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A motte and bailey CastleA motte and bailey Castle Easy to build. (They could be built in less than a Easy to build. (They could be built in less than a

week)week)Easy to defend. (And remember, the Normans were Easy to defend. (And remember, the Normans were an invading army)an invading army)Could easily be modified later (e.g. A stone tower Could easily be modified later (e.g. A stone tower rather than wooden tower)rather than wooden tower)Over 70 were built during William's reign as King of Over 70 were built during William's reign as King of England England

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Main features:Main features: Defensive featuresDefensive features:: The Motte is hard to attack, as its sides are The Motte is hard to attack, as its sides are

quite steep. quite steep. On average a Motte was no higher than 5 On average a Motte was no higher than 5

metres.metres. There are some examples of Motte's that There are some examples of Motte's that

were much higher than this though, Clifford's were much higher than this though, Clifford's Tower at York for example. Tower at York for example.

The ditches around both the Motte and the The ditches around both the Motte and the bailey would prove a difficult obstacle to bailey would prove a difficult obstacle to overcome for any attackers, with the fence overcome for any attackers, with the fence and possibly a drawbridge to overcome and possibly a drawbridge to overcome immediately after the ditch the castle immediately after the ditch the castle becomes a very strong fortress. becomes a very strong fortress.

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Main features:Main features: Defensive frailtiesDefensive frailties:: A Motte would be susceptible to collapse A Motte would be susceptible to collapse

under the weight of a castle, under the weight of a castle, whilst they were good in the short term the whilst they were good in the short term the

castle would require shoring up and possibly castle would require shoring up and possibly even rebuilding in the longer term. even rebuilding in the longer term.

Wooden fortifications are also susceptible to Wooden fortifications are also susceptible to simple methods of attack. simple methods of attack.

They burn for example and given time They burn for example and given time would rot due to inclement weather. would rot due to inclement weather.

Later stone structures on these sites would Later stone structures on these sites would of course overcome this problem (although of course overcome this problem (although the Motte itself would be placed under the Motte itself would be placed under greater strain).greater strain).

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Capturing a castle! Capturing a castle!

Launceston Castle

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Rochester Castle (1215)-the fall of this mighty Rochester Castle (1215)-the fall of this mighty fortification produced temporary loss of confidence in fortification produced temporary loss of confidence in castles. castles.

Dover Castle (1216)-mining of the castle was only Dover Castle (1216)-mining of the castle was only thwarted by a relieving army. It produced the building of thwarted by a relieving army. It produced the building of spur to stop the mining of castles. A spur is a wall or spur to stop the mining of castles. A spur is a wall or earthwork projecting sharply from main defences. earthwork projecting sharply from main defences.

Berkhamsted Castle (1217)-Henry III ordered his Berkhamsted Castle (1217)-Henry III ordered his constable of the castle to surrender on humanitarian constable of the castle to surrender on humanitarian grounds. grounds.

Bedford Castle (1224)-One of the best documented Bedford Castle (1224)-One of the best documented sieges. The garrison of the castle was hanged after sieges. The garrison of the castle was hanged after defeat. defeat.

Kenilworth Castle (1266)-the castle held out for six Kenilworth Castle (1266)-the castle held out for six months against Henry III, and only surrendered because months against Henry III, and only surrendered because of the lack of food and disease. of the lack of food and disease.

Here are some notable siegesHere are some notable sieges

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Attack the castle!Attack the castle! OffenceOffence:: 1. Direct 1. Direct

Assault Assault 2. Siege 2. Siege

Tower Tower 3. Trebuchet 3. Trebuchet 4. Battering 4. Battering

Ram Ram 5. Tunnel5. Tunnel

Defence:Defence: 6. Walls 7. Archers 8. Gatehouse 9. 6. Walls 7. Archers 8. Gatehouse 9.

MoatMoat

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Medieval Arms RaceMedieval Arms Race War in medieval times was about the control of land. War in medieval times was about the control of land. Garrisons of knights and other soldiers who lived in Garrisons of knights and other soldiers who lived in

castles controlled the land around their stone castles controlled the land around their stone fortresses. fortresses.

