knowt logo

AQA GCSE Product Design: 1.5 - Mechanical Devices

Mechanical Devices:

Types of Movement:

  • Linear -

    • Forward

  • Reciprocating -

    • Up and down movement

  • Rotary -

    • In a circle

  • Oscillating -

    • Side to side

Levers:

  • Mechanism -

    • A device that changes an input motion into a different output motion.

  • Lever -

    • A mechanism that moves around a fixed point (pivot)

    • The oldest type of mechanism

    • Changes an input movement and force (effort) into an output movement and force (load)

  • Load -

    • The object that needs to be moved

  • Effort -

    • Force applied to move the load

  • Fulcrum -

    • The point at which the load is pivoted

  • 3 classes of levers -

    • Class 1: L-F-E

    • Class 2: F-L-E

    • Class 3: L-E-F

Linkages:

A linkage is used to transfer force and can change the direction and movement. They are an assembly of levers. Reverse Motion Linkage Parallel Motion Linkage Crank and Slider Linkage
Bell Crank Linkage

Cams:

A cam mechanism has 3 parts: a cam, a slide and a follower. A cam mechanism can either go up, go down or stay still.

Pear-Shaped CAM Rotations

Pear-Shaped CAM

  • Torque -

    • The turning force that causes rotation

Gears:

Number of teeth on the driven gear

Velocity = -----------------------------------------------------------

Number of teeth on the driver gear

  • Friction -

    • Can cause thermal energy

    • Usually a problem that needs to be resolved

    • Breaking systems and pulley systems need high coefficients of friction

  • Coefficiency

    • How resistant a material is

Gear Trains:

Rack and Pinion Mechanism:

  • Pinion = circular gear

  • Rack= long gear

  • Linear motion

Rack and Pinion Mechanism

Crank and Slider Mechanism:

  • Rotary motion to linear motion

  • Used in pistons in car engines.

Crank and Slider Mechanism

Chain and Sprocket Mechanism:

  • Rotary motion to rotary motion

  • Used in bike chains

Chain and Sprocket Mechanism

Number of teeth on the driven sprocket

Velocity = ------------------------------------------------------------------

Number of teeth on the driver sprocket

Pulleys and Belts:

  • Pulley Systems -

    • Rotary to rotary motion

Number of teeth on the driven pulley

Velocity = -------------------------------------------------------------

Number of teeth on the driver pulley

T

AQA GCSE Product Design: 1.5 - Mechanical Devices

Mechanical Devices:

Types of Movement:

  • Linear -

    • Forward

  • Reciprocating -

    • Up and down movement

  • Rotary -

    • In a circle

  • Oscillating -

    • Side to side

Levers:

  • Mechanism -

    • A device that changes an input motion into a different output motion.

  • Lever -

    • A mechanism that moves around a fixed point (pivot)

    • The oldest type of mechanism

    • Changes an input movement and force (effort) into an output movement and force (load)

  • Load -

    • The object that needs to be moved

  • Effort -

    • Force applied to move the load

  • Fulcrum -

    • The point at which the load is pivoted

  • 3 classes of levers -

    • Class 1: L-F-E

    • Class 2: F-L-E

    • Class 3: L-E-F

Linkages:

A linkage is used to transfer force and can change the direction and movement. They are an assembly of levers. Reverse Motion Linkage Parallel Motion Linkage Crank and Slider Linkage
Bell Crank Linkage

Cams:

A cam mechanism has 3 parts: a cam, a slide and a follower. A cam mechanism can either go up, go down or stay still.

Pear-Shaped CAM Rotations

Pear-Shaped CAM

  • Torque -

    • The turning force that causes rotation

Gears:

Number of teeth on the driven gear

Velocity = -----------------------------------------------------------

Number of teeth on the driver gear

  • Friction -

    • Can cause thermal energy

    • Usually a problem that needs to be resolved

    • Breaking systems and pulley systems need high coefficients of friction

  • Coefficiency

    • How resistant a material is

Gear Trains:

Rack and Pinion Mechanism:

  • Pinion = circular gear

  • Rack= long gear

  • Linear motion

Rack and Pinion Mechanism

Crank and Slider Mechanism:

  • Rotary motion to linear motion

  • Used in pistons in car engines.

Crank and Slider Mechanism

Chain and Sprocket Mechanism:

  • Rotary motion to rotary motion

  • Used in bike chains

Chain and Sprocket Mechanism

Number of teeth on the driven sprocket

Velocity = ------------------------------------------------------------------

Number of teeth on the driver sprocket

Pulleys and Belts:

  • Pulley Systems -

    • Rotary to rotary motion

Number of teeth on the driven pulley

Velocity = -------------------------------------------------------------

Number of teeth on the driver pulley