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siege-engines-msg – 1/10/08
Catapults, trebuchets. Period and modern. Tabletop models.
NOTE: See also the files: crossbows-msg, p-archery-msg, archery-books-msg, c-archery-msg, crossbow-FAQ, arch-books-FAQ, pottery-wepns-msg, slings-msg.

This file is a collection of various messages having a common theme that I have collected from my reading of the various computer networks. Some messages date back to 1989, some may be as recent as yesterday.

This file is part of a collection of files called Stefan's Florilegium. These files are available on the Internet at:
I have done a limited amount of editing. Messages having to do with separate topics were sometimes split into different files and sometimes extraneous information was removed. For instance, the message IDs were removed to save space and remove clutter.
The comments made in these messages are not necessarily my viewpoints. I make no claims as to the accuracy of the information given by the individual authors.
Please respect the time and efforts of those who have written these messages. The copyright status of these messages is unclear at this time. If information is published from these messages, please give credit to the originator(s).
Thank you,

Mark S. Harris AKA: THLord Stefan li Rous

Stefan at


Military Engines
Inasmuch as you seem to think that you have described most of the

weapons which are convenient to have in naval warfare or in fighting on

horseback, I will now ask you to say something about those which you

think are most effective in besieging or defending castles.
All the weapons that we have just discussed as useful on ships

or on horseback can also be used in attacking and defending castles; but

there are many other kinds. If one is to attack a castle with the

weapons which I have enumerated, he will also have need of trebuckets: a

few powerful ones with which to throw large rocks against stone walls to

determine whether they are able to resist such violent blows, and weaker

trebuckets for throwing missiles over the walls to demolish the houses

within the castle. But if one is unable to break down or shatter a stone

wall with trebuckets, he will have to try another engine, namely the

iron-headed ram, for very few stone walls can withstand its attack. If

this engine fails to batter down or shake the wall, it may be advisable

to set the cat t to work. A tower raised on wheels ~ is useful in

besieging castles, if it is constructed so that it rises above the wall

which is to be stormed, even though the difference in height be only

seven ells; but the higher it is, the more effective it will be in

attacking another tower. Scaling ladders on wheels which may be moved

backward and forward are also useful for this purpose, if they are

boarded up underneath and have good ropes on both sides. And we may say

briefly about this craft, that in besieging castles use will be found

for all sorts of military engines. But Whoever wishes to join in this

must be sure that he knows precisely even to the very hour when he shall

have need for each device.
Speculum Regale
FROM: Simon the Strange

SUBJECT: War Engines

* Original: AREA.... MENSA

* Original: FROM.... Bruce Wilson

* Original: TO...... Dave Aronson
There was a front-page feature story in the July 30 Wall Street

Journal that might be of interest to you and other SCA types:

"A Scud It's Not, But the Trebuchet Hurls a Mean Piano"

"Giant Medieval War Machine Is Wowing British Farmers

And Scaring the Sheep"

It seems some guy in England's managed to build a full-size (some 4

stories tall) working trebuchet and uses it to hurl grand pianos,

small cars, and animal carcasses across the British countryside.

Some British parachutists want to try it, but the acceleration is 0

to 90 mph in 1.5 seconds and produces centrifugal force of 20 Gs,

which may be enough to burst human blood vessels.

One of his incentives to build the thing was a "nutter cousin" in

Northumberland who made a small trebuchet he used to hurl porcelain

toilets that'd been soaked in gasoline and set afire. The article

said that a local paper had headlined the story "Those Magnificent

Men and Their Flaming Latrines." :-)


* Origin: Aronson Consulting: TIDMADT 703-370-7054, voice x6508 (1:109/120)

From: JRECHTSCHAFF at hamp.hampshire.EDU

Date: 13 Nov 91 22:48:00 GMT

Organization: The Internet
Greetings unto the Rialto from Lyanna ferch Gwynhelek,
Concerning Siege Engines (also written by Pierre)
The trebuchet is basically a counter-weighted lever. The potential

energy of a weight is released across a fulcrum (pivit point) to import

kinetic energy to a projectile lodged at the far end of the lever.

It follows that the greater the weight the less the friction, the lower the

lever, the greater the mechanical advantage. The lighter more streamlined

the projectile, the greater the thrown distance.

The weight must fall through an arc to translate potential to kinetic

energy. It's vertical acceleration (ignoring friction) wil be 9.8m/sec.

squared. Now it will take a while for the weight to reach it's terminal

velocity. Aha! You say blinded by a brilliant flash of the inuitively

obvious. To get maximum acceleration my trebuchet counter-weight must

fall "x" feet which means that this sucker has got to be tall. Tall

equals big. How big? Try 120-150'. (See The Wall St. Journal Tuesday

31, July for an excellent article on a piano throwing modern trebuchet.)

