Machine Elements in Mechanical Machine Elements in Mechanical DesignDesign

Introduction 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.

What “Mechanical Systems” are What “Mechanical Systems” are you familiar with?you familiar with?

What “Mechanical Components” What “Mechanical Components” make up those mechanical make up those mechanical systems?systems?

Design Process (Section 1-4) 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

ApplicationApplication

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?

Text Example – Speed ReducerText Example – Speed Reducer

FunctionsFunctions

To receive power from the tractor’s 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.

Design RequirementsDesign Requirements

Integration of DesignIntegration of Design

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

Practice (10 minutes)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

Design Skills RequiredDesign Skills Required

Technical DrawingComputer-Aided Engineering (CAE)Manufacturing ProcessesStatics, Dynamics, and Strengths of

MaterialsKinematics and MechanismsVerbal and Written Communication

Mechanical Design ObjectiveMechanical Design Objective

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

Design PresentationDesign 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

The Engineering MethodThe Engineering Method

Recognize and understand the problemAccumulate data and verify accuracySelect the appropriate theory or principleMake necessary assumptionsSolve the problemVerify and check results

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

Problem PresentationProblem Presentation

Problem StatementDiagramTheoryAssumptionsSolution stepsIdentify results and verify accuracy

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

Design CalculationsDesign Calculations