I know it's not a crossbow...(Ballistas, Catapults, etc.)

First topic message reminder :

..but has anyone thought about making a scorpio or a full sized ballista? http://www.legionxxiv.org/catapulta/
I think I am going to start making a mini model of one for fun, hopefully leading to a larger one. It would be cool to design one based on modern materials just to see how much it could be improved upon.

Hey, added the pics.

The specs are pretty awesome guys.

Ivo

Hey everyone Nick and his big ballista are going again and things sound pretty good to rival or beat the Scorpyds speed!
http://wattsunique.com/blog/

Nicks limbs did not survive again, as predicted back in March:
“Since it appears the arms will retain original length thats okay
too. By June or July and several rounds of testing perhaps you will come
to the same conclusion about the arms as you did for the frame. Metal
is inherently stronger.”

– the “good” Capt’n….
I notice that the arm string relation was just past 90 degrees to each other. If he had stopped @ 75 degrees and 5000 lbs or thereabouts, we'd now have chrony results.
Its hard to beat results driven/proven design and engineering...











"

You know that song?...

. Don't Stop...Don't Stop till you get Enough...Don't Stop...Don't Stop till you get Enough...No

I guess that song applies...glad to see the man didn't have enough yet and is still at it. I was kinda anxious to hear the results *the blog doesn't say anything about the mishap*...is this from the forum?

And yeh, metal sounds like a way out. Interesting how he'll go about it...Personally I would love to see something better than just a set of steel bars stuck into the ropes. But I guess I'm not exactly to criticize here...after all - it is 3000-4000-5000lb he's dealing with.

Ivo

Warhammer1 wrote:Hey baileus.

In the inswinger outswinger wiki page, you post that the arm constantly is under acceleration when in actuallity it slows down almost imperceptedly.

I'm speaking of the rotational speed of the arm. I take it you're speaking of the forward speed of the arm's tips, right? If not, please explain in more detail.

On the Hatra design (original find) the arms were at rest postion at a 12 oclock position and full draw is 120. If you have followed my RAT postings on the subject I described a "lull" that occurs when arms horizontally opposed.

Later a mathematician plotted limb tip speed to string speed, thus proving up my theory.

Did he plot

a) relation of the limb tip speed to bowstring speed (with acceleration et al taken into account)
b) relation of arm rotation (degrees) to the forward movement of the bowstring (static modeling)

Latter (b) is easy to calculate or plot with CAD, former (a) is more difficult, especially if you want real speed figures (instead of just relative numbers).

On the Orsova design(with overdraw past the 12 oclock rest postion), there is actually two spots where that "lull" should occur - namely the normal 12 oclock rest position. I havent found a mathematician to work that out for me.

When using either as a rock flinger with a heavier weight it should not result in a sine wave in the string, but if too light a projectile is used from a 120 degree rotation release point, the string halves will accelerate toward each other and at the point where the string is normally slackest (90 degrees from rest) the strings will have enough energy and momentum to actually cross over each other during this "lull" and then have to straighten out as acceleration of limb and string begins again.

In other words, you're saying that the halves of the bowstring are not going directly forward (towards the target), but also towards each other/the stock? If so, it makes sense.

Here the strings direction changes from being at its widest, to its closest, and then moving apart again.

You mean the distance between the halves of the bowstring (at some point), not direction, right? Or the distance between the tips of the arm? Or the angle between the halves of the bowstring? Frankly, you lost me here...

With Nicks new extended rotation (22% jump in speed) the strings direction must again change direction where it is joined to the lever or limb. Only the middle of the string continues to accelerate as vertical acceleration has ended completely at the 12 oclock position and only a horizontal movement is available. Once past 12 oclock the the direction of the levers has actually reversed and headed back towards the user.