Now the overall height can be reduced by digging a pit between the

uprights, but physics is still physics and you still need clearence for the

weight so about 120' is it. Needless to say the greater the mass (the more

accelerated the counter-weight) the more convinient - try depleted urainium.

Seriously, the most readily available wieght is lead. Don't start messing

around with old batteries - nasty stuff can happen to you and mother earth.

A ton or two works well.

The longer the lever arm the better. Now we're into materials. I happen

to have an 80' ash pole but I like it in it's present form - as a tree.

Old growth spruce is hard to find. You're best off laminating (laminating

is period) up a pole from close grain spruce. Consult a wooden boat maker.

If you are building a machine you now have two uprights (telephone poles

are OK) about 6 to 8 feet apart, (obviously this isn't very portable),

a very long lever pivoting on trunions across the top of the uprights and

a counter weight fastened (hinged is best) to the short end of the lever.

You now put a cup on the throwing end of the lever sufficient to hold a

dead horse or a prisoner-of-war of choice. (See projectile below)

You collect a bunch of serfs, haul the long end down with a rope, load,

and have everyone let go. (In addition to a dozen rope burned palms, you

let the end of the rope loop around your ankle and neatly amputate it.

See trigger mechanisms) Assuming you have a pivoted or off-center counter-

weight the lever rotates from about 180 degrees (pointed down) up through

0 degrees (pointed up) over to 270 degrees (where the projectile falls

onto the ground) on down to the ground where it shatters while pegging

the idiots standing there (remember the trigger crew?) or rebounds and

jumps on its trunions or if your lucky, pendulums for a while.

Obviously you need to stop the arm at some point. The theretical

ballistically optimum turning point is 45 degrees. In practice however,

this does not allow for sufficient fall of the counterweight, for friction

etc. A practicle point is at about 30 degrees. The stop must be strudy

well padded and well braced lest the lever frame shatter. This gives rise

to an old medieval saying, "It is easy to build something that fires once

building one that fires twice is something else." If the frame is

built on skids the azimuth can be changed, if it is (was) more usual it is

anchored to the ground, the azimuth is fixed. Range can be altered by

changing the release (trigger) point or by building up the stop padding.

(Throw a few more sheep skins on the stop.)

Range can be increased by a third by use of a sling. The sling is

one-half the length of the lever and rides with it's projectile, in a

trough under the machine. There should be no slack. One end of the

sling is fastened to the lever, the other loops over a horn at the end of

the lever. (opps that should be that the sling is fastened to one end of

the lever, the other loops over a horn at the end of the lever). Note that

the release point is now changed by 1/2 the angle between the fastining point

and the horn. The simplest trigger (and its shortcomings not to mention

its tendency to foul the frame and sling) has been mentioned. A second

form of trigger is a wedged in bar across the lever. The wedge is knocked

out with a sledge hammer. However, one can be seriously killed by flying

crossbars the size of railroad ties.

Another trigger consists of a hook and eye released when a lanyard is

yanked by a whipped up group of draft animals (not squirrels.) Payne-Salwery

and others have illustrated some very nice trigger mechanisms that could be

made by any competent smith.

As with most medieval siege engines, tecbuchets were transported, knocked

down and erected on site. Philippe Contamine writes in Guerre dans le Moyens

Ages amusingly of an English king who spent months transporting and erecting

a monster trebuchet to besiege a castle in Scotland. When the enemy saw that itwas ready they marched out and tried to surrender. The king, understandably

piqued, refused, sent them back in, fired demolished half the castle and its

garrison and then honor being served accepted their surrender. It is possible

to build a trebuchet but not really worth the bother when you can build a

ballista or catapult equally portable, wit hvastly better performance. I

have a ballista with a 1000 # prod that I can carry by myself. It will shoot

a 2' 3/8" rebar bolt through a car door.

Reference projectiles. I propose an SCA standard, the humble common brick.

it's cheap, readily available and regular in siza and shape. It generally

conforms to the size of a medieval brick although it is significantly

heavier. It is self-replenishing - as you shoot down the wall, you get

more ammo!

