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Maybe you can search for my old trebuchet thread. I built 14 of them. As #3 seemed to have the very best geometry, I scaled it up and down. I made 6 tabletop versions for tossing olives and ice cubes (50') at banquets. Counterweights were the lead balls for fishing down-riggers. Sold them all for $50 each. Anything planned for more than 300lbs in the counterweight is essentially stationary. Castle wall busters were never mobile armament, especially on soft British soil after 6 weeks of rain!
 

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My best treb is right at the limit of portability for me. Some assembly required. Don't recall that there's even 300lb of steel in the counterweight. But, I can fling a 1lb ice cube over the roof top of a 3-storey building from 75ys away. Ice is best = the evidence disappears. Best is a ratio between 200:1 and 300:1 for mass.
The big ones don't weather well. Out at a Rod&Gun Club range. 2 or 3? summers, that was it.
Military secret: did you know that there are no written or picture references from medieval times to show what the trigger mechanism looked like?
 

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There are two fulcrums to locate correctly = the axle for the throwing arm and the axle for the swinging basket counterweight.

The really interesting that I learned, by about treb #4 or 5, was that they scale up and down arithmetically.
Then you can build anything that you can score the wood for. 300lbs is plenty to give the club trap shooters
some 1lb paper bags of flour to shoot at.

Thank you for the pictures of the triggers. Far more complex than I imagined.
One long rope from the basket back to a stout peg in the end of the slide under the counterweight.
That works just fine for a counterweight of approx 1,000lbs.

The "War Wolf" was supposed to have had some 30,000 - 40,000lbs rock in the counterweight.
Thus able to throw a 1,500 lb dead horse the needed 300+ yards into the castle courtyard.
Hugh Kennedy (Britain) has built one to confirm that claim. Mostly, he uses small cars,
grand pianos, dead pigs and flaming toilets.
 

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It was generally conceeded that a volley of arrows from the strongest of castle archers could kill a man at 300 yards.
If there ever was any "rule" about siege weaponry, that was it.

Hugh Kennedy (UK) built and operates a replica of the "War Wolf."

Best account I ever read: the bad guys built a treb (600lb rocks were the ammo of choice.) The King sent an emmisary out from his
castle to negotiate a peace settlement. The bad guys killed him, loaded him into the treb and tossed him back into the castle courtyard. Dead or not, the sudden stop unpon his arrival in the courtyard would have finished him off.
 

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Thanks for the wikipedia link. Wonderful replicas, particularly the human-powered wind up mechanism in the Danish unit. Everybody should build a few of these, just for fun. Just rig one up, maybe 250:1, for flinging 16oz ice cubes.
When I built the "just-barely-portable-in-pieces treb (#8?), I recall clearly that my GF observed: "That's the dumbest dang thing that I've ever seen you build." But guess who was the first one to brag about the power and distance? Like she helped a whole lot.

Have you seen the restrictions on treb design in the SCA rulebook? What a waste of destructive effort.
 

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You might do your own research, Manuka. Hugh Kennedy can fling a grand piano or a Hillman car more than 300m. Several YouTubes.
The throwing arm looks to be 40' long or so.

I agree that anyone claiming that the throwing arm was 100'+ long is 2 bricks short of a chimney. With half a mind to the design, let alone the 12th century wood available, 100' is quite absurd. Sit down, have a drink of water.

My challenge is still out here. I have built 14 functioning trebs. Are these posters posers? Have they built any trebs? All hat and no cattle? Believe me, when you settle down and put one together, it is a thing of beauty to function.
 

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Think about the castle wall construction, for which information abounds. Wall of stone on the outside, 4-6' thick rammed/packed earth and a wall of stone on the inside. OK? When a 600lb rock from a treb hits the wall, there's surprisingly little damage to see on the outside. Bummer. The shock wave travels through the wall and the inner face of the wall explodes into the courtyard, killing or maiming every living thing in the line of expansion. Of course with the integrity destroyed , the entire wall begins to collapse around the crater.

Anyway. Enough theory about the information that's out there. Inexperienced and subjective measurements can't help. Am I still the only WWT member who has posted pictures of even a few of the trebs they've built? If SWMBO has shut you down, that's a misery for you to reconcile.

