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In reviewing the shot fired yesterday into the rear of our pig’s head, it became apparent that the 183 gram bolt head detached from the shaft at the moment of impact.  The resulting loss of mass caused an abrupt decline in the forward momentum  of the shaft, while the stiff plastic fins acted like a brake as they tried to force themselves through the hole in the helmet.  In previous shots, when the bolt head stayed attached to the shaft,  there was enough forward momentum to strip the fins off as the intact bolt punched on through the helmet.  Of course in those cases the hit on the pig’s head had not been so solid as the one seen here, so I guess in the end it is hard to say how much the loss of the bolt head effected the final depth of  penetration.  Clearly it wouldn’t have made much difference to the wearer of this particular “helmet”.

A dissection of the pig’s head revealed an entry hole one inch to the right of the first cervical vertebrae.   The bolt sliced through the bone of the right occipital lobe and traversed the brain on an upward, diagonal path.    It exited the head by punching through the one inch thick frontal bone, directly in the center of the forehead.   In addition to this, the entire frontal bone was cracked laterally across the forehead for a distance of five inches.  See below:

Also evident was a small  1/4″ hole located just above the exit hole from the bolt.  This was presumably the work of the butcher that originally dispatched the animal with a .22 magnum.  A 2″ long splinter of the frontal bone was lifted off in this weakened area of the skull.   The bolt struck about an inch below the bullet hole, so it is unknown how much this may have effected the overall integrity of the frontal bone.  The exit hole in the skull made by this test hints at a square shape as seen on the Maiden Castle skull.  Clearly,  more testing is needed.

It seems reasonable to conclude that at fifty yards, Firefly is really  just too powerful to punch a discrete and unambiguously square hole in the side of a skull, ala Maiden castle.  The major parameter left to be explored in this matter would be what happens if we turn the power on Firefly way down.  Something on the order of 150 feet per second, half the speed of this last shot, seems like a good starting place.  Because it would take a prohibitively long development process to assure adequate accuracy with such a slow moving bolt at fifty yards,  such a test would need to be conducted at very close range to insure a proper hit on the skull.

I suspect that the most we will be able to conclude from this line of tests is that if a square sided hole can be generated in the side of a skull with a fired ballista bolt,  that will at least hold open the possibility that the Maiden Castle skull could have been perforated by something other than a pilum in some form of battlefield execution.

Wind was ten knots out of the North again today. This time I thought to put a mark on the back of Randi’s helmet.

By this mark I would gauge the success of our next shot, the results of which are seen in the following photo. Range is fifty yards.

Had I not held into the wind the fraction that I did, this shot would have been perfect and the X would be gone. This is the third data point that suggests winds of ten or fifteen knots are having almost no effect on the lateral dispersion of the shots at fifty yards. Yesterday’s shot was done in zero wind and was spot on. Today’s shot, done in ten knots, was also spot on in the sense that the two inches to the right where it hit, was also where the sights were actually held as I tried to compensate for the wind, (the wind apparently having no effect). More data points are needed for shooting in both calm and windy conditions, as well, of course, at longer ranges.

The bolt used in today’s test is seen in the next photo. At 6516 grains, it is an accurate duplicate of the bolts used in the previous two shots.

I didn’t have the chrono set up for this shot, and so there is no velocity reading to report. Clearly it was very close to the 305 fps of the previous two shots, as it shot into the same group that they did.

The bolt ripped through the replica helmet like it was tissue paper, and went on to course through the pig’s head, appearing to smash the thick frontal bone as it exited. I will have to perform a dissection of the head to know for sure. See below:

After breaking the video down into some stills, it became apparent that at the moment of maximum deceleration the bolt head became detached from the shaft, and found it’s own way into the pit (or somewhere), without the shaft for company. The bolt head is currently missing.

It is unfortunate that Firefly cannot be moved beyond the range of my overhead crane yet. Also, it is very difficult to sight accurately if the lights in the shop are left on. Filming Firefly in action, while also showing the hit on the target, is not that simple a thing to do with my current set-up.

Click for mildly, XXX gruesome video: 20111204144528(1)

Not to undercut these results or anything, but this set of tests might be a valuable analog for anyone suspecting that the Romans did battle with swine. ……That is, swine equipped with low grade, replica helmets.

The wind has been at zero today.  I was still dubious as to where Firefly was sighted.  Because testing of this sort is always a kamikaze mission for the bolt involved, there was no reason not to try and extract as much data as possible from what is still essentially a sighting shot.

This time around I added a 1/2″ thick steel plate to act as a final backstop for the bolt.  The idea being,  if there was a complete miss of the pig,  we might still gain some useful information as the hardened steel tip drove into the plate.

Click for mildly gruesome Video:     20111203150004(1)

Specs for this shot as follows:  Bolt weight is 6515 grains ,   head weight 2824 grains,  length 34″, FOC 10 %, velocity 306 fps,  energy 1354 foot pounds.

Porcus was thoroughly thawed out,  having being taken out of deep freeze four days ago.   The jauntily perched trooper helmet was a donation from  Clodius Secundus  LEGIO lll CYRENAICA.  Thanks Randy.  Your helmet is gaining some admirable drainage holes if I decide to use it as a planter.

