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To the best of my knowledge this catapult project is different from any others you may have heard about.  For a historically defined machine of this class and size, the one you see below is the most comprehensively tested, powerful, long-ranged, and accurate shooting ballista made since ancient times.  No brag, just fact.* Her name is Firefly. This blog is a journal of how she came to be. 

Capture XXA

Click for video: 000142 (2)       Click for another vid:  00017(1)

The impressive work of the Pumpkin Chunkers may seem like an obvious counter to this bold claim.  However,  they are working with an unlimited class of machine that is not concerned with matters of historical fidelity.  This journal details the day to day efforts it took to make a formidable, Fourth Century Roman ballista that did not stray outside the dimensional constraints of the artifacts it is based on.

Like any modern catapult reconstruction, Firefly is not a perfect duplication of the original machine.  Which is hardly possible as there are no intact ancient catapults,  just rusty old bits and pieces, and a few original texts that are inadequate in explaining how these machines achieved their reputedly high performance.

Firefly is in a ongoing state of testing and refinement. Many of you with a bent towards reenactment will no doubt find areas where she is not particularly convincing.  That is to be expected as Firefly is not a machine built primarily for display purposes.  As much as anything, she should be considerd a “proof of concept” shooting machine.  A historical test bed, if you will.   Perhaps polished a little more than is strictly necessary, but that’s a personal issue……

A word about my sometimes flippant tone — I’ve only got so much happy in me for this kind of trial and error marathon.  I find a certain amount of glibness necessary to keep buoyant after so many setbacks. Hopefully it doesn’t belie too much of the actual work.

And with that, here is the continuing saga of Firefly and our new machine, Phoenix…..

Nick Watts,  September 2015


* Believe it or not,  I really would appreciate it if someone would refute this claim.  Numbers, please.  Comments section is open.


What follows is essentially a set of field notes and facetious contemplations.  You will need a sieve.  If this wordy, highly detailed, maze of a blog is not to your taste, please try the following website for a more concise presentation:    

The two postings below will provide newcomers a glimpse into what this project is all about. They are a little older and are presented out of sequence. For the latest postings please go to the menu on the right and check out our other categories. Day one of the project defines the historical origins of this device and is easily accessible by clicking in the archives.   Actually reading through the rest of the days — that will take some stamina….



My old friends, Brian and Frank, were on hand for our first successful attempt at shooting a twelve shot group at Firefly’s maximum range.   They took some nice photos of our set up.  Here we see the newly installed Mk. X limbs just before being put into action for the first time.  (Click to enlarge.)

And next, here is a shot of that space blanket reflector we needed for the laser range finder. (Which worked extremely well, we are pleased to report.)

There happens to be a rock outcropping overlooking our firing line and Brian was able to get a good vantage point for this next video.  It takes some sharp eyes to catch the trace of that bolt across the screen, but it is there.  Click for vid:  20120918143324(2)(1)

From atop the rock, Brian and Frank were able to see the entire flight of the bolt out to it’s 800 yard endpoint.  Apparently, witnessing the scale of that arching trajectory in person is quite impressive.  It leaves me a bit jealous as I’m the muggin’s that always has to operate the machinery.  The most I get to see looks something like this:  Click for vid.   20120918144301(1)

But I ain’t complain’.  At least we got some data this time.  These next two charts show how the dispersion of the shots appeared when we finally went downrange to take some measurements.

This first one shows the overall range of the shots in yards and their dispersion to scale.  Bolt weight is 521 grams.  (Click to enlarge)



And this second image shows the dispersion of the shots up close and to scale, with the shots numbered in the sequence in which they were fired, their distance from the firing line, their muzzle velocity,  and the angle that they were found sticking in the ground. (Click to enlarge)



A quick analysis of these 12 shots reveals the following:  Shots numbers 1, 2 & 3 can be discarded when determining the overall group size for the simple reason that the wooden wedge I used to secure the tail of the machine had been inserted from the wrong side and fell out during use.  (Although 2 & 3 do seem to have all fallen very close to one another.  Something is going on here, so maybe the machine didn’t shift position after all.)   Anyway, the wedge issue was easily fixed and shooting resumed without further incident.   Shot number 7 we can call a flyer due to gusting winds at the time of firing.  The remaining 8 shots can be considered valid from a shooting standpoint, and basically fell inside a 60 foot radius.    That is just about enough precision to hit your average three story Mc’Mansion  at almost half a mile.  Not bad, but I know we can do better.

