 1903, 328 pp.




Recent additions, changes and updates to the Alexis site

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This site is to publicise the history and culture of Romania, and displays information from the Alexis Project Association

Alexis Project Filiasi/Romania
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