Yeah, that's what happens after the angle between the bowstring and the arms is past 90 degrees. However, in static models the bowstring movement is largest (in relation to arm rotation) after that phase. So, unless some nasty dynamic phenomenom kicks in, this last phase of arm rotation is very important in getting good velocities out of the ballista and should improve efficiency especially with light bolts.

IMHO, this should also result in funky business, but we will have to wait for the new arms on Nicks machine. He has also now got a 1200 frame per minute video cam. so we should be able to see things more clearly, and exactly what does happen.

The videos from that cam will be very interesting...

Of course its very easy to see on my low powered machines, but I like to have a second confirmation before publicly posting actual results or claims.

Why hold back? Videos with this "lull" phenomenom would definitely interest me.

So far I believe I am the only "ballista freak" doing extensive research and testing using much shorter arms expressed as a ratio of arm or lever length to axle to axle length.
While some figure I use the compounding design to change limb tip to string speed (which it does), it is far more productive controlling the angle of pull on the string which is all important.

All bows and ballistas are about is compounding the velocity, i.e. converting relatively low speed of the arm into a much higher velocity of the projectile. The same goes for pretty much all man-powered projectile weapons. Those who claim otherwise don't have a clue .

As I'm doing a scientific reconstruction of the cheiroballistra, I'm not at this point interested in trying to optimize the design, except within the limits that the text allows. I can tune it later as much as I want, but not right now. The original text seems very accurate, provided that one does not start changing numbers; doing that causes issues elsewhere.

The interesting thing about the cheiroballistra is that it needs to have 150-170 degree rotation or the draw length will be too short. Some amount of adjustment is possible by adjusting the length of the hooks (in the arms), the claw (which grasps the bowstring) and the handle (which apparently locks the slider in place). Still, reducing the angle of rotation beyond 150 degrees is challenging.

Anyways, last week I forged most of the remaining metal parts of the cheiroballistra, and the stock/slider combo is almost ready. Next I'll start assembling the pieces and then go for yet another round of forging. Hopefully I got the machine ready in a couple of month. Then I need to go butcher some reindeer/moose legs/backs to get tendons and make lots of sinew rope. It's not gonna be pretty, but necessary for science .

Warhammer1 wrote:
I've always been a contrary critter, and always insist on swimming upstream when the rest go with the flow.

+1

I have always found that a failed design will teach you more, if nothing else through process of elimination. Success requires many such failures and is too be expected.

And how do you know you've succeeded, unless you've failed earlier?

One day I hope others will pick up where I leave off, and help them poor scholarly types build something that works as its supposed to. Nick of course excluded.

I hope you're not counting me into those "poor scholarly types"? If you were, I would consider it an insult . I do agree, however, that most scientific constructions (of the cheiroballistra) have been pretty/very bad.

That said, I don't really consider Nick's ballista a strictly scientific reconstruction, provided the goal is to reproduce what the Romans had. For example, there was no motivation for the Romans to use the vernier plates to increase the spring diameter as Nick does: they could just have built a larger field-frame (and washers) in the first place. Also, the fact that he has had to use high-strength "super" steels in various parts of his ballista (e.g. the arch) would hint that Nick's machine is more powerful than the original Orsova ballista.

All this said, I think Nick is doing a great job, and to be honest, his reconstruction resparkled my interest in torsion ballistas; the existing scientific reconstructions had such a bad performance that I even gave up for a few years, concentrating on crossbows instead.

Since I use the same spring and power level in all builds, any performance must come from the engineering. While the range of the ballistas in this threads links have a max range of 200-300 feet with light bolts, that is my range in fps. The very lightest load for my machine is a 250 grain arrow which works out to over five grains per lb of pull, and the heaviest arrow is 1280 grains or some ridiculous amount for the power used.

Why don't you try building a torsion ballista? The way your power source works might not be 1:1 match with torsion springs, thus rendering the results less useful. If you don't have to limit your creativity for scientific reasons (like me), you could make even more interesting observations with a torsion weapon.

