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#1
Old 12-28-2005, 09:06 PM
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Explain the difference between catapults and trebuchets

We have been watching Lord of the Rings again, and trying to figure out what all the war machines are called. Some controversy has arisen as to the difference between a catapult and a trebuchet. We get that a ballista fires arrows or bolts, but is there a meaningful distinction to be made between a catapult and a trebuchet? Also, what is a scorpion as relates to catapult-like machines? George R. R. Martin mentions them often in A Song of Ice and Fire, but I can't figure out how they are distinguished from the others. Googling has only muddied the waters, and I've seen all kinds of devices labeled as all different things and am thoroughly confused now.

Fight my ignorance about medieval siege machines please! If you can direct me to accurate pictures and diagrams, that'd be helpful. Thanks.
#2
Old 12-28-2005, 09:26 PM
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The difference between the various old seige weapons are in how they generate the force to hurl the payload.

Trebuchet: The payload is at one end of an arm that pivots in the middle. A (heavier) weight is at the other end. When the catch is released, the weight swings down and the end with the payload is hurled upward.

Catapult: The arm holding the payload actually bends as it is pulled down, and the spring action of it straightening hurls the payload.

And, you didn't ask, but there's another basic category

Onager: The arm holding the payload pivots through a rope in several pieces. The rope is wound tightly so that when the catch is released and the rope unwinds, it hurls the arm and payload forward.
#3
Old 12-29-2005, 03:36 AM
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Quote:
Originally Posted by iamthewalrus(:3=
Trebuchet: The payload is at one end of an arm that pivots in the middle. A (heavier) weight is at the other end. When the catch is released, the weight swings down and the end with the payload is hurled upward.
Adding on here: most Trebuchets I've seen examples of had the counterweight considerably closer to the axis than the payload was (like this: C--x-------P). A science teacher I had in high school said that doing this would cause the farther out weight to have considerably more force behind it (since the counterweight will accelerate at the same speed regardless of where it is, having the payload farther away gives it more leverage or something).

Of course, the example he used was two fat guys and a skinny guy on a merry-go-round. They get it spinning, then the fat guys start climbing up to the middle while the skinny guy, not being told what's going on, tries to hang on at the end. Apparantly the skinny guy gets launched a good distance. They did this apparantly because the skinny guy was the non-contributing member of their project group for their physics class.
#4
Old 12-29-2005, 03:37 AM
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Oh, and slightly OT, at my school, the Resident's handbook has a rule specifically banning "Trebuchets, catapults, or other siege machinery" from the on-campus dorms. I would LOVE to hear the story behind THAT rule. :-D
#5
Old 12-29-2005, 04:10 AM
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Quote:
Originally Posted by Raguleader
Adding on here: most Trebuchets I've seen examples of had the counterweight considerably closer to the axis than the payload was (like this: C--x-------P). A science teacher I had in high school said that doing this would cause the farther out weight to have considerably more force behind it (since the counterweight will accelerate at the same speed regardless of where it is, having the payload farther away gives it more leverage or something).

Of course, the example he used was two fat guys and a skinny guy on a merry-go-round. They get it spinning, then the fat guys start climbing up to the middle while the skinny guy, not being told what's going on, tries to hang on at the end. Apparantly the skinny guy gets launched a good distance. They did this apparantly because the skinny guy was the non-contributing member of their project group for their physics class.
Actually, with a long arm the payload will have a good deal less force behind it, since this is the whole point of long levers - when you use a crowbar to lift a paving slab, you're on the long end of an asymmetric lever, and your force is multiplied according to the ratio of the lengths of the arms (distance from P to x divided by distance from C to x). But, you can make your counterweight as heavy as you like (as long as your trebuchet will stand it), and the payoff is that the payload will move much faster than the counterweight. (Also, you then have the leverage of the long arm to pull the counterweight back up for the next shot.) The heavy, slow moving counterweight is balanced by the light, fast missile (just as a gun and a bullet have equal and opposite momentum, but vastly different speed and hitting power).

