Prototyping a Design and Fabrication Experience for Sophomores in Mechanical
Engineering
THESIS
Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in
the Graduate School of The Ohio State University
By
Angelica Liu
Graduate Program in Mechanical Engineering
The Ohio State University
2011
Master's Examination Committee:
Dr. Blaine Lilly, Advisor
Dr. Gary Kinzel
Abstract
In autumn 2012, The Ohio State University will make the transition from a quarter to a
semester system. This thesis describes the design and development of a laboratory
module for a new required sophomore level design course which will be implemented
during the quarter-to-semester transition. Currently, there is no mandatory course in
which mechanical engineering students at OSU are given formal machining instruction;
many graduating seniors leave the university without ever learning how to properly use
machine tools, which will greatly aid their career prospects. Students going through this
new course will learn fabrication operations in the context of machining a two-piston
motor that runs on compressed air.
This MS thesis involves the design and development of the air motor which will be used
in the course. The motor was modeled after a design created by several OSU mechanical
engineering students during their senior-level design course. A primary constraint for
this design is that it be feasible for students with little to no prior fabrication experience
to machine and assemble the motor in six weeks. Based on the time it took for
fabrication, it is unlikely that students will be able to perform every individual operation,
but rather should have some processes done for them prior to lab. A great deal of
ii
guidance will have to be supplied by the instructional staff, and safety must be a priority
with the large number of inexperienced students operating equipment at one time.
iii
Dedication
This document is dedicated to my family.
iv
Acknowledgments
I would like to thank my advisor Professor Blaine Lilly, as well as Professor Lisa Abrams
for their help and guidance throughout this project. I would also like to thank Chad
Bivens from the OSU machine shop for his invaluable instruction, advice and time
throughout the development and fabrication processes.
individuals, this project would not have been possible.
v
Without the help of these
Vita
June 2006 .......................................................Upper Arlington High School
2010................................................................B.S. Mechanical Engineering, The Ohio
State University
2011................................................................M.S. Mechanical Engineering, The Ohio
State University
2010 to present ..............................................Graduate Teaching Associate, Department
of Mechanical Engineering, The Ohio State
University
Fields of Study
Major Field: Mechanical Engineering
vi
Table of Contents
Abstract ............................................................................................................................... ii
Dedication .......................................................................................................................... iv
Acknowledgments............................................................................................................... v
Vita..................................................................................................................................... vi
Table of Contents .............................................................................................................. vii
List of Tables ..................................................................................................................... xi
List of Figures ................................................................................................................... xii
Chapter 1: Introduction ....................................................................................................... 1
Chapter 2: Literature Review .............................................................................................. 3
2.1. Introduction .............................................................................................................. 3
2.2. Existing College Design Courses ............................................................................. 4
2.2.1. Multidisciplinary Design Courses ..................................................................... 4
2.2.2. Fabrication-Oriented Design Courses ............................................................... 5
2.2.3. Reverse Engineering-Based Design Courses .................................................... 6
2.2.4. Mechatronics Design Courses ........................................................................... 7
2.2.5. Open-Ended Design Projects ........................................................................... 10
2.2.6. Product Design Courses................................................................................... 11
vii
2.3. Stepper Motors within Mechanical Engineering Curricula.................................... 13
2.4. Air Motors .............................................................................................................. 14
2.4.1. Rotary Vane Motors ........................................................................................ 15
2.4.2. Piston Motors................................................................................................... 16
2.4.3. Gerotor Motors ................................................................................................ 16
2.5. Air Motors within Mechanical Engineering Curricula .......................................... 17
Chapter 3: Chapter 3: Design Constraints and Preliminary Concepts .............................. 21
3.1. Constraints Affecting Course Design ..................................................................... 21
3.2. Initial Design Concepts .......................................................................................... 26
Chapter 4: Air Motor Design and Development ............................................................... 30
4.1. ME 581 Air Motor.................................................................................................. 30
4.2. Critique of ME 581 Design .................................................................................... 32
Chapter 5: Air Motor Fabrication ..................................................................................... 35
5.1. Air Motor Fabrication Procedure ........................................................................... 35
5.1.1. Piston Block ..................................................................................................... 35
5.1.2. Piston Block Cover .......................................................................................... 54
5.1.3. Valve Block ..................................................................................................... 61
5.1.4. Valve Sleeves .................................................................................................. 75
5.1.5. Valve Rods ...................................................................................................... 76
5.1.6. Cam Follower .................................................................................................. 78
5.1.7. Valve Stopper .................................................................................................. 80
viii
5.1.8. Mounting Caps ................................................................................................ 81
5.1.9. Mounting Cap Spacer ...................................................................................... 85
5.1.10. Valve Block Cover ........................................................................................ 87
5.1.11. Crankshaft 1 ................................................................................................... 93
5.1.12. Crankshaft 2 ................................................................................................... 97
5.1.13. Crankshaft 3 ................................................................................................... 98
5.1.14. Crankshaft 4 ................................................................................................... 99
5.1.15. Crank Connecting Disks .............................................................................. 100
5.1.16. Spacer .......................................................................................................... 107
5.1.17. Piston Rods .................................................................................................. 108
5.1.18. Pistons.......................................................................................................... 113
5.1.19. Cams ............................................................................................................ 119
5.1.20. Additional Operations and Assembly .......................................................... 123
5.2. Budget .................................................................................................................. 129
5.3. Design Changes .................................................................................................... 129
Chapter 6: Conclusion and Future Work ........................................................................ 134
6.1. Tooling and Machining Requirements ................................................................. 134
6.2. Staffing ................................................................................................................. 135
6.3. Student Part Fabrication ....................................................................................... 136
6.4. Apprentice Piece .................................................................................................. 137
6.5. Instructional Videos ............................................................................................. 138
ix
6.6. Prony Brake and Accelerometers ......................................................................... 139
6.7. Student Safety ...................................................................................................... 140
6.8. Suggested Future Modifications........................................................................... 141
Works Cited .................................................................................................................... 143
Appendix A: Stepper Motor Information ....................................................................... 146
Appendix B: Basic Machining Instruction Outline ........................................................ 151
Appendix C: Assembly Drawings .................................................................................. 158
Appendix D: Budget ....................................................................................................... 183
x
List of Tables
Table 1: Table of stepping sequences (Laidman) ........................................................... 149
Table 2: Overall project budget ...................................................................................... 184
xi
List of Figures
Figure 1: 2011 OSU FEH Robot course ............................................................................. 8
Figure 2: Topics covered in VU‟s MEA&D course (Clayton, O'Brien and Kroos) ......... 13
Figure 3: Rotary vane motor (Air Motors) ....................................................................... 15
Figure 4: USCGA air motor drawing................................................................................ 18
Figure 5: Tufts final air motor assembly (Manno and Saigal) .......................................... 19
Figure 6: Steam engine examples from Carnegie Mellon University (Ambrose and
Amon) ............................................................................................................................... 20
Figure 7: Cal Poly air motor design (Hoadley and Rainey).............................................. 20
Figure 8: Preliminary manipulator design ........................................................................ 28
Figure 9: Original OSU air motor ..................................................................................... 30
Figure 10: Valve seals in original motor design ............................................................... 32
Figure 11: Preliminary ME 2900 air motor design ........................................................... 35
Figure 12: Layout overall length for piston block ............................................................ 37
Figure 13: Cut piston block stock using horizontal band saw .......................................... 38
Figure 14: Setup for fly cutting top surface of piston block ............................................. 38
Figure 15: Height gage (Hoose) ........................................................................................ 39
Figure 16: Using calipers, determine overall height ......................................................... 40
xii
Figure 17: Setup for establishing overall width of piston block ....................................... 41
Figure 18: Center drilled hole pattern for piston block cover attachment ........................ 42
Figure 19: Drilled hole for piston block cover attachment ............................................... 42
Figure 20: Tapped hole for piston block cover attachment .............................................. 43
Figure 21: Full tapped hole pattern for piston block cover attachment ............................ 43
Figure 22: Edges for pocket layout on piston block ......................................................... 44
Figure 23: Rough cut piston block pockets using band saw ............................................. 45
Figure 24: Cut piston block pockets (rough) .................................................................... 45
Figure 25: Mill piston block pockets to size ..................................................................... 46
Figure 26: Sawed center mounting arm ............................................................................ 46
Figure 27: Milled center mounting arm ............................................................................ 47
Figure 28: Finished pockets on piston block .................................................................... 47
Figure 29: Tapping head on a drill press .......................................................................... 48
Figure 30: Setup for boring piston cylinders .................................................................... 49
Figure 31: Center drill bored hole locations ..................................................................... 49
Figure 32: Drill through block on bored hole locations .................................................... 50
Figure 33: Dill through piston block at piston cylinder locations .................................... 50
Figure 34: Boring tool and head for boring piston cylinders ............................................ 51
Figure 35: Boring tool and piston cylinder in piston block .............................................. 51
Figure 36: Press in cylinder liners .................................................................................... 52
Figure 37: Setup for milling outlet ports........................................................................... 53
xiii
Figure 38: Outlet port in piston block with carbide end mill ............................................ 53
Figure 39: Completed outlet ports in piston block............................................................ 54
Figure 40: Rough hole layout for fastening to piston block ............................................. 56
Figure 41: Setup for drilling screw hole pattern ............................................................... 57
Figure 42: Damaged parallels ........................................................................................... 57
Figure 43: Drilled hole pattern in piston block cover ....................................................... 58
Figure 44: Measuring screw head height .......................................................................... 58
Figure 45: Counterbored hole pattern on piston block cover ........................................... 59
Figure 46: CNC milling O-ring grooves in piston block cover ........................................ 59
Figure 47: Finished O-ring grooves .................................................................................. 60
Figure 48: Required pipe tap tooling ................................................................................ 60
Figure 49: Pipe tapped holes in piston block cover .......................................................... 61
Figure 50: Saw valve block stock using horizontal band saw .......................................... 63
Figure 51: Un-filed edge ................................................................................................... 64
Figure 52: Deburred part ................................................................................................... 64
Figure 53: Skim cut top face of valve block ..................................................................... 65
Figure 54: Center drilled hole for valve block cover attachment ..................................... 66
Figure 55: Tapped hole for valve block cover attachment ............................................... 67
Figure 56: Threaded hole pattern for valve block cover attachment ................................ 67
Figure 57: Final counterbored screw holes for attachment to piston block ...................... 68
Figure 58: Bore dowel holes using end mill ..................................................................... 69
xiv
Figure 59: Ream dowel holes ........................................................................................... 69
Figure 60: Countersink dowel holes ................................................................................. 70
Figure 61: Check fit of dowel in hole ............................................................................... 70
Figure 62: Rough cut valve block ..................................................................................... 71
Figure 63: Surface finish using a band saw ...................................................................... 71
Figure 64: Setup for drilling valve block holes ................................................................ 72
Figure 65: Bottom view of valve holes ............................................................................. 73
Figure 66: Valve holes with one seal in place .................................................................. 73
Figure 67: Ream pipe tap holes ........................................................................................ 74
Figure 68: Pipe tapped holes in valve block ..................................................................... 75
Figure 69: Threading valve rod......................................................................................... 78
Figure 70: Setup for establishing overall width of mounting cap ..................................... 83
Figure 71: Center drill on mounting hole locations .......................................................... 84
Figure 72: Counterbored screw holes in mounting cap .................................................... 85
Figure 73: Use ground square piece to establish perpendicularity between faces ............ 89
Figure 74: Press one ground face to vise surface, and push finished block face against
other ground face .............................................................................................................. 89
Figure 75: center drilled screw holes for attachment to valve block ................................ 91
Figure 76: CNC mill the O-ring groove in the valve block cap........................................ 92
Figure 77: O-ring inserted into O-ring groove .................................................................. 92
Figure 78: Hand tapping setup for pipe tap ...................................................................... 93
xv
Figure 79: Face shaft stock in lathe .................................................................................. 95
Figure 80: Turn the outer diameter of the shaft to size ..................................................... 96
Figure 81: Milled flat on shaft for set screw ..................................................................... 96
Figure 82: Final crankshaft shaft components ................................................................ 100
Figure 83: Use cutoff tool to cut part slightly oversized ................................................ 102
Figure 84: Disk with center hole and correct overall length and diameter ..................... 102
Figure 85: Crank connecting disk with both holes complete .......................................... 103
Figure 86: Setup for drilling set screw holes .................................................................. 104
Figure 87: Center drilled hole for center set screw ......................................................... 104
Figure 88: Drill hole for center set screw ....................................................................... 105
Figure 89: Drill using larger diameter drill bit for beginning of set screw hole ............. 105
Figure 90: Power tap hole for set screw.......................................................................... 106
Figure 91: Deburred threaded set screw hole ................................................................. 106
Figure 92: Piston rod stock with holes drilled ................................................................ 110
Figure 93: Piston rod CNC fixturing components .......................................................... 110
Figure 94: Piston rod CNC fixturing step 1 .................................................................... 111
Figure 95: Piston rod CNC fixturing step 2 .................................................................... 111
Figure 96: Fully fixtured piston rod stock ...................................................................... 112
Figure 97: Piston rod with milled profile ........................................................................ 112
Figure 98: Fully chamfered piston rod profile ................................................................ 113
Figure 99: Piston with milled fork .................................................................................. 115
xvi
Figure 100: Piston reference surfaces for clamping part to mill ..................................... 116
Figure 101: Piston head setup for drilling pin hole with unclamped piston ................... 116
Figure 102: Piston head setup for drilling pin hole with clamped piston ....................... 117
Figure 103: Center drilled pin hole in piston head ......................................................... 117
Figure 104: Drilled pin hole in piston head .................................................................... 118
Figure 105: Reamed pin hole in piston head .................................................................. 118
Figure 106: Ream the shaft hole for the cam stock ........................................................ 120
Figure 107: CNC-ed cam profile on one side of the cam part ........................................ 121
Figure 108: One cam profile with milled flats on spacer for positioning ....................... 122
Figure 109: Cam part with both profiles milled.............................................................. 123
Figure 110: Detailed view of set screw hole with set screw ........................................... 123
Figure 111: Bored hole at shaft mounting location ........................................................ 125
Figure 112: Reamed hole at shaft mounting location ..................................................... 125
Figure 113: Finish for mounting hole ............................................................................. 126
Figure 114: Setup for drilling middle mounting hole ..................................................... 126
Figure 115: Wear on aluminum shaft from original nylon flanged sleeve bearings ...... 131
Figure 116: Current cam profile design (black) and proposed modification (red) ......... 132
Figure 117: Six wire unipolar stepper motor (Newton) .................................................. 147
Figure 118: Four wire bipolar stepper motor (Newton).................................................. 148
Figure 119: Conceptual model of a unipolar stepper motor(Laidman) .......................... 149
xvii
Chapter 1: Introduction
In autumn 2012, The Ohio State University will make the transition from a quarter to a
semester system. During this transition, the mechanical engineering department plans on
making major changes to the curriculum in order to improve the overall undergraduate
experience and better prepare students for their future careers. Among these changes is
the addition of a new sophomore-level design course. This course will be designed to
give students an introduction to fundamental mechanical engineering topics and concepts
that will be explored later in the curriculum. It will also give students an opportunity to
gain hands on experience in fabrication and design that will be extremely useful both in
future courses as well as in their industrial careers.
This project involved developing the fabrication portion of the lab for the design course.
Students will machine and assemble a two-piston motor that runs on compressed air.
During this process, they will learn basic machine shop safety as well as the proper
procedure for many common machining operations including sawing, drilling, turning,
milling and tapping.
Several schools currently offer fabrication courses similar to the air motor project, while
others have courses devoted to design and the design process. Most of the fabrication
1
courses, however, are elective classes that solely focus on machining processes, and very
few universities have attempted to combine the topics of design and fabrication into one
course. An overview of college design courses and fabrication courses is given in the
following chapter.
This thesis also documents the design and fabrication processes involved in developing
the air motor. An outline of the project constraints as well as a description and critique of
the original ME 581 design are given. In addition, a preliminary lab procedure was
developed with tooling requirements and step-by-step machining instructions. Finally,
suggestions are given for modifications to the air motor as well as requirements for safe
and effective implantation of the project into the course.
2
Chapter 2: Literature Review
2.1. Introduction
During the past few decades, there has been a major push for additional emphasis on
design in engineering curricula.
Increasingly, universities around the country are
integrating new or improved design courses into their programs. These courses generally
have come in the form of first- or occasionally second-year design classes, followed by
senior-level design projects. In a few cases, colleges have created four-year design
sequences, and some have even gone as far as creating new majors which combine
engineering and design. Furthermore, the accreditation agency for most engineering
programs in North America, ABET, now requires a substantial design component for all
engineering programs, culminating in a significant design experience during the senior
year.
Because the goal of this project is to create a new sophomore-level design course which
will be integrated into The Ohio State University‟s Department of Mechanical
Engineering curriculum, the following section will discuss existing sophomore
mechanical engineering design courses as well as additional relevant courses being
offered at other engineering programs in the United States.
3
2.2. Existing College Design Courses
American universities have taken very different approaches in their treatment of
freshman sophomore level design courses. Some are very different from courses that
OSU currently has or plans to implement, while others follow very closely with some of
the department‟s existing curriculum. Many other schools have essentially ignored the
sophomore year of the typical engineering curriculum, and only have design–related
experiences in first–year programs, and again in the senior year.
2.2.1. Multidisciplinary Design Courses
Universities such as Rowan University and Penn State University have decided to focus
on multidisciplinary or multinational teams.
At Rowan University, all engineering
students take part in two semester-long design courses during their sophomore year
(Marchese, Newell and Ramachandran). The first course or “clinic” is team-taught by
faculty from the chemical, civil, electrical, and mechanical engineering departments as
well as the communications departments. This course attempts to merge the topics of
engineering design and technical communication via an underlying theme of “Total
Quality Management” (TQM). Students go through four three-week engineering design
modules, one for each of the disciplines previously listed. The four modules include the
design of a product (i.e. can crusher), design of a process (i.e. heat treatment of Kevlar),
design of a structure (i.e. sheet pile wall) and simulation (i.e. analog electrical filters)
(Newell, Marchese and Ramachandran). The second sophomore-level clinic is a 16-week
4
long interdisciplinary design project involving students from the four engineering
departments. Students bring their experience from the previous clinics to this course, and
learn to work in a multidisciplinary group on a multidisciplinary project. These design
projects include topics such as landfill design, assistive technology for the disabled, and
design and development of a nondestructive aircraft inspection device; each project was
assigned at least one faculty member, though some were helped by multidisciplinary
faculty teams.
At Penn State, students in the honors program work with cross-national teams on
industry-sponsored design projects during their first year (Bilen, Devon and Okudan).
French industries and a French university formulate industry projects and give them to
the faculty at Penn State. The non-honors track has a similar industry-sponsored project,
however the projects involve local industries rather than international ones.
2.2.2. Fabrication-Oriented Design Courses
Other universities have chosen to emphasize fabrication skills during the second year. At
the University of Southern Alabama, mechanical engineering and material science
engineering students manufacture Mardi Gras medallions using copper in a one-credit
hour lab course during their first quarter of their sophomore year (Tsang and Wilheim).
The labs meet once a week for three hours and are team taught by a material science
faculty member and a design and manufacturing faculty member. Each student learns
basic fabrication skills, and material science principles such as the relationships between
5
material properties, structure and processing are built into the course. Technical writing
and oral presentations are also included in this course. MIT also offers a course that
emphasizes fabrication through the construction of a robot that is powered by compressed
air (James). Students learn basic mechanical engineering topics such as kinematics and
are also introduced to microcontrollers. The main portion of the course is devoted to
introduction to the machine shop through instruction on mills, lathes, band saws and drill
presses.
2.2.3. Reverse Engineering-Based Design Courses
Some engineering educators see reverse engineering as the key to developing early
design skills. At MIT, the US Air Force Academy (USAFA), and the University of
Texas-Austin, faculty have developed courses built around this idea (Otto, Wood and
Bezdek). Of these schools, USAFA is the only one that emphasizes reverse engineering
during design courses in the sophomore year. During this course, students test toys or
simple household products.
They then submit redesign proposal based on their
observations and finally write a parametric redesign results paper along with a final
presentation.
At University of Texas-Austin, though reverse engineering is not used in mechanical
engineering sophomore-level courses, it is emphasized at almost every other point in the
department‟s design curriculum. Freshmen reverse engineer mechanical products such as
toys, and discuss simplified reverse engineering principles such as why a part has a
6
specific form. During the junior or senior year, students take a higher level course that
not only involves reverse engineering a more complex product (i.e. one involving both
mechanical and electrical aspects), but they also go in depth on the redesign process
using tools like the House of Quality for quality function deployment (QFD) (Otto, Wood
and Bezdek). Additional courses are offered to UT-Austin students at the graduate level
which include working in interdisciplinary teams on reverse engineering projects as well
as individual products that allow students to redesign professional products.
At MIT, students encounter reverse engineering during the senior year. Again, students
analyze a household or professional product that has both mechanical and electrical
aspects (Otto, Wood and Bezdek). They then redesign the product, providing a cost
analysis, discuss marketing, and building and testing prototypes.
In most of these
courses, students start by choosing a somewhat complex product and disassembling it.
They determine the function of different components, why specific design decisions were
made, and are eventually asked to develop their own solutions as well as offer
suggestions on improving the original design. In this way, students do not simply start
off with a blank canvas, but rather learn from existing products.
2.2.4. Mechatronics Design Courses
Currently, mechanical engineering students at Ohio State University experience two to
three major design courses: one during the first year, one during the last year, and an
optional technical elective usually taken during the last year. In the first-year honors
7
program, students are given a quarter-long mechatronics project in which they design and
build an autonomous robot which must complete specified tasks (i.e. pick up and drop off
a box, detect light colors and react accordingly, etc.).
Figure 1: 2011 OSU FEH Robot course
Several universities have similar programs with varying levels of difficulty in their
sophomore-year curricula. These schools include the University of Houston, Georgia
Tech, and Kettering University. At the University of Houston, sophomore students enroll
in a design course during either their fall or spring semester (Bannerot). The team design