Hey. Just got back from the wiki personal torsion weapons. I found your effeciency study using arrow weight and mps. Seeing the 70% effeciency numbers for 30 gram arrow I was a little bummed till I re read and saw figures were for a 68kg draw weight.

My torsion based inswinger is just right at 50lbs pull or little over 20 kgs. Would you like to see how it performs with arrows ranging from 270 grains through 1280? The 270 grain was chronied at 215fps by Derrick who also was supposed to chrony the other ones I sent along.

Nicks 5000lbs of pull with 7500 grains is only 1.5 grains per lbs of pull.

The 270 grain is over five grains per lb of pull.

The 1280 grainer is about 25 grains per lbs of pull.

My calculations show that if I increase the pull to 150 - 175 lbs, 400fps plus is not out of the question for a 400 plus grain arrow, as 175 has already been accomplished with only 50 lbs.

I wanted to wring out as much performance as I could from what I considered the most in-effecient way of powering it before moving on up to a better power source. My design is now going to professional design and engineering, to produce a manufacturing ready proto or two.

By making the simple design a true torsion (as opposed to eccentric) the performance will be stepped up a tad. Anyhow, if you pm me your email address, you can see my little manuballista do its stuff. I think its performance as is is worth a wiki mention as an experimental.

I think the short arm design is well worth a mention.BTW, Duncan is having an article published in Dec - January that is bound to cause him grief (regarding romans and inswinger ballistas!) Sounds juicy and I can imagine the RAT discussions LOL.

Thats pretty good timing for the ATA.

W.

Just made my first ballista, with the artificial sinew i braided up for the torsion bands is about maxed out in it's current strength, it as about twenty-five pound draw weight. with this the simple trigger I built into it is about over-matched. it is around 24" long, the arms are Bamboo, the stock is Oak sandwiched between Walnut. the trigger is a one piece with a central pivot and three compression springs providing back pressure to the string when drawn. As i made this from my mind prior to any sort of investigation into other trigger methods or other investigation it is a bit rudimentary and as such i may retrofit a nut and sear trigger into the exsisting cavity. so what do you guys think?

Very interesting, how does it shoot?



Nice to see the amount of diversity we have here. I am sure we all can learn from each other this way.



Todd

First off, Welcome to the forums and what not.



That looks good. What stops the limbs after the shot, is it the string or the wood uprights?



Before you start messing with the trigger group. I'll second Todd and aks how does it shoot?

it shoots well, i have done a few different materials for the torsion cables and with the mount of shear stress they generate i end up snapping them. as for firing it performed well in my prelim testing but as i live in an apartment i have not done any good field tests, at 10' or so it managed to bend an aluminum arrowshaft, and put a 1/4" dent in some construction grade plywood ( close grain pine ) as for the arm swing having 2 younger brothers that wanted to play with it I also m now aware that being slapped by one of the arms as it discharges will raise a welt and leave a decent bruise.

As to your question basilisk the forward uprights absorb the brunt of the excess energy, to account for this i made the Prods excessively robust as well as the uprights ( which are water-cured south Texas walnut,seriously this stuff is like working with reinforced concrete, i almost tried to make my trigger out of it. ). the first time i made more wide thin arms and they split down the middle due to the impacts, these were about an inch at the narrowest point and 3/8' thick, i replaced them with 1/2' by 1/2' prods to better resist the impact. the uprighs are not really scuffed even after many impacts. i plan on making the forward uprights padded on my next project.

I have also woven a sling so i can fire rocks/marbles. I will definitely post more info on it as far as accuracy and power on range, as it is though i feel as if it is more than powerful enough for small game.

As for my next iteration i want to make a larger shoulder mount for deer hunting, with paracord for torsion bands and if possibly fiberglass recurve limbs/prods. as such i want to work out the trigger situation as everything else comes together rather quickly. i have some sketches but not my scanner to upload them but well i plan on using a Nut style trigger out of steel, stock kinda bullpup-esqe as the bed on the larger ballista must be longer for the increased powerstroke. but more on that as i get closer to manufacture.

