As Firefly moves closer to completion it seems appropriate to examine her intellectual underpinnings. (Sounds serious,  I’d better put the kettle on.)  The great conceit of this project has always been that if we somehow accurately  reproduce the original artifacts of the Orsova ballista and then design for them all of the ancillary components needed for a finished machine, and if we make and test the whole apparatus to encourage maximum performance;  then that result would be as near perfect an analog for the original machine as this researcher can muster. (phew! burnt my lip on that one.)

This approach respects the original Roman artifacts in two ways.    First,  our close adherence to the dimensions of the  parts dug out of the ground means that certain constraint dimensions will closely limit the size of the springs that will be allowable.  This will insure that the scale of our machine is in keeping with the original.  Second, by taking a ferocious interest in maximizing all issues related to performance, we can be confident our intent is exactly the same as the Roman engineers.   It’s a fair bet to suggest that there is probably no level of honorable* innovation that I can bring to this project that would not have been mirrored and bested by the Ancients.

Blend all that verbiage together and it follows that the most humble set of assumptions about how our finished machine should look and perform is to suggest an apparatus that is as mind bendingly kick-ass as possible.  We proceed accordingly.

A full scale poster of the original field frame is a useful binnacle for those days I get lost in the fog.   The old Vernier plate hanging to the right is one way to add on to the existing artifact and extract as much performance as possible from the whole field frame assembly;  e.g.  increased loads possible on the end caps to the field frames, fine gradation of torque on the spring bundles with a Vernier locking system for the washer.   There should be a variety of mumblings on Vernier plates and spring size  somewhere earlier in this tome.   While it is likely that the Romans used very stiff high collar bronze washers with the vernier hole pattern set into a thick  rim, for the moment our version  uses thinner forged steel washers combined with heavy Vernier plates because they offer more flexibility to change the design as desired.  The overall enhancement is pretty much the same with either construction approach, and so bears no violation to mar our conceits about authentic levels of performance.

(I had no idea one cup of tea could hold so much conceit.  Who knew I was supposed to tip it overboard?)

3 Responses to “A matter of scale”


  1. Captn Harpoon says:

    Your conceit is not misfounded. Firefly is truly an awesome machine and performance already beyond the norm before the proposed changes, rivaling the performance of todays high tech compounding and cammed crossbows. You have every reason to be proud of your work! It should have its own spot on “Mighty Machines”!

    MY conceit has led me to be foolish and reckless, and what possessed me to challenge the works of a mathamatician with a fistful of degrees. But thats me (basement inventor and crackpot), I’ll argue with anybody LOL.

    Mr. V.G Hart has written a paper entitled “Hatra Ballista a secret weapon of the past?” along with a MJT Lewis of the UK. Not perturbed at all he looks forward to Fireflys testing as do I. Heres what he had to say about my arguments:

    “Hi XXXX,

    I don’t doubt that if the angle of swing of the Hatra type ballista is increased by 15 or 20 degrees
    that we will observe an increase in performance, in particular in range of the projectile.
    But what I am saying is that it is unlikely that there will be a difference in kind of the performance-unless I am
    greatly mistaken. And I think that the overall result following the entire swing is the best criterion for judgement
    We shall see from your friend’s projected experiments I’m sure. The trebuchet is another question entirely;
    my theory does not cover its performance.

    But don’t hesitate to criticise please, I am not at all worried by comment on my paper.”

    Best regards,

    Vincent Hart

    – Yikes. If it wasnt for Firefly and previous testing, I might even be worried. Looking forward to completion and further testing/tweaking.

    Im very curious about the new limbs and cant wait to see what the final limb/string design is like. I have to confess the new string design idea is kind of like setting out breadcrumbs. If the new proposed string design can work on Firefly, I have another trick or two up my sleeve, should be good for another 50fps gain. Naturally I designed it to work within the parameters you have set out for historical authenticity.

    There have been many varied methods of accelerating mass and increasing velocity potential in weaponry. I believe that I have one more and significant contribution to make in introducing impact acceleration technology to Firefly.

    Somehow, explosive impacts and finely tuned high performance machines sound like the two would work well. Having tested it, I cant help but wonder how much more energy I can put into the projectile utilizing and extracting a large percentage of the arms energy at the end of the stroke. You have 5000 lbs of torque and a one lbs arrow. The 12-15 lb limbs will accelerate strongly for 100 degrees, and then is brought to a screaming halt.

    Thats a lot of dynamite to tap into. Firefly constantly inspires me to exceed and constantly challenge even my own findings haha.

    Having wondered why I never stop designing and never being happy,is that for some reason I seem to put myself into a pissing contest with old Philon, and his “doubling the cube” achievement.

    If I can again manage to again double the performance of a given size ballista,that I will consider his ass kicked. Now thats what I call conceit and wishful thinking. The only way to do that is to dream up a new acceleration componant (or two) to add to the existing mix.

    I have a feeling Firefly is undergoing her last metamorphisis for a while so you can take a well deserved rest. Your new arm design (and impact accel tech) awaits the craftsmans touch to bring primitive weapon hyper-velocity into existance, whenever your ready.

    Failing that it will find its way into my crossbow and manuballista designs, but I believe the honor should lie with Firefly. I would not have thought of it perhaps but for those big old logs you call limbs LOL. All that KE going to waste.

    Will be following progress, hope all is well.

    W.


  2. Captn Harpoon says:

    Sorry. I like to add its probly appropriate to include a passage of my communicae and the parts he disagrees with. Math seems to be a rather absolute solution and there is not much room to argue with. Anyhow, my claim or theory to which he was gracious enough to respond to:

    “Hi Joel,
    I don’t doubt that if the angle of swing of the Hatra type ballista is increased by 15 or 20 degrees
    that we will observe an increase in performance, in particular in range of the projectile.
    But what I am saying is that it is unlikely that there will be a difference in kind of the performance-unless I am
    greatly mistaken. And I think that the overall result following the entire swing is the best criterion for judgement
    We shall see from your friend’s projected experiments I’m sure. The trebuchet is another question entirely;
    my theory does not cover its performance.

    But don’t hesitate to criticise please, I am not at all worried by comment on my paper.

    Best regards,

    Vincent Hart

    PS I looked at the romanarmytalk.com site, and am impressed by the general enthusiasm shown for this

    topic. Also the inswinger model displayed in action. Marsden would be pleased.

    VH

    ——————————————————————————–

    From: Joel Maki [mailto:joelmaki622@hotmail.com]
    Sent: Fri 10/09/2010 10:05 PM
    To: Vincent Hart
    Subject: RE: Hatra

    Thank you and I will keep you informed of any experiment postings.

    Even though anything beyond basic math is foreign to me I nonetheless studied your paper with great interest and indeed it seems that your calculations and formulas would work just as well with the Orsova as with the Hatra, substituting the different values in lever arc or degree positioning and operation (if Im not mistaken).

    I am sorry but I still beg to differ on whether there is or is not any new insight to be gained from increasing the swing angle by 15 to 20 degrees. This will soon be resolved however by an ongoing round of current testing of the arms in the old position and then retested in their new position. Intial experiments performed by Nick verified my earlier findings in performance optimization.

    It is my stance that an inswinger having arms at a 12 oclock rest position (normal Hatra or Orsova arm position) and utilizing 90 degrees of movement will always have less performance than the same inswinger (also using only 90 degrees of movement) with arms at an outwardly pointing angle, 15-20 degrees past the normal rest positions of the arms. Just as the basic Hatra design will outperform the outswinger design.”

    So theres the rub. Can we both be right?


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