The (excellent!) merry-go-round gag is an instance of conservation of angular momentum. The angular momentum of the system remains constant - when you move the centre of mass inwards, the rotational speed rises to compensate. Ice skaters do the same by pulling in their arms during a spin.
#6
Old 12-29-2005, 10:02 AM
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Quote:
Originally Posted by iamthewalrus(:3=
Onager: The arm holding the payload pivots through a rope in several pieces. The rope is wound tightly so that when the catch is released and the rope unwinds, it hurls the arm and payload forward.
How do you wind (let alone unwind) a rope that's been cut in pieces?
#7
Old 12-29-2005, 10:19 AM
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Quote:
Originally Posted by Rubystreak
We have been watching Lord of the Rings again, and trying to figure out what all the war machines are called. Some controversy has arisen as to the difference between a catapult and a trebuchet. We get that a ballista fires arrows or bolts, but is there a meaningful distinction to be made between a catapult and a trebuchet? Also, what is a scorpion as relates to catapult-like machines? George R. R. Martin mentions them often in A Song of Ice and Fire, but I can't figure out how they are distinguished from the others. Googling has only muddied the waters, and I've seen all kinds of devices labeled as all different things and am thoroughly confused now.

Fight my ignorance about medieval siege machines please! If you can direct me to accurate pictures and diagrams, that'd be helpful. Thanks.
Here's a basic site with a couple of diagrams:

http://channel4.com/history/time...e_engines.html
#8
Old 12-29-2005, 10:49 AM
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Quote:
Originally Posted by iamthewalrus(:3=
Trebuchet: The payload is at one end of an arm that pivots in the middle. A (heavier) weight is at the other end. When the catch is released, the weight swings down and the end with the payload is hurled upward.
That's an example of a counterweight trebuchet, and is what the defenders of Minas Tirith used in the recent Return of the King film. Here's a picture.

Another type of trebuchet is the traction trebuchet, which is powered by people pulling down on ropes attached to the short arm instead of a counterweight attached to the short arm. A picture of one of these.

As for the "scorpion" mentioned in the OP -- it's the same thing as an onager or mangonel. When the throwing arm is extended upright, apparently it gives the impression of a scorpion with its sting raised. Furthermore, the "onager" term comes from the Greek onagros, or "wild ass", as when the projectile is released, the machine lifts up somewhat in the rear like a donkey kicking its back legs out.
#9
Old 12-29-2005, 11:07 AM
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The trebuchet was the Big Bertha of siege engines. Since catapults and onagers relied on the elasticity of materials, their payload was limited by the strain limits of the wood, sinew or rope that was being stretched (as well as fatigue failure, though that was less understood in the day). The counterweight system of the trebuchet had a much higher upper limit.

The trebuchet could throw loads that would actually stand a good chance of damaging a castle wall. Catapults and onagers were more effective against people.

Trebuchets took longer to reload and required a lot more wood (and stone/earth for the counterweight) to build, so they had those drawbacks.
#10
Old 12-29-2005, 12:09 PM
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One of the trebuchet shows I watched was one where modern riggers and engineers see if they can reconstruct ancient machines and make them work without killing themselves. They built trebs from at least two ancient pictures, and one was shown with wheels. the engineers saw that the wheels would let the thing lunge back and forth during the launch, and they feared that would cut down the performance. They tried it with the wheels chocked, and with them free. To their surprise, it flung the missile further with free wheels.
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#11
Old 12-29-2005, 01:07 PM
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This is why I love the Straight Dope. I now understand these various machines of war, as well as I'm going. Thanks, you guys!
#12
Old 12-29-2005, 02:50 PM
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Quote:
Originally Posted by Rubystreak
We have been watching Lord of the Rings again, and trying to figure out what all the war machines are called. Some controversy has arisen as to the difference between a catapult and a trebuchet. We get that a ballista fires arrows or bolts, but is there a meaningful distinction to be made between a catapult and a trebuchet? Also, what is a scorpion as relates to catapult-like machines? George R. R. Martin mentions them often in A Song of Ice and Fire, but I can't figure out how they are distinguished from the others. Googling has only muddied the waters, and I've seen all kinds of devices labeled as all different things and am thoroughly confused now.

