Mechanical Systems

Cards made for AQA GCSE Resistant Materials on mechanical systems

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  • Created by: Lucy :)
  • Created on: 31-05-13 09:58


  • they change input moton into output motion
  • designed so you can gain an advantage from using them
  • some change 1 type of motion to another
  • there are various types of motion:
    • Linear motion
      • moving one way in a straight line
    • Reciprocating motion
      • moving backwards + forwards in a straight line
    • Oscillating motion
      • moving backwards + forwards in an arc
    • Rotary motion
      • moving in a circle
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Gear Trains

  • gear trains transmit rotary motion
  • gears = toothed wheels that interlock
  • gear train = 2 or more gears linked together
  • if the driver gear turns the driven gear they will turn in different directions
  • if you use a 3 gear (called an idler) the driver + driven gear will turn in same direction
  • ^idler won't alter the speed of the other 2 gears
  • If the linked gears are different sizes they will turn at different speeds (one half the size will go quicker)
  • a compound gear train = more than 1 gear fixed to the same shaft
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Gears changing the motion

Rack + Pinion

  • used to turn rotary into linear motion
  • the pinion (a round gear) is turned to move a flat gear (the rack)
  • used on railways on steep sections of track to stop wheels slipping backwards

A Worm Drive + Worm Wheel

  • changes the direction of rotation through 90o
  • used for tightening guitar strings

Bevel Gears

  • also changes direction of rotation through 90o
  • the teeth are angled at 45o so the gears fit together at right angles
  • used in hand drills

EXAM TIP!! You might be asked to sketch and name it's parts so look up images of mechanisms

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More mechanisms

Belt Drives

  • transfer movement from 1 rotating shaft to another
  • used in pillar drills
  • flexible belt links the motor to the drill shaft

Chain + Sprocket

  • used on a bike
  • advantage = can't slip like a belt drive could
  • made up of 2 sprockets - the size effects the speed


  • 1 on its own changes the direction of the force required
  • same amount of force needed but pulling might be easier than lifting
  • 2 or more can make things feel lighter than they are
  • e.g. 1 fixed pulley + 1 moving pulley (a block + tackle) results in half the force needed to lift
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  • change rotary motion to reciprocating motion
  • has 2 main parts - the cam + the follower
  • they come in many different shapes + sizes
  • they always rotate
  • the follower rests on the cam + follows its shape
  • ^ it may have a small wheel to reduce friction
  • basic cam shapes:
    • Circular cam (also called offset or eccentric) - produces a uniform reciprocation motion
    • Snail cam - for half a turn the follower won't move then it will gently rise + suddenly drop, will only work in 1 direction
    • Pear cam - for half a turn the follower won't move then it will gently rise + fall
    • Four-lobed cam - has 4 lobes (looks like a toy flower windmill) for each turn the follower will rise + suddenly fall 4 times, will only work in 1 direction
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First Class leavers

  • load one end, have a pivot in the middle, effort the other
  • makes the load easier to lift
  • pivot closer to the load = easier to lift
  • e.g. = sisors

Second class leavers

  • pivot at one end of the leaver + effort at the other end
  • e.g = wheelbarrow
  • closer together pivot + load = easier to lift

Third class leavers

  • effort is in between the load + the pivot
  • e.g = fishing rods, cricket bats, garden spades
  • moving effort + pivot further apart = easier
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