The bolt sailed through the admittedly wimpy helmet,  cutting a 3″ long,  1/2″ deep furrow in the frontal bone of the pig’s forehead.   A rudimentary incision for inspection purposes revealed that this had left a trail of bone fragments spread along a  5″ puncture wound that traversed under the skin of the forehead up to a depth of  1  1/4″ inches.  After exiting the subject’s head, the bolt went on to shatter a 3″ thick piece of oak.  It then engraved a 2″ long divet into the mild steel plate used for a backstop.  The damage to the bolt head was caused entirely by it striking the steel backstop that was set at an angle to the trajectory of the bolt by approximately thirty degrees.  It was this collision that caused the loud clank sound in the video.

Here is a photo of the damaged bolt head.

And here is a photo of the impact point on the steel plate.

If I can cobble together another Dura bolt for tomorrow when Josh comes over, we’ll have a go at trying for a more squarely placed hit on the cranium.  Our investigations continue ……

A few years back I posted about the nature of visible technology,  and how catapults were an excellent example of a time when the devices humans created were completely transparent and understandable.   The antithesis of this is displayed in a fascinating little lecture by Kevin Slavin speaking at the TED talks.

I am not having a great deal of success getting the above address to post as a link.   If it were a piece of flint I would probably know how to handle it.   A goggle search on,  “Kevin Slavin, how algorithms shape our world”, will also take you there.

There are days when I feel that our efforts here in the Little Catapult Factory are just too  precious and twisted.  I mean, really!  A catapult in a world of mega-powerful algorithms!   A reverence for the visible, disseminated by the sublimely invisible.   It is all too rich.

The bolt seen in the following video was  sheltered from the wind for the last 15 yards of its flight.   The first 35 yards were pretty windy.

Click for the mildly gruesome video:   20111202131812(1).    Range is 50 yards.

Note the black fin falling from the sky a few seconds after the hit.   This type of testing is always a one way trip for the bolt.   If the valuable steel head can be recovered,  I am grateful.

The wind was from the North at an unsteady fifteen knots.  Gusts were probably topping twenty.  The chances of making this shot were inordinately low,  not just because of the strong wind, but because this was my first shot with a completely different weight bolt.  The sights were set all wrong and I could not correct them without first making a trial shot.  Given that whatever bolt I used would almost certainly self-destruct,  there was no reason not to make the attempt on Porcus, even for the first sighting shot.  Against all odds, it worked out.

Here is a photo of the mildly tapered, Dura Europos style bolt that was used.  The head is of the four sided, quadrobate type.  It is made from 4140 steel,  hardened to about 35 Rockwell.

Bolt weight is 6528 grains (423 grams),   head weight 2824 grains,  length 34″ , FOC 10 %, velocity 304 fps,  energy 1339 foot pounds.  Fletching length has been reduced to 7″,  from the 8″ previously used.  Bolt flight was superb, even in the wind.

The next photo shows exactly how the test items appeared after they had tumbled into the shooting pit.  Note the broken shaft buried sixteen inches into the frozen sand.

I have no idea how exact an analog for an actual Roman trooper helmet this modern replica might be.   However,  the bolt ripped through the .050″ thick mild steel like it wasn’t even there.  It then struck the pig’s forehead at an extremely oblique angle,  and went on to explode into fragments as it buried itself into the backstop.  Depth of penetration into the sand was sixteen inches,  the first six of which were frozen solid.   This shot caused a grazing wound of inconsequential depth across the pig’s forehead.  This shows up next to the small dark spot from the slaughter-man,  three inches above the pig’s left eye.  Close, but not exactly the broadside hit I was hoping for.

Tomorrow promises to be calmer.  At least for the weather.

I quote the following from Mr. Basileus writing in the Arbalist Guild:

“That said, I don’t really consider Nick’s ballista a strictly scientific reconstruction, provided the goal is to reproduce what the Romans had. For example, there was no motivation for the Romans to use the vernier plates to increase the spring diameter as Nick does: they could just have built a larger field-frame (and washers) in the first place. Also, the fact that he has had to use high-strength “super” steels in various parts of his ballista (e.g. the arch) would hint that Nick’s machine is more powerful than the original Orsova ballista.”

It is very true that Firefly is not a strictly scientific reconstruction.   She is, I have been told, equal parts science and art, with a bit of mindless irony thrown in to keep things from bogging down in a slew of humourless narcissm. She is just an exercise afterall.

The ballistic data and shooting characteristics  qualify as “science” inasmuch as I have always reported the data exactly as it is generated.   The testing of any particular hypothesis is not always a cut and dried matter in catapult development.   This is especially true when the project being worked on is burdened with so much aspiration;   lofty ideals are often forced to comply with the expediencies of constructing  a whole and functioning machine with modern materials and techniques.   This is where the true art of modern catapult reconstruction building comes in.  That being said,  there are couple of details I would like to respond to from the passage quoted.