Fight my ignorance about medieval siege machines please! If you can direct me to accurate pictures and diagrams, that'd be helpful. Thanks.
Incidentally, in the Siege of Minas Tirith scene from the movie, Sauron's forces were using catapults, while the defenders had trebuchets.
#13
Old 12-30-2005, 02:08 AM
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Doesn't the word "Engineer" come from the old English word for the guys who ran these things? Apparantly they were the front-line eggheads of their day, equivilant to the guys who play with the computers that launch sophisticated missiles in today's militaries
#14
Old 12-30-2005, 06:10 AM
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More pictures than you might want:

http://images.google.com/images?q=tr...=Search+Images

If this doesn't work, go to google.com, type in trebuchet, hit Images and then ENTER.
#15
Old 12-30-2005, 06:22 AM
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Quote:
Originally Posted by iamthewalrus(:3=
Catapult: The arm holding the payload actually bends as it is pulled down, and the spring action of it straightening hurls the payload.
Cite? I've never seen this as the driving force in any period examples. All period catapults I've seen are either counterpoise or torsion.

There's a problem with terminology because the Ancients and medievals were fast-and-loose with theirs, and in any case weren't a monolithic culture. What it's called in 100 BC Persia may be very different from what the same thing is called in 12thC Andalusia.

I tend to use the word "catapult" for any indirect trajectory weapon, so onagers/scorpions/mangonels, and the whole fustibalus =>pierrier=>bricole=>mangoneau=>trebuchet continuum* are all catapults, but ballistae and "arbalette a tour" are not.

* the progression goes somewhat like this for me:
fustibalus (slingstaff) =>
pierrer (multi-human-powered catapult) =>
bricole (a pierrer with a counterweight to aid the pull team) =>
mangoneau/mangonel** (a catapult powered by fixed counterweight alone) =>
trebuchet (a catapult powered by a free-swinging counterweight).

...but I must emphasise that this is my definition list, and others will differ.

** Yes, the word is used for both a torsion and counterweight engine in different sources. That's just the way things are.
#16
Old 01-03-2006, 02:16 PM
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There are basically 4 classes of siege engines:

Tension: arrow/bolt slingers (ballistas) which are based on bow and arrow technologies. NOTE: The crossbow was the first weapon outlawed by the Pope for giving an unfair advantage because it did not require any degree of "skill" to use (compare a gatling gun to a cannon).

Torsion: Winding ropes tightly and then releasing (onager)

Counterweight: men pulled down heavy weights (several tons) and then release causing long arm to thrust forward and propel objects (trebuchets)

Traction: men pull down and release (some catapults). This was the least used type.

The names of siege engines is not as important as how they were powered. It is the source of ultimate power that distinguishes them.

The earliest siege engine is the ladder. The most advanced midieval siege weapon was the siege tower which contained multiple types of siege weapons.

The most modern type of siege weapon are probably on the order of the smart bombs we used in Afghanistan.

Quote:
Originally Posted by MrDibble
Cite? I've never seen this as the driving force in any period examples. All period catapults I've seen are either counterpoise or torsion.

There's a problem with terminology because the Ancients and medievals were fast-and-loose with theirs, and in any case weren't a monolithic culture. What it's called in 100 BC Persia may be very different from what the same thing is called in 12thC Andalusia.

I tend to use the word "catapult" for any indirect trajectory weapon, so onagers/scorpions/mangonels, and the whole fustibalus =>pierrier=>bricole=>mangoneau=>trebuchet continuum* are all catapults, but ballistae and "arbalette a tour" are not.

* the progression goes somewhat like this for me:
fustibalus (slingstaff) =>
pierrer (multi-human-powered catapult) =>
bricole (a pierrer with a counterweight to aid the pull team) =>
mangoneau/mangonel** (a catapult powered by fixed counterweight alone) =>
trebuchet (a catapult powered by a free-swinging counterweight).

