Machine Elements in Mechanical Design

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. What “Mechanical Systems” are you familiar with?

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

5. 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

6. 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?

7. Text Example – Speed Reducer

8. 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.

9. Design Requirements

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

11. 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

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

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

14. 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

15. 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

16. 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

17. Design Calculations