Mechanical Desktop for Machine Design

							         Mechanical Design Desktop for Machine Elements
                                            by
                                     Anuj Subramanian
                              Dr.Arvid Myklebust, Chairman
                                  Mechanical Engineering
                                       (ABSTRACT)


The design of machine elements such as belts, chain and sprocket, gears, cams, bearings,

etc., is a complex procedure. The analytical procedure to design such elements is non-

linear, often based upon statistical information and frequently heuristic in nature. The

procedure is iterative and involves choosing various weighing factors based upon the

application and usage. The procedure is greatly influenced by a designer’s intuitive skill

and experience. Due to the increased popularity of the Internet as a source of information,

a number of machine element manufacturers have published design procedures for the

design of machine elements. Here, an attempt has been made to arrange all the formulae,

tables, charts, standards, and web resources, which are inherent to the design process, to

best aid the designer.



A number of computer applications for machine design have been developed in the recent

past but are limited in scope and utility as they tend to allow the designer to change only

certain parameters while assigning fixed values to most parameters. This stifles the

designer’s creativity and diverts focus on the computer program rather than the physical

problem. An attempt has been made here to allow the designer flexibility in design and

increased productivity, by keeping a record of the various steps undertaken by the

designer, in a particular design process.



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                               Acknowledgements

First and foremost, I would like to thank my advisor, Dr. A. Myklebust, for his guidance
and counsel without which my efforts would not have borne fruit. His broad range of
knowledge and enthusiasm in pursuing various diverse interests will be a perennial
source of inspiration.


I would like to extend my appreciation to Dr. J.H. Bøhn and Dr. R. H. Sturges, Jr., for
extending their valuable time to serve on my committee and reviewing my work.


I would also like to thank Ben Poe, Jamie Archual and Darell Early for their frequent and
prompt help with the computing facilities and software licenses.


I would also like to thank all my friends here at Virginia Tech for their constant support
and for making my stay at Virginia Tech a truly memorable experience.


Thanks to my parents and family for their unconditional love and support. It is their
dedication, sacrifice and unstinted faith in me that has made my pursuit of higher
education possible.




Note: Microsoft ® Visual Basic 6.0, Microsoft Access® 97and Microsoft® Word 97 are
registered trademarks of Microsoft Corporation. TKSolver® is a registered trademark of
UTS.




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Table of Contents

Abstract…………………………………………………………………………………….i

Acknowledgements………………………………………………………………………..ii

Table of Contents…………………………………………………………………………iii

List of Figures……………………………………………………………………………..v

1.0 Introduction…………………………………………………………………………..1

2.0 Research Objectives and Thesis Organization……………………………………..7

2.1 Problem Definition…………………………………………………………………….7

2.2 Research Objectives…………………………………………………………………...9

2.3 Proposed Method…………………………………………………………………….10

2.4 Thesis Organization………………………………………………………………….13

3.0 Literature Review…………………………………………………………………..14

4.0 System Analysis …………………………………………………………………….16

4.1 The Environmental Model…………………………………………………………...17

     4.1.1 The statement of purpose…………………………………………………..18

     4.1.2 The Context Diagram………………………………………………………19

     4.1.3 The Event List……………………………………………………………...21

4.2 The Behavioral Model……………………………………………………………….22

     4.2.1 Data Flow Diagrams……..……….…………………………………….….23

     4.2.2 Entity Relationship Diagram……………………………………………….44



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5.0 Results……………………………………………………………………………….46

6.0 Conclusions ………………………..………………………………………………107

7.0 References………………………………………………………………………….109

Appendix A. Source Code………………………………………………………..…...114




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List of Figures

Figure 1.1: The phases of design………………………………………………………….2

Figure 4.1: The context diagram for the Mechanical Design Desktop system…….…….20

Figure 4.2: Event 1: Machine designer selects the machine element to be designed…....25

Figure 4.3: Event 2: Machine designer specifies the design limitations/constraints…….25

Figure 4.4: Event 3: Machine designer selects the design equation……………………..25

Figure 4.5: Event 4: Machine designer provides input design parameter values by
                     referring to the relevant graph……...………………………………25

Figure 4.6: Event 5: Machine designer provides input design parameter values by
                     referring to the relevant table………………..………………..……26

Figure 4.7: Event 6: Machine designer provides input design parameter values by
                     referring to the relevant standard……………………………..……26

Figure 4.8: Event 7: Solver solves for unknown design parameter……………………...26

Figure 4.9: Event 8: Machine designer checks for the compliance of the calculated
                    design parameter with design limitation…………..………………..27

Figure 4.10: Event 9: Machine designer standardizes calculated design parameter.…….27

Figure 4.11: Event 10: Machine designer generates datasets for dependent and
                       independent design parameters…………………………….……28

Figure 4.12: Event 11: Machine designer plots datasets to observe the effect of
                       changes in design parameter values..…………………….……...28

Figure 4.13: Event 12: Machine designer searches the Internet for design information
                       on the machine element………………………………….……...28

Figure 4.14: Event 13: Machine designer catalogues the design information…………...29

Figure 4.15: Event 14: Machine designer refers design information.……………………29


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Figure 4.16: Event 15: Machine designer is prompted to refer source…………………..29

