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.

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.

• 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

Crank and Slider Mechanism:

• Rotary motion to linear motion

• Used in pistons in car engines.

Chain and Sprocket Mechanism:

• Rotary motion to rotary motion

• Used in bike chains

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