The Ballista

Firefly is the kind of muscle intensive device that would benefit greatly if served by a crew of athletic young technicians, rather than ….. well…..me.   The ancient Lightning ballista, referred to in previous posts, was apparently wound up by a couple of dudes applying themselves to a pair of spoked wheels.  No doubt a couple of young Schwartzenegger types were chosen for this task.

The wide spacing between the winch sprockets, means that Firefly will have plenty of room between the two cocking levers for a couple of stout fellows to operate.   The finishing details on the winch could still benefit from a good old brainstorming session on body mechanics and crew dynamics.    Sounds fancy, don’t it?  Perhaps I’d better get some help:

Firefly is having a good old think about what she would prefer in terms of a pit crew.

Goofy, freaking project.

The Rebecca has rendered an opinion on the new stand.

“Nice…”, we are told, “… but if it gets any shinier it will detract from the machine itself.”   This is the problem with with being mildly OCD,  you can never quit fiddling with the background.

Messing around with details, I managed to get the trunnions cut to length and capped to restrict lateral movement.

Firefly’s balance is easily adjustable within a range sensible for good shooting.   The square headed nuts are a concession to modern fastening techniques and the need to disassemble the machine as required to make progress on new designs.    From what I’ve seen of Roman metalworking,  it would be pretty easy for them to use heavy rivets in place of the nuts and bolts seen here.    When we finally settle on an ideal balance point, perhaps I will make up a simpler, non adjusting version of the trunnion bracket.  Occam would prefer that;  parsimonious little fashionista, that he is.

As this halftime show continues, the reader should not get too discouraged for fear the main event will never arrive.  Shooting is relatively near, at least in catapult time.   I have been counseled by the Immortal Catapult Deities that under no circumstances am I to have a go at using the new hand winch until the cocking levers are finished to the  Nth degree, whatever that is.  It’s an eat your brussel sprouts first kind of thing.  These cocking levers, with their spring assisted pawls, alloyed steel shanks and hickory staves,  are going to have a very high opinion of themselves.

Here’s praying they work as well as advertised.

From the description rendered by Mr Anonymous of the Lightning Arrow Firer that I posted a few days back, one thing seems self evident,  Mr. “A” was deeply impressed with the machine that he saw demonstrated along the banks of the Danube.

Now it may be that this shy and ancient author was the type of fellow who was easily impressed.   On the other hand, in the late Roman empire,  Mr.  Anonymous probably had plenty of opportunity to witness all types of torsion catapults.  That he should call such special attention to the “lightning arrow firer”  as: “….essential for the defense of fortifications, is superior to any others in velocity and power”,  says he at least believed that this new iron based machine was an improvement over any of its predecessors.   It is interesting that he mentions only “iron” and “sinew” as construction materials used in the Lightning.  Probably the stock was still made from wood, but it seems logical to infer that the machine he is describing used much less of this material than previous models.

Superior performance, not much wood,  that’s a strategy I can sign up for when making powerful torsion engines.  The simple truth is that a ballista made largely from timber,  no matter how fancy the joinery or shock absorbing scheme,  is always going to be  more prone to splitting and breaking under sharp shock loads than  a well designed iron based machine.  It seems that after centuries of development the Romans finally figured out that  wood was an inferior material for making the more highly stressed portions of their catapults.

The guild of wooden catapult makers will probably have a major grumble at that one.   When they get too loud, I will remind them that by “iron”  we also mean, of course,  steel.

…. Zing!  Is that a chisel quivering in my door jamb?

Now that she’s on a stand,  Firefly’s  ability to quickly change her incline  has lead to the need for some positive stops on the rails of the steel bolt groove.    If I am not careful to secure the trigger assembly it has a tendency to run down the rail and clobber the wood when I swing her into an upward pointing position.   Some superficial splits in the wood shoulder at the end of the bolt groove have been repaired with epoxy.    At least with the ears seen below,  Firefly will suffer no more such damage as the result of my clumsiness in managing gravity.   On a project like this, the gravity police  enforce obedience just when you least expect it.

tlbtlbtlbtlbtlbtlbtlbtlbtlbtlbtlbtlbtlbtlbtlobtlbtlobtlbtlbtlbtlbtlbtlbtlbtlbtlbtlb

Teddy wants to know when his  ride will be finished.  Impatient little bear.  There is no hurry.  Don’t you know that the having of a thing is not always as satisfying as the wanting of it might seem to indicate.

Until Firefly came along, Teddy had no idea that he was left eye dominant.

Silly bear.   Didn’t they teach you anything in school?

The chalk scribblings of the Lady Rebecca can be seen clinging to Firefly’s nose.  Something about an all seeing eye.   I will have to consult with the Catapult God’s to see if such a thing is to their liking.  Can never forget the Origins.  They control everything.

There is something odd about this photo.  All of a sudden Firefly looks like a table top model that somebody has photoshopped into my shop.  Don’t believe it!  She’s for real alright. The time has come to make her cocking levers.

