1. Machine Elements in Mechanical Design

2. 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.

3. 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

4. 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?

5. Text Example – Speed Reducer

6. Functions
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.

7. Design Requirements

8. Integration of Design Speed Reducer Assembly: One Housing Four Gears
Three Shafts
Six Bearings
Several Keys and Seals
Etc.

9. 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

10. Design Skills Required
Technical Drawing
Computer-Aided Engineering (CAE)
Manufacturing Processes
Statics, Dynamics, and Strengths of Materials
Kinematics and Mechanisms
Verbal and Written Communication

11. Mechanical Design Objective
Produce a useful device that is safe, efficient, economical, and practical to manufacture.

12. 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

13. 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