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I am very pleased to report that a fellow Washingtonian is working on another version of the Orsova ballista.  His machine is still in the prototype phase but it has already done some preliminary shooting.  Currently, like all decent catapults, it is being upgraded.  Here is the Orsova ballista made by Mr. John Payne of Sumner Washington.

 

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John has an abiding interest in ancient history, and as a talented fabricator with the gumption to give ballista-ing a go, promises to bring a fresh look at the mechanical secrets of the Orsova artifacts.  Perhaps John’s machine (as yet unnamed) can meet up with Firefly.   They could discuss why two torsion freaks had brought them into existence in the first place.  Is it something in the water in Washington State? Perhaps we could get Jay Inslee to send us to Rumania so we can do a proper job of getting nose to nose with the Orsova finds.    It could be one of those boonydoggles,  hands across the water, historical connectedness or something…..

But seriously,  nice work John.   There are a few of us that appreciate what it took to get this far.

P.S.  I haven’t forgotten those dimensions you wanted.  Give me a moment …

Limbs are 2″ thick white ash.  The limb irons are an important feature.  See archives, April of 2012.

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I’m going to have to double down finding a soft hillside or embankment to catch the bolts as we do this 100 to 300 yard testing. If there are any locals brave enough, or bored enough, to be reading this interminable blog  — I’m getting antsy for data.  Moondust would do. And not too many rocks.  Just something to decelerate the bolt within a foot or two after impact. And big, like a hillside 20 feet high, and with a range attached,  500 yards would be nice, but a couple of hundred would get things started…… and, as long as I’m dreamin’…… something with a coffee maker, and a chaise lounge …… and a young assistant with a good back ….and knees …. knees would be good…

But seriously, it’s a particularly bad fire season this year, level three evac. and all that.  Shooting will have to resume in the fall.  Firefly is not in the least pyrotechnic, but I don’t need the rep of being out shooting any kind of anything under conditions like these.  Pesky old fire season.

For a long time now I have wanted to do some serious accuracy testing at 100, 200 and 300 yards.   Unfortunately, the place I found for today’s shoot had a backstop loaded with rocks that were hidden in the sand. My bolts and that hillside really did not get along. The hardened steel tips are undamaged by their ordeal, but the bamwood shafts shattered in many places.

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The style of shooting I used in today’s jaunt could be best described as standing offhand.   There is no rear support for the machine other than my shoulder.  Where my shoulder goes, the machine points. Here is a video where you can see the fluid nature of Firefly’s aiming potential.  (The weight bearing down on my shoulder is about 20 lbs.) Click for vid:  00014(2)

And here are today’s shots in order of appearance:

(1) The target at 150 yards is a piece of 1/2″ plywood 24 inches square and painted white. The first shot was made with Firefly’s peep sight set at something that was just a wild guess.  At 150 yards the first shot hit ten feet low and to the right three feet.  Richard reckoned the flight time at 1 1/2 seconds.  My mental ticker estimated 2 seconds.  (Must bring a stopwatch next time.)  Muzzle velocity with 520 gram bolt was 305 fps.  (I guess that makes Richard’s brain clock, spot-on)

(2) A sight adjustment had the second shot strike just beneath the bottom edge of the target, and a few inches from it’s right hand edge.   (This is the shot seen in the above video.)

(3) Another sight adjustment and the third shot hit one foot low and six inches to the left of the plywood square.

(4) After another sight adjustment we hit a couple of inches away from the left hand edge of the plywood and in line with it’s lower edge.

(5) Yet another sight adjustment and, bingo!  Click for vid:  00017(1)(1)

(6) With the sixth and final shot I omitted making a change in the sight position and decided to use a little Kentucky windage to try and center the shot better.   It went high and right by a foot.  I figured my allowance had been a tad enthusiastic.  In any event, bolts were shattering on that hillside at an alarming rate, so I called off the proceedings.

Even with all the sight changes that were made, it was possible to see the shots from the machine respond fairly precisely to the adjustments I was putting into the rear sight.  My sense is that she will shoot into a one foot circle at that range.  But that, of course, is something we’ll have to prove with more rigorous testing.

Clearly, a better hillside is in order.

And, finally, Oona shows her stuff when it comes to bolt retrieval.  Click vor vid:  00015(1)

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Back in the day  (20 odd years ago) I gained a bit of experience shooting different types of bolts out of this old fellow. It was my first machine and I called it the “Gallwey” .