My favorite is still the one which can be partially disassembled and stuffed into the back of my Suburban (with the seats folded down!) The throwing arm is solid oak 2x4, 3X wide over the axles.
Axles are both 3/4" steel rod.
Overall, the arm is 69.5" in length. Proportions from sling finger to axle: 53", from there to the counterweight pivot axle: 14". The arms of the counterweight are welded 1x2 steel with a bunch of 2x2x16" steel bars for mass. Don't forget that a basic principle in this was portability. So, standing, the sling finger isn't more than about 80" above the slide surface.

The treb theorists can see that the proportions of the arm dictate the tower height and slide length.
The width of the slide depends on the mass and shape of the projectiles, that won't compromise any of the tower support timbers.

I planned this for 200:1 so a 400g/14oz ice cube is excellent and the evidence disappears.
Sadly, the biggests talkers here were very worried to see this treb in action, one jumping about, wide-eyed, screaming about liability. What did he think a treb was for? All of the others have become strangely silent.

I hope a few members build some trebs, I'd like a serious discussion of changing trigger designs with changing counterweight mass. I'd like to learn more about sling finger and take-off angles.
 

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What stops you good people from building a trebuchet?
I set up my treb, described above and elsewhere, for a 2nd yr class of college
physics students. In that 3-hr lab period, I suppose I tossed 2 dozen ice cubes.

Somebody contributed a grapefruit. Everything went right. We all watched that
grapefruit sail over the parapet of the 3-storey roof-line of the gymnasium.
Best toss ever. Wonderful sense of satisfaction in the function of that design.
 

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Bad. 'F' for the segway in this thread.

I feel sorry for the lot of you that don't have the opportunity to build trebuchet (what's the correct plural?) Whatever your inhibitions, you need to shed them. . . soon.

For me, it has made the reading of historical information all the more interesting. I've been there. I've done that 14 times. Plus, some contributed pictures of trebs, triggers and all. Build one like that. Try as you might, see if you can make those trigger work with 30,000 lbs in the counterweight. Horse-puckey. Don't you see? The trigger is the military secret.

Given the scaled geometry of a treb, can you imagine that I can carry the complete treb design, any size you can dream of, as a length of knotted cord in my pocket?
 

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The largest functioning trebuchet that I know of is the replica of the "War Wolf," built and operated by Hugh Kennedy in England. He explained that he'd found an historical claim that the WW was capable to tossing a horse into a castle court yard from 300 yards away. He reasoned that if the account were true, it should be possible to replicate the feat. He did exactly that, using an assumption that the horse would have weight some 1,500lbs. Anybody who uses Hillman and Renault cars for ammo impresses me with their design skill.
Only from video that I've seen, the arm is jointed/assembled like a split cane fly fishing rod, possibly 4-5 feet in diameter over the counter weight and likely 50+ feet in length. That means that the tower must be 30-40 feet tall or more. Yes, it is almost indescribably immense.

Be that as it may, I enjoy the entertainment of any treb with payloads of 20 lbs or less. Designed at 200:1, 4,000lbs in the counterweight is not unreasonable.

If you haven't found them so far, I suggest you look at the results from the trebuchet section of the Punkin Chunkin Contest, an annual veggie tossing event in the United States. If memory serves me, the record for the air cannon section is 4,000+ feet/1,230m, across a freeway and into the filed on the other side. They have a contest site. That implies that all the siege engines have to be trucked to the site and assembled.
 

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I haven't given any thought to treb design for more than a decade. Yes, I am an experienced trebuchet builder with published pictures of examples.

Period Machines: I think that we've seen the best of them come and go. Were I to mount a campaign of conquest using trebuchet, you can bet your last dollar that my engineers would have the design figured out. Logically, that means that there was a lot of military research and development that we will never read about. The plans didn't come to them in a dream. Even the angle of the sling finger for proper release. The size limit might be reached by several things: the modulus of elasticity of woods available for the arm. Laminations are certainly superior to a log. They would have known that from long bow construction, even the correct orientation of the growth rings. Friction on the slide with the sling basket. Grease can only do so much. For my part, a little 5W30 motor oil on axle parts has quite a dramatic effect. Inertia = how do you get the mass of the projectile to even begin to move? A rock would have fewer and more intensly confined pressure points on the slide, than a horse.

