I am a bit lost on the pre-tension/ tension twisting the washers bit. Could you point me somewhere where I can read up on that, please? From your words I understand pre-tensioning was done by stretching the cord tight, not twisting it. How would that be achieved in the model under discussion?
@agrimensor Sorry, can't spot the mistake :oops: But if I goofed somewhere, please all insert correct phrase in approriate spot.
Ammianus definitely specifies using a mallet/hammer to release the arm, but a latch and lanyard is certainly much safer.
Both Heron and Vitruvius discuss the methods of stretching and pre-tensioning the bundles. There is also an excellent modern article on spring behavior. I'll try to locate it. If you can get access to a copy of Eric Marsden's "Greek and Roman Artillery: Technical Treatises", it is probably the best resource for catapult research.
According to the sources, they had a special machine to stretch the cord as it was wound through the washers. As each wrap was pulled tight it was locked in place with a wedge until the next pass was made. They "tuned" the strands by plucking them to hear the tone.
P. Clodius Secundus (Randi Richert), Legio III Cyrenaica
"Caesar\'s Conquerors"
OK, that seems clear BUT this is a takedown model, not a strung ballista. So that would put the pre-tensioning in a whole different perspective IMHO. Unless the rope would have been wound after the onager had been assembled. This would then however be conflicting with the idea of rapid deployment, would it not? I think I have worked out a way of tightening the bundle, though. Using two wedges with the pointy ends towards one another, this should tighten the cords when these are hammered into place through the loops at the end of the bundel.
Considering the force on the trigger, it is not surprising a hammer should be used to get the locking clamp to release, should a trigger mechanism like the ones on ballista be used. In order to opperate this with a cord, a lever mechanism would be required to release it, much like the Seacatch. This should not be too difficult to build/forge fairly authenticly.
Ammianus said, "...between these beams, through the holes, powerful ropes are stretched, preventing the structure from falling apart." I wouldn't dwell so much on the onager being any form of rapid deployment weapon. Although they could be disassembled for easy transport, they were still part of the seige trains and not a field piece. They would be brought up and reassembled as part of the siege preparations.
Most experts (Marsden included) choose to ignore the last phrase about the spring holding the frame together. I think that it's just one of the elegant efficiencies of the design. If you are just building one for demonstration purposes, you should be able to get away with just pulling the cords as tight as you can by hand and twisting in some more power after the arm is in place. It won't give you the machine's full potential that way, but it will make it much easier to handle.
Philon did come up with a wedge method for tightening the bundle on a euthytone engine, but there's no evidence anyone ever adopted it.
P. Clodius Secundus (Randi Richert), Legio III Cyrenaica
"Caesar\'s Conquerors"
For the sake of adding to the knowledge, I do want to approach this in a way that will stick as closely as possible to the archeological (if any) and written record. So I am taking the words of Ammianus as "gospel" in trying to work with all those willing to participate and to come up with a design that will allow us to prove (or disprove) the possible interpretation of his writings. You spoke earlier of using a wooden washer. Is there a picture or drawing somewhere of what this could look like and how it would work in an onager?
Also, as you argued in your posts in the earlier thread, there seems to be much of the workings of the onager that is not described. So for many of the details (size of the drum, placement of the holes to wind it, the use of a ratchet, the trigger mechanism, the way the sling was attached and loaded), we are left guessing. It’s like reconstructing a Batavian farmhouse on the basis of a floor plan of postholes and the odd textual reference by someone of the era, who would not mention all that is obvious or self-explicatory to those of that time. Like did they have windows?? Then there is the fact that in an onager, the rope bundle is both much larger and much longer than those on a ballista or another device with two arms propelling a bowstring.
I feel there is a lot to learn here and much fun to be had in the process mile:
Quote:I hope this thread inspires a lot of onagers being build, as they would seem really handy weapons and relatively simple to both make and transport.