project is different every year, but always requires students to complete a specific task
given a list of constraints. Constraints can include size, weight and time limits. Some
past projects include separating ping pongs and golf balls, and throwing golf balls at a
target.
Georgia Tech‟s Creative Decisions and Design course is a sophomore mechanical
engineering design course that integrates technical communication and mechatronics
8
concepts in the team design project (Vaughan, Fortgang and Singhose). The project is
very similar to the honors robotics course. While the theme changes from year-to-year
(i.e. Mission to Mars, Charlie and the Chocolate Factory, War of the Worlds), the tasks
that their “machine” must complete remain fairly consistent. These tasks include moving
their “machine”, collecting items, and removing items from specified areas of the arena.
Because the course is a semester-long rather than quarter-long course, this project is not
assigned until the later part of the semester. The beginning of the semester is devoted to
training students in the machine shop, giving them experience with controllers and
electronics, and allowing them to exercise team working skills.
Faculty at Kettering also realized the need for an early mechanical engineering
mechatronics course after implementing two senior-level elective courses in 1997
(Hargrove). They integrated mechatronics design and prototype fabrication into two
existing sophomore-level courses which were already part of the core curriculum. These
courses are now an eight-credit hour series called “Introduction to Mechatronics Design”.
The final mechatronics project gives students the opportunity to design, construct, and
program a device to complete a set of faculty-specified tasks.
For example, the pilot
course created a competition in which student-designed vehicles had to remove different
sized blocks from an arena. The block sizes had a corresponding point value, and the
goal was to reach exactly 100 points. These vehicles use microcontrollers, sensors and
actuators to complete their task in the same way that robots in OSU‟s first-year honors
program function.
9
2.2.5. Open-Ended Design Projects
During the senior-level design project at OSU, students either choose or are assigned
projects by faculty members. These are open-ended projects and have varying levels of
difficulty. Some students choose to work with industry sponsors, while others are funded
through the department. Universities such as Purdue and the University of Utah have
similar open-ended design projects in their sophomore level courses; however these
generally focus on thermodynamics or fluid dynamics, which are taught concurrently.
Purdue calls their class a “cornerstone design course” (Starkey, Midha and DeWitt).
Their goal is to bridge the gap between problem solving skills in the math and science
areas and problem solving skills for open-ended engineering projects. Projects have
included a supplemental car heater to warm drivers before the engine heater is warm, a
quick cooler for warm beverages, and a high-pressure water toy for 12-year-old children.
Each of these projects has a significant thermal or fluids component, and allows students
to use information learned in concurrent courses.
Similarly, the University of Utah has implemented two design courses into the
sophomore year called “Introduction to the Design of Sustainable Energy Systems I & II”
(Roemer, Bamberg and Kedrowicz). These courses are part of Utah‟s four-year design
course sequence which they refer to as the Student-driven Pedagogy of Integrated,
Reinforced, Active Learning (SPIRAL) approach.
During the first quarter of their
sophomore year, students learn about fluid dynamics and are given a team-based design
project that allows them to apply these principles. For example, one project involved
10
designing, building, and analyzing a wave-powered electricity generator. The second
quarter is set up in the same way, with a focus on thermal and energy systems. An
example of a project under these topics is the design of an inexpensive “crockpot” that
has temperature control capabilities to prevent the system from overheating if left
unattended.
2.2.6. Product Design Courses
The last optional OSU design course is offered as a technical elective. This class differs
from the previous two courses in that it focuses mainly on the design process itself rather
than the more technical aspects of the project. Tools such as the House of Quality are
discussed, and prototyping as well as user input are emphasized. Similar sophomorelevel customer-driven/ design process-focused projects exist at Olin College, Virginia
Tech, and Rensselaer Polytechnic Institute (RPI).
Olin is a small, nontraditional
engineering college that offers design projects every semester (Rubin).
During the
sophomore year, students create new products after interviewing clients such as operating
room nurses and bicycle messengers. Students are asked to identify a need, and using
product development methods, create a prototype for a new product that satisfies that
need.
At Virginia Tech, mechanical engineering students are required to take ME 2024 which
provides an introduction to product design and development (Spangler and Filer).
Students from other disciplines such as industrial, civil, and construction engineering
11
oftentimes elect to take this course as well. During the course, students work in teams to
develop some sort consumer product. Past projects have included an automated pet
feeder, collapsible office chair, and electrically powered car jack. In recent years, the
department has worked to integrate the use of tablet PC‟s into the project to allow for
more effective team collaboration and documentation.
RPI has a unique dual degree program called “Product Design and Innovation” (PDI)
which integrates mechanical engineering and science, technology and society Bachelor of
Science degrees (Gabiele, Bronet and Kagan). The main goal of this program is to
prepare students to be innovative designers who can integrate engineering concepts
within the current social environment. During the first semester of students‟ sophomore
year, students focus on industrial design. Rather than simply focusing on the traditional
issues of shape and form, the course also greatly emphasizes the user-product interface.
Project teams look at problems such as how shin sheets of metal can be used for furniture
fabrication in third world countries or how wireless communication can help with work
in the kitchen.
The new sophomore-level course being developed at OSU is different from those
discussed above in that it will be used to not only give students experience in using the
design process as well as teach basic fabrication skills, but also introduce students to
general mechanical engineering topics that will be covered in depth over the following
two years. The most similar course that was found is at Villanova University. Their
12
“Mechanical Engineering Analysis and Design” (MEA&D) course introduces students to
the technical aspects of mechanical engineering and is centered on hands-on projectbased laboratories (Clayton, O'Brien and Kroos). The main difference between this and
OSU‟s course is that the labs do not contain one cohesive project, but rather several
smaller lab activities. The topics covered in the Villanova course can be seen below in
Figure 2.
Figure 2: Topics covered in VU‟s MEA&D course (Clayton, O'Brien and Kroos)
2.3. Stepper Motors within Mechanical Engineering Curricula
The fabrication portion of the new OSU ME 2900 design course will be centered on the
machining of a two-piston air motor, and the inlet of the air motor will be controlled by a
stepper motor operated valve.
Stepper motors are a commonly used device within
mechanical engineering curricula, and are used in numerous labs. Many colleges used
13
them to teach about microcontrollers, and they are often available options for robotic
design courses. Universities such as St. Louis University and the University of South
Carolina use these motors within their mechanical engineering labs.
At St. Louis
University, the motors are used in a senior-level lab course called “principles of
Mechatronics” (Mechancial Engineering Courses). In this class, students are introduced
to basic mechatronics components such as sensors and transducers, and use these for
motor control (Mechancial Engineering Courses). Students then apply these principles;
they are asked to work with industrial robots, conveyor belts, and program robots
(Rehan). A similar microcontrollers course is offered at the University of South Carolina
(Giurgiutiu). This also teaches students about sensors and controls in order to actuate
motors. The stepper motor portion of the course emphasizes direct digital control without
system feedback. Additional information on stepper motors can be found in Appendix A.
2.4. Air Motors
Air engines and motors have been around since the 1800‟s, however after the invention
of the internal combustion engine, there was very little research into the technology
(Finkelstein and Organ). Recently, there has been an increased interest in the area due to
increased environmental awareness.
There are several types of air engines which include rotary vane, axial piston, radial
piston, gerotor, turbine, V-type, and diaphragm (Air Motors). The most commonly used
14
designs are the rotary vane, axial piston, radial piston, and gerotor air motors because
they operate with the highest efficiencies.
2.4.1. Rotary Vane Motors
Rotary vane motors can produce continuous rotary power from compressed air. They are
composed of axial vanes fitted into radial slots that run the length of the rotor (see Figure
3) (Air Motors). The rotor itself is mounted eccentrically with the motor housing. Each
of the vanes is pushed against the housing via a spring located between the vane and the
rotor. Torque is produced as pressure acts on one side of the vanes.
Figure 3: Rotary vane motor (Air Motors)
Most rotary vane motors have anywhere from three to ten vanes (Victrex PLC). More
vanes allows for more uniform rotation, especially at lower speeds. However, it also
increases friction and cost while decreasing efficiency (Air Motors). In order to increase
torque, higher air pressure can be applied; however this also increases costs and leads to
15
increased wear. These motors are generally used for low to medium power output
applications such as in power tools.
2.4.2. Piston Motors
Piston air motors usually have between two and six cylinders, arranged either radially or
axially within the motor (Air Motors). Those with four or more cylinders have relatively
smooth strokes with little vibration when the power pulses overlap. The power generated
by these motors depends on the inlet pressure, the number of pistons, and the piston area,
stroke, and speed (Finkelstein and Organ). Output speed is limited by the inertia of the
moving parts and the design of the inlet and exhaust valves.
Radial piston motors have the highest starting torque of all the air motor designs, and
have smooth operation. Axial piston motors are more compact and run more smoothly
than radial piston motors, however they are also more expensive. Both types of piston
motors provide high power and can be accurately controlled at low speeds.
2.4.3. Gerotor Motors
Gerotor air motors can deliver relatively high torque at low operating speeds. The outer
gear is held fixed while the inner gear or gears rotate (Air Motors). Because of the low
inertia design of the motor, it is possible to instantly start, stop, or change direction by
changing the air supply. In addition, the design of the motor prevents it from coasting or
being back driven.
16
2.5. Air Motors within Mechanical Engineering Curricula
As mentioned previously, part of the main project in the OSU sophomore-level design
course is the fabrication and assembly of an air motor. Several universities have found
these motors useful in the context of design projects. The principles behind this motor
will be discussed in later sections. Universities that use air and steam engine fabrication
include Cornell University, the US Coast Guard Academy, MIT, Tufts, Carnegie Mellon,
and California Polytechnic State University. These motors are used to teach real-world
fabrication skills and illustrate the importance of tolerance as well as discuss energy
principles.
Cornell students gain this experience through a class called “Mechanical Synthesis”
which is offered during their sophomore year (Ju). The motors built in the class run on
compressed air and students design them to drive a flat cart up a slight incline. Air motor
fabrication is one of two projects in the course; the other involves stamping a dog tag
with “CU”.
The mechanical engineering department at the United States Coast Guard Academy also
offers their air engine fabrication course during students‟ sophomore year (Dixon,
Wilczynski and Ford). During the course, students learn how to use the lathe, mill, drill
press, grinder, and several hand and woodworking tools. Prior to the fabrication portion,
instructors also introduce CAD software and have students produce CAD drawings of
17
their air engines. The engine, shown in Figure 4 is relatively simple, and materials cost
per engine is less than $10.00.
Figure 4: USCGA air motor drawing
Prior to MIT‟s current robot design course which was described earlier in this section, the
school offered a sterling engine project in the same sophomore-level course (Morris).
The sterling engines were fabricated in 36 hours over two weeks. Students worked in
groups of four to an engine, and fabricated parts in pairs with one student watching while
the other operated the machine. Faculty at MIT decided to change the course so a
microcontroller component could be added (James).
The air motor course at Tufts is somewhat different than those previously mentioned in
that it is divided into two sections: a fabrication portion and an instrumentation portion
(Manno and Saigal). Students are divided into two groups at the beginning of the
semester; half of the students start with fabrication and the other half with
instrumentation. Midway through the semester, the two groups switch. Also unlike
previously discussed courses, the projects in this course are individual. During the
18
fabrication portion, students build their own air motor like the one seen below in Figure
5. While the fabrication students are learning machining techniques and shop safety, the
instrumentation students learn about transducer and computer-based data acquisition.
Once the motors are finished, the instrumentation students determine the operating speeds
using their setups. At the end of the semester, students are able to measure the speed of
motors they built themselves using instrumentation and code they developed themselves.
Figure 5: Tufts final air motor assembly (Manno and Saigal)
Carnegie Mellon University uses miniature steam engines in their first-year
Fundamentals of Mechanical Engineering course (Ambrose and Amon). They use the
engine as an opportunity to get students excited about the major and introduce basic
mechanical engineering topics in an integrated format. Students work in teams to design
and assemble the engines and use them along with Meccano sets to drive a vehicle or
generate power for lighting a light bulb. Two examples can be seen below in Figure 6.
The course integrates lectures, classroom demonstrations, and labs into the project in
order to give students practical applications to mechanical engineering topics.
19
Figure 6: Steam engine examples from Carnegie Mellon University (Ambrose and
Amon)
At California Polytechnic State University, freshmen engineering students are required to
take a manufacturing processes course (Hoadley and Rainey). Three courses are used to
teach machining, foundry, and welding. The machining course uses ten three-hour labs,
and students are given a final project that consists of fabricating an air motor. Teams of
five are formed, and each team creates half of the components for the motor. An
exploded view of the final motor is shown in (Hoadley and Rainey).
Figure 7: Cal Poly air motor design (Hoadley and Rainey)
20
Chapter 3: Chapter 3: Design Constraints and Preliminary Concepts
3.1. Constraints Affecting Course Design
When creating a totally new course, especially a course with goals as ambitious as this
one, numerous factors need to be considered in order to develop a class that is both
challenging and beneficial to students without being completely overwhelming. These
factors include logistical considerations such as the amount of time that students will
spend in lecture and lab, as well as the capabilities of individual students, based on their
educational and cultural backgrounds. In addition, the new class has to fit well with the
rest of the curriculum while accomplishing specific pedagogical goals.
The logistics of the course are perhaps the easiest to determine. The course is designed to
be a full semester (14 week) course that will include 2.5 hours of lecture per week, along
with two hours per week in the machine shop/laboratory. The initial two lab periods of
the semester will be devoted to looking at real engineered products, with an eye toward
understanding the choices of material, process, and product architecture that were chosen
by the designers. The primary lab project for the semester, the air motor that is discussed
at length in this document, is allotted roughly six weeks‟ time during the semester. This
leaves the final six weeks for students to design and build a mechanical load – i.e., a
21
pump, a mechanism, etc. – which will be driven by the air motor. Each lab session will
be two hours in length, with students working in teams of two or four. The demands of
the projects will no doubt require additional time, beyond the regularly scheduled lab, for
the students to work in the machine shop.
The majority of students entering the class will be in the second semester of their second
year, and will be formally entering the mechanical engineering major in this semester:
this class is explicitly designed as their introduction to the discipline of mechanical
engineering. During the first year, all students would have taken one of three tracks
through the First–Year Engineering (FYE) course sequences. The first of these tracks, the
standard „FE‟ program, is the equivalent of Engineering 181 and 183 courses under the
academic quarter curriculum. In these courses, students learn basic drafting, computer
modeling using Autodesk Inventor, basic MATLAB, and experience a ten–week project
requiring the design of either a model roller coaster design or a basic nanotechnology
project.
The second first–year course option is the Engineering Scholars program, offered initially
in AY 2010–2011. In this program, there is an emphasis on green engineering. Students
learn many of the same skills as those in the regular program, but also gain additional
programming experience along with a more complex design project. During the second
quarter of the sequence, the students design and build a small “AEV”, which is basically
a small circuit board suspended on a rail, propelled by a small electric motor driving a
22
propeller, and which stops and starts at several pre–determined spots along the
curvilinear rail. The AEV is controlled using the Arduino open–source hardware and
software environment. Students program the Arduino to switch the electric motor on
and off at predetermined times. Students gain basic proficiency in programming the
microcontroller, as well as integrating it into a working circuit. This project is intended to
serve as the default project for all non–Honors First–Year Engineering tracks under the
semester curriculum.
The third first-year course sequence option is the First-Year Honors (FEH) program. In
the quarter system, this sequence consists of three courses rather than the two in the FE
and Scholars options. The first course again covers drafting and computer modeling.
The second course consists of basic programming in C, C++ and MATLAB. The third
course is a quarter-long robotics project in which students design, build and program a
small autonomous robot that must perform specified tasks as quickly as possible. This
option provides much more in the way of open–ended design experience for the students
who pursue it, and is regarded as one of the best programs of its kind in the United States.
However, because it is so successful, the result is that approximately one–third of the
students entering the ME major at OSU have had a much better design experience than
the remaining two–thirds. Not only must the new course take the widely differing
backgrounds of the students into account, it must also do so in a way that will not bore
the students who have completed the FEH program.
23
It is no exaggeration to say that after completing First Year Engineering, students
generally have very different levels of experience, particularly in programming and
fabrication. This is based not only on the course option they have followed, but also on
the specific role or roles they have assumed in the design projects offered in each track.
Students will naturally gravitate toward those areas in which they feel most comfortable;
as first–year students, few have the self-confidence needed to challenge themselves to
master a new skill. Students who come into these classes with some skill in programming
tend to gravitate toward programming; those who have any experience at all with
machining will become the „machinist‟ for their group. Instead of forcing the students to
broaden their skill set, these courses allow them to become specialists.
As a result, many students come to mechanical engineering with a very wide variance in
skill levels in programming, fabrication, and drawing. For this reason, it was important
that the new course, ME 2900, be specifically designed to “level the playing field” so that
all students would leave the class sufficiently prepared for the demands of the mechanical
engineering curriculum. This also means that the course will require all students to go
through the same series of tasks: the students will not have the option to specialize, at
least not during the initial eight weeks of the semester. Every student leaving this class
will have a basic level of proficiency in fabrication, programming, drawing, writing, and
presenting that will equip them well for the rest of their time in mechanical engineering at
Ohio State University.
24
Creating a course that is challenging but not impossible also required us to consider the
courses that students would be taking concurrently during the semester in which they take
ME 2900. For students who follow the mechanical engineering „bingo sheet‟, the other
courses they will enroll in for this semester are: ME 2020 (strength of materials), ME
2030 (dynamics), ME 2850 (Numerical Methods in Mechanical Engineering), and Math
2174 (Engineering Math II). Clearly, this course load makes for a very difficult semester,
which also was a very important constraint when designing this new course.
The course will require a considerable amount of time to construct both the air motor and
the open–ended design that will be driven by it. On the other hand, the lecture material
that accompanies the lab project will not, in general, be highly theoretical. It will instead
provide the „domain knowledge‟ required for the students to fully understand what they
are constructing in the lab. Some of this domain knowledge will consist of very basic
engineering „common knowledge‟ that many of our students often lack, because there is
no formal way of teaching it. This category includes material such as standard fastener
sizes and types, basic knowledge of engineering materials, electric motor types, and
standard machining methods. The second category of material taught in the lectures will
consist of the theory necessary to understand the lab project from an engineering
standpoint. Students will gain a better understanding of basic engineering fundamentals
such as power, stress, strain, torque, open–loop control, and the design of air motors.
25
The course is designed around the design projects, rather than the more usual case of the
laboratory work supplementing the theory taught in lecture. Students will be exposed to
material in lecture on an „as needed‟ basis, so that they will be able to immediately apply
what they learn to the practical demands of building a functioning motor and
programming a small micro–processor to control it. We believe that this method of
teaching will result in a far higher level of retention than is typically the case in other
courses, and at the same time, students will learn basic skills that they will be able to use
throughout their careers as engineers.
3.2. Initial Design Concepts
There were several initial design concepts for the lab portion of this course. The main
concept that was discussed was a stepper-motor-controlled manipulator. The original
plan was that the students would build a functioning stepper motor, which they would
then learn to control by use of a small micro–controller such as the Arduino©. The idea
of having students build their own stepper motor was abandoned when it was decided that
the fabrication tasks involved did not match well with the overall requirements for the
class.
In the second iteration, it was proposed that students would be given a stepper motor,
micro controller, and access to additional material.
They would then be asked to
complete a task or set of tasks and possibly compete with one another based on time and
26
accuracy. The idea was to give students a fairly open-ended design project and have
them go through the entire design process in a group of three to four students. Possible
tasks that were discussed included picking up pressure sensitive blocks and moving them
from one point to another, or gathering randomly shaped objects within a certain size
constraint.
A preliminary design can be seen in Figure 8 below.
The idea here was that the
manipulator would be composed of a rail which could pivot on a stand. The vertical
position of the manipulator could be controlled by moving the weight (labeled “W” in
Figure 8) back and forth on the rail using a stepper motor (labeled “M”) at the end of the
rail. A damper attached to the end of the rail could be adjusted to control how fast/slow
the rail pivoted. In addition, a clutch could be added to both the manipulator and the
weight so the same stepper motor could control two separate operations independently.
This design could be used to introduce many different mechanical engineering concepts
including screw design, clutch design, control systems, measurement principles, etc.
27
Figure 8: Preliminary manipulator design
After devoting some to the development of this idea, it was decided that this project
concept was too similar to the FEH robotics project that students going through the
honors program would experience. As previously noted in this chapter, approximately
30% of incoming students in ME have gone through the FEH program, therefore it was
thought that this project would not be interesting or challenging enough for these
students.
In order to make the project more useful to students, it was decided that greater emphasis
should be placed on learning proper and safe fabrication skills; hence the air motor
project. Not only would the air motor project give instructors a tool that is at the right
level of complexity for showing practical applications to a wide range of mechanical
engineering topics, but it would also allow the instructional team to attach a more open–
28
ended design project (that would be connected to the air motor) and thus give students the
tools to create a more complex project later in the curriculum.
Our decision was clearly informed by the extensive research we did on similar courses at
other engineering schools and universities, as noted in the previous chapter. The air
motor is appealing on a number of levels. First, it is complex enough to require a
relatively high level of skill in machining the component parts. Once students complete
this project, they will have a good feel for the meaning of tolerances, because the motor is
built to standard (±0.001 inch) engineering tolerances. Secondly, the motor provides us
with a platform with which we can introduce a very wide range of mechanical
engineering topics: machine design, fabrication methods and machine tools,
thermodynamics, fluid flow, vibrations, and controls. Thus it fulfills the primary
constraint of the course, that it introduce students to the entire discipline of mechanical
engineering, not only machine design. Hence the title of the course, “Introduction to
Design in Mechanical Engineering”, not “Mechanical Engineering Design”.
At this point, we feel very optimistic that we have created a project that will give our
students an experience unlike anything previous students in mechanical engineering at
Ohio State have had. In the following chapter, the design and fabrication of the basic
motor is covered in exhaustive detail. The motor itself is evolving as the course nears the
time of its first offering. We fully expect that the motor will continue to co–evolve with
the course over the next several years.
29
Chapter 4: Air Motor Design and Development
4.1. ME 581 Air Motor
The original OSU air motor was created by four OSU mechanical engineering students
for a senior design project. As seen Figure 9, the motor was a two-piston design that ran
on compressed air.
Figure 9: Original OSU air motor
The engine block was one solid piece, with a separate cap for the air chamber that
connected to the air inlet. Copper pipe was used to connect the valve system to the two
30
piston cylinders. The pistons cylinders were blind holes that were bored into the main
block, with air outlets milled into the top of the block.
Three disks were used to create the offset in the crank shaft, with the central disk thicker
than the other two. Couplers with set screws connected these disks to small sections of
shaft, and the piston rods sat between the disks with spacers to keep them aligned. It
appears that the pistons themselves were made from aluminum, and there may have
originally been a clearance issue between the piston rods and the sides of the piston
cylinders. Two fly wheels were attached to the ends of the crank shaft, and the crank
shaft was held in place by roller bearings.
The cam was composed of three parts: two separate cams and a spacer in between to keep
the followers aligned. These three components were attached to the shaft using set
screws. Unlike normal cam systems, the followers were not in contact with the cam at all
times; rather the followers only rode on the cams when they were at the rise or dwell
sections. The cams were used to control the air valves that allow air into the piston
cylinders. Each of the cam followers was threaded onto a small shaft that led to the air
chamber. On the opposite side of the shaft was another threaded portion with a metal
disk. A spring pushed the cam follower towards the cam, and sealed the disk against an
O-ring loaded lip seal as seen in Figure 10 below. The threaded shaft allowed for
adjustment of the valve length so the cam followers could be properly positioned.
31
Figure 10: Valve seals in original motor design
According to the student team, the motor peaked at 2750 rpm at around 50 psi inlet
pressure and had a stall torque of about 20 kg-cm.
4.2. Critique of ME 581 Design
Several design changes were made to the original OSU air motor design for the course.
These were done in hopes of both improving performance and aiding in
manufacturability. One of the most notable changed was the addition of two more shaft
supports. Although this would make it harder to align the crank shaft, it would provide
added stability that was not present in the original design and reduce vibration when the
motor was running. At these mounting points, detachable caps were added so that the
crank shaft could be removed in one whole piece rather than disassembling the entire
shaft and having to realign components upon reassembly.
32
The roller bearings that originally held the shaft at the mounting points were replaced
first with nylon sleeve bearings, and later changed to bronze sleeve bearings. The change
to nylon sleeve bearings was done to reduce cost; however they did not work as well as
expected and were replaced with similar bronze sleeves.
An end cap was added to the piston block so that there would be no need to drill blind
holes for the piston cylinders. This gave a more precise piston cylinder length. It also
made it easier to press in bronze cylinder liners which were added to avoid aluminum-onaluminum contact between the cylinder wall and the pistons. This type of contact can
lead to failure when surfaces are rubbing against one another and therefore should be
avoided.
The shaft size was increased from 1/4" to 1/2" to reduce deflection in the rod. An
additional disk was added to the crank rod to accommodate a new section of shaft for one
of the added mounting points.
The overall length of the rod increased also to
accommodate the additional mounting points.
All the original shaft couplers were
removed because they were somewhat bulky and unnecessary. These were replaced with
set screws, which were backed up with additional set screws so they would not vibrate
loose during operation.
Different air fixtures were used; at the air inlet, a small valve was added to control the
inlet pressure. The copper pipe connecting the valve assembly to the piston cylinders
was replaced with 1/8” NPT fittings and 1/8” tubing to allow for greater flexibility and
33
ease of fabrication. The valves remained relatively similar with the threaded adjustment,
but an O-ring was added to the outside of the air chamber for a better seal, and a sleeve
was placed inside the valve block for the valve rods. In addition, the cam was scaled up
to fit the larger shaft diameter, and the two cams and spacer were integrated into one part.
These were attached to the shaft by two set screws so they could be moved to adjust the
valve timing.
34
Chapter 5: Air Motor Fabrication
5.1. Air Motor Fabrication Procedure
The following section outlines the fabrication process that was used for the preliminary
ME 2900 air motor. A model of the preliminary design is shown below in Figure 11.
Figure 11: Preliminary ME 2900 air motor design
5.1.1. Piston Block
The piston block consists of three crank shaft mounting points, two piston cylinders, and
two slots that function as air outlets. Several threaded hole patterns are required for
35
attaching additional components. The mounting points are created by milling material
from the solid piece of aluminum. Piston cylinders are bored into the part, and the
threaded holes are drilled and tapped on location.
Machines