...but I must emphasise that this is my definition list, and others will differ.

** Yes, the word is used for both a torsion and counterweight engine in different sources. That's just the way things are.
#17
Old 01-03-2006, 05:11 PM
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And before anyone yells "cite" the crossbow was banned for use against Christians by Pope Urban II in 1097 and the Second Lateran Council banned arbalests (another type of crossbow) in 1139. They were seen as "unchivalrous and a threat to social order" because of their range and lack of expertise required to operate (i.e., peasants could kill nobles anonymously (from wikipedia).

Quote:
Originally Posted by Cillasi
There are basically 4 classes of siege engines:

Tension: arrow/bolt slingers (ballistas) which are based on bow and arrow technologies. NOTE: The crossbow was the first weapon outlawed by the Pope for giving an unfair advantage because it did not require any degree of "skill" to use (compare a gatling gun to a cannon).

Torsion: Winding ropes tightly and then releasing (onager)

Counterweight: men pulled down heavy weights (several tons) and then release causing long arm to thrust forward and propel objects (trebuchets)

Traction: men pull down and release (some catapults). This was the least used type.

The names of siege engines is not as important as how they were powered. It is the source of ultimate power that distinguishes them.

The earliest siege engine is the ladder. The most advanced midieval siege weapon was the siege tower which contained multiple types of siege weapons.

The most modern type of siege weapon are probably on the order of the smart bombs we used in Afghanistan.
#18
Old 01-05-2006, 04:56 AM
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After two years of lurking here, I finally had to "de-cloak" and post this link. If you've never seen this, then boy are you in for a larf. They're both animated gif's so make sure you can view them in IE or whatever you're using.


Part 1

Part 2
#19
Old 01-05-2006, 05:57 AM
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Quote:
Originally Posted by AskNott
One of the trebuchet shows I watched was one where modern riggers and engineers see if they can reconstruct ancient machines and make them work without killing themselves. They built trebs from at least two ancient pictures, and one was shown with wheels. the engineers saw that the wheels would let the thing lunge back and forth during the launch, and they feared that would cut down the performance. They tried it with the wheels chocked, and with them free. To their surprise, it flung the missile further with free wheels.
I remember this from a C4 documentary on the construction of two such machines, one with wheels, one without.

The idea IIRC is that without wheels, the counterweight is forced to move through an arc downwards. With wheels, the base of the trebuchet moves and the counterweight falls more or less directly downwards, making it accelerate faster and therefore the payload is launched with more force.

Poorly explained and needs pictures I know, but that's the jist of what was happening.
#20
Old 01-05-2006, 06:04 AM
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That's funny!
#21
Old 01-05-2006, 06:31 AM
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Quote:
Originally Posted by Detigr
After two years of lurking here, I finally had to "de-cloak" and post this link. If you've never seen this, then boy are you in for a larf. They're both animated gif's so make sure you can view them in IE or whatever you're using.


Part 1

Part 2
::picks himself up off the floor, holding ribcage, wiping tears from his eyes::
#22
Old 01-05-2006, 09:07 AM
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That parody was one of the funniest things I've seen in a long time.

For anybody interested in watching siege engines at play, look into Pumpkin Chucking.
#23
Old 01-05-2006, 10:01 AM
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Quote:
Originally Posted by Pushkin
The idea IIRC is that without wheels, the counterweight is forced to move through an arc downwards. With wheels, the base of the trebuchet moves and the counterweight falls more or less directly downwards, making it accelerate faster and therefore the payload is launched with more force.

Poorly explained and needs pictures I know, but that's the jist of what was happening.
I think this trebuchet is designed to address that idea.
#24
Old 01-05-2006, 10:16 AM
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I have seen 3 designs for making the weight fall straighter: Wheels, bucket, and floating arm (as in above link)

NOVA episode where they made wheeled and bucket Treb:
http://pbs.org/wgbh/nova/lostempires/trebuchet/
http://shoppbs.org/product/index...entPage=family

Brian
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