Mechanical Engineering ST EST AST SE Mechanical Engineering Chapter 13 Observatory pp. 424-454

What is Mechanical Engineering? 426 What is Mechanical Engineering? Mechanical Engineering is the branch of engineering that focuses on the design, production, analysis, working and improvement of technical objects with moving parts. Main Topics Links Guiding Transmission Transformation

2. Linking in Technical Objects 427 2. Linking in Technical Objects Linking is the mechanical function performed by any component that connects different parts of a technical object.

Characteristics of Links You must know the main characteristics of links Chart on p. 428 in textbook.

Links Direct OR Indirect Rigid OR Flexible Removable OR non-removable Complete OR Partial

Degrees of Freedom of Movement 428 Degrees of Freedom of Movement The Degrees of Freedom are the set of independent movements that are possible for a given part in a technical object. E.g. A door can only rotate around the hinges – 1 degree freedom E.g. A manual transmission gear shift moves forward/back and left/right – 2 degrees of freedom

Degrees of Freedom Chart pg 429

431 3. Guiding Controls A Guiding Component or Control is a component whose mechanical function is to guide the motion of moving parts.

431 Types of Guiding Translational Guiding ensures the straight translational motion of a moving part. E.g. a vertical window groove Rotational Guiding ensures the rotational motion of a moving part. E.g. a bicycle wheel hub Helical Guiding ensures the translation motion of a moving part while it rotates about the same axis. E.g. threaded screw.

Six Symbols for Motion Types of Motion Symbols Unidirectional Translation Bi-directional Translation Unidirectional rotation Bi-directional rotation Unidirectional helical motion Bi-directional helical motion

Adhesion and Friction of Parts 433 Adhesion and Friction of Parts Adhesion is the phenomenon by which two surfaces tend to remain in contact with each other without slipping. In mechanics, Friction is a force that resists the slipping of one part over another. Lubrication is the mechanical function performed by any component that reduces friction between two parts.

5 Factors affecting friction Nature of materials (eg: steel on asphalt vs. rubber on asphalt) Presence of a lubricant like oil or wax Temperature: the colder the temperature the less the adhesion Surfaces (rough vs. smooth) Mass of the object (a heavy object will have better adhesion, more friction)