Horizontal band saw

Vertical mill

Arbor Press
Tooling
Tool Type
Scale
Scribe
Layout dye
Height gage
Angle plate (2)
Toe clamps
C-clamps (2)
Dowel rods (2)
Vise
Dial indicator
Parallels
Edge finder
1-2-3 Blocks
File
Fly cutter
Calipers
Drill chuck (keyless)
Center drill
Drill bit
Tap
Tapping fluid
Drill bit
End mill
Reamer
End mill (w/ corner radius)
Size
6”
~2” long; same diameter
Over 2”
Over 7”
#4
#7 (.201”)
1/4”-20 UNC
7/32”
.2505
5/8” diameter 1-1/4” length
36
Operation(s)
Layout
Layout
Layout
Layout
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Deburr edges
Establish overall size
Establish overall size
Holes
Tapped holes; dowel holes
Tapped holes
Tapped holes
Tapped holes
Dowel holes
Dowel holes
Dowel holes
Pockets
Drill bit
Drill bit
Boring head
Boring tool
Deburring tool
End mill
Piston cylinders
Piston cylinders
Piston cylinders
Piston cylinders
Deburr holes
Exhaust port
3/16” (carbide)
Materials
Material
Aluminum Rectangle (1)
Bronze Sleeve Bearing (2)
Size
2 X 6 X ~7.25 inch
1-1/4" ID 1-1/2" OD 2-1/2" Length
Procedure
1. Layout overall length on stock. Leave about .250” for finishing.
Figure 12: Layout overall length for piston block
2. Using a horizontal band saw, cut stock at layout line.
37
Figure 13: Cut piston block stock using horizontal band saw
3. Deburr all edges with a file.
4. Establish the overall height of the part.
4.1.
Set up angle plate on vertical mill table using toe clamps and a dial indicator.
Make sure that the front surface is straight along the x-axis.
4.2.
Clean off back surface of the part, and place two equal diameter dowels under
the part. Clamp part to angle plate with C-clamps while pushing part down on
dowels.
Figure 14: Setup for fly cutting top surface of piston block
38
4.3.
Apply layout dye to top surface. Skim cut (.002”-.004” material per pass) until
no dye remains on top surface.
4.4.
Deburr edges of newly finished surface. Using a surface plate and height gage
like the one in Figure 15, layout the overall part height. The finished surface
will be face down on the surface plate, and the overall height will be measured
from the surface plate up.
Figure 15: Height gage (Hoose)
4.5.
Again set up part on dowels with finished side down. Make sure C-clamps
allow for caliper access to measure overall height.
4.6.
Fly cut until just above layout line.
4.7.
Use calipers to determine overall height dimension.
39
Figure 16: Using calipers, determine overall height
4.8.
Based on caliper reading, adjust dial on table height indicator so it will read
zero when part is to size.
4.9.
Fly cut to size.
Check when within .010”-.005” and adjust table height
indicator if necessary.
4.10. Take finished pass (speed up cutter and slow down feed rate). Check height
before unclamping part from angle plate.
4.11. Deburr all new edges.
5. Establish overall width of the part.
5.1.
Set up second angle plate using additional toe clamps and check if square with
table with dial indicator.
5.2.
Again place dowels under part. Clamp part to both angle plates as shown in
Figure 17.
(It is okay if one dowel is not snug; we want to establish
perpendicularity with the surfaces against the angle plates.)
40
Figure 17: Setup for establishing overall width of piston block
5.3.
Repeat steps 4.3 through 4.11 from establishing the overall height.
6. Create threaded holes for mounting the piston block cover.
6.1.
Roughly mark hole locations on the bottom face using a permanent marker.
You may want to also write out x- and y-locations of these holes based on a (0,
0) at the center of the part face.
6.2.
Clamp part to angle plate like you did when establishing overall height; you do
not need to used dowels, but make sure all surfaces are clean (including mill
table) and all edges are deburred. The bottom of the part should be face-up.
6.3.
Using an edge finder, establish (0, 0) on the mill readout at the center of the
face.
6.4.
Center drill holes on location.
Move from one hole to another in a
counterclockwise direction. (This helps with location accuracy.)
41
Figure 18: Center drilled hole pattern for piston block cover attachment
6.5.
Drill holes .650” deep with #7 (.201”) bit. You can determine the depth of the
hole using the quill readout. Zero the readout when the bit it at the top surface
of the part, and drill until it reads correctly.
Figure 19: Drilled hole for piston block cover attachment
6.6.
Power tap holes .500” deep using a 1/4-20 tap and tapping fluid at a very slow
speed. Again use the quill readout, and remember to re-zero it for the tap.
Keep in mind you can immediately change from forward to revers on the mill;
42
you do not need to stop the machine in-between. Be sure to stay alert and do
not bottom out in the blind hole.
Figure 20: Tapped hole for piston block cover attachment
Figure 21: Full tapped hole pattern for piston block cover attachment
6.7.
Clean out tapped holes
7. Create dowel holes and threaded holes for valve block alignment
7.1.
Roughly mark hole locations on left surface with permanent marker. Make
sure they are in the correct location relative to the tapped holes you have
43
already made. Write x- and y-locations of holes based on a (0, 0) at the top
middle of the part (where the center of the shaft mount will eventually be).
7.2.
Clamp part to angle plate like you did when establishing overall width with the
left side up. Again, you want to make sure all surfaces are clean and edges
deburred.
7.3.
Using an edge finder, establish (0, 0) on the mill readout at the top middle of
the part (where the center of the shaft will eventually be). Be sure to account
for the offset from the radius of the edge finder when going from just one edge.
7.4.
Center drill at each dowel and tapped hole location.
7.5.
Drill the two dowel holes using drill bit.
7.6.
Bore dowel holes using end mill.
7.7.
Ream dowel holes using reamer.
7.8.
Drill the two tapped holes .450” with a #7 (.201”) drill bit.
7.9.
Carefully power tap tapped holes .375” deep using a 1/4”-20 tap and tapping
fluid.
7.10. Deburr dowel holes and clean out tapped holes.
8. Mill pockets for crank rod.
8.1.
Layout pocket boundaries using surface plate and height gage.
Figure 22: Edges for pocket layout on piston block
44
8.2.
Rough cut pockets using band saw. Cut out small sections at a time and do not
try to turn the part sharply. Keep shop safety in mind; make sure you always
have an “out” and your hand will not slip towards the blade.
Figure 23: Rough cut piston block pockets using band saw
Figure 24: Cut piston block pockets (rough)
8.3.
Set up vice so that it is square with the table (using dial indicator). Clamp
block in vise so it is upright.
8.4.
Establish x-zero on the center of the top surface of the part with an edge finder
using the far right and far left faces of the block.
45
8.5.
Mill pockets to size using a two flute end mill; determine proper final xlocation of end mill based on the dimensions given and adjusting based on the
diameter of the end mill. Mill all surfaces in small increments. For the two
outer forks, mill close to the layout line, and check with calipers or
micrometers.
Figure 25: Mill piston block pockets to size
8.6.
Saw center mounting arm down to size, leaving material for finishing.
Figure 26: Sawed center mounting arm
46
8.7.
Deburr new edges. Set up part in mill as done in 8.3. Mill center mounting
arm to size using end mill. Deburr new edges.
Figure 27: Milled center mounting arm
Figure 28: Finished pockets on piston block
9. Create threaded holes for mounting caps.
9.1.
Mark locations of all mounting holes. Determine their x- and y-coordinates
based on a (0, 0) at the center of the top face of the part.
9.2.
Clamp part in vise as done when milling the pockets (step 8.3).
47
9.3.
Establish (0, 0) at the center of the top face of the part with an edge finder.
Use the front and back surfaces of the middle fork and the far right and far left
faces of the block.
9.4.
Center drill at threaded hole locations.
9.5.
Drill .650 deep at threaded hole locations using .201” drill bit.
9.6.
Power tap holes .500” deep using a 1/4-20 tap and tapping fluid at a very slow
speed. You can also use a tapping head on a drill press as shown in Figure 29.
Figure 29: Tapping head on a drill press
10. Bore piston cylinders.
10.1. Mark cylinder locations based on (0, 0) at the center of the top face of the part.
10.2. Set up and align angle plate. Place a thick parallel or 1-2-3 blocks under the
part. Using C-clamps, clamp part to plate.
10.3. Establish (0, 0) at center of top face of the part using an edge finder.
48
Figure 30: Setup for boring piston cylinders
10.4. Center drill on hole locations.
Figure 31: Center drill bored hole locations
10.5. Drill through part on hole locations using drill bit. Be sure to remove the
parallel before drilling through.
49
Figure 32: Drill through block on bored hole locations
10.6. Rotate part and re-establish (0, 0) at the center of the bottom face of the block.
10.7. Drill through part on hole locations using drill bit.
Figure 33: Dill through piston block at piston cylinder locations
10.8. Check hole diameter using telescoping gage and micrometers.
10.9. Using boring head and boring tool, bore hole to size. Check hole diameter
with telescoping gage and micrometers when close to final dimension.
10.10. Take finished pass for final dimension.
50
Figure 34: Boring tool and head for boring piston cylinders
Figure 35: Boring tool and piston cylinder in piston block
10.11. Deburr all new edges.
11. Using a press, fit cylinder sleeves into block. Press in the liners from the bottom.
They should be flush with the bottom surface of the block and an interference fit.
51
Figure 36: Press in cylinder liners
12. Mill outlet slots.
12.1. Mark location of slots using the x- and y- coordinates of the center points of
the rounds based on a (0, 0) at the bottom center of the block.
12.2. Mount the part to the mill table using toe clips and 1-2-3 blocks. Using a dial
indicator, make sure the bottom surface of the part (surface facing the back of
the mill) is straight along the x-axis of the mill.
12.3. With an edge finder, set (0, 0) on the mill readout at the middle of the bottom
edge of the part (middle of edge towards the back of the mill). Remember to
account for the offset of the edge finder in the y-direction.
52
Figure 37: Setup for milling outlet ports
12.4. Using a 3/16” carbide end mill, mill back and forth between your outlet port
center point coordinates for one slot, incrementing by .003”-.005” each pass; do
not go all the way to the specified point each time, but mill to size every few
passes. You should not need to adjust the y-location at all (lock the mill in that
direction when on location).
Figure 38: Outlet port in piston block with carbide end mill
12.5. Repeat step 12.4 for other outlet.
53
Figure 39: Completed outlet ports in piston block
5.1.2. Piston Block Cover
The piston block cover was an aluminum piece that was fastened to the bottom of the
piston block via six 1/4-20 socket head cap screws. It had two circular grooves CNC
milled into it for O-rings to seal the pistons. At the center of each groove was a 1/8” pipe
tapped hole for the air fixtures leading to the valve system that allowed the piston
cylinders to be pressurized.
Machines

Vertical band saw

Vertical mill
Tooling
Tool Type
Scale
Scribe
Layout dye
Size
Operation(s)
Layout
Layout
Layout
54
Parallels
Vise
Edge finder
File
Deburring tool
Sandpaper
Fly cutter
Mill
Calipers
Center drill
Drill bit
Counterbore
End mill
Drill bit
Reamer
Pipe tap
Pipe tap handle
Center for chuck
Tapping fluid
Mill setup
Mill setup
Mill setup
Deburr edges
Deburr hole edges
Deburr edges
Skim cut surfaces
Establish length
Establish overall size
Screw hole pattern
Screw hole pattern
Screw hole pattern
O-ring grooves
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
9/32” (.281”)
1/4”
Ball nose
R (.339”)
1/8”
Materials
Material
Aluminum Rectangle (1)
Size
1/2 X 2 X ~7.25 inches
Procedure
1. Layout part length. Leave about .250” extra for sizing and finishing.
2. Saw stock using band saw at layout line. Deburr all edges.
3. Establish overall length of part.
3.1.
Position part on parallels and clamp in vise. Make sure top surface of the part
comes above the top of the vise jaws. Apply layout dye and skim cut top face.
Deburr new edges.
3.2.
Rotate part and repeat step 3.1 for the bottom face.
55
3.3.
Move the part so the right and left sides are past the sides of the vise jaws.
Make sure the part is flat on the parallels. Clean up the right face using a mill
and skim cutting. Deburr all new top edge.
3.4.
Using an edge finder, set the newly finished edge as x-zero. Make sure to
account for the offset from the radius of the edge finder.
3.5.
Measure diameter of milling tool. Mill starting on the unfinished surface until
the digital readout it the overall length of the part AND the radius of the
cutting tool (you must account for the offset due to radius of the cutting tool).
3.6.
Deburr all new edges.
4. Create counterbored hole pattern for screws.
4.1.
Mark screw hole locations and x- and y-coordinates based on a (0, 0) at the
center of the bottom face of the part.
Figure 40: Rough hole layout for fastening to piston block
4.2.
Clamp part in mill using parallels for flatness. Using an edge finder, establish
(0, 0) on the mill readout at the center of the face.
4.3.
Center drill holes on location.
56
Figure 41: Setup for drilling screw hole pattern
4.4.
Double check that part in firmly clamped. Remove parallels by sliding them
from under the part, otherwise you could drill into them as shown in Figure 42.
Figure 42: Damaged parallels
4.5.
Drill through part on hole locations using a 9/32” drill bit.
57
Figure 43: Drilled hole pattern in piston block cover
4.6.
Change to 1/4" counterbore bit. Without turning on the mill, bring tool down
to part so that the smaller portion of the bit is within a drilled hole and the step
to the larger portion is on the top surface of the part. Zero the quill readout on
the press.
4.7.
Determine the height of the screw head and counterbore each hole 1/32” more
than the height of the screw head.
Figure 44: Measuring screw head height
58
Figure 45: Counterbored hole pattern on piston block cover
4.8.
(Optional) Countersink the top edge of the counterbore.
5. Create grooves for O-ring seal.
5.1.
Clamp part into vise on CNC. Make sure the non-counterbored side is facing
up.
5.2.
Set (0, 0) at the center of the part (or wherever you have defined it in your
program).
5.3.
Using CNC program, mill O-ring groove.
Figure 46: CNC milling O-ring grooves in piston block cover
59
5.4.
Remove part from vise and deburr new edges.
Figure 47: Finished O-ring grooves
6. Create pipe taps for air fixtures.
6.1.
Clamp part in vertical mill with O-ring groove side down. Pick up (0, 0) at the
center of the face using an edge finder.
6.2.
Center drill on location for both holes.
Figure 48: Required pipe tap tooling
6.3.
Drill both holes on location with an R (.339”) drill bit.
6.4.
Ream holes with reamer.
60
Hand tap holes using 1/8” pipe tap and tapping fluid until about 7 threads are
6.5.
remaining above the hole on the tap.
Figure 49: Pipe tapped holes in piston block cover
5.1.3. Valve Block
The valve block is a separate section from the main piston block. One shaft mount is
located on the right side of the block, and two screws go through the block for attachment
to the piston block. Two dowels are used to accurately position the block in relation to
the piston block. The valve rods run from the top to the bottom of the block, with seals at
the bottom of the block where the air chamber is attached. Air fixtures connect just
above the location of the seal. These are used to pressurize the piston cylinders.
Machines

Horizontal band saw

Vertical band saw

Vertical mill
61
Tooling
Tool Type
Scale
Scribe
Square
Layout dye
Height gage
Parallels
Vise
Edge finder
Angle plate (2)
Toe clamps
C-clamps (2)
Dial indicator
1-2-3 Blocks
File
Deburring tool
Fly cutter
Calipers
Center drill
Drill bit
Tap
Tapping fluid
Drill bit
Counterbore
Drill bit
Boring end mill
Reamer
Countersink (optional)
End mill
Drill bit
Drill bit
End mill
Drill bit
Drill bit
Reamer
Pipe tap
Pipe tap handle
Center for chuck
Tapping fluid
Size
#7 (.201”)
1/4”-20 UNC
9/32” (.281”)
7/32”
.2505”
7/32” (.2188”)
.625”
.500”
9/32” (.2813”)
R (.339”)
1/8”
62
Operation(s)
Layout
Layout
Layout
Layout
Layout
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Deburr edges
Deburr hole edges
Establish part size
Establish overall size
Holes
Tapped holes
Tapped holes
Tapped holes
Screw hole pattern
Screw hole pattern
Dowel holes
Dowel holes
Dowel holes
Dowel holes
Pocket
Valve holes
Valve holes
Valve holes
Valve holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
Materials
Material
Aluminum Rectangle (1)
Size
3 X 3-1/2 X 2-1/4 inches
Procedure
1. Layout part width. Leave about .250” extra for sizing and finishing.
2. Saw stock on layout line using a horizontal band saw.
Figure 50: Saw valve block stock using horizontal band saw
3. Deburr all edges.
63
Figure 51: Un-filed edge
Figure 52: Deburred part
4. Establish overall part length.
4.1.
Place part on parallels in vise and clamp so right face is on top. Apply layout
dye to top face. Skim cut until no layout dye remains on surface.
64
Figure 53: Skim cut top face of valve block
4.2.
Deburr new edges. Layout overall height using surface plate and height gage.
Make sure newly finished surface is against the angle plate and the unfinished
surface is above the layout line (it will be fly cut in the next step).
4.3.
Place part on parallels in vise so that the newly finished face is down. Fly cut
part until you are close to the layout line.
4.4.
Using calipers, measure the overall length of the part. Adjust the table height
indicator so that it will be at zero when the part is to size.
4.5.
Continue milling until .010”-.005” of material remains. Re-check length of
part using calipers, and adjust table height indicator if necessary.
4.6.
Make finished pass (speed up tool, slow down feed). Check dimension before
removing from vise.
4.7.
Deburr all new edges.
5. Establish overall width.
5.1.
Clamp part in vise using a 1-2-3 block or similar square ground surface to
make sure newly finished surfaces are perpendicular with the vise (see Figure
73 and Figure 74 for reference). One of the saw-cut surfaces (front or back of
the part) should be face up.
5.2.
Skim cut surface using fly cutter and layout dye. Deburr all new edges.
65
5.3.
Repeat steps 4.2 through 4.7 for establishing the overall width using the
opposite face.
6. Drill and tap holes for valve block cover.
6.1.
Mark hole locations and x- and y-coordinates for the holes using a (0, 0) at the
center point of the hole pattern.
6.2.
Clamp part bottom face up in vise. Pick up (0, 0) with x-zero at the center of
the part in the x-direction and y-zero at the center of the hole pattern.
6.3.
Center drill holes on location.
Figure 54: Center drilled hole for valve block cover attachment
6.4.
Drill holes .650” deep with .201” drill bit using the quill readout to determine
hole depth.
6.5.
Slowly power tap holes .500” deep with1/4-20 tap.
66
Figure 55: Tapped hole for valve block cover attachment
Figure 56: Threaded hole pattern for valve block cover attachment
7. Create screw holes for attachment to piston block
7.1.
Mark through hole locations and coordinates assuming (0, 0) is center on the
top left edge of the part, where the center of the shaft hole will eventually be
located.
7.2.
Clamp part into vise with left face facing up. Using an edge finder, pick up (0,
0) on the center of the top left edge. Be sure to account for the offset from the
radius of the edge finder when going off of one edge.
7.3.
Center drill at the screw hole locations.
67
7.4.
Drill through part at the two screw hole locations using 9/32” drill bit.
7.5.
Counterbore 1/32” deeper than the height of the screw head using a 1/4"
counterbore and the quill readout.
Figure 57: Final counterbored screw holes for attachment to piston block
7.6.
(Optional) Countersink top edge of counterbored holes.
8. Create dowel holes for alignment with piston block.
8.1.
Mark dowel hole locations and coordinates on right face assuming (0, 0) is at
the middle of the top right edge of the part.
8.2.
Clamp part in vise with right face up. Pick up (0, 0) at the middle of the top
left edge of the part using an edge finder.
8.3.
Center drill at each dowel location.
8.4.
Drill holes .375” deep using a .250” drill bit.
8.5.
Bore holes .375” deep using a .250” end mill.
68
Figure 58: Bore dowel holes using end mill
8.6.
Ream holes using a reamer.
Figure 59: Ream dowel holes
8.7.
Countersink the edge of the dowel holes using countersink.
69
Figure 60: Countersink dowel holes
8.8.
Check dowel fit using 1/4" dowel. It should be snug, but not a press fit.
Figure 61: Check fit of dowel in hole
9. Create cutout for crank shaft.
9.1.
Using layout dye, surface plate and height gage, layout boundary of cut-out
area on front face.
9.2.
Rough cut pockets using band saw; be careful not to cross layout lines.
70
Figure 62: Rough cut valve block
Figure 63: Surface finish using a band saw
9.3.
Clamp parts in vice so front face faces the front of the mill.
9.4.
Establish x-zero on the far right edge of the part using an edge finder.
Remember to account for the offset from the radius of the edge finder.
9.5.
Mill pockets to size using a two flute end mill; determine proper final xlocation of end mill based on the dimensions given and adjusting based on the
diameter of the end mill. Mill all surfaces in small increments. Check the
dimensions of the cutout section when you are close to the layout lines to
determine how much to take off for the final dimensions.
71
10. Create multi-diameter valve block holes.
10.1. Set up two perpendicular angle plates on the mill table with toe clamps. Make
sure they are straight along the x- and y-axes of the mill using a dial indicator.
10.2. Mark x- and y-coordinates of holes on bottom surface of the part assuming (0,
0) is at the center point of the two hole locations.
10.3. Make sure all surfaces are clean and all edges are deburred. Clamp part to
both angle plates using C-clamps so that the bottom face is facing up, the right
face is against an angle plate, and the front or back face is against the other
angle plate (see Figure 64). Use a 1-2-3 block under the part to make sure the
top surface is parallel with the mill table.
Figure 64: Setup for drilling valve block holes
10.4. Pick up (0, 0) so that x-zero is midway between the two holes (1.125” from the
right face; remember to account for offset from edge finder) and the y-zero is
at the center of the width of the part.
10.5. Double check that your C-clamps are secure. Center drill on location for both
valve holes.
10.6. Drill through block on hole locations using 7/32” (.2188”) drill bit. Make sure
you remove the 1-2-3 block before drilling through.
10.7. Using a drill bit and quill readout, drill .625 deep on valve locations.
72
10.8. Using .500” end mill and quill readout, bore .100” deep on valve locations.
Figure 65: Bottom view of valve holes
Figure 66: Valve holes with one seal in place
10.9. Deburr new holes and make sure bottom face is smooth. Unclamp part and flip
so that the right side is again against one of the angle plates and either the front
or back face is against the other angle plate. Again, place a 1-2-3 block under
the part and clamp to both angle plates using C-clamps.
10.10. Pick up (0, 0) in the same location as step 10.4 (center point between the two
holes).
73
10.11. Drill .400” deep using 9/32” (.2813”) drill bit. This will be for the valve
spring.
11. Create pipe taps for air fixtures leading to the piston block.
11.1. Mark locations and coordinates of the pipe taps on the front face of the part
based on a (0, 0) where x-zero is midway between the two tap locations
(1.125” from the right edge) and y-zero is the bottom surface of the part.
11.2. Pick up (0, 0) at the mid-point described in step 11.1, being sure to account for
the edge finder radius.
11.3. Center drill holes on location.
11.4. Drill holes with R (.339”) drill bit, looking through valve holes to make sure
you do not hit the opposite wall of the hole.
11.5. Ream holes with reamer, again looking through valve hole to make sure you
do not go too far.
Figure 67: Ream pipe tap holes
11.6. Hand tap holes using 1/8” pipe tap and tapping fluid until about 7 threads are
remaining above the hole on the tap. Make sure the tap is perpendicular to the
part.
74
Figure 68: Pipe tapped holes in valve block
5.1.4. Valve Sleeves
The valve sleeves are pressed into the valve block. They are brass sleeves used to keep
the shaft from rubbing against the aluminum wall and reduce wear on the part.
Machines