(1)  The vernier plates,  (also called underplates or counterplates on wood framed machines) :  Consider that the Orsova artifacts only show four holes in each end cap on the field frames.  Given that it is essential to achieve a minimum of 7 1/2 degrees of discrimination in the washer rotation  (evident by our tuning experiments so far) and it becomes problematic as to how to achieve this without more holes in the end cap for locking the washer in place.   In my judgment,  putting more holes in the washer would weaken it too much.   It follows then that there must have been an additional component to carry said holes, i.e. a vernier plate.

As for just “building a larger field frame”:  well that is just a matter of elegance, isn’t it?  Why make something bigger, heavier and more cumbersome if you don’t have to?  Besides, that would just change the scale of the machine.   Like a dog chasing its tail, you would never know when to stop. The primary premise of the Firefly project has always been to completely maximize the potentialities apparent in the  artifacts,  without changing their original dimensions.   It may well be that this approach leads to a reconstruction that is not at all like the original machine;  but without any evidence to the contrary,  it seems logical to proceed with this doctrine of maximization.   It is surely what the Romans would have striven for.  More power, more accuracy, more reliability, easier maintenance, lighter weight,  a more compact size;  they would have wanted it all.   While Firefly probably falls short of these ideals in any number of ways,  her Vernier plates are at least consistent with this guiding principle.

It is very apparent from my experiments that an iron framed machine of this type would simply collapse under load if it were not for the diagonal struts connecting the field frames back to the stock.   It would certainly not be able to achieve the level of shooting accuracy Firefly has demonstrated, without these struts. That being the case, there had be some place to attach said struts.  Again, a missing component similar to my vernier plate would seem to be the logical solution to creating such an attachment point.

As an aside:   In an interesting example of convergent evolution, we see a similar use of struts on the Big Joe crossbow from OSS fame in World War Two.

But I digress……

(2)   Regarding the “super steels”:    There are no exotic steels used in Firefly’s construction.  Her metalwork is largely mild steel, with some carbon steel used in critical areas like the kamerion.  Simple spring steel was clearly available to Roman armourers.  If it were not, then the famous Roman gladius, or short sword, would have had little utility in a combat situation.  By forge welding together one hundred or so short swords,  the Romans would have had all the “super steel”  needed to build a high powered ballista.  There is no metalwork on Firefly that could not be created in a competent blacksmith’s shop.   (Trust me on this.  I have been a professional in the metal working trades for forty years.   Once the correct design is figured out,  this is all pretty simple stuff to forge out.  The Romans were not exactly slouches in this department.)

All of this leads me to conclude that our humble efforts on Firefly are not anything remarkable by Roman standards.   As mentioned before, if someone could figure out the exact nature of the metallurgy in the original kamerion, that would go a long way to suggesting the actual capabilities of the Orsova machine.  Because Firefly started off with a narrower mild steel kamerion and field frames, that began to buckle under 4500 + lbs  of draw weight, this at least provides an indication of how much stress the original could handle if it was indeed made of just mild steel or wrought iron.   On the other hand,  if the original was constructed with certain critical parts made from spring steel,  …….. well,  you take my point I’m sure.

My thanks to Mr. Basileus for bringing attention to these matters as it afforded the opportunity to explore all this in greater detail.  Like I always say, “it’s all in good clean fun”.

Photo from, Greek and Roman Artillery, by E. W. Marsden.

At the start of this blog I posted the following about the famous Maiden Castle skull:

“For many years researchers had suggested that the square hole visible in the side of this ancient skull from the Maiden Castle siege in Dorset, England, was the work of a square headed ballista bolt.  Recent studies have fired bolts from a replica Skorpion ballista at sheep skulls and concluded that a neat four sided hole would not be the likely wound signature from a ballista bolt. Apparently the dried out sheep skulls shattered into multiple fragments, rather than perforating cleanly. The researchers concluded that this hole was more likely made by the thrust of a Roman pilum (a type of spear),  probably in some form of battlefield execution.  This may well be the case, however the sheep skull experiments do not seem to cover all the variables that might influence how a human skull will react to this kind of intrusion.  Perhaps freshly killed pig skulls would be a more accurate model.”

We have arrived at a point where “a more accurate model” is within of our capabilities.  As soon as the wind stops blowing, and Firefly is sighted in with the new sharp tipped bolts,  we will have a go on the fifty meter range at penetrating Randi’s trooper helmet with our organically raised pig’s head inside it.  Living in the country is so well suited to catapult research.

It should be noted that the series of experiments that is to follow on this blog are basically just reprising the work of Alan Wilkins and his team of researchers that presented evidence in a BBC program that covered the likely cause of the wound seen in this particular artifact.  Their methodology involved firing ballista bolts from a replica Skorpion three span catapult at dried out sheep’s skulls.  To their credit the program forthrightly acknowledged that dried out sheep bone was probably not a good analog for a wet and alive human cranium.  Hopefully our experiments here will address some of those deficiencies by using fresh pig’s heads as test subjects.   The gory details that will  follow in this blog are the inevitable consequence of our mandate to be nothing if not thorough.  Our apologies in advance for any squeamishness this might promote in the reader.   Animal lovers are reminded that no animals were harmed in these experiments.

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