Modern Machines: I am not, nor ever was, a materials engineer. As parts of university dendrology courses, I did teach the fundamentals of mechanical and non mechanical properties as they apply to wood. Look for specifics on your own time.
What would I try, from the materials I'm aware of?
Arm: Boron-doped, carbon fiber lay up. The design might be eliptical in XS, the long/strong axis parallel to the plane of rotation. Roller bearings. ball bearings (which is best?) for the two axle points.
Swinging counterweight, made of and loaded with the densest element in the Periodic Table (can't find my reference book but I know for sure it isn't Uranium.)
Limits: Besides friction on the slide (travelling carriage?), overcoming the inertia of the projectile is not going to go away.
Risks: The counterweight is falling due to gravity as the arm begins its rotation. When the sling loop comes off the finger and the projectile is released, the arm does not come to a sudden freakin' halt.
The overtravel goes into quite violent recoil oscillations (very disconcerting if you aren't ready for it.)
As you know from reading, both the arm and the counterweight are flapping about. This is where I think that the failure will occur.
Desires: give me an automated disk brake damping system on the arm/counterweight pivot point. It's delayed beyond the release of the sling loop from the finger.

If it wasn't my money, I'd try an arm, 60' total. The tower and slide are not an issue. Loading would be least risky by lifting the counterweight, not pulling down on the arm. You've seen those people-powered wind-up mechanisms? Why do you suppose they went that way in the design? Huh? What did they break most easily? It is one big Hello of a surprise when the arm breaks. Cable trigger, not some box-latch screw-up. Can you imagine an iron counterweight and an electromagnetic latch?

Find a materials engineer, young person. Bring them up to speed and pitch the same question to them.
 

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Possibly there would be merit in building bigger castle busters but I suspect that the medieval engineers knew what they faced (from R&D experience) in the form of materials failure. Plus, maybe his castle is nicer than mine and I'd like to live in it, not smashed up too badly.

Correct me if I'm wrong, but hand to hand combat was still popular.
A broken castle wall and a substantial invasion force often meant defeat for the current occupant. The tunnel guys did a fine job of collapsing castle walls until the innovation of a moat.

It has to be built in situ. If any of the King's scouts/patrols catch my stone masons quarrying and dressing 600+lb rocks, those guys are done for. Liberally applied receational torture and somebody is bound to give up my game. As an option, I'm not about to fling a 2,000lb ox into the castle couryard as a gift of food for the besieged inhabitants.

Best account (second or third hand) that I ever read was the story of the Spanish conquistadores vs the Aztec. The Aztec didn't want to give up his castle, gold and jewels. So the Spanish decided to build a big trebuchet and bomb the guy out of his house. So they built the treb. First shot, they got the trigger finger wrong. The sling released early. The rock went nearly straight up in a really tight arc and came down on the treb.

Size matters. My table top banquet-busters have just a 5lb ball off a trolling/fishing down-rigger. They go off like a gunshot, basically nothing to see unless you are focused on the head table. Big trebs go off creaking in a sweep of grandeur. The forces involved and the speed of the projectile still aren't readily appreciated until you hit something. Apples and oranges are good.

You know, one thing just occurred to me. If trebs were popular and effective, how come it is that there aren't more identified artifacts in the form of BIG round stones/projectiles? I know that lots of big stones from various stone circles were cut up and carted off for building material.
 

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You make excellent points. Thank you.
Old cordless telephones and oranges of the same mass have entirely different aerodynamic flights. I do not know if that would apply to siege loads.

With a basket in the sling, rock dressing might aid the release = it would be bad form indeed to have the rock stuck in the rope weave of the basket and not release.

I tried water balloons. They either rolled out the back or failed to release and smashed on the treb. Glad it was not solid.

I know that HK used a hook on the small cars.

Spies and traitirs? The King saw the treb. Sent an emmisary to negotiate a peace. The poor fellow was bundled up and tossed back into the castle as the reply. Regardless of his condition, he was certainly and suddenly dead upon arrival.
 

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MJ = post #70. Thank you so much! What a fantastic sight. Relief for my curiosity, at last.

It's one thing to have the treb set up correctly, it's another to have the projectile wheeling away to the right or left in the sky. Otherwise, we could use square bullets, yes? Ask a competition, big bore pistol shooter about "key-holing".
Believe me. Spherical projectiles are a joy to fling.

The rest of you: back off. This is a thread about the sheer enjoyment of mayhem and destruction.
You need to shed your parental inhibitions and just have a good time smashing things. I am so happy to know that I was brought up to appreciate these things.

As a short note added in proof. My reputation preceeds me. I can set up a "banquet-buster."
Positively ensures that after-dinner speeches are short and sweet, much to the disappointment of the general audience.
 
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