Lathe
Tooling
Tool Type
Facing tool
Cutoff tool
Calipers
File
Size
Operation(s)
Facing
Establish length
Establish length
Deburr edges
Materials
Material
Brass Sleeve (1)
Size
7/32" OD, 2” long
75
Procedure
1. Using a collet, clamp stock in lathe.
2. Face stock and deburr new outer edge.
3. Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the newly
faced surface. Zero the lathe readout, and move tool slightly more than the length of
the part, leaving material for finishing.
4. Remove stock from lathe and clamp part in lathe, with the unfinished side exposed.
5. Face unfinished surface. Deburr outer edge.
6. Remove part from lathe and measure overall length. Re-clamp part in lathe and face
to size. Deburr outer edge.
7. Measure part to check dimension.
8. Repeat steps 0 through 7 for second sleeve.
9. Make sure all edges are deburred, and press sleeves into valve block.
5.1.5. Valve Rods
The valve rods connect the cam followers to the air cutoffs. They are precision ground
stainless steel rods that are threaded on both ends. The threading at the air cutoff allows
for adjustment of the distance from the cam follower to the cutoff itself. The valve rods
sit inside the valve sleeves.
Machines

Lathe
Tooling
Tool Type
Facing tool
Size
Operation(s)
Facing
76
Cutoff tool
Calipers
File
Die
Establish length
Establish length
Deburr edges
Thread rod
10-32
Materials
Material
Stainless Steel Shaft (2)
Size
3/16” diameter, 3-1/2” long
Procedure
1. Establish overall length
1.1.
Using a collet, clamp stock in lathe.
1.2.
Face stock and deburr new outer edge.
1.3.
Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the
newly faced surface. Zero the lathe readout, and move tool slightly more than
the length of the part, leaving material for finishing.
1.4.
Remove stock from lathe and clamp part in lathe, with the unfinished side
exposed.
1.5.
Face unfinished surface. Deburr outer edge.
1.6.
Remove part from lathe and measure overall length. Re-clamp part in lathe
and face to size. Deburr outer edge.
1.7.
Measure part to check dimension.
1.8.
Repeat steps 1.1 through 1.7 for second rod.
2. Thread both ends of the valve rod.
2.1.
Clamp part in lathe. Using a 10-32 die, carefully thread the outside shaft on
both ends, threading one end .250” deep and the other end .375” deep. Make
sure die is square with rod when starting thread.
2.2.
Using a nut, make sure threads fit standard size. Otherwise, adjust die and
recut threads, following the original threads.
77
Figure 69: Threading valve rod
5.1.6. Cam Follower
The cam follower threads onto the valve rod. It runs on the cam, and is used to push the
valve open at certain times of the piston cycle to allow compressed air to enter the piston
cylinders.
Machines

Lathe

Vertical mill
Tooling
Tool Type
Facing tool
Turning tool
Cutoff tool
Calipers
File
Vice
Parallel
Size
Operation(s)
Facing
Establish diameter
Establish length
Establish length
Deburr edges
Mill setup
Mill setup
78
Edge finder
End mill
Center drill
Drill bit
Tap
Mill setup
Mill flat
Threaded hole
Threaded hole
Threaded hole
#21
10-32
Materials
Material
Brass Rod (2)
Size
1/2” diameter; 1/2” long
Procedure
1. Establish overall width.
1.1.
Using a collet, clamp stock in lathe.
1.2.
Face stock and deburr new outer edge.
1.3.
Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the
newly faced surface. Zero the lathe readout, and move tool slightly more than
the length of the part, leaving material for finishing.
1.4.
Remove stock from lathe and clamp part in lathe, with the unfinished side
exposed.
1.5.
Face unfinished surface. Deburr outer edge.
1.6.
Remove part from lathe and measure overall length. Re-clamp part in lathe
and face to size. Deburr outer edge.
1.7.
Measure part to check dimension.
1.8.
Repeat steps 1.1 through 1.7 for second cam follower.
2. Create threaded hole for attachment to valve rod.
2.1.
Clamp part vertically in mill so that the two flat surfaces are against the vise
jaws and at least half of the part is above the vise jaws.
2.2.
Mill part to size using an end mill.
2.3.
Using edge finder, pick up (0, 0) at the center of new top face.
79
2.4.
Center drill on tapped hole location.
2.5.
Create hole using drill bit.
2.6.
Power tap hole using 10-32 tap.
5.1.7. Valve Stopper
The valve stopper is a small disk that is threaded onto the valve rod. When the cam
follower hits the high point on the cam, it pushes the valve rod down and separates the
valve stopper from the valve seal, opening the valve and allowing air into the
corresponding piston cylinder.
Machines

Lathe
Tooling
Tool Type
Facing tool
Cutoff tool
Calipers
File
Vice
Parallel
Edge finder
End mill
Center drill
Drill bit
Tap
Materials
Material
Aluminum Rod (2)
Size
Operation(s)
Facing
Establish length
Establish length
Deburr edges
Mill setup
Mill setup
Mill setup
Mill flat
Threaded hole
Threaded hole
Threaded hole
10-32
10-32
Size
1/2” diameter; 1/4” long
80
Procedure
1. Establish overall height.
1.1.
Using a collet, clamp stock in lathe.
1.2.
Face stock and deburr new outer edge.
1.3.
Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the
newly faced surface. Zero the lathe readout, and move tool slightly more than
the length of the part, leaving material for finishing.
1.4.
Remove stock from lathe and clamp part in lathe, with the unfinished side
exposed.
1.5.
Face unfinished surface. Deburr outer edge.
1.6.
Remove part from lathe and measure overall length. Re-clamp part in lathe
and face to size. Deburr outer edge.
1.7.
Measure part to check dimension.
1.8.
Repeat steps 1.1 through 1.7 for second valve stopper.
2. Create center tapped through hole for threading onto valve rod.
2.1.
Center drill on tapped hole location using lathe.
2.2.
Drill through part using SIZE drill bit.
2.3.
Tap hole using 10-32 tap.
5.1.8. Mounting Caps
The mounting caps are secured to each of the four mounting points on the piston and
valve blocks. They are design to allow for easy access to the crank shaft. Rather than
disassembling the entire crank shaft to remove it, you can unscrew the four caps and lift
the entire assembly from the main body of the motor. The caps themselves are relatively
81
simple. They have two screw holes for mounting, and one semicircular cutout for the
shaft‟s sleeve bearings.
Machines

Vertical band saw

Vertical mill
Tooling
Tool Type
Scale
Scribe
Square
Layout dye
Parallels
Vise
Edge finder
File
Deburring tool
End mill
Center drill
Drill bit
Counterbore
Size
Operation(s)
Layout
Layout
Layout
Layout
Mill setup
Mill setup
Mill setup
Deburr edges
Deburr hole edges
Establish part size
Screw hole pattern
Screw hole pattern
Screw hole pattern
9/32”
Materials
Material
Aluminum Rectangle (1)
Size
1/2 X ¾ X 2-1/4 inches
Procedure
1. Layout overall width of the four parts, adding about .250” for finishing and an
additional .125” for the saw blade after the first layout line.
2. Saw stock at layout lines. Deburr all edges.
3. Establish overall width of the parts.
82
3.1.
Clamp part so that the front face is past the vise jaws and the part is sitting on a
set of parallels.
3.2.
Finish the front face of the part using a mill tool. Un-clamp part and deburr
new edges.
3.3.
Repeat steps 3.1 and 3.2 on remaining three parts.
3.4.
Rotate part so that unfinished edge is past the vise jaws. Use a mill stop to
mark the location of the front face relative to the edge of the vise jaws as
shown in Figure 70. This will allow you to mill multiple parts without picking
up the x-zero location on every part.
Figure 70: Setup for establishing overall width of mounting cap
3.5.
Pick up x-zero at the finished edge, accounting for the offset from the radius of
the edge finder.
3.6.
Measure the diameter of the milling tool. Mill the unfinished edge until xreadout is the width of the part plus the radius of the tool. Deburr all new
edges.
3.7.
Place next part in vise, on parallels and against the mill stop. As mentioned
previously, you will not need to pick up x-zero since you are using the mill
stop.
83
3.8.
Repeat step 3.6.
3.9.
Repeat steps 3.7 and 3.8 on remaining mounting block pieces.
4. Create screw holes for mounting.
4.1.
Place part top side up on parallels and clamp in vise. Use mill stop to locate
front edge of the part.
4.2.
Pick up (0, 0) at the center top face of the part using an edge finder.
4.3.
Center drill at the two hole locations, using coordinates based on (0, 0) at the
center of the part.
Figure 71: Center drill on mounting hole locations
4.4.
Slide parallels from under the part (do not unclamp part). Drill through on
hole locations using a 9/32” drill bit.
4.5.
Counterbore holes 1/32” deeper than the height of the screw head.
4.6.
Repeat steps 4.3 through 4.5 using the mill stop to clamp the part in the same
position.
4.7.
Deburr all holes.
84
Figure 72: Counterbored screw holes in mounting cap
5.1.9. Mounting Cap Spacer
The mounting cap spacer is located between the center mount of the piston block and its
mounting cap. This allows for easier machining of the middle mounting hole. It is very
similar to the mounting caps, however it does not have the counterbore for the screw
head, and the top and bottom faces are finished.
Machines

Vertical band saw

Vertical mill
Tooling
Tool Type
Scale
Scribe
Layout dye
Parallels
Vise
Size
Operation(s)
Layout
Layout
Layout
Mill setup
Mill setup
85
Edge finder
File
Deburring tool
End mill
Center drill
Drill bit
Mill setup
Deburr edges
Deburr hole edges
Establish part size
Screw hole pattern
Screw hole pattern
9/32”
Materials
Material
Aluminum Rectangle (1)
Size
1/2 X ¾ X 2-1/4 inches
Procedure
1. Layout overall width of the part, adding about .250” for finishing.
2. Saw stock at layout lines. Deburr all edges.
3. Clean up top and bottom surfaces.
3.1.
Place part upright on parallels to the top surface is above the vise jaws.
3.2.
Apply layout dye on top surface, and skim cut using end mill. Deburr new
edges.
3.3.
Rotate part so bottom surface is face up.
3.4.
Apply layout dye on bottom surface and skim cut using end mill. Deburr new
edges.
4. Establish overall width of the parts.
4.1.
Clamp part so that the front face is past the vise jaws and the part is sitting on a
set of parallels.
4.2.
Finish the front face of the part using a mill tool. Un-clamp part and deburr
new edges.
86
4.3.
Rotate part so that unfinished edge is past the vise jaws as done in Figure 74
from the mounting cap section. You will not need to use the mill stop in this
case.
4.4.
Pick up x-zero at the finished edge, accounting for the offset from the radius of
the edge finder.
4.5.
Measure the diameter of the milling tool. Mill the unfinished edge until xreadout is the width of the part plus the radius of the tool. Deburr all new
edges.
5. Create screw holes for mounting.
5.1.
Place part top side up on parallels and clamp in vise. Pick up (0, 0) at the
center top face of the part using an edge finder.
5.2.
Center drill at the two hole locations, using coordinates based on (0, 0) at the
center of the part.
5.3.
Slide parallels from under the part (do not unclamp part). Drill through on
hole locations using a 9/32” drill bit.
5.4.
Deburr all holes.
5.1.10. Valve Block Cover
The valve block cover is used to create an air chamber. A pipe tapped hole connects to
the pressure inlet fixture. The air chamber is sealed using an O-ring, and four screw
holes are used to connect the cover to the valve block.
Machines

Horizontal band saw

Vertical mill

CNC mill
87
Tooling
Tool Type
Scale
Scribe
Square
Layout dye
Height gage
Parallels
Vise
Edge finder
1-2-3 Blocks
File
Deburring tool
End mill
Calipers
Center drill
Drill bit
Counterbore
End mill
End mill
Drill bit
Reamer
Pipe tap
Pipe tap handle
Center for chuck
Tapping fluid
Size
Operation(s)
Layout
Layout
Layout
Layout
Layout
Mill setup
Mill setup
Mill setup
Mill setup
Deburr edges
Deburr hole edges
Establish part size
Establish part size
Holes
Screw hole pattern
Screw hole pattern
Air chamber
O-ring groove
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
Pipe tap holes
9/32”
Ball nose
R (.339”)
1/8”
Materials
Material
Aluminum Rectangle (1)
Size
1 X 2 X 2-1/2 inches
Procedure
1. Layout overall width of the part, adding about .250” for finishing.
2. Saw stock at layout lines. Deburr all edges.
3. Establish overall length of the part.
88
3.1.
Clamp part in vise using a 1-2-3 block or similar ground square block to
establish perpendicularity. When clamping part, push 1-2-3 block down on
vise and push top surface of the part (should be factory surface) to the 1-2-3
block.
Figure 73: Use ground square piece to establish perpendicularity between faces
Figure 74: Press one ground face to vise surface, and push finished block face against
other ground face
3.2.
Clean up right face of the part using end mill. Deburr new edges.
89
3.3.
Layout the overall length of the part using surface plate and height gage. The
finished surface should be against the surface plate, and the unfinished sawed
surface should be above the layout line.
3.4.
Clamp part in vise with finished surface down (you do not need to use a 1-2-3
block for this setup since the new surface will be parallel with the one you just
finished).
3.5.
Mill surface until you are slightly above layout line.
3.6.
Use calipers to determine overall length dimension.
3.7.
Based on caliper reading, adjust dial on table height indicator so it will read
zero when part is to size.
3.8.
Fly cut to size.
Check when within .010”-.005” and adjust table height
indicator if necessary.
3.9.
Take finished pass (speed up tool and slow down feed rate). Check height
before unclamping part from angle plate.
3.10. Deburr all new edges
4. Create screw holes for attachment to valve block.
4.1.
Mark through hole locations and coordinates based on a (0, 0) at the center of
the part.
4.2.
Clamp part in mill using parallels for flatness. Using an edge finder, establish
(0, 0) on the mill readout at the center of the face.
4.3.
Center drill holes on location.
90
Figure 75: center drilled screw holes for attachment to valve block
4.4.
Double check that part in firmly clamped. Remove parallels by sliding them
from under the part.
4.5.
Drill through part on hole locations using a 9/32” drill bit.
4.6.
Change to 1/4" counterbore bit. Without turning on the mill, bring tool down
to part so that the smaller portion of the bit is within a drilled hole and the step
to the larger portion is on the top surface of the part. Zero the quill readout on
the press.
4.7.
Determine the height of the screw head and counterbore each hole 1/32” more
than the height of the screw head.
4.8.
(Optional) Countersink the top edge of the counterbore.
5. Create air chamber.
5.1.
Make sure all surfaces are clean and all edges are deburred.
5.2.
Clamp part in vise on CNC mill. Make sure the orientation is correct based on
your program, and the counterbores from the screw pattern are face down.
5.3.
Using edge finder, establish (0, 0) based on your program.
5.4.
CNC mill your air chamber using an end mill and your program.
5.5.
Do not remove part from mill; you can use the same setup for milling the Oring groove in the next step.
91
6. Create O-ring groove.
6.1.
If you have a different (0, 0) in your O-ring groove program, pick up your new
coordinate system.
6.2.
CNC mill your air chamber using an end mill and your program.
Figure 76: CNC mill the O-ring groove in the valve block cap
6.3.
Check the fit of the O-ring in the new groove.
Figure 77: O-ring inserted into O-ring groove
7. Create pipe tap for air inlet fixture.
92
7.1.
Clamp part in vertical mill with O-ring groove side down. Pick up (0, 0) at the
center of the face using an edge finder.
7.2.
Center drill on location for pipe tap hole.
7.3.
Drill hole on location with an R (.339”) drill bit.
7.4.
Ream hole with reamer.
7.5.
Hand tap holes using 1/8” pipe tap and tapping fluid until about 7 threads are
remaining above the hole on the tap.
Figure 78: Hand tapping setup for pipe tap
5.1.11. Crankshaft 1
Crankshaft 1 is the first shaft section of the crankshaft. It is located on the right side of
the motor, and runs through the center of the first mounting point. One flat is milled at
the end of the shaft that fits in a crank connecting disk. This allows a set screw to hold
the shaft in position.
93
Machines

