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 \n 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