To conquer a territory, an attacking army would have To conquer a territory, an attacking army would have to strike and take these central strongholds. to strike and take these central strongholds.

To do so, they would launch a siege. To do so, they would launch a siege. Over the centuries, medieval armies developed Over the centuries, medieval armies developed

military strategies to fight a siege. military strategies to fight a siege. Weapons of war also evolved, often in response to Weapons of war also evolved, often in response to

the technological advances of the enemy. the technological advances of the enemy. By the mid-12th century, siege warfare had By the mid-12th century, siege warfare had

developed into a science, practiced by an engineer developed into a science, practiced by an engineer corps called corps called ingeniatores.ingeniatores.

Here we describe some of the major weapons and Here we describe some of the major weapons and strategies used in what became a medieval arms strategies used in what became a medieval arms race. Let the siege begin. race. Let the siege begin.

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Direct AssaultDirect AssaultA direct assault was the A direct assault was the

most dangerous way for most dangerous way for attackers to try to take a attackers to try to take a castle. castle.

Soldiers either scaled Soldiers either scaled walls with ladders or walls with ladders or overran castle walls overran castle walls breached by tunnels, breached by tunnels, battering rams, or artillery. battering rams, or artillery.

Sometimes they attacked Sometimes they attacked two or three spots around two or three spots around the castle at once to the castle at once to surprise their foe or divide surprise their foe or divide castle defences, castle defences,

and sometimes they and sometimes they approached the wall approached the wall hidden within a trench hidden within a trench or tunnel. or tunnel.

Archers and Archers and crossbowmen would crossbowmen would cover soldiers while cover soldiers while they tried to break a they tried to break a wall or storm over it.wall or storm over it.

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Direct AssaultDirect AssaultDefenders, perched on the Defenders, perched on the

castle wall or in narrow castle wall or in narrow windows called loopholes, windows called loopholes, literally had the upper hand. literally had the upper hand.

Archers rained arrows down Archers rained arrows down on attackers, on attackers,

Soldiers Soldiers pushed ladders off the wall pushed ladders off the wall

with forked poles, with forked poles, dropped rocks or dropped rocks or fire pots filled with burning fire pots filled with burning

tar, or poured scalding tar, or poured scalding water, wine, or hot sand water, wine, or hot sand (which could enter armour) (which could enter armour) down onto those below. down onto those below.

Attacking armies sometimes Attacking armies sometimes blockaded a castle instead blockaded a castle instead

Though safer than Though safer than fighting, starving fighting, starving occupants out of a castle occupants out of a castle was not always was not always straightforward. straightforward.

Attacking armies were Attacking armies were reluctant to wait out a reluctant to wait out a winter without permanent winter without permanent housing. housing.

Castle dwellers kept Castle dwellers kept stockpiles of food and stockpiles of food and drilled water wells within drilled water wells within the castle's walls. the castle's walls.

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Siege Tower or Siege Tower or BelfrieBelfrieAttackers sometimes built a Attackers sometimes built a

siege tower to scale castle siege tower to scale castle walls. walls.

Soldiers lay in wait inside Soldiers lay in wait inside the structure as others the structure as others wheeled it to the castle. wheeled it to the castle.

Once there, the soldiers Once there, the soldiers lowered a drawbridge at the lowered a drawbridge at the top of the tower onto the top of the tower onto the castle wall. castle wall.

Some towers were almost Some towers were almost 100 feet high, and in the 100 feet high, and in the siege of Kenilworth Castle, siege of Kenilworth Castle, fully 200 archers and 11 fully 200 archers and 11 catapults were crowded into catapults were crowded into a single tower. a single tower.

Siege towers were difficult Siege towers were difficult and time-consuming to and time-consuming to build, build,

Castle defenders could Castle defenders could burn them down with burn them down with fire arrows or firepotsfire arrows or firepots

Sometimes castle Sometimes castle knights launched knights launched surprise raids on a tower surprise raids on a tower to destroy it during to destroy it during construction. construction.

To protect their siege To protect their siege engine, attackers engine, attackers draped it with rawhides draped it with rawhides of mules or oxen. of mules or oxen.

