Author Topic: A new Roman arrow firing machine  (Read 23882 times)

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orcbow

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Re: A new Roman arrow firing machine
« Reply #45 on: August 17, 2008, 07:42:29 pm »
Keep us posted on the progress! I've got a stash of oak 2 1/2x5's that i'm going to make one of these someday. I really liked seeing how the trigger mechanism works (from an earlier post of 3-D drawing). Good work!!

Offline Dane

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Re: A new Roman arrow firing machine
« Reply #46 on: August 18, 2008, 05:49:51 am »
Thanks, Orcbow. Any advice or documents or whatever if you decide to build one, don't hesitate to ask me about. Oak would be a fine choice of wood for building one of these things.

Dane
Greenfield, Western Massachusetts

Offline Warhammer1

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Re: A new Roman arrow firing machine
« Reply #47 on: January 24, 2011, 11:05:32 am »
It is rather the engineering and design rather than the springs themselves that produce the effeciency (transfer of energy).The rope bundles themselves are suspect to effeciency. In VG Harts paper, he compares the performance of two identical designs the outswinger ballista (greek) and inswingng (roman).
The inswinger coughted up a 48% greater range.

"Reviewing these figures we see taht it is relevant to note that the Hatra machine may be said to be more effecient that the Greek machine; indeed, since their missile kinetic energies at launch amount to 38% amd 30% of their respective strain energies. Also, spring friction represents 72% of total energy for the Hatra machine, and 78% for the Greek."

My work has involved improving the effeciencies of the machines, primarily through engineering. In as much as a recurve bow of eithe modern or primitive design represents a very high degree of effeciency by eliminating friction, I offer the test results of my little inswinger designs from a small ballista bow powered by a single extension spring providing only 18lbs of pull at full 26 inches of draw. Might I add that it is a simple compound design with two pulleys mounted on the end of each arm, the string looping around and coming back to the main chassis to ward the trigger assembly.

Velocities recorded for a 584 grain arrow was 30 mps, and 24 fps for a 974 grain arrow. While not horrifically fast, thats 32 grains per lbs of pull with the lighter arrow, and 54 for the larger arrow.

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author=orcbow link=topic=6909.msg118115#msg118115 date=1217760988]
I have recently watched a 6 part series called "Ancient Discoveries", that I got from the library. It was basically about the inventions of the classical world and how we should give them so much more credit for how advanced their technology and understanding of scientific principles was. Like the raw efficiency of the ballista's coiled rope springs. On the show, was even a reproduction of Heron of Alexandria's chain drive, repeating balista!
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Offline Dane

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Re: A new Roman arrow firing machine
« Reply #48 on: January 24, 2011, 11:25:03 am »
Warhammer, this thread is almost 3 years dead.

I've checked out some of your ideas on RAT. While interesting, my interest in torision and tension machines is to try and replicate what ancient Romans and Greeks were building and using for military applications and finding out what kind of peformance they actually had, not what we can do with modern theories, construction, or material. 

I seriously doubt that Heron or Vitruvius would have been building compound arrow machines. W

ith respect, I dont intend to go anywhere close to reengineering and "improving" ancient engineering. Leave that to Wilkins and his ilk.

Dane
Greenfield, Western Massachusetts

Offline Warhammer1

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Re: A new Roman arrow firing machine
« Reply #49 on: January 24, 2011, 11:43:39 am »
David, there continues to be. As for my work, I debated with some other catapult builders (ballistarie in Latin) about how the arms are positioned. One school of thought is that the end of the arms has to slam into the inner stanchion back edges to absorb the energy as you discharge the weapon. I feel strongly that the inner arms don't do that, but possibly do hit the outer facing sides of the inner stanchions (why I plated them), but mostly, the bow string absorbs the energy, much like a bow does. Under no circumstances do you want the arms to slam into the outer stanchion recesses (the half moon looking cutouts). That is a good recipe for cracked stanchions and arms.

The only reason arms would slam into the stanchions is if the string had no tension at rest, which would greatly increase effeciency and allow all available energies to be transferred to projectile. In this case, the stanchion has no choice than to act as a simple fulcrum, with the rope bundle absorbing the brunt of arm momentum, until the string lost its apparant slack. In the above example it is assumed it is a single stanchion machine, with no  stanchion arresting movement of the arms "heel" (Aitor)



Doubting this, I invite you for next Orsova field trials where such an occurance happens regularly. 5000lbs of pull WILL stretch the rope out of shape temporarily. Or simply watch the videos.