Figure 4.17: Event 16: Machine designer documents the design………………………..30

Figure 4.18: The top-level dataflow diagram for the Mechanical Design
             Desktop system…………………………………………………………….31

Figure 4.19: 1.0: Process design information…………….…………………..………….32

Figure 4.20: 2.0: Process design limitations……………….…………………………….33

Figure 4.21: 3.0: Process design equation………………….…………………………....33

Figure 4.22: 4.0: Process design parameter values…………….…………………….…..34

Figure 4.23: 4.2: Refer design data source….……….…………………………………..34

Figure 4.24: 6.0: Solve for output design parameters……………….…………………...35

Figure 4.25: 7.0: Generate Plot…….…………………………………………………….36

Figure 4.26: 8.0: Process design document…………………….…………………….….37

Figure 4.27: The entity relationship diagram for the Mechanical Design
             Desktop System………………………………………………………..…..45

Figure 5.1: The main screen of the application……………………………………….….47

Figure 5.2: The web browser window…………………………………………………...51

Figure 5.3: Information to be copied by the designer…………………………………....53

Figure 5.4: The screen for saving information………..…..……………………………...54

Figure 5.5: The destination folder and file where the information needs to be saved…...55

Figure 5.6: The contents of the belt folder……………….……………………………....56

Figure 5.7: The contents of the file: tension.txt………………..………………………...57

Figure 5.8: The form for entering specification names……………………………….….58

Figure 5.9: The transfer of specifications onto the main form……………..…………....59

Figure 5.10: The limitations imposed on the given test case……………………………60




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Figure 5.11: The design equations involved in the design of a V-belt drive…………….61

Figure 5.12: Selection of a design equation and the displayed prompt for input
             design……………………………………………………………………….62

Figure 5.13: The list of tables viewed on clicking the Table menu……………….……..63

Figure 5.14: The view of Table 17-9 for the selection of the service factor, Ks…..…….64

Figure 5.15: The input parameter values specified for the design equation……………..65

Figure 5.16: The value of calculated design parameter Pd,
             displayed in the results section...……………………………………….…..66

Figure 5.17: The input parameter boxes for the second design equation…………….….67

Figure 5.18: Reference table for Standard designations for various V-belts for
             the selection of minimum sheave diameters…………….………………....68

Figure 5.19: First trial calculations for selection of optimum sheave diameters………...69

Figure 5.20: Second trial calculations for selection of optimum sheave diameters……...70

Figure 5.21: Calculations for the small angle of contact, Thetas………………………...71

Figure 5.22: Calculation of the pitch length, Lp, for the V-belt………………………....72

Figure 5.23: Selection of length conversion quantity from Table 17-4………………….73

Figure 5.24: Calculation of the inside circumference of the V-belt………………….….74

Figure 5.25: Table for the standardization of V-belt lengths…………………………….75

Figure 5.26: The table to be referred for the value of parameter, Ka...………………….76

Figure 5.27: Table for the selection of parameters C1, C2, C3 and C4………………….77

Figure 5.28: The design equation for the calculation of power rating…………………...78

Figure 5.29: The design equation for the correction of the power rating…………….….79

Figure 5.30: Graph to be referred for the value of correction factor, K1…………….…..80

Figure 5.31: The table for the selection of Length Correction factor, K2……………….81

Figure 5.32: The corrected power rating for the V-belt drive…………………………....82



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Figure 5.33: The calculated value of belt speed………………………………………....83

Figure 5.34: The calculation for the number of belts required for the V-belt drive……..84

Figure 5.35: The documentation of the design can be done in a Microsoft® Word 97
             Document………………………………………………………………..…85

Figure 5.36: The transfer of the selected design parameter value
             into the Copy Value box.…..…………………………………………….…86

Figure 5.37: The highlighting of the design parameter value in the Copy Value box…...87

Figure 5.38: The transfer of contents from the Main screen to the design document…...88

Figure 5.39: TKSolver can be instantiated by clicking the Open TKSolver
             menu item……………………..……………………………………………89

Figure 5.40: The user interface for TKSolver……………………………………………90

Figure 5.41: The Variable sheet after entering the design parameter values…………….91

Figure 5.42: The List Fill Window……………………………………………………....92

Figure 5.43: The dialog box for List Fill………………………………………………...93

Figure 5.44: First six elements of the C list……………………………………………...94

Figure 5.45: The first six calculated values of Thetas…………………………………...95

Figure 5.46: The Table sheet…………………………………………………………….96

Figure 5.47: The names of the lists comprising the table…………………………….….97

Figure 5.48: The Plot Wizard in TKSolver……………………………………………....98

Figure 5.49: The window for selecting the table in the Plot Wizard…………………….99

Figure 5.50: The selection of the table to plot………………………………………….100

Figure 5.51: The window depicting the various plotting options……………………....101

Figure 5.52: The various options under the Style tab…………………………………..102

Figure 5.53: The plot for the variation of Thetas and C………………………………..103

Figure 5.54: Pull down menu for the plot……………………………………………....104



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Figure 5.55: The paste special option in Microsoft® Word 97………………………...105

Figure 5.56: The plot pasted in the design document…..………………..…….…….…106




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