And I'm glad to see that you (and pretty much everyone else; e.g. Brigitte Cech) has decided on the de Reffye model, as revived and publicized in Osprey's Greek and Roman Artillery book. :wink:
[attachment=5842]DeReffye_onager.jpg[/attachment]
Nice picture! I do wonder about the technecalities of it all, though. The drum where the cord is would is very thin, but this is were a large force is excerted, that and the fact that for each full rotation, very little rope is wound for the effort taken.
Randi, you spoke earlier of using a wooden washer. Is there a picture or drawing somewhere of what this could look like and how it would work in an onager?
Quote:Nice picture! I do wonder about the technecalities of it all, though.
My sketch -- wonderfully brought to life by the excellent Brian Delf -- was necessarily theoretical since (a) nobody has ever built the size of onager described by Ammianus, and (b) I have only ever seen rather poor photographs of de Reffye's onager.
Prior to 2003, any and all reconstruction paintings depicted the Payne-Gallwey design. My picture was intended to fire the imagination of craftsmen like you! :wink:
If Robert does not mind me going a little off topic for a moment I have been looking at the picture of that huge machine shown by D B Campbell, also if an ornager of this size could be dismanteled and transported is there any evidence of the Romans also transporting their amunition as well.
For here is a picture of a Roman Stone Ball found at the side of one of the three lane Roman Roads found here in the north of England by the late Raymond Selkirk, this stone is a very heavy one that is in the region of 35cm and the road where it was found runs parallel to the Roman Dere street on the eastern side of the Cheviots.
It's not really off topic, because in one of my previous posts I postulated the Romans carried their ammo on the cart with the onager. As with any artillery, weighted and matched shot will very much improve the gunnery. Even heavier and lighter munitions could be used to get the rocks to fall on target, as that would be one of two variables, the other being the amount the spring was wound. Nice round stone ball!
That onager ball is no longer where the picture shows it for a friend and I threw it over the gate and hid it amongst undergrowth, and it is well we did for the farmer or land owner later removed all the Roman stonework from what had been a bridge over a stream 20 meters away and may well have thrown that also.
I have to say that it did take both of us to lift it at 35cm diameter which does make one understand just how heavy a job it would have been loading these onager weapons so the rate of fire was not so rapid.
Depends on how far you can depress the throwing arm, as the sling may be lowered to the ground and the ball could be rolled into the sling pocket, after which the third rope with the release ring could be hooked to the arm. I presume more time would be taken in winding back the arm to cock the weapon then to actually load it.
Quote:BUT this is a takedown model, not a strung ballista. So that would put the pre-tensioning in a whole different perspective IMHO. Unless the rope would have been wound after the onager had been assembled. This would then however be conflicting with the idea of rapid deployment, would it not?
I don't think anyone has ever suggested that these were rapid-deployment machines, Robert. I certainly wouldn't subscribe to the notion of "quick assembly", except in the sense that Roman engineers settling down for a siege would be able to knock some up in fairly short order, especially if they had brought the major components with them. (Sadly, the sources do not describe how this worked.) The word "rapid" doesn't really suit the onager: Ammianus seems to suggest (during the siege of Amida) that, once deployed, they were a major pain to manoeuvre about. I tried to give a flavour of this in the cover painting of Siege Warfare in the Roman World, which shows onagers being deployed in defence of a walled town:
[attachment=5847]Siege_Warfare_in_the_Roman_World.jpg[/attachment]
Quote:I have been looking at the picture of that huge machine shown by D B Campbell, also if an ornager of this size could be dismanteled and transported is there any evidence of the Romans also transporting their amunition as well.
In my opinion, ammunition was prepared on the spot, as well as the machine. The Romans show no particular diligence in collecting "ballista balls" after use, which is why we find so many of them.
Also, please remember that Brian Delf's painting is of the large onager described by Ammianus. I tried to calibrate it as a one-talent machine (i.e. the spring is powerful enough to launch a 26kg boulder) requiring eight men to winch back the arm. I have no doubt that there were smaller versions!
mile:
