Structures and Mechanisms

Structure or Mechanism? Can you identify a Structure within this bicycle? Can you name a mechanisms on this bicycle? Frame = Structure Chain and Sprocket = One example of a mechanism

Introduction Vehicle Frame High Rise Building Bridge Supporting Roadway Residential Dwelling Structures can be seen all around us in our everyday lives.

Introduction Machinery is a central part of life today. How many can you identify? Drill Tractor CarLuasExercise Bicycle

Introduction Rack and PinionPulley Wheels Cam and Follower All these machines have working parts called –Mechanisms

Introduction Look at the following items. 1. Bicycle2. Wheelbarrow 3. Wrench Can you identify and name the mechanisms and/or structure in each of these items? 4. Entrance

Mechanisms, Motion and Force Mechanism A system of moving parts that performs some function. Motion The process of continual change in the position of an object “movement” Collins Dictionary

Motion and Force What input is needed for a drill to work? Input:The lever of the drill is pulled down Output:The chuck of the drill moves down Exertion or the use of exertion against a person or thing that resists. Collins Dictionary Force “Strength or Power”

Motion There are four main types of motion. Linear motion – Train Oscillating Motion – Pendulum of a clock Reciprocating Motion – Hacksaw Rotary Motion - Shaft Pendulum Train Shaft

Motion Linear motion – movement in a straight line A train on its tracks moves in a linear motion Can you give other examples of linear motion?

Motion Reciprocating Motion - backwards and forwards movement The engine pistons and valves above move up and down (reciprocate) continuously. Can you suggest other examples?

Motion Oscillating Motion Forward and backward movement in an arc The pendulum of a clock or a child on a swing are examples of oscillating motion. Rotary Motion - Motion in a circular direction, which can also be called circular motion. The wheels of a bike move in a rotary fashion.

Force There are five main types of force: 1. Compression 2. Tension 3. Shear 4. Bending 5. Torsion Columns in Compression A rope in Tension Pipe Bending Torsion forces Shear forces

Force Compressive and Tensile Forces Spring in Tension, this is where a load pulls an object apart. This is where a load presses or squashes objects together Can crushed by compression

Force This is where loads push at right angles to the surface of the object. E.g. scissors Torsion and Shearing forces Shearing Force This is where the load causes an object to twist Torsion Torsion force

Force This is where the load causes an object to Bend A piece of metal Bending a piece of metal Bending and Static Forces Dynamic Load – a car which is not fixed to any one specific point, e.g. a car travelling along a road Static Load – a load which is fixed at one point, e.g. a building