NOTES

• Movement and motion:

  • Motion is the action of something being moved
  • Motionless is something at rest
  • There are different types of motion which can be added together and even changed from one to another
• Linear motion:

  • Movement in one direction along a straight line
• Reciprocating motion:

  • A reciprocating saw blade cuts by travelling back and forth along the same path at high speed
• Oscillating motion:

  • A repetitive back-and-forth motion along a curved path
  • The pendulum on a grandfather clock oscillates to keep time
• Rotary motion:

  • Objects moving in a circular motion usually around a fixed axis
• Levers:

  • Levers help provide mechanical advantage (MA)
  • They have two parts – a bar and a pivot also known as the fulcrum 
• First class lever:

  • Class 1 levers act in a seesaw or scissor action
  • The load and effort are at opposite sides with the fulcrum positioned at any point between
• Second class lever:

  • Class 2 levers act in a wheelbarrow action or that similar to a nutcracker
  • The effort is at the opposite end to the fulcrum, with the load positioned between
• Third class lever:

  • Class 3 levers have a pincer-like action seen with tweezers and tongs
  • The load is at the opposite end to the fulcrum, with the effort positioned between
• Equilibrium:

  • When the effort and the load are equal, equilibrium can be created in a mechanism
• Linkages:

  • Linkages are mechanisms that use rigid parts to:
  • Change the magnitude of a force 
  • Change the direction of a force
  • Transform it into a different motion
• Reverse motion linkage:

  • changes the direction of the input motion
  • If the input is pulled, the output will push
  • The linkage uses a fixed central pivot
• Reverse motion linkage:

  A) ixed

  B) oving

  
• Parallel motion linkage:

  • Also known as push / pull linkage as it keeps the direction of the output the same as the input
• Parallel motion linkage:

  A) nput

  B) utput

  C) ixed

  D) oving

  
• Bell crank linkage:

  • Input direction is converted through 90 degrees
  • It changes horizontal motion to vertical and vice versa 
  • Often found in steering and throttle mechanisms on vehicles
• Bell crank linkage:

  A) ixed

  B) oving

  
• Crank and slider:

  • Crank and sliders convert rotary motion into reciprocating motion and vice versa
  • A linkage commonly found in engines to transfer the energy from pistons
  • The slider is guided along a set path
• Crank and slider:

  A) rank

  B) lider

  
• Treadle linkage:

  • Treadle linkages convert rotary motion into oscillating motion and vice versa
• Treadle linkage:

  A) rank

  B) oving

  C) ixed

  
• Rotary systems:

  • Rotary systems drive mechanisms in machinery and equipment
  • A rotating axle called a camshaft is used to drive, or is driven by, other mechanical components
  • Cams are shaped pieces of material that are attached to the camshaft
  • Cams change rotary motion into reciprocating motion through a follower 
• Rotary systems:

  A) ollower

  B) ircular

  
• Types of cams:

  A) ccentric

  B) ear

  C) nail

  D) eart shaped

  
• Types of followers:

  A) lat

  B) nife edged

  C) oller

  
• Gear trains:

  • Cog wheels are meshed to create gear trains
  • A simple gear train has a drive cog or ‘gear’ which rotates the ‘driven gear’
  • Gear ratios can be worked out by comparing the number of teeth on each gear
• Gear train:

  
• Idler gear:

  • An idler gear ensures that the direction of the drive gear and the driven gear are the same 
  • The idler gear sits between the two gears and directly transfers the drive
• Idler gear:

  
• Pulleys and belts:

  • Drive belts are used to transfer drive from one pulley to another
  • Belts rely on friction to grip the pully and are often made from rubber but also many other materials
  • A pulley is often grooved to help increase the friction on the belt
• Pulley:

  
• Block and tackle systems:

  • Block and tackle systems combine pulleys to lift heavy weights
  • A rope is looped around pulleys in a block to form a tackle, to reduce the effort needed to lift
  • As more pulleys are added, the lighter it becomes, although more rope needs to be pulled through