Basilius - "Why don't you try building a torsion ballista? The way your power source
works might not be 1:1 match with torsion springs, thus rendering the
results less useful. If you don't have to limit your creativity for
scientific reasons (like me), you could make even more interesting
observations with a torsion weapon."

- I had to think about this one for awhile as to ascertain your intended question. I think you meant to ask why dont I build a rope bundle spring torsion machine as opposed to steel spring powered?

If so, I can answer that. First, I had Nick to build the rope spring bundles - charged myself in optimizing the same. Through emails we discussed many areas where ineffeciences existed, but none as sever as within the rope bundle itself

I did however experiement and study the principles of rope bundle torque a good bit.
In lieu of using a properly constructed spring bundle, I desired to know exactly how torque was created and what influenced it to have varying amounts. Exactly what conditions produced the fastest rotation speeds.

I would invite you to do the same. The tools I used were a red clay housebrick, a length of string, and a board with many screw in hooks like a coffee cup holder.

If you loop the string through the brick and and then attach both ends of the string to the hooks, you can use gravity to create torque. This would be like say the top half of the spring, and twisting the brick is like rotation of the arm or lever. Gravity is a constant force and not subject to deviations (manually applied force).

As you twist the brick, the string length shortens and the brick moves closer to the string ends and hooks. Upon release gravity goes to work returning it to its natural resting positon (producing torque).

If you move the string ends that are attached to the hooks either in or outwardly so that the distance between the two ends of the string changes, it will effect the amount of torque suppplied resulting in different speeds.

You will n notice that after so much rotation, it the force required to continue twisting it suddenly dies off after the two sides of string contact each other and start to wrap around.

It does not take much to effect the amount of torque available, robbing it of potential energy. Whenever you move or force the bundle out of balance, you not only lose torque,but total rotation as well.

Other - Nick should begin testing within a day or two I guess. The arms are on as is the string, and a new chrony has been attached to the front ready for action.

On the past two occasions break downs have occured as he was tensioning up the bundles. I hope things go ok this time around.

More twaddle. There is probly a good reason why it is not done this way, but given the broken limbs incurred this round I have to wonder if it might not be wiser that while under minimum power, load the machine until you reach the highest level of rotation desired and no more. Then slowly tension the spring bundles (tighten) until you reach 5000 lbs at the desired maximum rotation point. If there is not enough tension at rest position, then one should reduce the amount of total rotation, until the desired string tension at rest is obtained.

How is the cheiroballista coming along now?

Guess I finally pushed Nick too far and he's chased me off. I was wondering when he'd get around to doing that as I am something of a pain in the you know what, and always giving him advice when it was not only not needed perhaps but unwanted.

My abrasiveness might have somegthing to do with my health though, and wanting to see the Firefly project finished before I croak off. Still no excuse except I wanted more progress in a shorter time span - my bad.

Anyway here is my last entry to his blog, and I am verbotten. You will notice that I am a smart -azz to the end.
"Its nice to assume the ancient romans who were barely out of the bronze age could go down the street and pick up tempered steel, and have a place they could send it to for proper tempering to withstand the stresses you inflict upon your machine. That it was too expensive and you did it yourself has little to do with it.

Its not me that lives in a pretend world, I have real world results driven research I've been trying to share with you, and in doing share it with the wider international audience you have, advancing or correcting past assumptions or knowledge.

I shouldnt have to point out the obvious to you, yet you insist on ignoring little things like a proper string will net you a gain on bolt velocity.

400fps was always within your grasp. You didnt need me or any advice. Stronger steel and more power - yeah. I engineered my stuff with mild steel and it works just fine.

So continue along with your own way to rock and roll. Fine with me, just dont pretend your build has anything to do with the ancient builds of two thousand years ago,or that they shot any so sissy as the tooth picks your using on a full sized war machine.