Offline Warhammer1

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Re: A new Roman arrow firing machine
« Reply #50 on: January 24, 2011, 12:22:51 pm »
I am aware of the disdain in which my work is regarded. Nonetheless, my work has served its purpose in helping Nick attain his goals while improvement in performance using my engineering. Nick is way ahead of you guys, Marsden Wilkins etc. While I respect their contributions, certainly you must agree that they produce less than optimal performance in relation to performance reported in treatises.

In defence of their work though, they will serve well enough for outswingers, but clearly for inswingers my work is undesputable with reproducable results upon demand. Previous calculations for outswingers has NO place in inswinger engineering, but merely used as a reference or starting point. 

Why else do you think I can argue with complete confidence with Mr. Harts contributions and pure research? Results are results. Solving the riddle of ballista performance is akin to solving the mystery of the pyramid construction. This I have accomplished, and am trying to share it. You are a hard headed lot for sure.

Is no the least bit curious in solving the performance calculations for the inswinger as they relate to outswinger formula's????? It sure sucks being a pioneer in the field for sure. With a grade ten education it has not been an easy task for sure, but nothing compared to the effort required to changed academic opinion and way of thinking. I do not blindly accept doctrine, and it is my nature to challenge accepted doctrine and methodology.

Yes I know this thread is three years old, but so calculations you use are a couple thousand. dont worry, my health is failing fast, and I have no help from the scientific community whatsoever. The ideas and concepts are all I wil be able to leave you guys, evidenced in help building the worlds fastest balista past or present. NOt even NIck understands my work but must accept the results as performance is his primary goal.

NIcks machine is only a stage one design. I am many years ahead of that, daring to challenge supersonic capabilities as a design challenge.  A 500fps ballista will be my legacy to leave behind. Who knows maybe one day in a museum. I will walk my own path, and lead the way for the more bold . That will not stop me from admiring your work and craftmanship, and although my voice not welcome , will continue to voice my opinions and research where and when permitted.
I look forward to seeing more work from you.

If there is a more recent contribution regarding ballistas and pure science or research here or anywhere else, please let me know.

 

Warhammer, this thread is almost 3 years dead.

I've checked out some of your ideas on RAT. While interesting, my interest in torision and tension machines is to try and replicate what ancient Romans and Greeks were building and using for military applications and finding out what kind of peformance they actually had, not what we can do with modern theories, construction, or material. 

I seriously doubt that Heron or Vitruvius would have been building compound arrow machines. W

ith respect, I dont intend to go anywhere close to reengineering and "improving" ancient engineering. Leave that to Wilkins and his ilk.

Dane

Offline Dane

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Re: A new Roman arrow firing machine
« Reply #51 on: January 24, 2011, 01:49:19 pm »
Warhammer, you are probably a nice guy, and sincere, but you have to understand my perspective, which will not change in the case of Roman and Greek torsion and tension engineering. The whole point of researching the machines and building working interpretations of a Vitruvious or Heron machine is this: to understand the probable capabilities and performance of ancient artillery. Not what they may do if you reengineer them, but what a Roman army in 79 AD would have had as way of field artillery available in the then-here and now.

What you are doing, while it is important for you to break new ground, is contrary to what some of us are doing. An example would be to explore a medieval English yew war bow, but make it out of fiberglass, and replace clothyard arrows with fiber arrows. What do you gain? More performance than is possible with a 14th century bow, but if you are trying to understand what actual medieval bows could do, you learn nothing of historical value.

Another is to take a rifled musket reproduction from the US Civil War, glass bed the barrel, rework the trigger, replace the sights, and optimize the weapons in every other way possible. You have a much more accurate weapons than a soldier of 1863 would have had, but you don’t learn much about the accuracy and shooting characteristics of an actual weapon from that conflict.

The outswinger vs. inswinger battles – I agree with how much more effective inswingers are, and probably were much more prevalent in the ancient world than some think they were. Hartra had to be an inswinger, and it appears to be thus via Trajan’s column. Perhaps even all stone throwing machines in mid empire were inswingers. My own little machines are based on earlier machines, and I think outswinging configuration is fair and was probably the primary ways of setting up a scorpion. If I were to build a metal framed arrow machine, it would be most definitely an inswinger.