Before going on this field trip I only had time to put four shots through Firefly after the new limb installation.  I suspect the bundles are still moving towards a stable equilibrium and that this is causing some of the velocity variation we are seeing in the above chart. Looking at the shots in numerical order it does seem as if there is a gradual decrease in velocity and range that tends to stabilize at the end of the string.    Unfortunately the chrono showed error readings with the last few shots, but if we consider only the last five consecutive shots it is clear from the chart coordinates that the group size shrinks to something like a 30 foot radius, which seems pretty darn good to me.  I certainly wouldn’t want to be standing inside that circle if some hotshot ballista crew were taking potshots at me from half a mile away.

Today’s tests show that this level of precision would make machines of this type effective against massed adversaries to the full extent of their range.  I have no doubt that with lighter bolts of the Dura pattern,  Firefly’s  maximum range could exceed 1,000 yards. With a bit more tuning the heavier 521 gram bolts we are shooting here should clear 850 yards with ease.  Given how hard it was to extract the bolts from the ground, and considering their average 10 1/2″ of penetration into the packed and dry topsoil, it seems clear they would have been brutally effective on cavalry and lightly armoured troops.

Also of interest:  The shooting session had varying winds from zero to eight knots and was less than ideal for our purposes.  Because time was limited for my two compatriots, we took to the field with a minimum level of tuning on the new Mk. X limbs. There appears to be some asymmetry in the way these limbs are tracking in their planes relative to the deck of the machine, the starboard limb rising perhaps an inch high and the port limb a similar amount low. All fixable by more tuning.  Apart from that, the limbs behaved brilliantly, with no observable curvature at full draw, and sacrificing only perhaps 15 fps from the 1/2 pound increase in their weight from the spreaders and extra bindings etc.  This we should be able to make up, and more, when we final tune the machine.  The average velocity with the 521 gram bolts we are using in this test is 308 feet per second.  All shots were fired with a launch angle of 44 degrees.

And to give some more scale to the proceedings, here is a video with Brian acting as a human laser reflector as we map out the position of the bolts in our group.  Click for vid:  20120918151232(1).   Frank was kind enough to drive back to the truck and retrieve my binoculars that have an internal compass in them.  This made measuring the angles out to each shot a snap, and combined with the laser range readings off Brian’s chest, plotting the locations of these twelve shots only took a few minutes.

In this next video we can see the laser range finder in action as it takes a reading back to the reflector at the firing line.   Click for vid:  20120918150853(1).    The rock outcropping mentioned before is visible on the horizon line of the field we are standing in, just to the right of center screen and at the end of the video.  For reference, that tiny dot to the left of the outcropping  and in the middle of the screen, is the truck and radar reflector.  Can’t see it?  Well it looks a very long way away when seen in person too.

Here is a quick pan across the field of carnage.  click for vid:  20120918153451

And finally, a couple of photos of the new Mk. X limbs sharing the full draw weight of 5,000 lbs.

Note the lack of  bending as compared to those snapshots of the Mk IX’s from a few days ago.  I wonder if it is a good thing that shooting Firefly is not quite as terrifying as it used to be.   No doubt the Catapult Gods will keep me apprised about all that.

This stalwart group of time travelers has just braved wind and cold and bumpy roads to witness this Sunday’s ballistic recreation from the Fourth Century.    On the left is George Baumgardner, on the right is Dr. Walter Henze, and in the middle, our beloved and intrepid lab assistant: the Rebecca.   Richard Rough, who has been out on these jaunts with us before, was also present to observe our attempt to poke holes in the sky and bring home some fresh data.

The small size of this group of shots is remarkable.   They were all fired consecutively from a carefully positioned 44 degree launch angle.  George and Walter’s bolts are only 13 feet apart, while the average range for these  shots is  790 yards.    So at this range Firefly is tossin’ them into a 20 minute of angle group.  This is exactly the kind of performance I’ve been dreaming about these last four years.  To the gunnies out there, 20 MOA at 800 yards is pretty lame to be sure, but I don’t recall anyone recording that kind of performance from a modern reconstructed ballista before.

Before we get to the data, here is the only video we could get of the parabolic flight path of a 521 gram heavy bolt.  I believe it is that same bolt that Walter is standing next to.  The footage shows only the first two seconds of it’s ten second journey, so it takes some pretty quick eyeballs to see it at all .   Click for video:  20121104130331(1).