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TrebuchetTrebuchetDuring peacetime, During peacetime,

castle commanders castle commanders used trebuchets to used trebuchets to launch roses at ladies launch roses at ladies during tournaments.during tournaments.

But during a siege, But during a siege, these missile launchers these missile launchers were one of the most were one of the most fearsome weapons of fearsome weapons of medieval times. medieval times.

Early trebuchets were Early trebuchets were powered by muscle, but powered by muscle, but later versions relied on later versions relied on a huge counterweight a huge counterweight that swung a long arm. that swung a long arm.

When the When the counterweight counterweight was dropped, the was dropped, the device launched device launched a missile from a a missile from a sling at the end sling at the end of the arm. of the arm. http://www.pbs.org/wgbh/nova/lostempires/trebuchet/destroy.html

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TrebuchetTrebuchetTrebuchets could Trebuchets could

launch missiles launch missiles hundreds of yards in hundreds of yards in large, lobbing arcs at or large, lobbing arcs at or even over a castle wall. even over a castle wall.

The best trebuchets The best trebuchets fired stone missiles fired stone missiles weighing up to 400 weighing up to 400 pounds—big enough to pounds—big enough to do serious damage to a do serious damage to a castle wall.castle wall.

Attackers also used Attackers also used them to launch dung or them to launch dung or dead animals into the dead animals into the castle with the intention castle with the intention of spreading disease. of spreading disease.

Sometimes they shot out the Sometimes they shot out the severed heads of enemy severed heads of enemy soldierssoldiers

If a trebuchet was set up too If a trebuchet was set up too close to a castle, archers close to a castle, archers would harass its builders with would harass its builders with arrows shot from bows or arrows shot from bows or bolts from crossbows. bolts from crossbows.

Castle defenders would try to Castle defenders would try to destroy rising trebuchets destroy rising trebuchets with catapults shot from the with catapults shot from the castle wall or with sneak castle wall or with sneak attacks to burn it down. attacks to burn it down.

Caerlaverock Castle

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Battering RamBattering RamSiege armies used a battering ram to break down a gatehouse door or even smash a castle wall.

To shield themselves from attack, they built a covered shed, in which they hung a thick tree trunk on chains suspended from a beam above.

Carpenters tapered the trunk into a blunt point and capped it with iron.

The slow forward movement The slow forward movement as the battering ram was as the battering ram was wheeled toward the castle wheeled toward the castle wall earned it the nickname wall earned it the nickname "tortoise." "tortoise."

Soldiers swung the hanging Soldiers swung the hanging trunk back and forth, and the trunk back and forth, and the forward end of the trunk forward end of the trunk moved in and out of the shed moved in and out of the shed like a tortoise's head, like a tortoise's head, battering its target. battering its target.

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Battering RamBattering Ram

Castle defenders tried to burn the shed Castle defenders tried to burn the shed down with flaming arrows, though attackers down with flaming arrows, though attackers responded by covering the shed with animal responded by covering the shed with animal pelts or earth to make it fireproof. pelts or earth to make it fireproof.

Defenders sometimes dropped mattresses Defenders sometimes dropped mattresses down to cushion the blows or lowered down to cushion the blows or lowered grappling irons to grasp the trunk, grappling irons to grasp the trunk, preventing it from swinging. preventing it from swinging.

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TunnelTunnelMen called sappers Men called sappers

sometimes dug tunnels to sometimes dug tunnels to gain entrance to a castle gain entrance to a castle and thereby launch a and thereby launch a sneak attack, but more sneak attack, but more often, these miners dug often, these miners dug tunnels beneath a castle tunnels beneath a castle wall to destabilize and wall to destabilize and topple it. topple it.

They supported their They supported their tunnels with timbers, tunnels with timbers, which they then burned to which they then burned to collapse the tunnel—and, collapse the tunnel—and, hopefully, the wall above. hopefully, the wall above. A special member of the A special member of the team was the torchman. team was the torchman. He would set the tunnel on He would set the tunnel on fire and run for the tunnel fire and run for the tunnel opening .opening .

