I have to agree here, that is a nut from a crossbow, although not a rolling nut like Comitatus used.
It looks like when you pulled up on the trigger, the front part of the z-bar dropped, which made the nut pivot forward allowing the drawstring to be released. This seems very likely, but you would have to have a mechanism to keep the trigger locked in place when the drawstring was pulled back.
The other part does look like a handle, I think it bears resemblance to construction of sword hilts.
The Article says the spot was never searched again. If these iron pieces survived, I wonder if there were some bolt heads around other parts of the skeleton, possibly the z-bar trigger?
Quote:I would like, however, to get any information or diagram from somebody on how the arcuballista rolling nut/trigger mechanism's parts look, and how they interact to hold the bolt in place until the time to loose it.
I will draw a diagram showing my thoughts on how the mechanism of the arcuballista might looked like/worked. Just be patient
I would think that bone nut would roll OK round the pivot point. There is a small lip below, which the trigger bar would stop against. Being small, it should make it easier for the trigger to slip off when the lever of the trigger is drawn up towards the tiller or stock of the bow. The string would then slip off the top of the nut. It looks to me that the flat "bar" behind the pivot point would stop the nut rolling too far over and presumably would allow the bowman to flip the nut back, before engaging the trigger again.
Quote:If these iron pieces survived, I wonder if there were some bolt heads around other parts of the skeleton, possibly the z-bar trigger?
From the Gothic onward, rolling-nut crossbows had an iron trigger. To protect the nut from being worn down by the iron trigger, the nut was reinforced with an iron wedge. In earlyer periods nuts didn't have such a reinforcement, wich means that the triggers must have been made out of an material softer than iron. So what materials were used?
As the nuts were made out of antler or bone (without any kind of reinforcement), the triggers were also made out of said materials. I know of three construction methods:
If the nut from Burbage belonged to a Roman crossbow, the fact that it has no reinforcement might indicate that the triggers of Roman crossbows weren't made out of iron, but out of antler or bone.
Quote:"[...] but you would have to have a mechanism to keep the trigger locked in place when the drawstring was pulled back.
The three mentioned examples have one thing in common: A notch located on the underside of the trigger and slightly behind the hole for the trigger axle. According to Hans Harter (cf. the article about the trigger found in Schiltach), said notchers were pressed against a recess cut in the stock of the crossbow when the string pulled on the two "nut-fingers" prodruding from the surface of the stock. So thanks to the notch, the force of the cocked string could wedge the trigger between the nut and the stock; the trigger bar became some kind of "self-locking security mechanism". Before you pull back the string, you could turn the nut back to its former position and press down the trigger until its notch touches the recess; this would press the front end of the trigger into the lip of the nut and thus arresting the nut. The friction between the trigger and the trigger slot mortised into the stock would lock the whole mechanism until the crossbow is cocked.
Quote: I'd imagine the Romans would put a spring into it so the trigger would snap back, I know they did it with doorknobs.
If arcuballistae had the kind of self-locking trigger mentioned above, a spring wouldn't be necessary. According to Josef Alm, such springs were introduced in the 15th century.
Quote:Do you have a diagram of how the trigger mechanism and the notch on the nut works?
Yes, I do
Just take a look at the attached graphic (click on it in order to show it as a whole):
[attachment=7649]ArcubMech.jpg[/attachment]
Keep in mind, that this is just a quick drawing, so I didn't pay much attention to measurements. Nonetheless I think that the drawing clearly shows how the mechanism works. I also left out the nut socket.
There is something puzzling about the drawings/depictions of the two crossbows. The handle at the back seems to be a seperate element. It is very close to the revolving nut. The archeological remains also show such a (bone) handle found with the revolving nut. In the drawing by Thomas, this is pretty much the mechanisme of later crossbows, with a trigger being depressed to free the nut. However, the drawings/depictions allow little room for such a mechanisme, as the shown distance between the nut and the square end is rather slight. Then, that handle, which is both depicted and found, is strange, for why extend the stock with a seperate handle!
OK, here comes a totaly new theory on the design of the trigger! What if the handle sticking out the back was part of the trigger mechanisme:?: With a straight sliding bar for a trigger, it would only need to slide back an inch to free the nut. Also, when pushing the trigger forward again, the nut was locked in place, this would allow carefree cocking of the crossbow, as that nut is not going anywhere, as it is underpinned by the triggerbar. To shoot, you aim the crossbow using both hands, one supporting the stock, the other gripping the handle and then just move your hands apart (left or right hand forward) slightly. This would also allow for a steady shot, as not much force is needed to slide back the triggerbar from under the nut. Ahhh, I think I will build one of these someday!
