John L Errington MSc

John Erringtons Engineering Design Website

Year 1: Mechanical Engineering: 

Year 1 Design for Industry; Topic overview;

The role of the engineer; Common vocabulary; Example: hardness; Mohs hardness scale; Physical and Mechanical properties of materials;

Designs with moving parts;

Axes and degrees of freedom; Joints: movable and fixed; 1 degree of freedom: rotation; 2 degrees of freedom; 4 degrees of freedom; Sliding mechanisms; Designs with moving parts; How to restrict movement; Friction; What causes friction?; Examples of coefficients of friction; Factors affecting the friction between surfaces; Dry surfaces; Well lubricated surfaces; How Lubricants Work; Lubricated surfaces; Bearings; Bearings keep shafts in place; Plain bearings; Dry plain bearings; Plain Bearings; Lubrication of plain bearings; Anti friction bearings; Antifriction bearings; advantages and disadvantages of plain bearings vs antifriction bearings.; Rolling Friction; Typical values for rolling friction; Types of antifriction bearing; Single-Row Ball Bearing. Non-Filling Slot; Roller Bearings (antifriction); Cylindrical Roller; Tapered Roller; Needle Roller; Thrust bearings; PTFE; More about plain bearings; Plain lubricated bearings; Tin-Lead & Tin-Copper Alloys (white metal bearings); Circumferential Groove Bearings; Pressure Bearings; Multiple Groove Bearings; Hydrostatic Bearings; Antifriction Bearings;


Loaded Beams; Loaded beam; Joists and floorboards; Floor loading; Steel and concrete; Steel sections; Bending moment for a point load; Calculate reaction in supports; Bending moment for beam with point load; Bending moment and shear force for point load; Bending moment for a distributed load; Calculate reaction in supports; Bending moment for beam with distributed load; Bending moment and shear force for distributed load; TO BE CONTINUED; Calculate maximum stress in beam and radius of curvature of neutral axis; ? / y = M / I = E / R; Maximum stress; Radius of curvature; How far does the beam sag?; Moment of Inertia Defined; Moment of Inertia; Mass at a Radius; Rigid Body Rotation; Point and Ring; Moment of Inertia of common shapes; Moment of Inertia of a Cross Section ; Other shapes; Comparison of moments of inertia for different shapes all having the same cross-sectional area; Parallel Axis Theorem; Perpendicular Axis Theorem; To Increase the Moment of Inertia; Summary;


King Edward VII bridge and Redheugh bridge; Early bridges; Modern Bridge Designs; Cantilever bridge; Forth Rail bridge; Truss Bridges; QE2 bridge Newcastle; Sydney Harbour Bridge; Concrete arch bridges; Krk bridge, Croatia; Natchez Trace Bridge; Cable-Stayed Bridges; Tatara Bridge; Suspension Bridges; Suspension bridges; Combination spans; San Francisco-Oakland Bay Bridge ; Bridge Design: beams; Examples of the three common travel surface configurations; Truss - simple types; Pratt truss variations; Warren Truss; Howe truss; About space frames; A Simple Truss; Reaction Forces in a Simple Truss; Member Forces in a Simple Truss; Joint Forces in a Simple Truss; Joint Forces in a Simple Truss; Joint Forces in a Simple Truss; How Do We Determine Tension and Compression in the Members?; How Do We Determine Tension and Compression in the Members?; Force analysis of a simple truss; Compression and Tension; Forces and moments at point B; Tension and Compression; Forces in a Truss; Limitations of a Truss; References;


Structures in compression; Types of compression failure; Buckling; ; Bending moment for a column; Solution for critical value of P; Solution; Critical load for buckling; Unbalanced loads; Ways to prevent buckling; Maximum safe load for a column; Rules of thumb; Local buckling; Moments of Inertia;

Design Study of Electric drill

Electric drill; engineering considerations for design; Rotary drill: De Walt 241; Specification: Dewalt Dw241L 110V Rotary Drill 13Mm 701W; Schematic of gearbox and chuck; Electrical components and housing; Rotary and fixed hammer drills (SDS +); Dewalt D25002K 240V Sds Plus Rotary Hammer ; Mechanical components of sds+ impact drill; Electrical parts and casing of sds+ impact drill;

Design Study electric table lamp;

Metal body table lamp; Insulating body table lamp; Design criteria; Electrical safety regulations; Class 1; Class 2; Practical considerations for design of electrical appliances; Static and dynamic equilibrium; Fire safety; Alternatives; Antique (c. 1900) ceramic & brass bayonet lampholder; Switches; Cable strain relief components;

Failure of Materials;

Axial forces; Measuring stress/strain; Shear modulus; Torsion; Poisson's ratio; Values for E, G, ?; Typical stress-strain curves; Dislocations and Strengthening; What's happening?; Role of dislocations; Edge dislocation; Screw dislocation; Slip systems; Slip in crystal structures; How many dislocations?; Polycrystalline materials; Strengthening of materials; Grain size reduction; Solid solution strengthening; Strain hardening; Failure; Failure mechanisms; Fracture; Ductile failure; Brittle fracture; Stress concentration; Crack propagation; Griffith model; Mystery failures - de Havilland Comet; Fatigue; S-N curve; Summary;


