Structures and Mechanisms Structure or Mechanism n Can

Structures and Mechanisms

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

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

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

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

Introduction Look at the following items. 1. Bicycle 2. Wheelbarrow 4. Entrance 3. Wrench Can you identify and name the mechanisms and/or structure in each of these items?

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

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

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

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

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

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

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

Force Bending and Static Forces This is where the load causes an object to Bend A piece of metal Bending a piece of metal 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