|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: http://www.florilegium.org
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.
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Mark S. Harris AKA: THLord Stefan li Rous
Stefan at florilegium.org
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.
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
-Pierre D'Ussf, Artificer
aka Peter Maleady
From: ddfr at quads.uchicago.edu (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
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
David Friedman (Cariadoc has never heard of torque--he gets his
physics from Aristotle)
From: cctimar at athena.cas.vanderbilt.edu (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
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
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
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
Model Secondary School for the Deaf
at Gallaudet University,
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
15 May 92
From: rday at magnus.acs.ohio-state.edu (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 morgan.ucs.mun.ca (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. 01gk17u2m8b48ww44w>