To defend themselves, To defend themselves, castle dwellers put out castle dwellers put out a bowl of water and a bowl of water and watched for ripples that watched for ripples that might indicate digging. might indicate digging.

Sometimes the castle's Sometimes the castle's garrison built counter-garrison built counter-tunnels; if the two tunnels; if the two tunnels met, fierce tunnels met, fierce battles ensued battles ensued underground. underground. Mining was undertaken at Rochester Castle in 1215, at Mining was undertaken at Rochester Castle in 1215, at

Dover Castle in 1216, and at Dryslwyn castle in 1287Dover Castle in 1216, and at Dryslwyn castle in 1287..

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The The mangonelmangonel The The mangonelmangonel was was

introduced to the Normans introduced to the Normans by the Byzantines. by the Byzantines.

This siege engine was used This siege engine was used for a century after the for a century after the Norman Conquest in 1066, Norman Conquest in 1066, and it is also referred to as a and it is also referred to as a Mangon. Mangon.

It consisted of a heavy It consisted of a heavy frame which supported a frame which supported a long arm with a cup or sling long arm with a cup or sling at the free end. at the free end.

The other extremity passed The other extremity passed through a ropes, called a through a ropes, called a skein, stretched between skein, stretched between upright posts. upright posts.

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The The mangonelmangonel The ropes would be twisted by capstans, The ropes would be twisted by capstans,

called capitals, and then the free end was called capitals, and then the free end was pulled down by a winch or windlass. pulled down by a winch or windlass.

When it was in a horizontal position the When it was in a horizontal position the arm would locked into position and the cup arm would locked into position and the cup or sling would be loaded with a stone or or sling would be loaded with a stone or incendiary material. incendiary material.

The arm would be released and it flew up The arm would be released and it flew up by the whip effect until it hit a horizontal by the whip effect until it hit a horizontal padded stop between the upright arms of padded stop between the upright arms of the frame. the frame.

The projectile would have a low inaccurate The projectile would have a low inaccurate trajectory. The range would have been trajectory. The range would have been around 200 yards. around 200 yards.

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ArchersArchersBoth attacking and Both attacking and

defending armies had defending armies had archers, though those archers, though those shooting arrows from the shooting arrows from the castle had a great castle had a great advantage.advantage.

First, castle archers were First, castle archers were almost always launching almost always launching arrows from a higher arrows from a higher position than castle position than castle attackers, which extended attackers, which extended their range and provided their range and provided them with a good view of them with a good view of their human targets. their human targets.

The castle wall also The castle wall also protected them well.protected them well.

Loopholes, the narrow Loopholes, the narrow slits that archers shot slits that archers shot through, were often through, were often splayed to the inside, splayed to the inside, allowing castle archers a allowing castle archers a wide latitude of targets. wide latitude of targets.

The design enabled The design enabled archers to hide off to the archers to hide off to the side of the loopholes side of the loopholes while reloading, giving while reloading, giving them protection from them protection from the rare arrow that did the rare arrow that did find its way in. find its way in.

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ArchersArchersHorizontally cut Horizontally cut

loopholes gave castle loopholes gave castle archers an even greater archers an even greater range. range.

The archer had two The archer had two weapons to choose weapons to choose from. from.

The most powerful was The most powerful was the crossbow. the crossbow.

Barbs on the head of a Barbs on the head of a bolt, the stout arrow bolt, the stout arrow shot from a crossbow, shot from a crossbow, were often coated with were often coated with beeswax to help them beeswax to help them pierce armor. pierce armor.

Crossbows took longer Crossbows took longer to load than the simple to load than the simple bow or the longbow.bow or the longbow.

A longbow archer could A longbow archer could shoot about 12 arrows shoot about 12 arrows in the time it took to in the time it took to launch a single bolt. launch a single bolt.

Moreover, the longbow Moreover, the longbow could send arrows as could send arrows as far as 1,000 feet. far as 1,000 feet.

But longbows took But longbows took tremendous strength to tremendous strength to shoot and much shoot and much practice to control. practice to control.

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GatehouseGatehouseThe gatehouse, the The gatehouse, the

castle's entrance, was the castle's entrance, was the early castle's most early castle's most vulnerable point. vulnerable point.