How things break; The study of fracture; A goad to understanding; The first major step toward understanding fracture; Why stress is concentrated by a flaw; More on strain energy and fracture; The sixty-four thousand dollar question; Tensile fracture depends chiefly on:; Fracture energy; Fracture energy; Fracture energy; What makes a material "tough"?; Approximate tensile strengths and work of fracture of some solids; What makes a material brittle vs tough?; The dislocation mechanism; What is the dislocation mechanism?; Biological materials and work of fracture; How do you tell whether something will fracture or not?!; Griffith's theory; Example: piece of elastic material, stretched and then clamped at both ends; What is the energy bill to propagate a crack?; Where is the energy coming from?; The core of Griffith's theory; Griffith energy release; The consequence; Calculating Lg; Biological/scaling consequences; Composite materials revisited;

Fundamental principles of engineering;

Fundamental principles; So we need to learn some physics!; Fundamental principles 1: Newton's laws (1642 -1727); Mass : the amount of matter in a body; Force; Forces in equilibrium; Forces in equilibrium; Restoring force; Elastic and plastic; Hooke's law as applied to a wire under tension ; Stress; Strain; Hooke's law; Moment and torque; Torque; Summary: concepts and equations;

Further material properties;

Important kinds of engineering materials; Properties of materials 1:Metals; Properties of materials 2: non-metals; 1. flexible thermoplastics; 2. rigid thermoplastics; 3. rigid thermosets; 4. elastomers or rubbers ; Impact resistance; The first elastomer; Tying it All Together; Polymerization of isoprene; Other elastomers; Crosslinked polymers - thermosets; Cross-linking; Environmental Stress Cracking and Crazing (ESC); Common engineering polymers; Resources;

Joining materials

Wood, Metal and Plastics; Types of joint; Permanent and temporary joints; Temporary Fixings; Adhesives; Joining wood 1: Screws, nails, glues and knock-downs; Screws ; Types of screws; Screw heads; Machine screws; Self-tappers; Self-drilling screws; Some different woodscrews; Nails; Glues; Knock-down joints ; Joining wood 2: frame joints; Simple frame joints; More complex frame joints; Brazing and soldering; Soldering and welding; Rivets; Joining plastics; Nutserts and blind fasteners;


Molecular bonding types; adhesion mechanisms; different types of adhesives, surface finishes.

Lamp parts

Antique (c. 1900) ceramic & brass bayonet lampholder; Switches; Cable strain relief components;

Simple machines;

Simple Machines; Mechanical advantage; Friction; Static Friction; Examples of static friction; Kinetic Friction; Examples of kinetic friction:; ; ; Inclined plane; Lever; Three Classes of Levers; First-class Lever; Lever ; Wedge; Wedge ; Pulley; Pulley ; Block and Tackle; Block and Tackle; Block and Tackle; The mechanical advantage of a block and tackle is simply found by counting the number of ropes from the bottom pulley system.; More pulleys; Screw; Screw ; Wheel and Axle; Wheel and axle; Gears; Gear teeth; 'A' frame; Examples of simple machines; Worked example: lever; Worked example: lever; Worked example – pulley system; Worked example – pulley system;

Introduction to properties of materials;

Classes of Materials; Important engineering characteristics of materials; Other concerns about materials; Recycling; Strength; Hardness; Ductility; Toughness ; Since the properties we are concerned with all deal with how structures deform in response to forces, we need some way to normalize:; How to normalize force; Torsion is really a combination of tension, compression, and shear; How to normalize deformation; What would plots of different materials look like?; Strain hardening; So far we've considered only solid materials; Basic types of materials:; Stresses and states of matter; Caveat; How to classify solids; What's the difference between simple and composite materials?; Composite materials; Representative rigid materials; Testing for toughness: Charpy V-Notch Test; Charpy V-Notch Test (continued); Impact toughness vs temperature; Transition temperature; Factors affecting material properties; Properties of materials 1:Metals; Properties of materials 2;

Class exercise on fundamental concepts and properties of materials;

Fundamental concepts; Properties of materials; Choose new materials for everyday objects; Example: Solid Table Top ; More examples; Support column for typists swivel chair; Kitchen work surface; Car body; Bicycle frame; Packing material; Disposable /recyclable container for hot drinks; Packing sleeve for ready meal; Closure;

Structures and stress;

Outline; Beam Deflection; Differences in Deflection; Types of Forces on a Bending Beam; Compression, Tension, and Torsion; Design Optimization; Moment of Inertia; Summary;


Brainstorm: uses of timber; Timber; Description of Wood Properties (1); Description of Wood Properties (2); Description of Wood Properties (3); Description of Wood Properties (4); Table of properties of common woods; Man made boards; Chipboard; MDF; Blockboard; Hardboard; Plywood;

ASSESSMENT: Bridge building contest