-Pierre D'Ussf, Artificer

aka Peter Maleady


From: ddfr at (david director friedman)

Date: 14 Nov 91 05:23:41 GMT

Organization: University of Chicago Computing Organizations

"It's vertical acceleration (ignoring friction) wil be 9.8m/sec.

squared. Now it will take a while for the weight to reach it's

terminal velocity." (Lord Pierre D'Ussf, discussing the physics of a


The figure you give for acceleration would be appropriate for a mass

falling free by itself. The counterweight of the trebuchet, however,

is accelerating the throwing arm and the projectile as well--and

their weight is pushing in the other direction, since they are on the

other side of the pivot. Furthermore, the relation between vertical

acceleration of the weight and angular acceleration of the arm etc.

changes with the angle. When the arm reaches vertical, for example, a

small rotation produces no vertical displacement, since at that point

the velocity of the counterweight is horizontal.
Since this is a rotational problem, it is much easier to solve it in

terms of rotational dynamics. Angular acceleration is torque divided

by moment of inertia. The torque is ((mass of the counterweight times

its distance from the pivot) minus (mass of the rest of the system

(the stuff on the other side of the pivot) times the distance of its

center of mass from the pivot)) times sin of the angle of the arm

from vertical.
I do not see the relevance of terminal velocity. You reach terminal

velocity when air resistance exactly balances torque. I doubt that is

likely to happen at any plausible speed.
"Needless to say the greater the mass (the more accelerated the

counter-weight) the more convinient- try depleted urainium." (Lord

The acceleration of a falling body does not (air resistance aside)

depend on its mass, as Galileo pointed out some years back.

Increasing the ratio of the mass of the counterweight to the mass of

the rest of the system will increase acceleration (see my verbal

equation above)--but that would not be true if your original

statement (quoted before this one) were correct.

I think you may be confusing weight with density. You can get plenty

of weight with a box full of dirt and stones, which I think is what

they mostly used.
"The theretical ballistically optimum turning point is 45 degrees. In

practice however, this does not allow for sufficient fall of the

counterweight, for friction etc. A practicle point is at about 30

degrees." (Lord Pierre)

Forty-five degrees is the optimum angle if velocity does not depend

on the angle. With a trebuchet velocity is increasing as the

counterweight falls. The effect can be exactly calculated--that part

is not a matter of "practical points." Patri, back when he was

teaching physics classes, used to give it as a problem to his

students. Friction is more complicated.

With a sling, the velocity of the projectile when it is released is

no longer at right angles to the arm, as it is with a rigid throwing

arm. That means that it should be possible to combine the optimal

angle for the projectile's velocity (45 degrees from vertical) with

maximum velocity (throwing arm upright, counterweight all the way

down), giving a longer range than would be possible for the same

trebuchet without a sling.
"It is possible to build a trebuchet but not really worth the bother

when you can build a ballista or catapult equally portable, wit

hvastly better performance." ((Lord Pierre)
To build a ballista or catapult you need big twisted skeins of very

strong cord--and there are, I believe, problems as you try to scale

the beast up. All a trebuchet needs is wood, a little metal for

release mechanism and such, and dirt (what they filled the

counterweight with).
David Friedman (Cariadoc has never heard of torque--he gets his

physics from Aristotle)

From: cctimar at (Charles)

Date: 18 Nov 91 05:51:21 GMT

Organization: Vanderbilt University student of numerology
His Grace, the Duke Cariadoc of the Bow writeth:


> "The theretical ballistically optimum turning point is 45 degrees. In

> practice however, this does not allow for sufficient fall of the

> counterweight, for friction etc. A practicle point is at about 30

> degrees." (Lord Pierre)


> Forty-five degrees is the optimum angle if velocity does not depend

> on the angle. With a trebuchet velocity is increasing as the

> counterweight falls. The effect can be exactly calculated--that part

> is not a matter of "practical points." Patri, back when he was

> teaching physics classes, used to give it as a problem to his

> students. Friction is more complicated.
Two points need to be considered, here. The first is that the optimum

angle is the angle at which you are hitting your target, which is not

necessarily the angle that throws the projectile the farthest. Of course,

if you are overshooting, you will probably correct by removing a stone

from the counterweight, rather than trying to adjust the stop.
The second is that, because of air resistance, the longest range for a

fixed firing velocity can usually be achieved by firing the projectile at

35-40 degrees above vertical. The best way to compute the actual angle is

to do a computer simulation. The second best is just trial and error - I

would start by subtracting 5 degrees from the angle that you compute the

way Cariadoc suggests.

Of course, there is also some friction involved in the arm spinning on its

axis. I don't know how large an effect this will have.