Later, military engineers Later, military engineers bolstered it with bolstered it with impressive defenses. impressive defenses.

A drawbridge could be A drawbridge could be pulled back, lifted, or pulled back, lifted, or pivoted like a see saw, pivoted like a see saw,

while portcullises—iron-while portcullises—iron-covered wooden grills covered wooden grills that moved up and down that moved up and down in front of the gatehouse in front of the gatehouse door—provided additional door—provided additional protection. protection.

Castle dwellers could Castle dwellers could also slide wooden also slide wooden beams behind the doors beams behind the doors to reinforce them. to reinforce them.

If attackers broke down If attackers broke down the outer door and the outer door and entered the gate's entered the gate's passageway, they ran passageway, they ran the risk of being the risk of being trapped. trapped.

Sometimes defenders Sometimes defenders would drop a portcullis would drop a portcullis behind them.behind them.

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GatehouseGatehouseRoofs above gate Roofs above gate passages often passages often had so-called had so-called "murder holes" "murder holes" through which through which castle soldiers castle soldiers could drop burning could drop burning oil, hot sand (able oil, hot sand (able to enter armor), or to enter armor), or scalding water scalding water onto enemy onto enemy soldiers. soldiers.

Loopholes in the Loopholes in the walls of the gate walls of the gate passage also gave passage also gave defending archers—defending archers—only feet away from only feet away from trapped attackers—trapped attackers—a deadly advantagea deadly advantage. .

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MoatMoatMoats surrounding Moats surrounding castles protected castles protected them from siege them from siege towers and towers and battering rams, war battering rams, war machines that were machines that were only effective when only effective when wheeled to the wall. wheeled to the wall.

It also made digging It also made digging tunnels underneath tunnels underneath the wall far more the wall far more challenging. challenging.

To get across a To get across a moat, the attacking moat, the attacking army sometimes army sometimes filled the moat with filled the moat with rocks and soil or rocks and soil or built portable built portable wooden bridges. wooden bridges.

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From inside the castleFrom inside the castle From inside a castle's walls, soldiers had a From inside a castle's walls, soldiers had a

somewhat restricted selection of weapons to somewhat restricted selection of weapons to use to defend their lord and his fortress. use to defend their lord and his fortress.

In addition to arrows, the garrison frequently In addition to arrows, the garrison frequently threw down stone missiles, crushing threw down stone missiles, crushing invaders. invaders.

They also relied upon "Greek fire", a volatile They also relied upon "Greek fire", a volatile combination of petroleum and oil and other combination of petroleum and oil and other natural products, which generated a highly natural products, which generated a highly flammable substance that burned on water flammable substance that burned on water and was excruciatingly hot. and was excruciatingly hot.

Apparently, Greek fire was used to make Apparently, Greek fire was used to make incendiary arrows, but could also be blown incendiary arrows, but could also be blown through tubes. through tubes.

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From inside the castleFrom inside the castle The 13th century saw the modification The 13th century saw the modification

of swords, which could then rend a of swords, which could then rend a knight's protective armour. knight's protective armour.

Short stabbing daggers were also Short stabbing daggers were also used, as were a variety of axes (some used, as were a variety of axes (some of which were equipped with spikes), of which were equipped with spikes), clubs, maces, spears, crossbows, and clubs, maces, spears, crossbows, and the sling. the sling.

The most significant development of The most significant development of weapons technology during this weapons technology during this century was the longbow, mastered by century was the longbow, mastered by the Welsh decades earlier.the Welsh decades earlier.

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THE BALLISTATHE BALLISTA The ballista was, in The ballista was, in

effect, a very large, very effect, a very large, very powerful crossbow powerful crossbow usually mounted on a usually mounted on a tower, on the castle tower, on the castle wall, or in the hoarding.  wall, or in the hoarding. 

To use it, a soldier To use it, a soldier would wind back a would wind back a winch using a crank, winch using a crank, take aim by swivelling it take aim by swivelling it on the mount, and pull on the mount, and pull the trigger mechanism the trigger mechanism releasing the tension on releasing the tension on the rope and firing.  the rope and firing. 