I'll still follow along, make my comments which you can delete with a keystroke, and still wish you the best of luck.

I still say Firefly will now do at least 425fps, properly tuned and with less than 90 degrees of full rotation.

Have at it and prove me wrong!!"

Warhammer.

I am such an ass eh?

Sometimes I apply the rule - "Don't give advise unless asked." ... also I guess it depends on the tone, I'm normally always smiling and will probably do that till the day I crossover...a jolly beer bellied, white bearded geezer...at least that's my dream.

I love giving Christmas presents while breathing fire to sinister music too by the way.



It's all good, cheer up Warhammer.

We got your back.

Ivo

hell, I'll be just fine and really dont blame Nick one little bit. The day started off bad when I phoned him in the morning forgotting that there was a three hour time difference and woke him up. Yikes, the straw that broke the camels back.

On his blog I wrote many often antagonizing posts, and I guess that over time they had an effect. If I was him, it would not have taken me so long to get pissed. He really is a patient fellow, and does really nice work.

Well, I guess there is no longer much reason to continue with using my very heavy mild steel components, and can use stronger/lighter materials.

Friday I got on the phone and ordered a brand spanking new Telson 130 to play with and mod out. The design I have planned for it is pretty exciting for me to try out. It brings into play some of my more radical "tin-foil cap" theories, based on the scientific principles involved on my science and physics links.

I also ordered a new Hickory Creek inline vertical drawloc, with the new and improved trigger system that is supposed to rival the best trigger out there. What I like about it is that I can get up to a full 30 inches of draw length and is able to use the long draw I have built in to the designs.

With a little money behind me now perhaps custom left and right wound torsion springs and double torsion springs can now be used. Because the ATA is coming up fast I am sinking a lot of personal funds into things and can only hope things pay off.

The more versions of alternative powered weaponry being displayed at the ATA the better, especially if they get to "test drive" them. I had an ower of both a RDT165 and Kodabow say that if spring powered weapons would be legal, then he would rather have one of my designs than anything else after watching the new build vid.

Anyhow, if I dont show up here too much for the next while be sure Im busy working away on something. I look forward to sharing once IP protection is in place, as there are already some exciting things happening here at the Guild.

Take care - W.

Oh no! Nicks about to chop up his ballista. I have been following his progress and see he has run into problems getting any kind of rotation or performance. His friend Pat advised him that a lot of tension in string at rest was great. In tensioning the front end however, he was also tightening up the back end of the rotation (reducing rotation capability).

However if you look closely at the pictures showing the rope bundle under load, it appears the bundle is being forced apart at the middle (or arm), with only the smallest amount of twist actually happening near and within the collar. To me anyways it appears the rope bundles are being pulled apart rather than twisted.

If you see the small amount of twist in the rope bundle itself,and consider the small amount of rotation of the arms, the numbers posted are pretty decent.

Other: the Hickory Creek in line draw loc arrived yesterday, complete with foot stirrop, whisker bisket and trigger assembly. It has an incredible amount of drawlength I can use.

The Telson and extra set of limbs arrive Monday or Tuesday by UPS. I ordered the black model if they have it in but the camo version will do.

I will be ordering the new Spiderweb 1.5 target I think. Well back to tinkering around at the blacksmiths...

jake-owa wrote:..but has anyone thought about making a scorpio or a full sized ballista? http://www.legionxxiv.org/catapulta/
I think I am going to start making a mini model of one for fun, hopefully leading to a larger one. It would be cool to design one based on modern materials just to see how much it could be improved upon.

I built a 3/4 ton ballista using translations of original Greek and Latin engineering documents. It shot a 3.1 lb., 4" diameter stone shot up to 265 yards. Maybe I'll build another fun toy like that in the future. That project taught me things about ancient engines that no academic in Oxford could learn.