Lathe

Vertical mill
Tooling
Tool Type
Facing tool
Turning tool
Cutoff tool
Calipers
File
Vise
Parallel
End mill
Size
Operation(s)
Facing
Establish diameter
Establish length
Establish length
Deburr edges
Mill setup
Mill setup
Mill flats
Materials
Material
Aluminum Rod (1)
Size
1/2" OD, 3-1/4” long
Procedure
1. Establish overall length
1.1.
Using a collet, clamp stock in lathe.
1.2.
Face stock and deburr new edge.
94
Figure 79: Face shaft stock in lathe
1.3.
Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the
newly faced surface. Zero the lathe readout, and move tool slightly more than
the length of the part, leaving material for finishing.
1.4.
Remove stock from lathe and clamp part in lathe, with the unfinished side
exposed.
1.5.
Face unfinished surface. Deburr outer edge.
1.6.
Remove part from lathe and measure overall length. Re-clamp part in lathe
and face to size. Deburr edge.
1.7.
Measure part to check dimension.
2. Establish overall diameter of the shaft.
2.1.
Clamp part in lathe.
2.2.
Turn diameter to size, machining slightly over half the length of the part, and
then flipping part to complete the other side.
95
Figure 80: Turn the outer diameter of the shaft to size
3. Create flat for set screw.
3.1.
Snugly clamp shaft sections in mill vise, using a thick parallel to be sure part is
level. The top of the vise jaws should be slightly above the center of the shaft.
3.2.
Mill small flat about roughly centered .250” from shaft edge with .250” end
mill. The main idea is that the flat will not be visible when the shaft is in
place.
Figure 81: Milled flat on shaft for set screw
3.3.
Deburr new edges.
96
5.1.12. Crankshaft 2
Crankshaft 2 is the section of the crankshaft that is connected to the piston rod. Two are
needed (one for each piston), and two flats are required, one at either end. These flats
should be parallel for the crank alignment to be correct.
Machines

Lathe

Vertical mill
Tooling
Tool Type
Facing tool
Turning tool
Cutoff tool
Calipers
File
Vise
Parallel
End mill
Size
Operation(s)
Facing
Establish diameter
Establish length
Establish length
Deburr edges
Mill setup
Mill setup
Mill flats
Materials
Material
Aluminum Rod (2)
Size
1/2" OD, 2-1/4” long
Procedure
1. Repeat steps 0 through 3 from the procedure for crankshaft 1.
2. After step 3, leave part clamped in the same position on the vise. Move to the
position of the section flat and repeat step 3.
97
5.1.13. Crankshaft 3
Crankshaft 3 is very similar to crankshaft 2, however it is slightly longer. It goes through
the center mount on the piston block. Two parallel flats are also located on either end of
the shaft, and are used for alignment. These are important because they insure the pistons
are offset by 180°.
Machines

Lathe

Vertical mill
Tooling
Tool Type
Facing tool
Turning tool
Cutoff tool
Calipers
File
Vise
Parallel
End mill
Size
Operation(s)
Facing
Establish diameter
Establish length
Establish length
Deburr edges
Mill setup
Mill setup
Mill flats
Materials
Material
Aluminum Rod (1)
Size
1/2" OD, 2-1/2” long
Procedure
1. Repeat steps 0 through 3 from the procedure for crankshaft 1.
2. After step 3, leave part clamped in the same position on the vise. Move to the
position of the section flat and repeat step 3.
98
5.1.14. Crankshaft 4
Crankshaft 4 is longer than the other shaft sections. It goes through two mounting points,
and holds the cam for the valve timing. One flat is milled on one end for the set screw
from one of the crank connecting disks.
Machines

Lathe

Vertical mill
Tooling
Tool Type
Facing tool
Turning tool
Cutoff tool
Calipers
File
Vise
Parallel
End mill
Size
Operation(s)
Facing
Establish diameter
Establish length
Establish length
Deburr edges
Mill setup
Mill setup
Mill flats
Materials
Material
Aluminum Rod (1)
Size
1/2" OD, 5-1/4” long
Procedure
1. Repeat steps 0 through 3 from the procedure for crankshaft 1.
99
Figure 82: Final crankshaft shaft components
5.1.15. Crank Connecting Disks
Four crank connecting disks are used to connect the different portions of the crank shaft
and offset the piston shafts from the center of rotation. Coupled with the flats on the
shafts, they are used to align the shaft.
Machines

Lathe

Vertical mill
Tooling
Tool Type
Center drill
Drill bit
Facing tool
Turning tool
Cutoff tool
Calipers
File
Size
Operation(s)
Middle/ outer holes
Middle/ outer holes
Facing
Establish diameter
Establish length
Establish length
Deburr edges
100
Vise
Aluminum soft jaws
Dial indicator
Edge finder
Dowels (2)
Mill stop
Reamer
Countersink
Center drill
Drill bit
Drill bit
End mill
Tap
Tapping fluid
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Middle/ outer holes
Middle/ outer holes
Set screw holes
Set screw holes
Set screw holes (clearance)
Outer set screw hole
Set screw holes
Set screw holes
1/2”
10-32
Materials
Material
Aluminum Rod (2)
Size
2-3/4" OD, 3/4” long
Procedure
1. Create center hole in disks.
1.1.
Clamp stock in lathe chuck.
1.2.
Carefully drill through the center of the stock using a 1/2" drill bit.
2. Turn the outer diameter of the stock to size to establish overall diameter.
3. Establish overall length of the disks.
3.1.
Face end of stock. Using a file, deburr new edge.
3.2.
Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the
newly faced surface. Zero the lathe readout, and move tool slightly more than
the length of the part, leaving material for finishing.
101
Figure 83: Use cutoff tool to cut part slightly oversized
3.3.
Repeat steps 3.1 and 3.2 for three remaining disks.
3.4.
Remove stock from lathe and clamp one disk in lathe, with the unfinished side
exposed.
3.5.
Face unfinished surface. Deburr outer edge.
3.6.
Remove part from lathe and measure overall length. Re-clamp part in lathe
and face to size. Deburr edge.
3.7.
Measure part to check dimension.
3.8.
Repeat steps 3.4 through 3.7 for remaining three disks.
Figure 84: Disk with center hole and correct overall length and diameter
102
4. Create second offset hole.
4.1.
Clamp disk in soft jaws on mill.
4.2.
Pick up center of the existing hole using dial indicator and set as (0, 0).
4.3.
Ream center hole using reamer.
4.4.
Move to location of second hole.
4.5.
Center drill second hole on location.
4.6.
Drill second hole using 1/2" drill bit.
4.7.
Ream second hole using reamer.
4.8.
Repeat steps 4.1 through 4.7 with the three remaining disks.
4.9.
Countersink all hole edges using hand drill and a countersink.
Figure 85: Crank connecting disk with both holes complete
5. Create set screw holes
5.1.
Place dowels through 1/2" holes and reorient as shown in Figure 86. Set up a
mill stop so you only need to pick up (0, 0) once.
103
Figure 86: Setup for drilling set screw holes
5.2.
Pick up (0, 0) using disk thickness for the y-direction and the dowel diameter
for the x-direction.
5.3.
Clamp vise tightly and remove dowels.
5.4.
Center drill set screw hole for center hole on location.
Figure 87: Center drilled hole for center set screw
5.5.
Drill to the center of the hole using a #25 (.149”) drill bit.
104
Figure 88: Drill hole for center set screw
5.6.
Drill .700” deep using quill readout and a #7 (.201”) drill bit.
Figure 89: Drill using larger diameter drill bit for beginning of set screw hole
5.7.
Power tap set screw hole using 10-32 tap and tapping fluid. Make sure the
hole is fully tapped (do not stop too early). You also do not want the tap to hit
the opposite wall of the middle 1/2" hole.
105
Figure 90: Power tap hole for set screw
5.8.
Move to location of outer set screw.
5.9.
Using an end mill, create a flat for set screw hole. Only mill until the end mill
creates a fully circular flat.
5.10. Repeat process described above for the center set screw, drilling .400” deep
with the #7 (.201”) drill bit instead of .700”.
5.11. Deburr the threaded holes.
Figure 91: Deburred threaded set screw hole
5.12. Repeat steps 5.1 through 5.11 with remaining three disks.
106
5.1.16. Spacer
The spacers locate the crankshaft so that it stays aligned with the piston block. They are
located between the middle mount of the piston block and the crank connecting disks on
either side of the mount.
Machines

Lathe
Tooling
Tool Type
Facing tool
Cutoff tool
Calipers
File
Size
Operation(s)
Facing
Establish length
Establish length
Deburr edges
Materials
Material
Plastic Spacer (2)
Size
.505” ID; 1/2” long
Procedure
10. Using a collet, clamp stock in lathe.
11. Face stock and deburr new outer edge.
12. Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the newly
faced surface. Zero the lathe readout, and move tool slightly more than the length of
the part, leaving material for finishing.
13. Remove stock from lathe and clamp part in lathe, with the unfinished side exposed.
14. Face unfinished surface. Deburr outer edge.
107
15. Remove part from lathe and measure overall length. Re-clamp part in lathe and face
to size. Deburr outer edge.
16. Measure part to check dimension.
17. Repeat steps 0 through 7 for second spacer.
18. Make sure all edges are deburred.
5.1.17. Piston Rods
The piston rods are used to connect the crankshaft to the pistons. At one end, a flanged
bronze sleeve is pressed into the part. At the other end, a pin is used to connect the piston
rod to the piston.
Machines

Vertical band saw

Vertical mill

CNC mill
Tooling
Tool Type
Scale
Scribe
Square
Layout dye
Parallels
Vise
Edge finder
File
Deburring tool
Center drill
Drill bit
Drill bit
Size
Operation(s)
Layout
Layout
Layout
Layout
Mill setup
Mill setup
Mill setup
Deburr edges
Deburr hole edges
Holes
Large hole
Small hole
108
Reamer
Counterbore
End mill
Countersink
Small hole
Screw hole pattern
CNC profile
Chamfer profile
Materials
Material
Aluminum Rod (2)
Size
1/4 X 1 X 4-1/4 inches
Procedure
1.
Layout overall length of the part, adding at least .250” for milling. Layout second
piece, adding .125” for the saw blade.
2. Saw stock at layout lines. Deburr all edges.
3. Create holes on location.
3.1.
Place part on parallels so the left face is facing up. Clamp using vise on
vertical mill.
3.2.
Pick up center of the face and set as (0, 0) on the mill readout.
3.3.
Center drill on location of .625” hole making sure enough room is left on the
outer edge for thickness of piston rod.
3.4.
Drill through hole using .625” drill bit.
3.5.
Center drill on location of .188” hole.
3.6.
Drill through hole using .188” drill bit.
3.7.
Ream hole using reamer.
3.8.
Deburr all hole edges.
109
Figure 92: Piston rod stock with holes drilled
3.9.
Fixture part on the CNC mill as shown in Figure 93 through Figure 96 using
newly drilled holes.
Figure 93: Piston rod CNC fixturing components
110
Figure 94: Piston rod CNC fixturing step 1
Figure 95: Piston rod CNC fixturing step 2
111
Figure 96: Fully fixtured piston rod stock
3.10. Pick up (0, 0) as defined in your program using an edge finder/
3.11. Run CNC milling profile to create the piston rod profile.
Figure 97: Piston rod with milled profile
3.12. Change tooling and adjust program settings. Run again to put a chamber on
the profile.
112
Figure 98: Fully chamfered piston rod profile
3.13. Flip part and re-fixture. Chamfer new side.
5.1.18. Pistons
The pistons connect to the piston rods via a clevis pin. They sit inside the bronze sleeves
that were pressed into the piston block. The parts are fabricated from aluminum rods,
and a fork is milled into the top of the part to accommodate the piston rod connection.
Machines

Lathe

Vertical mill

CNC mill
Tooling
Tool Type
Facing tool
Turning tool
Cutoff tool
Size
Operation(s)
Facing
Establish diameter
Establish length
113
Calipers
File
Deburring tool
Vise
Dial indicator
Edge finder
Angle plate (2)
1-2-3 Blocks
C-clamps (2)
Parallel
End mill
Center drill
Drill bit
Reamer
Establish length
Deburr edges
Deburr hole edges
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill fork
Pin hole
Pin hole
Pin hole
.188”
Materials
Material
Aluminum Rod (2)
Size
1-1/4" OD, 1-1/4” long
Procedure
1. Establish overall diameter of the parts.
1.1.
Clamp stock in lathe.
1.2.
Turn stock to .500” diameter. Make sure you clean up enough stock for both
pistons. Leave stock clamped in lathe for the next operation.
2. Establish overall height of the parts.
2.1.
Face unfinished right surface of stock. Using a file, deburr the new edge.
2.2.
Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the
newly faced surface. Zero the lathe readout, and move tool slightly more than
the length of the part, leaving material for finishing.
2.3.
Repeat steps 3.1 and 2.2 for the second piston.
2.4.
Remove stock from lathe and clamp one piston in lathe, with the unfinished
side exposed.
2.5.
Face unfinished surface. Deburr outer edge.
114
2.6.
Remove part from lathe and measure overall length. Re-clamp part in lathe
and face to size. Deburr edge.
2.7.
Measure part to check dimension.
2.8.
Repeat steps 2.4 through 2.7 for the other piston.
3. CNC mill the piston forks.
3.1.
Clamp a piston to CNC mill using soft jaws.
3.2.
Pick up (0, 0) on part corresponding to your milling program.
3.3.
Run CNC program to mill out piston fork.
3.4.
Remove part and repeat steps 3.1 through 3.3 for second piston.
Figure 99: Piston with milled fork
4. Drill pin holes for the clevis pin.
4.1.
Referring to Figure 100, clamp piston so surface A is against vertical reference
(i.e. angle plate), surface B is against a vertical reference, and surface C is
against a removable horizontal reference (i.e. a parallel). An example of this
setup can be seen in Figure 101 and Figure 102.
115
A
B
C
Figure 100: Piston reference surfaces for clamping part to mill
Figure 101: Piston head setup for drilling pin hole with unclamped piston
116
Figure 102: Piston head setup for drilling pin hole with clamped piston
4.2.
Pick up (0, 0) at center of cylinder in x-direction and at surface A in ydirection. Be sure to account for the offset from the edge finder radius.
4.3.
Move to hole location and center drill pin hole.
Figure 103: Center drilled pin hole in piston head
4.4.
Make sure piston is clamped tightly and remove the parallel. Drill through
both fork arms using a #15 (.180”) drill bit.
117
Figure 104: Drilled pin hole in piston head
4.5.
Ream holes using .187” reamer.
Figure 105: Reamed pin hole in piston head
4.6.
Repeat steps 4.1 through 4.5 for the second piston.
118
5.1.19. Cams
The cams were made in once piece. This insured that the two cam profiles would be
offset by exactly 180°, and allowed the set screws to be placed in the spacer between the
two profiles to prevent interference. Flats were machined into the spacer to align the
second profile in the CNC, and they were also used for the set screws.
Machines