Ballistae were generally Ballistae were generally used against advancing used against advancing infantry during a siege.  infantry during a siege. 

The ballista fired a The ballista fired a wooden dart, about five wooden dart, about five feet long with brass feet long with brass flights to keep it's firing flights to keep it's firing trajectory straight and trajectory straight and an iron head to an iron head to penetrate armourpenetrate armour

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Destroy the CastleDestroy the Castle The trebuchet was one of the most devastating weapons of the The trebuchet was one of the most devastating weapons of the

Middle Ages. Middle Ages. Using trial and error, medieval engineers adjusted the trebuchet Using trial and error, medieval engineers adjusted the trebuchet

to make sure its missile hit the castle wall—and destroyed it. to make sure its missile hit the castle wall—and destroyed it. NOVA's science game, "Destroy the Castle," is very much like NOVA's science game, "Destroy the Castle," is very much like

the real thing. There are five elements you can adjust in your the real thing. There are five elements you can adjust in your trebuchet: trebuchet: – stone ball weight stone ball weight – sling length sling length – counterweight design counterweight design – distance from the castle distance from the castle – whether to add wheels whether to add wheels

Build it right, and you will crush the wall. Build it right, and you will crush the wall. Build it wrong, though, and you may have to face some painful Build it wrong, though, and you may have to face some painful

consequences. consequences.

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How Your Trebuchet How Your Trebuchet WorksWorks

How you design your trebuchet will decide How you design your trebuchet will decide the fate of the castle wall—and it may also the fate of the castle wall—and it may also decide your fate as well. decide your fate as well.

With some choices, your missile might land With some choices, your missile might land too short or fly too far. too short or fly too far.

With others, your missile may hit the castle With others, your missile may hit the castle wall, but not with the force necessary to wall, but not with the force necessary to destroy it. destroy it.

With an even more unfortunate combination, With an even more unfortunate combination, your launched ball will land on your head or your launched ball will land on your head or an arrow may pierce your medieval heart. an arrow may pierce your medieval heart.

To learn how your design choices will To learn how your design choices will influence the results of your attack, read influence the results of your attack, read these explanations: these explanations:

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Wheels/No WheelsWheels/No Wheels When modern engineers looked at medieval drawings of When modern engineers looked at medieval drawings of

trebuchets, they found they often had wheels.trebuchets, they found they often had wheels. They thought that the wheels were added to roll the weapon They thought that the wheels were added to roll the weapon

around the landscape and to help aim it. But when they began around the landscape and to help aim it. But when they began to build these life-sized models, they realized that they were to build these life-sized models, they realized that they were too heavy to roll on medieval roads, much less battlefields. too heavy to roll on medieval roads, much less battlefields.

They also noticed something else: those with wheels could fire They also noticed something else: those with wheels could fire much farther than their stuck-in-the-mud cousins. They much farther than their stuck-in-the-mud cousins. They believe medieval engineers discovered the same thing. believe medieval engineers discovered the same thing.

Why is a trebuchet with wheels more stable and powerful than Why is a trebuchet with wheels more stable and powerful than those without? those without?

One of the design flaws of the wheel-less trebuchet is its One of the design flaws of the wheel-less trebuchet is its tendency to rear up into the air as its arm begins to spin and tendency to rear up into the air as its arm begins to spin and then slam back down. This lurch can destroy the trebuchet then slam back down. This lurch can destroy the trebuchet completelycompletely

Rolling wheels stop this occurring. Instead, energy is Rolling wheels stop this occurring. Instead, energy is channelled into the trebuchet's arm and missile. channelled into the trebuchet's arm and missile.

Wheels add power as the trebuchet rolls forward. Like a Wheels add power as the trebuchet rolls forward. Like a bowler in cricket who leans forwards as he bowls, the forward bowler in cricket who leans forwards as he bowls, the forward motion adds extra speed to the ball. A higher speed results in motion adds extra speed to the ball. A higher speed results in a farther throw. a farther throw.

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Sling LengthSling LengthWhen the sling was added When the sling was added to the trebuchet it gave the to the trebuchet it gave the tossed projectile more tossed projectile more velocity. velocity.