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The bolt seen here  does not project through the opening in the box frame.   Shorter bolts like this can tend to make the shooter a tad squeamish when it comes time to pull the firing lanyard.  A machine with unbalanced thrust in the spring bundles could easily cause a short bolt to  jump it’s groove.  If it hit one of the stanchions in the box frame, parts of a shattered bolt  might bounce back in surprising and unpleasant ways. It’s all great fun ….. until somebody puts out an eye……

And so, we might coclude that conventional outswingers, of the type seen above, are not  ideal for use with shorter bolts.  Now why would the Romans be interested in shooting shorter bolts like this? Or, for that matter, really short bolts, perhaps half the length of the one seen here? (Ref: Dura Europos bolt dimensions, archives, Dec 2008)   If you are trying to develop a precision sniping weapon,  short bolts have many advantages.  With a properly designed short bolt (i.e. not a long javelin type, something maybe 18 to 36 inches long) you get the following: higher velocity, flatter trajectory, better aerodynamics, greater range, better penetration due to the reduced cross section, and because it is so stiff relative to it’s length, the issues of spine that can beset longer projectiles, are virtually eliminated.*  On this latter,  I have many times witnessed the kind of oscillation than can occur in a long and under-spined  ballista bolt/javelin. Unless they are of large enough diameter (and therefore, unduly heavy) longer style shafts tend to buckle under all that power and get a case of the wobblies.  Very underwhelming indeed.

So, all in all, my experience suggests that a relatively short bolt, of appropriate mass, is a better projectile for making picked shots.   As a work of experimental archaeology, Firefly is purpose built to explore Roman sniping capabilities.  In that role,  flat trajectory* may not be everything, but it’s pretty close in my book.

Which brings us to the virtues of inswingers.  I have done extensive shooting with both outswingers and inswingers for a couple of decades now, at power levels guaranteed to put a sizable dent in my noggin if something goes wrong.  I can only say it feels a lot safer using an inswinger when one is shooting short bolts.  There are no stanchions for a misfired bolt to crash into. Knowing any unpleasantness will be cast harmlessly out the front of an inswinger, does wonders for reducing that pesky old flinch factor that can disturb accurate shooting.

*  And let’s not forget, with short bolts the storage and transport of ammunition is more efficient.   Short bolts would probably be less expensive to produce given the smaller amount of material they use in the shaft and head. Also, there is less chance of the shafts warping.  Short bolts would be harder to see in flight and, therefore, less easy to dodge.  Short bolts rule says the quartermaster.

*  “Flat trajectory” is a relative term.  We are not talking about rifle ballistics here.  After all, Firefly is really just an overgrown crossbow, not a 30’06.

I have been asked, not for the first time, how much would I be willing to sell Firefly for?  I provide my usual response.

 

 

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The purpose of today’s test was to see if we had anymore waggle tails.  Pleased to report they are gone.  Suspected cause of the two we had last trip is that the machine’s spring bundles had to settle down again after being mothballed for two years (it was the first two shots of that previous outing that were errant)

 

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There are 4 shots visible here and they all fell into a 35 foot circle.  The center of the group is at 760 yards.  A fifth shot could be called a flyer because it ended up 40 feet to the right of the group shown.  As usual, the bolts are my 520 gram “heavies”.  Velocities in fps, as follows:  322,  error, 316, 315, 302.   I had applied a brand new serving on the string and I think that is why we were getting higher speeds at the start of this string of shots.  Once it had abraded a bit the speed came down closer to 300 fps, which is normal for the settings I am using.  These fluctuations are very minor in the overall scheme of things and clearly did not mar the group size by much.

More remarkable is that this group was shot in a relatively high head-wind (15 mph, gusting to 20).  Before today I would never have thought it possible to do this well when the wind is up that high.   That it was a head-wind rather than a side-wind must be relevant; no way it could do that with a side-wind.  I am very glad Bob and Jane Thompson were there to witness it. Otherwise it would  sound like some tall tale, and that just ain’t my thing.  Here is a video of all the high drama as seen through the eyes of Bob and Jane.  Time stands still when the bolt is in flight.  Click for vid:   00017

And not to be left out,  Princess Oona seems to be taken with the proceedings.  Fetch the bolt girl…..  yeah, it’s out there 1/2 a mile, good luck with that….  00021

Bob and Jane inspect some Dura Europas bolts.  The blue bolt can go 900 yards and the smaller orange one can hit 1000 yards when it has a light tail wind.

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Today we shot Firefly for the first time in 2 years.  I was able to get good velocity readings on all 5 shots.  Those are as follows, consecutively, and in feet per second :  307, 304, 304, 313, 301.  The bolt weight was 521 grams.  These speeds are exactly the same as we were getting before she was put into storage; so it seems fair to conclude that, at least with nylon springs, there is no loss of performance due to the torsion springs being kept in an uncocked, yet pre-tensioned condition.    Sitting in storage for that long did not effect her performance at all.   Firefly’s feelin’ frisky again.