-- Charles, student, in Glaedenfeld, Meridies

From: PAMCCOY at GALLUA.BITNET ("Pat McCoy a.k.a. Bones")

Date: 26 Nov 91 22:49:00 GMT

Organization: The Internet
Greeting unto all on the Rialto from Padraigin nic'Aodha!
I am enclosing a message from the physics teacher to all

who responded to our inquiries concerning siege machines

that chunk punkins, pianos and cars. :-)
"I am the physics teacher (and non-SCA member) who has been

asking questions (through a member on the Rialto) about

trebuchets. I have taken great pleasure in the responses

Pat McCoy had forwarded me from the Rialto and appreciate

the resource you have been to me and my students.
In early October, I assigned my introductory Physics students

the following problem: "Design a machine which can throw an

8-10 pound pumpkin as far as possible, using the limited materials

available." The students took sevel different approaches to the

problem, from creating original designs to researching ancient

siege machines.

The trebuchet idea cropped up from a Wall Street Journal article

on an Englishman's current project, (cited here incidentally).

However, there was not enough information from that article to

build a machine. The tips and suggestions (including excellent

references) provided from several members on the Rialto set us off

in a better direction.

One team of students, (an all-girls team, by the way), constructed

a small trebuchet, a simple counter lever device, (16-foot throwing

arm, 225 lb. counterweight) and proceeded to tromp the other high

school contenders. Our best throw was only about 37 yard with a

6-pound pumpkin, but the sight of that machine working was beautiful.

The sling just sailed magnificently up and over, releasing the pumpkin

at least a yard above the throwing arm. We adjusted parameters,

(counterweight mass, length of sling lines, sling attachment,

weight of the pumpkin, etc.) and collected data that is going to

provide us with problems for much of the rest of the year. We have

videos which will be analyzed in slow motion for other data.
The class's three machines (the trebuchet, a catapult style and a

centrifugal design) were carted to Delaware on November 2nd to

participate in an annual pumpkin throw with adult teams from the

local area. We were the only high school group to throw. Best

throw of the day was 702.6 feet, somewhat short of the world record

set last year at 776 feet. These throws were accomplished by an

adult team with a centrifugal machine consisting of a 30-foot arm

driven with a belt from the rear axle of a pick-up truck.

(I apologize for this non-period stuff if it is not of interest.

I didn't know how much to share about this rather extensive project,

after getting such kind responses from the many of you who shared

your knowledge.)

There seems to be a clamor from physics-student-wannabe's for a

repeat performance next year. Now that we know a little more about

what we are doing and have some references in hand, I hope to throw

in the 'several hundred feet' range mentioned graciously in several

Rialto postings.
The class and I thank all of you who responded to our queries and

commended you on your preservation of the Middle Ages. May the Age

of Chivalry live on forever.
In debt to the Society,
Mary S. Ellsworth

Science Department

Model Secondary School for the Deaf

at Gallaudet University,

Washington, DC"
Thus ends the letter from MSSD and I also thank you for your help

in this endeavor!

Padraigin nic'Aodha - Barony of Storvik - Kingdom of Atlantia

Pat McCoy - Washington, DC

Trebuchet blues

15 May 92

From: rday at (Robert E Day)


Organization: The Ohio State University
In article <01GK17U2M8B48WW44W at LEO.BSUVC.BSU.EDU> 00MJSTUM at leo.bsuvc.bsu.EDU wr


>Greetings unto all gentles who may read this!


>I have nearly finished a "quickie" prototype of a trebuchet. The arm

>is merely 4 ft. in length. However, I have now come to that difficult

>position of attaching a sling. My first attempts (with a hacked up

>badmitton net) were, um, less than successful. I tied the ends of the

>"sling" in such a manner that it would have a cupping effect... however

>when the sling is released from its hook the projectile merely rolls

>up the length of the sling and gets caught in the end. I've tried

>remedying this in several ways with either no change or even worse side-



>Can anyone, who has made one, enlighten me with a description? I would

>me _most_ grateful!


I have a friend who made one with an arm about 8 feet long. He used a small

piece of leather(about 6" square) attached to rope as the sling. One end of

the rope was attached to the arm only by a ring which hung on a hook and the

other was securely attached to the arm. He used it to throw 8" warrer ballons.


If the price that I must pay to obtain my * Robert E. Day/Syr Otto von *

freedom, is to acknowledge that the Gov- * Schwartzkatz, Shire Mugmort *

ernmet was granted the power to infringe * Barony Middle Marches, *

on them, then I am not free. Paul Anderson* Middle Kingdom *

15 May 92

From: amlsmith at (Andrew Smith 8848111)


Organization: Memorial University of Newfoundland

Greetings unto the Rialto from Sebastien. Located in far off

Ar n-Eilean-ne, (Nfld., Canada).

I have reason to believe that I am the last siege engineer

before hitting Drachenwald. I too, am searching for information.

The choice of the Trebuchet is a good one, less stesses are involved

and therefore, safer.

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