This meant the trebuchet This meant the trebuchet could send a lighter could send a lighter projectile farther, providing projectile farther, providing more distance between more distance between those who fired the those who fired the machines and deadly machines and deadly enemy archers at the castle. enemy archers at the castle.

Here's how it works. The Here's how it works. The sling lies on a track at the sling lies on a track at the base of the trebuchet. base of the trebuchet.

As the arm of the As the arm of the trebuchet begins to trebuchet begins to move, the sling drags move, the sling drags the ball before lifting it the ball before lifting it into the air. This gives into the air. This gives the swinging arm time the swinging arm time to pick up speed. to pick up speed.

The sling is an The sling is an extension of the extension of the beam's reach. beam's reach.

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Sling LengthSling Length At the time it is launched, the sling is At the time it is launched, the sling is

actually moving faster than the actually moving faster than the beam, creating a whipping motion. A beam, creating a whipping motion. A faster flung stone will deliver a faster flung stone will deliver a stronger punch to the wall. stronger punch to the wall.

With the extra velocity (which can be With the extra velocity (which can be converted into a longer throw), the converted into a longer throw), the trebuchet can also be moved back to trebuchet can also be moved back to a safer distance from the castle wall.a safer distance from the castle wall.

There's an important catch, however. There's an important catch, however. If a sling is used to extend the range If a sling is used to extend the range

of a trebuchet, a lighter ball must be of a trebuchet, a lighter ball must be used to reach the wall. But used to reach the wall. But remember that light is not good, remember that light is not good, when you are attacking stone walls!when you are attacking stone walls!

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Ball WeightBall Weight Provided with the same amount of energy, lighter Provided with the same amount of energy, lighter

balls launched from a trebuchet will fly farther than balls launched from a trebuchet will fly farther than heavier ones. heavier ones.

This makes sense in our everyday experience: This makes sense in our everyday experience: Using the same arm, you can throw a tennis ball Using the same arm, you can throw a tennis ball quite a bit farther than you can a cricket ball, for quite a bit farther than you can a cricket ball, for example. example.

However, the ball's weight affects more than the However, the ball's weight affects more than the distance it will fly. distance it will fly.

A lighter ball travelling at the same velocity as a A lighter ball travelling at the same velocity as a heavier ball will land with less force. heavier ball will land with less force.

That's why some of the lighter stone balls launched That's why some of the lighter stone balls launched in our trebuchet simulation hit the mark, yet in our trebuchet simulation hit the mark, yet bounce off harmlessly. bounce off harmlessly.

The stone's mass is not great enough to break The stone's mass is not great enough to break through the sturdy castle wall. through the sturdy castle wall.

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Ball WeightBall Weight With too heavy a ball, you may suffer the same fate With too heavy a ball, you may suffer the same fate

as you wished to inflict upon your enemy: as you wished to inflict upon your enemy: The ball could fly straight up and back down. The ball could fly straight up and back down. That's because your trebuchet cannot provide That's because your trebuchet cannot provide

enough energy to counteract the pull of gravity that enough energy to counteract the pull of gravity that holds your heavy ball down. holds your heavy ball down.

There is danger, as well, in erring in the direction of There is danger, as well, in erring in the direction of too light a ball. too light a ball.

Too light a ball might not be able to accept all the Too light a ball might not be able to accept all the energy that the trebuchet's swinging arm can energy that the trebuchet's swinging arm can deliver. deliver.

Where does the energy go? Where does the energy go? It may go into the trebuchet's axle pivot, its base, It may go into the trebuchet's axle pivot, its base,

or into its scaffolding, destroying your trebuchet or into its scaffolding, destroying your trebuchet rather than the enemy castle's wall. rather than the enemy castle's wall.

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DistanceDistance How far from the castle you situate your trebuchet How far from the castle you situate your trebuchet

matters for a few reasons. matters for a few reasons. The closer the trebuchet, the more likely you are to The closer the trebuchet, the more likely you are to

hit your target. hit your target. However, the opposite is also true, which is that the However, the opposite is also true, which is that the

closer you are, the more likely it is that enemy closer you are, the more likely it is that enemy soldiers will hit you—with an arrow. soldiers will hit you—with an arrow.