Here is a video of my dear old friend Tony Laurent, just over from New Zealand for a visit.   Click for vid:  20150708094923    I had just managed to break the cord that holds the front sight and Tony is checking to make sure his old mate has not lost all his marbles yet.  (“Yet” is a long time, right?)  And now the NZ contingent witnessing the main event:  20150708095008(1)(1)

The first 2 of these 5 shots were waggle tails, and although their muzzle velocities were consistent with the rest of the shots, the wobble in their flight clearly reduced their range by 20% or so.  In this informal test run the machine was elevated to 40 degrees rather than 45 and so, in addition to that pair of waggles, the overall range of all the shots is about 100 yards less than usual.  The two waggle tails naturally fell quite short at 559 yards and 628 yards.  The last three shots fell neatly into a 40 foot circle, the furthest making it out to a tepid 683 yards, again due to the reduced elevation (I keep saying that, don’t I?).  The wind was very mild, perhaps 1 or 2 mph.

I am anxious to to do more formal shooting for group size at 200 and 300 yards, however, until the waggle tails are eliminated there is not much point in that.   On our next outing we will see if the problem is with the projectiles themselves, or if the machine is misbehaving somehow.  I suspect the former.

Sure hope the CG’s don’t become aggrieved at the temerity of that prediction….

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The brothers Laurent seemed to dig it all.   Some definite ooh’s! and ah’s! from that quarter when shooting commenced.

Just ordered this little truck crane.

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It’s time Firefly stepped forth from her usual bed.

Not at all related to our catapult projects, comes this equine distraction I cooked up for our local theater group.

Photo by Walter Henze.  Truly a candid shot because we just had the horses stacked up for rehersal when someone happened to open the back door for ventillation at the same time Walter came by.  Nice work!

There are six of these kinetically animated hobby horses for our production of Cat Ballou.  While they are all equipped with coconuts to make clipity-clop sounds, only Rudolfo  (second from the right and also seen in this next video)  has the ability to emote dynamically through his carpet head.

click for vid:  Rudolfo

And also  a puppy…. my kingdom for a puppy.

This is Oona.  She is a well bred German Shepard with pure German and Checkoslovakian bloodlines.  She is just 37 days old and this is her first trip outside to romp around in the grass and cast fretful glances at all the new sights and sounds.  Find the bolt Oona!  Find it girl!   Ruff-ruff….

Beyond making sure that obvious parameters like the draw weight and draw length are the same between our two model mangonels, there are some subtleties to this experiment that need to be considered.

If we utilize ball-bearing races between the washers and the counter-plates, that should remove enough of the erratic, frictional element to make putting a spring scale on the end of the washer tightening wrench a viable technique for getting torque readings on the pre-load tension of the torsion spring.  Thus we can garner more data on the sinew/nylon dynamic. (And then again, it may be just as valid to compare the pre-tension directly off of draw weight readings taken just as the arm starts to move off of it’s impact buffer.   This is only about comparison.   The KISS  principle is everything.)

It will be important to make suitable gauges to insure that the volume of  each of the two springs is as nearly identical to one other as possible.  Nylon and sinew have different densities,  and so weight is not a good comparative measure.   Besides, the limiting factor in fitting a spring into a field frame is clearly the volume, not the mass.

The larger we make these models the more accurate they will be as analogs for full sized machines.  The nylon powered version will be easy enough to prepare a spring for,  however, the sinew spring  leaves me feeling greedy for more elk backstraps to process. When it comes to scale: the more, the bigger, the better.

While we can make the models very accurate dimensionally to one another, and situate them securely and level for the testing, that does not necessarily prove that the initial launch angle of the projectile is the same between the two machines.   For this we will need the video camera and some kind of graduated backdrop to film against.

There is going to be a fair amount of work in making the models for this comparative analysis between sinew and nylon.  Because our approach is that of an actual bricks and mortar model shop, rather than just mathematical modelling based on a variety of assumptions about modulus of elasticity and permanent and temporary deformation etc, etc., it follows that we must be as scrupulous as possible in how these little wood and steel torsion engines are  designed and constructed. The same is true for how they are tuned and tested.

If we tune and perfect the shooting of the sinew based mangonel before finishing up the nylon spring,  this will allow us to know exactly what diameter that latter should be when it has had it’s pre-tension applied.  Proper sequencing, like this, will obviate any concerns about the  “tension/diameter shrinkage” ratio, and insure that the two different springs have equal volume.

We only aim to predict that if a competently rendered,  modern reconstruction that is powered by nylon, could shoot a given payload to a  range of X, then all other things being equal, it would likely shoot that same payload to a range of Y if powered by sinew.  Trying different values of arm rotation, and also different levels of pre-tension, should tell us a lot about the performance envelope of both materials.   That is all this about.  It is very important to define the focus at the outset.

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