Lathe

Vertical mill

CNC mill
Tooling
Tool Type
Center drill
Drill bit
Reamer
Facing tool
Cutoff tool
Calipers
File
Vise
Aluminum soft jaws
Dial indicator
Parallel
Edge finder
End mill
Center drill
Drill bit
Tap
Tapping fluid
Size
Operation(s)
Shaft hole
Shaft hole
Shaft hole
Facing
Establish length
Establish length
Deburr edges
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
CNC cam profile
Set screw holes
Set screw holes
Set screw holes
Set screw holes
10-32
119
Materials
Material
Steel Rod (1)
Size
1” diameter; 1-3/4” long
Procedure
1. Create shaft hole.
1.1.
Face end of stock. Using a file, deburr new edge.
1.2.
Drill .500” hole through center of stock.
1.3.
Ream hole using a reamer.
Figure 106: Ream the shaft hole for the cam stock
2. Establish overall length of the part.
2.1.
Cut stock using a cutoff tool. Line up the right edge of the cutoff tool with the
newly faced surface. Zero the lathe readout, and move tool slightly more than
the length of the part, leaving material for finishing.
2.2.
Remove stock from lathe and clamp part in lathe, with the unfinished side
exposed.
2.3.
Face unfinished surface. Deburr outer edge.
120
2.4.
Remove part from lathe and measure overall length. Re-clamp part in lathe
and face to size. Deburr edge.
2.5.
Measure part to check dimension.
3. Create cam profiles
3.1.
Clamp part with right face up in soft jaws on CNC mill.
3.2.
Establish (0, 0) as defined in the cam profile program.
3.3.
CNC mill cam profile.
Figure 107: CNC-ed cam profile on one side of the cam part
3.4.
Mill flats on top and bottom of the spacer section with part in the same position
as when the cam profile was milled. This will be used for positioning the part
for the second cam profile.
121
Figure 108: One cam profile with milled flats on spacer for positioning
3.5.
Remove the part and rotate so left side is now facing up. Clamp part in soft
jaws, using flats for alignment. Make sure the existing cam profile is 180°
offset from the one that will be milled.
3.6.
If it has changed, pick up (0, 0) on the part and re-run the cam profile program.
3.7.
Carefully deburr all new edges without scratching cam surface.
5. Create set screw holes.
5.1.
Clamp cam to mill so that one flat is facing up and opposite flat is sitting on
flat surface
5.2.
Center drill for set screw hole at roughly the center of the flat section.
5.3.
Drill through wall to center of part using drill bit.
5.4.
Power tap hole using 10-32 tap. Make sure the tap cuts fully.
5.5.
Rotate part and repeat steps 5.1 through 5.4 of opposite flat.
5.6.
Deburr threaded holes.
122
Figure 109: Cam part with both profiles milled
Figure 110: Detailed view of set screw hole with set screw
5.1.20. Additional Operations and Assembly
Some operations should be performed during assembly rather than individual part
fabrication. This is especially true for features such as holes whose diameters span two
separate parts (i.e. piston block and mounting cap).
123
Machines