The farther away your trebuchet, the farther you'll The farther away your trebuchet, the farther you'll have to send your missile. have to send your missile.

And the farther your missile must travel, the longer And the farther your missile must travel, the longer the force of gravity will be pulling on its flight. the force of gravity will be pulling on its flight.

To counteract gravity's steady pull, you must To counteract gravity's steady pull, you must convey more energy to the ball. Can you see how convey more energy to the ball. Can you see how you might do this?you might do this?

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DistanceDistance There is another solution, which is to reduce There is another solution, which is to reduce

the weight of your ball as you move it the weight of your ball as you move it farther away. farther away.

A lighter ball will travel farther because A lighter ball will travel farther because there is less mass to move. there is less mass to move.

However, a problem arises when this However, a problem arises when this principle is taken too far. principle is taken too far.

A lighter ball will hit with a weaker force A lighter ball will hit with a weaker force than a heavier one. than a heavier one.

The result could be a stone dud that The result could be a stone dud that bounces harmlessly off the castle wall. bounces harmlessly off the castle wall.

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CounterweightCounterweight The most important design improvements that The most important design improvements that

medieval engineers in the design of its medieval engineers in the design of its counterweight. counterweight.

They understood the use of "the seesaw effect" of a They understood the use of "the seesaw effect" of a lever. lever.

As gravity pulls a heavier weight down on one side As gravity pulls a heavier weight down on one side of the seesaw, the lighter weight on the other side of the seesaw, the lighter weight on the other side of the seesaw's fulcrum is lifted. of the seesaw's fulcrum is lifted.

If the object on one side falls with great force, the If the object on one side falls with great force, the one on the other side might become airborne.one on the other side might become airborne.

When military designers created one arm longer When military designers created one arm longer than the other and raised the axle high above the than the other and raised the axle high above the ground, they had built their first functioning ground, they had built their first functioning trebuchet. trebuchet.

But how did these military men maximize the But how did these military men maximize the downward pull of the short arm? The answer: They downward pull of the short arm? The answer: They added literally tons of weight.added literally tons of weight.

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CounterweightCounterweight During the siege against the Scots castle of Stirling, During the siege against the Scots castle of Stirling,

Edward I of England sent orders out to strip all of Edward I of England sent orders out to strip all of the church roofs in the entire surrounding area of the church roofs in the entire surrounding area of lead. lead.

These gathered sheets of lead were believed to These gathered sheets of lead were believed to have been melted down and then attached to the have been melted down and then attached to the counterweight of the trebuchet. counterweight of the trebuchet.

The most efficient way for any counterweight to The most efficient way for any counterweight to respond to the force of gravity is by falling in a respond to the force of gravity is by falling in a straight line. straight line.

The hinged counterweight, however, is free to The hinged counterweight, however, is free to follow a straighter descent to the ground, providing follow a straighter descent to the ground, providing the trebuchet—and eventually the launched stone the trebuchet—and eventually the launched stone ball—with an even more devastating power. ball—with an even more devastating power.

http://www.pbs.org/wgbh/nova/lostempires/thttp://www.pbs.org/wgbh/nova/lostempires/trebuchet/destroy.htmlrebuchet/destroy.html

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Homework - It says:Homework - It says: Try out various combinations – hopefully at Try out various combinations – hopefully at

least one will hit the castle! least one will hit the castle! UnderlineUnderline your your choices before you fire. Then type in what choices before you fire. Then type in what happened – and if it did not work, why do you happened – and if it did not work, why do you think it went wrong? Write your answer on think it went wrong? Write your answer on the ‘Because’ line. the ‘Because’ line.

Even if you manage it, why did it work in the Even if you manage it, why did it work in the ‘Because’ line.‘Because’ line.

If you are lucky enough to hit the target in If you are lucky enough to hit the target in less than 4 goes, there is more than one less than 4 goes, there is more than one solution – see if you can find another one?solution – see if you can find another one?

If you manage it the message will be:If you manage it the message will be: The winning message isThe winning message is ‘ Congratulations,

you have smashed the castle wall’