Machine Elements in Mechanical Design

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Machine Elements in Mechanical Design
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Introduction

• Mechanical Systems or Devices are designed to
  transmit power and accomplish specific patterns
  of motion.
• Mechanical Components Gears, Bearings, Shafts,
  Keys, Couplings, Seals, etc.

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What Mechanical Systems are you familiar with?
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What Mechanical Components make up those
mechanical systems?
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Design Process (Section 1-4)

• Identify Customer Requirements
• Define functions of the device
• State design requirements
• Define evaluation criteria
• Propose several alternative design concepts
• Evaluate each proposed alternative
• Rate each alternative against each evaluation
  criteria
• Select the optimum design concept
• Complete detailed design of the selected concept

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Application

• How are customer requirements identified?
• Functions are high level requirements that tell
  what a device is supposed to do.
• Design requirements are detailed, specific,
  quantitative data expanding the functions.
• What evaluation criteria would be important?
• What does the detailed design look like?
• What next?

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Text Example Speed Reducer
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Functions

• To receive power from the tractors engine
  through a rotating shaft
• To transmit the power through machine elements
  that reduce the rotational speed to a desired
  value.
• To deliver the power at the lower speed to an
  output shaft that ultimately drives the wheels of
  the tractor.

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Design Requirements
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Integration of Design

• Speed Reducer Assembly
• One Housing
• Four Gears
• Three Shafts
• Six Bearings
• Several Keys and Seals
• Etc.

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Practice (10 minutes)

• Most small boat trailers must be submerged in the
  water to launch or retrieve the boat. This
  greatly reduces the life of the trailer,
  especially in salt water. A need exists for a
  trailer that will remain on dry land while it
  launches or retrieves the boat. No part of the
  trailer should get wet. User safety is of
  greatest concern, as is protection of the boat
  from damage.
• In Groups of four, develop design functions and
  requirements for this trailer.

Norton, R. L., Design of Machinery, 3rd ed.,
McGraw Hill, 2004
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Design Skills Required

• Technical Drawing
• Computer-Aided Engineering (CAE)
• Manufacturing Processes
• Statics, Dynamics, and Strengths of Materials
• Kinematics and Mechanisms
• Verbal and Written Communication

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Mechanical Design Objective

• Produce a useful device that is safe, efficient,
  economical, and practical to manufacture.

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Design Presentation

• Develop a specification set that communicates
  effectively all manufacturing information, safety
  information, usage information, etc.
• Specifications sets include
• CAD Models
• Drawings (Assembly, Detail, Stress Reports)
• Bills-of-Material
• Instructions
• Manufacturing
• Assembly
• Maintenance
• Usage

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The Engineering Method

• Recognize and understand the problem
• Accumulate data and verify accuracy
• Select the appropriate theory or principle
• Make necessary assumptions
• Solve the problem
• Verify and check results

Eide, et.al., Engineering Fundamentals and
Problem Solving, 5th ed., McGraw Hill, 2008
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Problem Presentation

• Problem Statement
• Diagram
• Theory
• Assumptions
• Solution steps
• Identify results and verify accuracy

Eide, et.al., Engineering Fundamentals and
Problem Solving, 5th ed., McGraw Hill, 2008
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Design Calculations
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