________________________________

….. well that last bit sounded hopelessly corny didn’t it?

You could just change it.

…… Nah.   Sometimes I like having a  shoe around with dog pooh on it.  It keeps me on my toes.

You’re an idiot to publish something like that in your blog.

……. Not if one of the reasons for the blog is to push inhibition into a corner to promote a deeper wellspring of creative thinking.  We didn’t get here by taking tap dance lessons,  you know.

Navel gazer!

…… Armchair general.

Well here’s a guy who’s obviously pleased with himself.    Click for Vid., 20110203114847

From Marsden’s treatise, “Greek and Roman Artillery” , we copy the following translation from the ancient Latin regarding the “Lightning” arrow firer.  This description from the fourth century is by that renowned scholar Mr. “Anonymous”.  (Curious how he keeps popping up through out all recorded history.)   Anyway,  here is what he has to say about an original machine that he had apparently witnessed in operation:

“It has been discovered by practical experience that this type of ballista, essential for the defense of fortifications, is superior to any others in velocity and power.  When an iron arch has been fitted above the stock, along which the arrow is projected, a powerful sinew rope is drawn back by means of an iron hook and, when released,  it propels the arrow with tremendous force at the enemy.  The size of the actual machine does not allow this rope to be pulled back by the manual exertion of the soldiers;  but two men, one to each of two wheels, draw the rope to the rear by pressing against the spokes in a rearward direction,  since mechanical force has been obtained to match the enormity of the task.   A roller- device now elevates and now depresses the machine, as may be necessary, in order to direct its missiles higher or lower.  This remarkably clever demonstration, a combination of so many different components, is directed by the control of one man only at his leisure, so to speak  —  control confined simply to loading the missile ready for projection; this is apparently to avoid the consequence that if a crowd of fellows was engaged in manning it, the ingenuity of the device would be reduced.  A missile projected from this engine, comprising so many important and clever devices, travels so much further that it has even the momentum to fly across the width of the Danube, a river noted for its size;  it is called the Lightning ballista and,  by its name, gives evidence of the effect of its powers.”

There are some interesting parallels between Firefly and the Lightning ballista as described by “Anonymous”.   The Fourth Century AD when this passage was written and the location mentioned along the Danube are both consistent with the Orsova find that Firefly is based upon.  Likewise, the potential for one man to aim and fire a machine like this is clearly demonstrated in the video at the beginning of this post.  The “roller-device”  that Anonymous describes to elevate and depress the machine is particularly interesting at this point in our project as I am about to complete the counterstay and prop upon which any elevation adjusting mechanism would likely bear.   In his footnotes,  Marsden comments that he took this “roller-device” to be the universal joint seen on the top of the stand, but this hardly seems compelling given that the universal joint had been in use on these types of machine for more than 700 years prior to this description, and would hardly provoke comment as something new and ingenious by the time the fourth century rolled around.   Also, the exact wording of “now elevates and now depresses” would seem to indicate that the “roller-device” causes the machine to elevate or depress, and not merely allow those functions to occur as is the case with a universal joint.  Now clearly these are all nit-picky little points, and whatever it was that Mr. “A” had in mind could easily be lost in translation; all that aside,   there is another factor that my own experience with these machines suggests is vital for accurate shooting.

We first need to understand that there are two basic styles of aiming and firing a machine like this.  They are: (1) shooting in an unsupported offhand manner as shown in the preceding video, and (2) shooting with a rest in a more deliberate and precise manner such as a sniper might use.  In this latter role, the prop and counterstay are used to form a solid rest while aiming and firing.  With the prop in place,  side to side adjustments are easily accomplished by slewing the machine right or left because the prop has wide latitude to move in those directions.  Aiming the machine up or down is a bit more problematic.  Gross adjustments can be made by sliding the prop up or down the angled counterstay,  but for the final hair splitting refinements this is hardly ideal.  Typically I have used wedges to slip in and out to make the precise vertical adjustments,  and that system can work quite well once you get used to it.  However,  it would be much smoother and faster to simply rotate an eccentric roller and have the machine elevate or depress a few fractions of a degree.     I believe that the  importance of such a “roller-device” cannot be underestimated once you actually get down to trying to make those impossible shots.

Perhaps I’d better put my current design for the prop and counterstay on hold,  and see what can be done to incorporate an eccentric roller controlled by a hand lever of some kind.

It seems like it’s time to break out my very special thinking cap and have a little vino to help lubricate the process.

Finally, our favorite beastie gets to pose on a pedestal befitting her rank.

The stand is made from Douglas fir and will be stained down to a much darker color to lose some of that lumber yard appearance.  A pivoting counterstay and adjustable prop should complete the look.  The fashionistas tell me that polished steel and dark wood tones will be all the rage this year.   Bronze accents are always a plus.  Note to self:   some fluffy sheepskin on the shoulder stock should serve to bring out her softer side.  What is it they say,  “When in doubt, accessorize.”