guns Simple version-cannon - PowerPoint Presentation

Slide1

gunsSlide2

Simple version-cannon

A= fuse hole

B = cannonball

Orginally stoneSoon metals for better destructionC = gunpowderGunpowder appeared in Europe in 1247Cannon introduced in 1327Hand cannon in 1364

breech

boreSlide3

Matchlock

Lock = ignition mechanism

Light rope

Use trigger to move rope into place

Stock = wooden handles

Barrel = metal tube that holds bullet and gunpowderSlide4

Flintlocks—flint and steel

Flint = very hard rock

Steel = iron alloy

Additives to make it harderUsed to light firesWhen flint strikes steelFlakes off ironIron is hot and immediately oxidizes Hot sparks ignite fuel (gunpowder) Slide5

Flintlock – put flint and steel in gun

Hammer = holds and accelerates flint

Mainspring = powers the hammer

Frizzen = holds the steel that flint strikesPan = holds small quantity gunpowder waiting for sparkFrizzen spring = holds cover attached to frizzen over pan to make flintlock weatherproofSlide6

Flintlock – mechanism to move hammer

Tumbler = holds and releases power of mainspring

Sear and sear spring = engage tumbler and release with triggerSlide7

Flintlock – firing

1- Half-cock hammer

2 – pour measure of gunpowder down barrel

3 – wrap lead ball in cloth or paper and ram down barrel on top of gunpowder4 – put small amt of gunpowder in pan5 – snap frizzen in place over pan

Half-cock position Slide8

Flintlock-firing part 2

6- fully cock hammer

7- pull trigger to fire gun

When you fire the gun, the flint strikes the frizzen and shaves off iron to create sparks. The hammer's blow also snaps the frizzen back to expose the gunpowder in the pan. The pan's gunpowder ignites, and it flashes through a small hole in the side of the barrel to ignite the gunpowder inside the barrel. The gun fires!

Full cock position Slide9

Flintlock - rifling

Smooth bore = sides of barrel are smooth

Rifling = engrave groves down inside of barrel in spiral

Typical: one twist in 48 inchesHard to load without being caught on grooves

Rifling improves accuracy

imparts spin to the bulletSlide10

Percussion Cap—the next step

Replace flint and steel with percussion cap

Mercuric fulminate

Hg(ONC)2Made from mercury, nitric acid and alcoholShock explosiveWhat the percussion lock does not have is the flint and

frizzen. Instead, there is a nipple that accepts the cap, and this nipple contains a tube that leads the flame from the cap down to the main charge of gunpowder in the barrel. The hammer is shaped to strike the cap on the nipple and cover it so the nipple does not get blown off. Slide11

Bullet design –internal ballistics

Issues

Form a seal with gun’s bore

(or gases leak instead of propel)Engage rifling but notDamage the boreDistorting the bulletWithout excessive FrictionSlide12

Bullet design—external ballistics

Shape

Spherical

orientation doesn’t matterForward center of mass keeps orientation

Rotation

imparted by rifling

Stabilizes bullet

Removes (or magnifies) asymmetrySlide13

Bullets-materials

Lead (

Pb

)—a classicCheap/availableSimple to fabricate by many formsLow melting pointEasy to work High density (KE = ½ mv2)soft

Make fabrication easier, but fouls grooves/riflingAlloy with Sn or Sb to increase hardness

Jacketed LeadAdd hard metal to outside E.g, Cu/Ni, Cu, steel

Full metal jacket

Completely encase

Soft point/hollow point

Tip not jacketed

Deforming of bullet increases stopping powerSlide14

Let’s combine: gunpowder, ball and ignition

bullet

cartridge

1 -- bullet = projectile2 -- case = holds all parts together3 – propellant like gunpowder4 -- the rim, which provides the extractor on the firearm a place to grip the casing to remove it from the chamber once fired

5 – primer = ignites propellantSlide15