Here is a snapshot of the three types of bolts we tested today.  The red one weighs 521 grams and is 36″ long.  The blue is 340 grams and 29 1/2″ long.  The orange is 276 grams and 21 1/2″ long.

Here is a scale chart showing an overview of all the shots in today’s shooting.  Click to enlarge.

And here is a closer look at the actual landing zone for the three different types of bolts we were testing today.

The reds, on the left, are the “heavies” we’ve been testing over these last few postings.  They form themselves into two distinct groups.  Numbers 1, 2 & 3 were fired at the beginning of the session when we had a 6 mph tail wind; while shot numbers 4, 5  & 6 were  fired at the end of the session when the tail wind had dropped to 3 mph.  This latter group is the one seen in the above photo that fell inside a 13 foot diameter circle.   It makes sense that the higher wind speed caused the greater dispersion of shots 1, 2 & 3.  Average velocity for the “reds” was 315 fps.

The oranges, on the right,  are the same orange bolts we used on the last field trip and can be considered functional duplicates of the famous Dura Europos bolt from the Third Century.  What caused them to string out in such an even fashion is unknown.  We’ll blame the wind.  I suppose, to a certain extent, we should also thank the wind for helping give us the longest shot Firefly has made to date:  947 yards.  It looks like it is going to take either a hefty gale from the south, or at least some more innovation, to get us striking beyond the 1,000 yard mark.   (Which, of course, is a meaningless,  arbitrary goal we probably shouldn’t be spending too much time on…. more — blah, blah, blah.)  Average velocity for the “oranges” was 360 fps.

The blues, in the middle, are something new.  They are the same as the orange Dura Europos bolt, except 6″ longer, and with heavier heads that boosts their weight to 340 grams.   They very neatly dropped themselves into a 20 foot diameter circle at an average range of 934 yards.  Not bad for the new kid on the block.  Average velocity for the “blues” was 348 fps.

Also of interest is the increased depth of penetration now that the ground has been thoroughly soaked with rain.

This heavy “red” bolt  has an overall length of 36″ and  has buried itself  to a depth of 18″.  When the ground was dried out over the summer these same bolts penetrated 10″ on average.  It should be noted that the ground on our firing range has a uniquely homogeneous consistency with no rocks or other anomalies.  It is some pretty fine grained stuff and, now that it has been wetted down, the bolts show amazing consistency in how far they penetrate.  The “blues” penetrated 15″ , and the “oranges” did 14″.   I am not sure what any of that means, but we record the fine quality of our target medium in deference to the large amounts of “moondust” we all must eat when the roads around here get dried out and driven over by big trucks with lumpy tires.   More yum than you can possibly imagine!

And, finally,  some photos to brighten up the page.

A “blue” looking pretty for the camera at the 895 yard mark.


And demonstrating the dispersion of the three shots in the “blue” group,  in the foreground we see George standing next to a bolt at the 904 yard mark,  while Walter and  myself are standing by ones back at the 896 yard mark.


And here the humanoids mark  the longitudinal positions of those lightweight orange bolts, the furthest of which made it out to 947 yards.

(Sorry! No photo of you Richard.  Are you camera shy?)



I have decided to put the Phoenix project on hold for the rest of the summer as there are more pressing concerns right now re: house building for my daughter.   Many thanks to those folks who have taken an interest in this project, and I’ll be back at it probably sometime in November.   Email dead for the duration.  Cheers,  Nick.


Two degree, counter-posed wedges, seem like a good starting point for our first attempt at an adaption of Mr. Philon’s souped-up torsion machine.



Those extra long wedges will be trimmed to length after the fine tuning is completed.   For experimental purposes the washers will also be capable of fine rotational adjustments.  There are 16 holes in the washers, each 22.5 degrees apart.   There is a 3 hole pattern in the vernier plate*,  with each hole set 15 degrees apart, so that the washers that control spring rotation can be locked down every 7 1/2 degrees.   The second set of three holes is so that there can be two locking pins for each station.   Next will be the radiused pusher bar that sits on top of the wedges.  And then on to springs and limbs.


*Counter plate, or counter washer, if you will.  I prefer “Vernier plate” as the Ampurias finds, whose geometry we are mimicking here, seem to contain the first deliberate use of a logarithmic scale similar to a modern day Vernier.


The notches and locking holes on Phoenix’s washers are complete.




Quite the labyrinth of mechanical possibility ain’t it?





Except for the locking holes and notches for the crossbars, the washers are about finished.