Purely improving performance of an ancient design is fine if that floats your boat, but the chances of Roman and Greek engineers having developed compound (wheels) technology is bordering on ridiculous (Kind of like SCA folks using duct tape and saying if they had it in the 14th century, they would have used it as way of justification). What you are doing is not engineering interpretations of ancient stone and arrow throwing machines, but something entirely different. I’m not really sure what the entire point of that is, as catapults and ballistas have been obsolete weapons systems for almost 2,000 years. Da Vinci did some fanciful sketches of theoretical war machines at a time when gun powder had doomed such weapons. Hence, they never got beyond design sketches.

Maybe you should focus on the pumpkin chuckers. Those guys are pushing catapult designs to the max, and you would feel right at home. The goal is to hurl a pumpkin 1 mile. I think they would welcome you with open arms. Google them, as there is tons of stuff online about what they do, videos, etc. Googling Team Tormenta will get you right to their site, if I recall. Nice group of folks, too.

Dane

Greenfield, Western Massachusetts

Offline Del the cat

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Re: A new Roman arrow firing machine
« Reply #52 on: January 24, 2011, 02:08:35 pm »
I know this is an old thread, I just wondered how it all turned out?
The skeins of rope should be made of horse hair or sinew for maximum power according to Sir Ralph Payne Gallwey.
I think linen thread is an alternative (that's what I used on my miniature seige engine).
Leather buffers stuffed with horse hair would seem like a good idea to absorb the arm impact.
The question of string tension is a V good one, I'd have though maybe share the tension between string and leather buffers, a completely slack string has got to be a bad idea.
I've seen a few TV show where they try to make Da Vinci style giant bows or suchlike (e.g Scrapheap Challenge) The usual mistake they make is a slack string which generally causes a broken bow when it bends the other way.
I did see one great prog' where they made a formidable Trebuchet which lobbed 300lb sandstone balls... ;D
Del
Health warning, these posts may contain traces of nut.

Offline Dane

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Re: A new Roman arrow firing machine
« Reply #53 on: January 24, 2011, 07:08:18 pm »
Del, I stopped working on the two catapults as I marshalled my thoughts and reimagined how I was going to make various metal parts (triggers, washers, etc). Finally, I am set to get back to it, but it was yikes, two years ago that I stopped progress.

Horsehair was secondary in preference to the ancients, who felt sinew was the best rope material. I feel they are correct, but dig this, not one reconstructed catapult has ever been made with actual sinew rope. I'd like to tackle that one day, but the amount of sinew to make 300 feet of rope is formidable. One builder from the 19th century, Dr. Schramm of Germany, did use horsehair in his reconstrucitons. To the best of my knowledge, most of his machines were destroyed during allied bombing missions - maybe your boys on night raids, or ours on daylight raids.

"Gentlemen, todays mission is....German catapult reconstructions...." "Gulp!" "Blimey, this one will be rough." "Jezz, only one more mission and I get to go home....this aint gonna be a milk run." 

One, a 3 span machine, apparently did survive the war.

So, no one today really does know how a Roman catapult may have behaved and performed. I do plan on making horsehair rope in an improvised ropewalk, but first the metal bits have to be completed.

Badger here on the forums was the bow expert for one of those shows, and he was on the show, Doing Da Vinci. You may want to ask him about his contribution. A weird circular bow powered stone thrower, if I recall right. It was just huge, that thing, and didn't perform particularly well, but not because of Badger's work.

Tribuchets are interesting, but hardly any one makes one to the huge sizes the medieval armies must have used. One show filmed in England had this landed gentry type fellow hurling small cars across his fields, and exploding fuel drums, as well. Boys will, of course, be boys.

Dane



Greenfield, Western Massachusetts

Offline Cameroo

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Re: A new Roman arrow firing machine
« Reply #54 on: January 24, 2011, 09:52:36 pm »

Badger here on the forums was the bow expert for one of those shows, and he was on the show, Doing Da Vinci. You may want to ask him about his contribution. A weird circular bow powered stone thrower, if I recall right. It was just huge, that thing, and didn't perform particularly well, but not because of Badger's work.


I just watched that episode on Youtube, it was quite interesting.  I enjoyed watching Steve work, but really have to give him credit for not strangling that obnoxious "Flash" character.  Too bad they didn't get better performance from that monster, but it was entertaining to watch the build.