Horizontal band saw

Vertical mill

Press
Tooling
Tool Type
Micrometers
Angle plate (2)
Toe clamps
C-clamps (2)
Dial indicator
Edge finder
Turned shafts (2)
File
Center drill
Drill bit
End mill
Reamer
Allen wrenches
Grease/ oil
Size
Operation(s)
Layout
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Mill setup
Deburr edges
Shaft hole
Shaft hole
Shaft hole
Shaft hole
Assembly
Assembly
Materials
Material
See BOM
Size
N/A
Procedure
1. Create mounting holes for the crankshaft.
1.1.
Measure height of each mounting cap and mark on cap. Make sure they are
completely deburred.
1.2.
Screw mounting caps to right and left mounting points of piston block, being
sure to center the caps.
124
1.3.
Mount assembly to vertical mill using two angle plates so that right side is
facing up. Pick up part using edge finder such that (0, 0) is at the middle top
edge of the mounting cap.
1.4.
Move to the hole location based on the height of the mounting cap.
1.5.
Center drill hole on location.
1.6.
Drill through mounting point on hole location using drill bit.
1.7.
Bore hole using 1/2" end mill.
Figure 111: Bored hole at shaft mounting location
1.8.
Ream hole using reamer.
Figure 112: Reamed hole at shaft mounting location
125
Figure 113: Finish for mounting hole
1.9.
Rotate part and repeat steps 1.3 through 1.8 on left mounting point.
1.10. Screw mounting cap to mounting location on valve block. Repeat steps 1.3
through 1.8.
1.11. Place dowels in screw holes for mounting cap and mounting cap spacer to
align the holes.
1.12. Clamp parts in mill as shown in Figure 114 and establish (0, 0) using edge
finder.
Figure 114: Setup for drilling middle mounting hole
126
1.13. Again, center drill, drill, bore, and ream the shaft hole as described in steps 1.4
through 1.8.
2. Assemble the valves.
2.1.
Press seals into .500” holes on the bottom face of the valve block
2.2.
Place Loctite on short threads of cam rods and thread cam followers onto valve
rods. Clean any excess Loctite from shaft.
2.3.
Place spring on shafts
2.4.
Push valve rods into valve block from the top (if you are having trouble, you
may need to deburr the sleeve using a reamer).
2.5.
Thread the valve stopper onto the ends of the valve rods.
3. Assemble the pistons.
3.1.
Press a short bronze flanged sleeve bearing into larger hole of the piston rod.
3.2.
Attach piston rod to piston using a clevis pin. Place nylon washers between
the forks of the piston and the piston rod to prevent rubbing.
4. Assemble the crankshaft and cam.
4.1.
Using dowels and screws, attach the valve block to the piston block. Makes
sure everything is aligned.
4.2.
Place bronze flanged sleeve bearings in mounting holes for the crankshaft.
4.3.
Using one long 1/2" rod, check the alignment of the mounting points. If
necessary, ream mounting holes for better fit.
4.4.
Slide crankshaft 1 into place, and use a set screw to attach to a crank
connecting disk. It will go through the center hole of the disk. Make sure the
set screw sits on the flat of crankshaft 1.
4.5.
Slide one of the crankshaft 2 sections into a piston rod. Put the piston in the
right piston cylinder and slide the crankshaft 2 section into the outer hole of the
crank connecting disk that is connected to crankshaft 1. Secure the shaft with a
set screw, using the shaft flat.
127
4.6.
Attach second crank connecting disk to crankshaft 2 by sliding the shaft into
the outer hole. Secure using a set screw on the shaft flat.
4.7.
Slide crankshaft 3 in place, through spacer and into the center hole of the
second connecting disk. Secure using a set screw on the shaft flat.
4.8.
Put spacer on other side of crankshaft 3 and attach third connecting disk to
crankshaft 3 using a set screw. Make sure the outer hole is opposite from the
outer holes connected to the first piston.
4.9.
Slide remaining crankshaft 2 sections into remaining piston rod. Put the piston
in the left piston cylinder and slide the crankshaft 2 section into the outer hole
of the crank connecting disk that is connected to crankshaft 3. Secure the shaft
with a set screw, using the shaft flat. Make sure it is offset by 180° from the
other piston. *You may have to remove the left piston block mounting cap to
get shaft in place.
4.10. Attach fourth crank connecting disk to crankshaft 2 by sliding the shaft into the
outer hole. Secure using a set screw on the shaft flat.
4.11. Slide crankshaft 4 through the far left mounting hole, through the cam (pressed
against the cam followers) and through the left piston block mount into the
center of the fourth crank connecting disk. Secure with a set screw on the shaft
flat.
4.12. Adjust the valve stopper so the cam followers are in the correct position (just
off the profile when not at a rise).
4.13. Adjust the cam location so that the timing is correct with the pistons (should
just hit the rise when the corresponding piston is closes to the bottom of the
cylinder). Secure with two set screws.
5. Assemble final air fittings.
5.1.
Put O-rings in the piston block and valve block covers. Put a little oil on them
before setting them in place.
5.2.
Screw on the piston block and valve block covers.
128
5.3.
Thread on air fixtures snugly.
5.4.
Attach hoses to air fittings, and connect air inlet to the pressure control.
5.5.
Mount motor securely.
5.6.
Apply grease or oil liberally to any moving/ rubbing parts.
5.7.
Connect to air supply and run.
5.2. Budget
The total material cost for development of this motor was about $1,115.44. A table of
purchased material can be seen in Table 2 of Appendix D. The material includes stock
pieces and components for creating three air motors. Based on the design described in
the above section, an air motor should cost about $104.57 for materials and components.
5.3. Design Changes
Since three motors were fabricated during this development process, several small design
changes were made during construction. Two different piston designs were used: one
design had a flat face, and the other design had a concave hemispherical shape. It was
thought that the hemispherical face may allow for better compression. In practice, the
hemispherical piston head appeared to result in a deeper engine sound, though we have
not had the opportunity to compare the outlet torques and speeds. It would be interesting
for the course to look at several different piston designs (possibly using an O-ring
between a smaller diameter piston and the piston cylinder) and different amounts of
clearance between the piston and the cylinder wall to compare the impacts these factors
129
have on performance. The results of the tests involving different clearances would be a
good way to show students the importance of proper tolerance and fit in manufacturing.
It would also be a good application for talking about geometric dimensioning and
tolerancing (GD&T).
Another major change that was made during fabrication was the material selection for the
sleeves housing the crankshaft and the crankshaft material itself.
Originally, nylon
flanged sleeve bearings were used at the crankshaft mounting points, and aluminum
shafts were used for the crankshaft shaft material. After assembling the first motor
however, we realized that the sleeves would begin to bind as the motor was run and the
aluminum developed grooves from rubbing against the nylon as shown in Figure 115.
We believe the nylon was heating up as the motor ran and the material expanded,
grabbing the aluminum shaft and slowing down the motor. We decided to change to
bronze flanged sleeve bearing to replace the nylon bearings, and swapped the aluminum
shafts out for steel ones. These worked much better, and the shaft stayed cool even after
running for several hours.
130
Figure 115: Wear on aluminum shaft from original nylon flanged sleeve bearings
Additional design changes should be considered before implementing the course. One of
the most important changes is updating the cam. The current cam profile is simply a
scaled up version of the profile used in the original ME 581 air motor. Ideally, we will
have students learn about cam design and create their own cam profiles. A general idea
of the changes that should be made can be seen below in Figure 116. The current cam
design has a slow rise and a very short dwell. The dwell is actually a straight line, which
is very bad for cam design as the follower will actually break contact with the cam during
the dwell at high speeds, and cause a lot of vibration and wear. In general, the new cam
profile should have a steeper rise and fall, and a much longer dwell. The valve should be
open the whole time the piston is travelling towards the air outlet, and close right before
the exhaust is opened.
131
Figure 116: Current cam profile design (black) and proposed modification (red)
In addition, the drawings should be changed to make the screw holes at more consistent
locations. Currently, the holes vary slightly as to how far they are from neighboring
walls, which may cause some confusion during fabrication. Doing this would also make
some of the drawings less busy and easier to read.
A better fly wheel design should also be implemented. The fly wheels that are on the
motors now were made from aluminum stock that was available in the machine shop.
New fly wheels should be made, preferably of a denser material, and there should be one
fly wheel per motor. This will leave the other end of the crankshaft free to drive the
students‟ design projects, which will involve attaching a coupler in order to transmit
power from the shaft to the driven device.
Finally, mounting block spacers should be used at each mounting point, not just the
center mounting point on the piston block. This will reduce material cost of the motor
and cut down on sawing and milling time for machining the pockets. It will also make it
132
easier to align the crank shaft and allow some adjustment that was not possible in the
previous design. An illustration of the preliminary design described in the procedure
above can be seen in Figure 117 below, and Figure 118 shows the modification using the
mounting spacers.
Figure 117: Unmodified piston/valve blocks and mounts
Figure 118: Modified piston/valve blocks and mounts
133
Chapter 6: Conclusion and Future Work
In the coming year, a great deal of additional work will be necessary in order to
implement this course. The two main sections of this course will be piloted during the
AU 2011 and WI 2012 quarter, with the fabrication portion described here being run
during the autumn quarter, and the Arduino - focused section run during the winter
quarter. These pilot courses will help greatly with determining lab time requirements and
overall feasibility of the course. The following suggested future work section is based on
my experience with the prototype air motor development, and should be re-evaluated
after the pilot course is completed.
6.1. Tooling and Machining Requirements
Based on the sheer number of students expected to come through the course each
semester, the department will need a great deal more tooling than it currently has. A lot
of time during development was spent finding tooling that would work or modifying
existing tooling so it would work because that was what was available. In addition, sharp
tooling makes machining much easier, teaches better practices, and makes for a safer
environment. Fighting with a dull drill bit can not only be frustrating, but it keeps
134
students from getting a good feel for the material and what the proper speed and feed
looks and sounds like for the operation. It would be very beneficial if each student team
could have their own set of tooling for machining each part, so they do not have to go
searching for it in the shop. It would also be useful for students to have their own set of
commonly used items such as a scale, square, scribe, calipers, and a permanent marker.
As far as the machines themselves go, the department should obtain new mills and lathes
in order for the course to run smoothly, or at a minimum rebuild the machine tools that
are currently in the machine shops. In addition, ideally all the vertical mills would have
variable speed heads rather than step pulley heads. This would be especially useful for
the staff in the machine shop.
I do not think that it is worth the students‟ or the
instructors‟ time to teach students how to properly change the belts in a step pulley head
because most of these types of machines are now only in personal shops rather than out in
industry. Therefore, it is unlikely that students will ever see a variable speed head in the
workplace. In addition, if students do not learn how to change the belts in the step pulley
heads, the instructional staff would most likely spend a majority of their time changing
mill speeds rather than supervising students.
6.2. Staffing
With so many inexperienced students in the machine shop at one time, special care
should be taken to insure shop safety. If possible, there should be one staff member for
135
every pair of students. This is especially true for the first few labs when students are
becoming acquainted with the machines and how they work. In addition, it is extremely
important that the staff members, be they professors, graduate teaching assistants, or
undergraduate teaching assistants, be very experienced in the operations that students are
performing so they can spot any dangerous practices early. It is important that students
feel comfortable asking questions if they are unsure about an instruction or how
something should be done, and the staff should encourage students to ask questions.
Open lab time will most likely be necessary in order for students to complete their
motors. During these times, there should be several staff members present to supervise
students and answer questions.
6.3. Student Part Fabrication
It is unlikely that students will have time to completely fabricate all parts of this motor,
but rather they will need to have some parts either fully or partially fabricated ahead of
time. Developers should have a better idea of how long operations will take to complete
for students after the pilot course during autumn quarter.
I would suggest partially or fully finishing the piston block. It would be useful to at least
rough cut the pockets for the crankshaft and drill the initial hole for the piston cylinders.
In this case, students would still have the experience of milling the pockets to size and
boring the piston cylinders to size.
136
One step that should be performed for students is cutting stock for the crank connecting
disks. Because of the diameter of the stock, and since it is made of aluminum, the cutoff
tool has a tendency to load up and it can be an extremely dangerous operation. Cutoff
tools can break during these kinds of operations, which can be especially hazardous with
a lot of students in the area.
While it would be good to give students CNC experience, it may be best to have students
CNC just the cam profiles and allow the staff to perform the other CNC operations (i.e.
milling the air chamber and O-ring grooves) to save time.
Logistically, it would also be helpful to rough cut the stock for students as well. I would
advise creating a “kit” that contains some of the commonly used items that were
mentioned earlier such as a scale, scribe, etc., and that also contains all the purchased
components (sleeve bearings, air fittings) and material that they will need rough cut and
labeled. This will be fairly time consuming for the instructional staff, but will save a lot
of time with sawing and waiting for saws for students during their lab times.
6.4. Apprentice Piece
If time allows, as an introduction to machining and prior to starting on the air motor, each
student should create a small apprentice piece. This would allow and require every
student to have experience doing every machining process, which can be a major
downfall of working in teams. The piece would be something like a small block that
137
must be machined to a specified size and within a specified tolerance. Students could
create two countersunk clearance screw holes, two threaded screw holes, drill, ream, and
bore a hole, and then face and turn a shaft to fit in the hole. This could also be an
opportunity for instructors to talk about and use go/no go gages. While having each
student create an apprentice piece is fairly time consuming, it will give them a very good
foundation for when they start their air motors, and allow instructors to determine which
students may need additional help.
6.5. Instructional Videos
It would be extremely useful for students to have access to short five- to ten- minute
instructional videos on the machining operations they will be performing. The idea
would be that students watch these videos before lab, and the instructional staff could
then demonstrate the process in person and go into more depth on proper practices and
safety precautions. The students could use the videos as refreshers later on when they are
actually performing the operations themselves.
MIT has similar videos online (http://techtv.mit.edu/collections/ehs-videos/videos);
however, for the most part these videos are too long for a quick reference for students. If
students are given an electronic version of the fabrication procedure on Carmen for
instance, these videos could be hyperlinked throughout the procedure. For example, if
the procedure says “Drill hole .375” deep using a #7 (.201”) drill bit”, the word “Drill”
138
would be hyperlinked to a video that shows the proper procedure for drilling a hole and
how to use the quill readout to determine the proper hole depth. Appendix B gives a
suggested outline of what should be included in these videos.
In order for students to have access to these videos while they are working, computer
space must be available in or close to the machine shop in an area that is away from the
machines themselves. Space for laptop use or department desktop computers devoted to
the course would make things run more smoothly, rather than having students run back
and forth between the shop and the computer labs.
6.6. Prony Brake and Accelerometers
In order to test the motor‟s output torque, a Prony brake will need to be made. A fairly
simple design will be created before the start of the class for students to create, and a
second test setup will be designed by course developers to test the accuracy of the student
instruments. In addition, it would be interesting to see the amount of vibration in the