Why “modiolus of doom”?  Because right now I need some kind of hairy provocation to keep this project alive.

Time has a way of elongating, right before it runs out.  You think you have all the time in the world to finish something, and then …. Blam!… you’re done.  The meter runs out.  Which leaves the Catapult Gods smirking at you for the rest of eternity.   Damn their temporal omnipotence anyway!

Also, my laptop is getting hinky.  Email is down.  Correspondence not possible until I get it fixed.

…If I get it fixed.  A hermit-like submergence seems somehow linked to my ability to self-motivate.  Go figure.


I tried to utilize the web to figure the optimum size ratio for an ancient Roman torsion spring, (e.g. it’s length vs. it’s diameter).   The varying opinions quickly got me disoriented.  It was all a bit of a muddle.

So I’ve decided to use a “cut the chatter” kind of strategy and act from what I know already.  Because Firefly’s springs have proven themselves highly successful over the years, especially with the short limb rotations we are currently exploring, I will use that same spring ratio on Phoenix.  That is:  6.6 times as long as they are wide in diameter.  6.6 to 1, if you will.

Firefly has not had her springs adjusted in the last 4 years and has always shot a very consistent 316 fps, plus or minus 10 fps.  Her power is enough to shoot a 520 gram bolt 800 yards.  I believe that if there are gains to be made in performance they will be found somewhere other than the spring ratio.  “The spring ratio is not to be monkeyed with!”,  says my executive function.  A voice that demands obedience from the other functions that keep this project puttering along.

Developing Firefly’s torsion springs was not an easy process.  When gains are hard-won, one tends to be less flippant in considering potential “improvements”.  Counting one’s blessings can make a lot of sense.

Here is a preview of one of Phoenix’s washers, shown in cross section.



The new washers will be 2  3/4″ inches long.  This will make Phoenix’s springs about 16 1/2 ” long, and with their 2 1/2″ diameter, they will be 6.6 times longer than they are wide.

And so, in a gesture of mathematically precise conservatism, Phoenix’s spring ratio will be exactly the same as her older sibling, because, well … why not?  That’s how pleased I am with the performance generated by Firefly’s spring ratio.  No changes needed for Phoenix in this area.

‘Nuff said.

Many thanks to long time contributor to this blog, Mr. Charles Fink, for sending us some handsome billets of Bois d’arc timber from Texas.




The unique properties of this wood (also known as osage orange)  will make some exceptionally strong ballista limbs.  They have been cut recently and Charles waxed their ends to help prevent checking as they dry out.  I have stored them in a cool area of the shop so that they have every chance of seasoning properly over the next year or so.

The authenticity police will no doubt censor us for using a New World wood on one of our Old World mechanisms, but, given the relative difficulty of obtaining high end timber these days, I am not overly concerned with their typically manic ravings.   The Romans must have had an enormous selection of premium timber from the ancient forests of their far flung empire.  We moderns are at a natural disadvantage when it comes to being choosy about the wood we utilize in these reconstructions.  Allowances must be made.

That being said, Phoenix’s first set of limbs will be made from white ash, just like Firefly’s.  All very authentic and tickety-boo.

It is important to let the new billets from Texas dry out slowly and completely before fashioning them into limbs.  Thanks again Charles!  They are some truly beautiful pieces of wood.  Just the right size for Phoenix and unbelievably straight grained for this species.

Mr. John Payne is currently the tip of the spear with his wedge machine efforts on Vlad.  (That’s, Vlad the Impaler, of course.  Cool name for a remote skewering device, huh?)



Some serious iron frame wedgies going on here.  Make those strands work for a livin’.

This is capital work!  Nice and straight on the springs too.  Just like Mr. Philon ordered.

I am hoping John will be able to make a first thrust at this whole question of “balance of power transfer”.    Wedge balancing a ballista is the game.  Doing it in a way that generates lots of power to boot, is the trick we must master.

Meanwhile I am setting up to cut out Phoenix’s washers and vernier plates.  Chips can fly in earnest next week.

And a slight pause ensues as I grub around in trenches to help build a house for daughter dear.


Meanwhile: Rebecca writes a limerick about everyone’s favorite canine ……

“There once was a doggie named Oona, who wanted to go to the Moona, the rocket’s a dud, it fell over thud, and everything went Kablooma!”

I suspect my wife is a tad psychic;  foreshadowing our national election with dogly doom.

And that’s all the news fit to print up here in the Okiedokes.  Our benign little arms race should resume shortly.




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