Hmmm, I hope the above is clear (edit: I added a quick drawing to illustrate, using the one Thomas did as a starting point).... Well, rip into this theory :woot:
That's an ingenious theory Robert. It would explain why the bone nut and handle were found, but no iron or bone trigger was ever found. You wouldn't even have to pull the handle back an inch, it could be much much less and the crossbow would still fire (it would reduce recoil to have a "hair trigger" because of the way it was held). The Romans were masters at making existing technology better.
You are right in stating it would be less then an inch on reviewing the measurements of the nut, but hé .... I'm metric. Also, it would be very hard te recognise the trigger as a trigger, as it could just be a short rod of iron. I think I will perfect this design and build a few of these. Put them up for aution on RAT :-)
It's still a well dried quarter log of straight grained ash :-) . First, I need to draw and build one that works, then I can consider selling it or making more.
The theoretical construction also may explain why the retaining lip (where a LOT of the force goes when the bow is cocked) of the found nut is so thin and bone (or antler or ivory) can be used for the nut.
Anyways, I agree, proportionally the stock seems to be about 40-50cm with a 15cm handle based on the haute-loire. Bow is about 90cm. Just roughing those measurements. The article gives measurements for the nut and handle finds, best to go on those. I'd imagine the handle parts found would be at the base where the handle meets the stock. You then pull the whole handle back to fire it.
You have to click on the pictures in order to see them completely!
Quote:However, the drawings/depictions allow little room for such a mechanisme, as the shown distance between the nut and the square end is rather slight.
Quote:.The theoretical construction also may explain why the retaining lip (where a LOT of the force goes when the bow is cocked) of the found nut is so thin and bone (or antler or ivory) can be used for the nut.
I also encountered these two problems, when I attempted to draw a possible reconstruction of an arcuballista. Your mechanism would eliminate mentioned problems, obviously.
Your mechanism would also be relatively easy to make. You would need two holes (one for the nut's axle, one for the trigger) and a rectangular mortise (for the nut). Add a bolt groove, a socket for the bow and a hole for the binding, and the stock is done .The trigger would just be a rod with a handle
Quote:Also, it would be very hard te recognise the trigger as a trigger, as it could just be a short rod of iron.
I made a drawing of a trigger consisting of an iron rod and an antler handle. As the trigger doesn't wear off the nut (unlike the triggers of conventional nut locks), I think you could in fact use iron.
[attachment=7651]ArcubExp.jpg[/attachment]
[attachment=7652]ArcubX.jpg[/attachment]
Quote:Anyways, I agree, proportionally the stock seems to be about 40-50cm with a 15cm handle based on the haute-loire. Bow is about 90cm. Just roughing those measurements. The article gives measurements for the nut and handle finds, best to go on those.
I used the two reliefs, the measurements of the human body and the measurements of the Burbage finds as a guideline. If I would build an arcuballista, the stock would be 50 centimeters long and 4 centimeters wide. The socket accomodating the bow would be 7 centimeters deep. As the drawlength of the bow would be 36 centimeters the distance from the middle of the nut to the end of the stock would be 7 centimeters. The attached drawings show a 8 centimeters high stock for a yew bow 56 millimeters high. If a less higher bow is used, the height of the stock can be reduced accordingly. Said yew bow would be 120 centimeters long. The measurements of the wooden bow were extrapolated from medieval exampples. A composite bow however could be shorter and still reach a drawlenght of 36 centimeters. If the composite bow would be 90 centimeters long (as you suggested), the bow-stock ratio would match the ones from Solignac. The handle would be14 centimeters long and would have a diameter of 27/40 millimeters (parallel part/thickest part). A ron rod with a diameter of 12 millimeters would protrude 10 centimeters from the front end of the handle. The overall lenght of the crossbow would be 64 centimeters.
[attachment=7653]ArcubTopview.jpg[/attachment]
Pretty cool drawings!! Why is the recess to hold the bow in the stock that deep? Also 36 cm drawlength does not seem a lot for a bow 90 cm wide.
There is another thing puzzling me. Neither of the two pictures show the bow being fastened with lashings. What are your thoughts on the way the bow was fastened to the stock. Is there an ancient text that descrides such a lashing and does it indeed apply to this type of crossbow.