motors. This could be done by mounting accelerometers onto a test stand, and fastening
each motor to the stand. Data could be taken over a range of speeds, and students could
attempt to determine the natural frequency of the motor.
Students could use LABVIEW for data acquisition, and possibly MATLAB for data
analysis. Most students will already have some experience with MATLAB, however this
139
would most likely be the first time that many of them have seen LABVIEW, so the DAQ
system should be relatively simple.
6.7. Student Safety
Student safety is a top priority for the department. The nature of this portion of the
course, having totally inexperienced students learning machining at the same time, is
inherently dangerous. It is extremely important that students understand and appreciate
the dangers involved in operating the machinery prior to stepping foot in the machine
shop. It is equally important for students to be reminded of these dangers as they
progress through the course and become more confident around the mills and lathes.
When students become comfortable, they are likely also to get careless, which leads to
accidents. At no time should students be operating machines without a member of the
instructional staff or machine shop staff in the room.
A recent tragedy has drawn national attention to the dangers in student shops. A Yale
student who was operating a lathe alone late at night in her student shop got her hair
caught in the chuck and died. She had had machine shop training and had taken courses
in fabrication. We must make sure nothing like this happens at Ohio State.
140
6.8. Suggested Future Modifications
Several modifications can be made to the motor once the course is somewhat established.
Since the motor was designed to be modular in that the valve block is separate from the
main piston block, a different valving system can be implemented relatively easily. It
would be interesting to try to use the Arduino to control timing for the pistons by
determining when air enters each of the cylinders via a servo-controlled valve or similar
system. This would, however, remove the cam development and fabrication from the
project and greatly reduce the amount of fabrication involved.
A second modification that would be interesting is making the motor even more modular
by separating the two pistons.
Students could experiment with different piston
orientations and measure the effect that the angle between the two pistons has on the
overall vibration of the motor.
Finally, this motor could be integrated into several other labs within the ME curriculum.
It is unclear whether students will keep the motors, or if the department will hold onto
them. In either case, there will be a lot of these motors floating around the department,
and it would be nice to utilize them in additional lab courses. It may also make students
more interested in the labs since they will be well acquainted with the motors and how
they work.
A great deal of work still needs to be completed in order to get this course up and
running, however, if done right, this course could radically change the overall experience
141
in the mechanical engineering undergraduate program here at The Ohio State University.
It will not only give students an introduction to the curriculum and get students excited
about the major, but also provide valuable fabrication experience that students can use in
later courses and that industry recruiters look for.
142
Works Cited
Air
Motors.
Ed.
Penton
Media.
2011.
10
12
2010
<http://www.hydraulicspneumatics.com/200/TechZone/FluidPowerAcces/Article/
True/6422/TechZone-FluidPowerAcces>.
Ambrose, Susan A. and Cristina H. Amon. "Systematic Design of a First-Year
Mechanical Engineering Course at Carnegie Mellon University." Journal of
Engineering Education (April 1997).
Bannerot, Richard. "Hands-on Projects in an Early Design Course." ASEE Annual
Conference and Exposition. Pittsburgh, PA, 2008.
Bilen, Sven G., Richard F. Devon and Gul E. Okudan. "Cumulative Knowledge and the
Teaching of Engineering Design Processes." ASEE Annual Conference.
Montreal, Quebec, Canada, June 16 - June 19, 2002. Session 2325.
Clayton, Garrett, et al. "Introduction to Mechanical engineering - A Hands-On
Approach." 2010 Annual ASEE Conference. 2010. AC 2010-1048.
Dixon, Gregg W., Vincent Wilczynski and Eric J. Ford. "Air Engine as a Manufacturing
Project in an Introductory Design Course." Prodeeings of the ASEE annual
Conference. Montreal, Quebec, Canada, 2002.
Finkelstein, Theodor and Allan J. Organ. Air engines : the history, science, and reality of
the perfect engine. New York: ASME Press, 2001.
Gabiele, Gary A., et al. "Product Design and Innovation: Combining the Social Sciences,
Design, and Engineering." American Society for Engineering Education Annual
Conference & Exposition. Salt Lake City, UT, 2004.
Giurgiutiu, Victor. "EMCH 367 - Microcontroller in Mechanical Engineering Syllabus."
22 March 2010. Univeristy of South Carolina: College of Engineering and
Computing.
12
December
2010
<http://www.me.sc.edu/courses/syllabi/ABET/EMCH367.pdf>.
Hargrove, Jeffrey B. "Curriculum, equipment and student project outcomes for
mechatronics education in the core mechanical engineering program at Kettering
University." Mechatronics (2002): 343-356.
Hoadley, Rod and Paul Rainey. "A Manufacturing Processes Course for Mechanical
Engineers." 2007 ASEE Annual Conference. 2007. AC 2007-244.
143
Hoose, Frank J. "Height Gauge." 2001. Mini-Mill Accessories. 12 May 2011
<http://www.mini-lathe.com/Mini_mill/Accessories/Layout/layout.htm>.
James, Jeremy P. Design Upgrade for 2.670 Compressed Air Robot. Undergraduate
Thesis. Cambridge, MA: Massachusetts Institute of Technology, 2009.
Ju, Anne. "Mechancial engineering students' air motors draw a crowd." Cornell Chronicle
4 May 2009.
Kenjo, Takashi. Stepping Motors and Their Microprocessor Controls. USA: Oxford
University Press, 1994.
Laidman, Russel. Stepper Motors and Control. 1999. 20
<http://www.stepperworld.com/Tutorials/pgUnipolarTutorial.htm>.
12
2010
Mandayam, Shreekanth A., Anthony J. Marchese and John L. Schmalzel.
"Nondestructive Evaluation of Aircraft Skin: Product Design and Development in
the Sophomore Engineering Clinic." Proceedings of the Frontiers in Education
Conference. Phoenix, AZ, 1998. Session S3D.
Manno, Vincent and Anil Saigal. "An Innovative Integration of Data Acquisition and
Manufacturing Practice as an Introduction to Mechanical Engineering." 2002
ASME Curricular Innovation Award Paper (November 2002).
Marchese, Anthony J., et al. "The Sophomore Engineering Clinic: An Introduction to the
Design Process through a Series of Open Ended Projects." ASEE Annual
Conference and Exposition. Charlotte, North Carolina, June 20-23, 1999. Session
2225.
Mechancial Engineering Courses. 2011. 10 12 2010 <http://www.slu.edu/x26065.xml>.
Morris, Stacy J. Development of the Machine Shop Instruction and the Stirling Engine
Project for 2.670: ME Tools. Undergraduate Thesis. Cambridge, MA: MIT, 1996.
Newell, James A., et al. "Multidisciplinary Design and Communication: a Pedagogical
Vision." International Journal of Engineering Education (1999): 376-382.
Newton, James. "Motor wiring diagrams." 4 5 2011. Stepper Motor Wiring. 9 5 2011
<http://www.piclist.com/techref/io/stepper/wires.htm>.
Otto, Kevin, et al. "Building Better Mousetrap Builders: Courses to Incrementally and
Systematically Teach Design." ASEE Annual Conference. Seattle, WA, 1998.
Session 2666.
144
Rehan. "Mechatronics projects." 4 April 2008. True SLU Blogs. 15 December 2010.
Roemer, Robert, et al. "A SPIRAL Learning Curriculum in Mechanical Engineering." the
117th Annual Conference of the American Society for Engineering Education.
Louisville, KY, 2010. AC 2010-1903.
Rubin, Debra K. "Olin College Trains New Engineers By Going Its Own Way;
Massachusetts school has cash, more women students, and few rules."
Engineering News 30 October 2006: 42.
Spangler, Dewey and Kimberly Filer. "Implementation of Tablet PC Technology in ME
2024 Engineering Desing and Economics at Virginia Tech." 2008 Annual ASEE
Conference & Exposition. Pittsbugh, PA, 2008.
Starkey, John M., et al. "Experiences in the Integration of Design Across the Mechanical
Engineering Curriculum." 1994 Frontiers in Education Conference. 1994. 464468.
Tsang, Edmund and Andrew Wilheim. "Integrating Materials, Manufacturing and Design
in The Sophomore Year." Proceedings of the Frontiers in Education Conference.
Atlanta, GA, 1995. Session 3c4.
Vaughan, Joshua, et al. "Using mechatronics to teach mechanical design and technical
communication." Mechatronics (2008): 179-186.
Victrex
PLC. "Vane Pumps." 2007.
Pump School.
<http://www.pumpschool.com/principles/vane.htm>.
145
13
12
2010
Appendix A: Stepper Motor Information
146
Stepper Motors
Stepper motors, unlike AC and DC motors, are brushless. They have very good low
speed and holding torque, and are generally rated in terms of their holding torque
(Kenjo). Unlike servo motors, they can hold a position without supplied power, which is
also known as the detent torque.
There are two main types of stepper motors: unipolar and bipolar. Unipolar motors
Figure 119) have 5, 6 or 8 wires, whereas bipolar motors Figure 120) only have 4
(Newton). This review will only look at the unipolar version, which is easier to control
than a bipolar motor.
Figure 119: Six wire unipolar stepper motor (Newton)
147
Figure 120: Four wire bipolar stepper motor (Newton)
Unipolar stepper motors have two separate wire coils, each of which has a center tap
located midway between the two terminals. When current is sent through a coil, a
magnetic field is produced which attracts the permanent magnet rotor. By controlling the
current in the coils, it is possible to control the position of the rotor and allow it to turn
continuously. For example, in a four-phase sequence, the center tap is connected to
positive supply and one of the two terminals is grounded (see
Figure 121) (Laidman).
148
Figure 121: Conceptual model of a unipolar stepper motor (Laidman)
In some drive sequences, two terminals are supplied power at the same time, one from
each coil (Laidman). Three sequences are shown below in Table 1. The direction of the
motor can be reversed by reversing the drive sequence.
Table 1: Table of stepping sequences (Laidman)
Sequence
Name
Description
0001
0010
0100
1000
Wave
Drive, Consumes the least power. Only one phase is
One-Phase
energized at a time. Assures positional accuracy
regardless of any winding imbalance in the motor.
0011
0110
1100
1001
Hi-Torque,
Two-Phase
Hi Torque - This sequence energizes two adjacent
phases, which offers an improved torque-speed
product and greater holding torque.
0001
0011
0010
Half-Step
Half Step - Effectively doubles the stepping
resolution of the motor, but the torque is not uniform
for each step. (Since we are effectively switching
149
0110
0100
1100
1000
1001
between Wave Drive and Hi-Torque with each step,
torque alternates each step.) This sequence reduces
motor resonance which can sometimes cause a motor
to stall at a particular resonant frequency. Note that
this sequence is 8 steps.
Stepper motors are very useful for open loop control systems. They allow for controlled
movement without system feedback, and are used in applications such as scanners,
printers, and CNC machines.
150
Appendix B: Basic Machining Instruction Outline
151
Machining Videos
1. Layout techniques
1.1. Rough layout with scribe
1.1.1. Apply layout dye to you can scribe lines on your part
1.1.2. Use a square and metal ruler with a scriber to score part
1.1.3. If are rough cutting multiple parts from a piece of stock, leave about a saw
blade and a half during layout to give you excess material to work with in
sizing and finishing
1.2. More precise layout with height gage
1.2.1. Deburr edges
1.2.2. Apply layout dye to appropriate surface
1.2.3. Make sure surfaces are clean, and place part on surface plate with a
finished surface on the surface plate
1.2.4. Zero the height gage on surface plate
1.2.5. Set height gage to appropriate height and score part
2. Vertical mill operations
2.1. Clamping parts
2.1.1. Clean mill table
2.1.2. Determine setup using angle plates, c-clamps, toe clamps, parallels, stops
etc.
2.1.3. Clamp largest fixturing component (i.e. angle plate) to mill table so
clamps are snug but not fully tightened
2.1.4. Line up component with x- and y-axes of the mill using dial indicator and
dead blow hammer
2.1.5. Slowly tighten clamps while aligning component until fully secured and
aligned
2.1.6. Repeat with additional fixturing components; check alignment when
necessary
152
2.2. Pick up part
2.2.1. Deburr any sharp edges
2.2.2. Clamp part to table
2.2.3. Attach drill chuck to mill
2.2.4. Insert and secure edge finder
2.2.5. Adjust mill speed to relatively high rpm
2.2.6. Lower edge finder past top surface of the part
2.2.7. Slowly approach edge until edge finder “breaks”
2.2.8. If setting zero to edge
2.2.8.1.
Zero readout before moving
2.2.8.2.
Raise edge finder
2.2.8.3.
Move the amount of the offset
2.2.8.4.
Re-zero readout
2.2.9. If setting zero to midpoint between two surfaces
2.2.9.1.
Zero readout before moving
2.2.9.2.
Raise edge finder
2.2.9.3.
Move to point past the opposing edge
2.2.9.4.
Lower edge finder
2.2.9.5.
Slowly approach edge until edge finder “breaks”
2.2.9.6.
Raise edge finder and observe mill readout
2.2.9.7.
Divide readout by two, and move to that location
2.2.9.8.
Re-zero readout
2.3. Center drill hole
2.3.1. Secure center drill in drill chuck
2.3.2. Move to location of hole
2.3.3. Adjust speed if necessary (should be relatively fast)
2.3.4. Turn on mill and drill using quill feed lever
2.3.5. Do not go past angled section of the center drill
153
2.4. Drill hole
2.4.1. Secure drill bit in drill chuck
2.4.2. Move to location of hole
2.4.3. Adjust speed if necessary (should be relatively slow depending on the
diameter of the bit)
2.4.4. Turn on mill and drill using quill feed lever
2.4.5. If necessary, oil can be applied to lubricate the tool
2.4.6. For deeper holes, periodically raise the tool to break and remove chips
2.5. Bore hole with boring end mill
2.5.1. Find proper size collet for tool
2.5.2. Secure collet and tool in mill
2.5.3. Move to location of hole
2.5.4. Adjust speed if necessary
2.5.5. Turn on mill and bore using quill feed lever
2.6. Reaming
2.6.1. Find proper size collet for tool
2.6.2. Secure collet and tool in mill
2.6.3. Move to location of hole
2.6.4. Adjust speed if necessary (should be very slow)
2.6.5. Apply oil
2.6.6. Turn on mill and ream using quill feed lever
2.7. Power tapping
2.7.1. Secure tap in drill chuck
2.7.2. Move to location of hole
2.7.3. Adjust speed if necessary (should be very slow)
2.7.4. Apply tapping fluid
2.7.5. Turn on mill and bring tap down until it engages the part
2.7.6. Release quill feed handle
154
2.7.7. Reverse mill direction when proper depth is reached; be sure not to bottom
out
2.7.8. When tap disengages part, bring tap up using quill feed lever
2.8. Fly cutting
2.8.1. Find proper size collet for tool
2.8.2. Secure collet and tool in mill
2.8.3. Engage brake on quill
2.8.4. Turn on mill and adjust speed if necessary
2.8.5. Adjust table height for first pass
2.8.6. Use manual or auto fee to move table in x- or y- direction
2.8.7. Raise table height for next pass, and repeat previous step
2.8.8. Continue until <.010” of material remains
2.8.9. Take finished pass (slow down feed and increase cutter speed)
2.9. Milling
2.9.1. Find proper size collet for tool
2.9.2. Secure collet and tool in mill
2.9.3. Engage brake on quill
2.9.4. Turn on mill and adjust speed if necessary
2.9.5. Adjust table height for first pass
2.9.6. Use manual or auto fee to move table in x- or y- direction
2.9.7. Raise table height for next pass, and repeat previous step
2.9.8. Continue until <.010” of material remains
2.9.9. Take finished pass (slow down feed and increase cutter speed)
2.10. Skim cutting
2.10.1. Apply layout dye to surface you want to skim cut
2.10.2. With tool spinning, bring part up to cutting tool slowly until it just touches
2.10.3. Move table in the x- or y-direction (whichever direction you will be
cutting in) until tool is no longer touching the part
155
2.10.4. Bring up the table .001”-.002” and auto-feed at a slow feed rate and high
tool rotation speed
2.10.5. Continue taking .002”-.003” off at a time until layout dye no longer
appears on the surface
3. Lathe operations
3.1. Turning
3.1.1. Secure material in lathe using either a collet or chuck
3.1.2. Place proper tool in tool holder
3.1.3. Adjust lathe speed if necessary
3.1.4. Determine starting distance of tool from center point of the part; do not
remove too much material at once
3.1.5. Using auto feed or manual control, move along the part laterally to the
desired turning length
3.1.6. Return to the original starting point off the part and adjust tool location for
next pass
3.1.7. Repeat until desired diameter is reach
3.2. Facing
3.2.1. Secure material in lathe using either a collet or chuck
3.2.2. Place proper tool in tool holder
3.2.3. Adjust lathe speed if necessary
3.2.4. Slowly approach end face of the part until the tool touches the surface of
the part
3.2.5. Move the tool away from the center point until it is no longer in contact
with the part
3.2.6. Move the tool laterally so that additional material will be removed during
facing; do not remove too much material in one pass
3.2.7. Using the auto feed or manual control, move the tool to the center of the
part
156
3.2.8. Move laterally away from the part once the tool cuts to the center
3.2.9. Move tool away from the center of the part until you are past the part, and
adjust the lateral location for the next pass
3.2.10. Continue taking passes until desired dimension is reached
3.3. Rough cutting
3.3.1. Secure material in lathe using either a collet or chuck
3.3.2. Place cutoff tool in tool holder
3.3.3. Adjust lathe speed if necessary
3.3.4. Move cutting tool away from the center of the part so that it will not
intersect the part
3.3.5. Move tool laterally so the right edge lines up with the edge of the part
3.3.6. Zero lathe readout
3.3.7. Move tool slightly farther than the length of the part laterally using the
lathe readout
3.3.8. Carefully move the tool toward the center of the part; be careful of load up
157
Appendix C: Assembly Drawings
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
Appendix D: Budget
183
Table 2: Overall project budget
184