That's an awesome machine, Darious.....

Mac

Ahh yes, Darius and his amazing machine at Pennsic War... and there's the senator... what was his name? Nautius Maximus? Or was it Claudius?
A good time was had by all anyhow.
I believe Darius ended up selling that machine for about the cost of materials... you just can't get a good price for a balista anymore, since the T-38's came out.

I'd settle for a Panzer Mk II, Iolo (Geezer)...

If some are interested I have a short vid of me putting my 50lbs pull manuballista up against the new Bowteck SZ380 for penetration testing using the world finest target backstop the spiderwebb 1.5XL rated for 450fps.

Of course the bowsin the video dont shoot that fast, but remember Im shooting with only about 50lbs pull. While the video does show some awesome results, only a chrony will tell the truth. None the less, Im sure you will agree, win, lose or draw at the ATA it will have been worth the journey.

Yesterday I managed to get a couple of new springs so I took out the hacksaw and chopped off the arms, installing new ones I had made up a while ago. I think I managed to increase the power up past 60lbs now. Its not a lot, but remember Im shooting in the house! Oh yeah, for the vid pm me your email.

Where the heck is Jeep? Im looking forward to his next entries? When I get a really decent spring, Im gonna test against the Middleton DTM375 and Scorpyd Telson 130.
I had some custom limbs done up for the Telson and she is now up to 418fps.

So now I have one of the (if not the) fastest Telson in the world. I'd like to offer after market limbs for speed freaks one day. I havent been around much lately or doing much as I've not been feeling that great.

Apparantly my wife read about new breakthoughs for "reconditioned lungs" and contacted the facility. They called me the other day and it was kind of funny. The person and I chatted a bit and it was strange to me we could talk about getting a new set of lungs almost like ordering take out. I'll have to think about that some more I guess.

Anyhow, the ATA is getting closer less than 45 days. I hope my design company can deliver or Im screwed. The ATA show is THE show to be at. Wish me luck, Im nervous as hell.

I am still there but very busy. I am finishing box for antique navigation tool. I'll come back to crossbow next week ,i by a crank cocking device from Barnett and i have to adapt it , i will also change the arms and there fixing. Well nearly n° 4 model.

I've been looking around and my friend and I are going to design a ballista of sorts. Might be big, might be small... not sure yet. Smaller would probably be safer and less expensive.

My only question that I haven't been able to find an answer for is what stops the limbs? Is the bowstring supposed to stop them? Are they supposed to slam the supports in order to stop? Either way, that's a massive amount of force to deal with and I'll end up buying the best material for the job.

My upcoming project fits into this thread, somehow.

As some of you may know I specialize in slingshots, and rubber based weapons. Now vulcanized rubber wasn't invented before the mid 1800's.

What did the Dennis the Menace kind of boys used before Mr. Goodyear's useful invention?

Well, we know about the "David Sling", and the related throwing sticks. But these weapons require lots of practice. No problem for sheppards, but what did the offspring of an urban Roman/medieval family use when he was up for shenanigans?

Torsion based weapons, using twisted rope, were clearly well known back then. So it is likely that toy sized versions were made, too.

I want to find out if a handheld slingshot, based on twisted rope rather than rubber bands, is feasible. Of course it needs to fire rocks and lead/steel balls, and of course it has to be somewhat accurate.

I bought some 4mm hemp rope and tested the concept - it works! I chose an inswinger design for power and a larger swing angle. The hemp rops is very unelastic, and the swing has to be limited to about 90 degrees. If I go above, the draw gets too strong at the end of the motion. Keep in mind no trigger and no stock. Just a very wide fork with the rope casings at the end.



Should be interesting!

Joerg,

I look forward to seeing it!

Have you checked out the "mini ballista" in the article I posted on this thread? https://thearbalistguild.forumotion.com/t715-renaissance-folding-assassin-s-crossbow#6805

Mac