mechanical design · 2019-12-23 · mechanical design ian mackenzie general principles simplicity...
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![Page 1: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/1.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Mechanical Design
Ian Mackenzie
November 17, 2007
![Page 2: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/2.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Ian Mackenzie
I Involved in FIRST since 1998
I Member of team 188 from 1998-2002
I Recruiter/organizer for FIRST Canadian Regional in2003
I Lead mentor for team 1114 in 2004, created SimSwervecrab drive system
I Planning committee member for Waterloo Regionalsince 2005
I Head referee at Waterloo Regional, Toronto Regional,Wonderland
I Currently planning committee chair for WaterlooRegional and mentor for 1114
I Scheduling algorithm developer, inspector, gamedesigner, Lego League referee, webmaster. . .
![Page 3: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/3.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Outline
General PrinciplesSimplicityDisassemblyMultifunctionalityTheoryIterationWeight
How To. . .Power TransmissionChainsMotorsCAD
![Page 4: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/4.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Simplicity
I Simplicity is the key todurability
I To come up with a complexsolution to a complexproblem is hard; to come upwith a simple solution to acomplex problem is evenharder
![Page 5: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/5.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Design for Disassembly
I Access holes
I Common tools
I Think twice about glue,welding etc.
I Think about how hard itwould be to remove a partfor repair
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Multifunctionality
I Figure out where you can useone part or mechanism formultiple tasks
I One arm to pick up a balland hang from a bar
I One rod as both a pivotand a structural member
I One shaft for both armsand wheels (OK, maybe not)
I Can save weight andcomplexity
I Careful of conflictingrequirements
![Page 7: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/7.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Theory
I BREAKING NEWS: Theoryactually works
I Calculate gear ratios
I Determine whether a motorhas enough torque
I Calculate forces and torqueson joints
I Swerve drive kinematics
I Work-energy arguments
![Page 8: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/8.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Qualitative Theory
I Self-locking mechanisms
I Directions of forces ortorques
I Rate of change offorce/stress/torque etc.
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Iteration
I Design is iterative!
I Rethink old ideas
I Eliminate leftovers
I In the early stages, it is oftena good idea to throw outdesigns and redo them fromscratch
I Every time you restart, youknow the problem a lotbetter
I As my Grade 9 mathteacher used to say,“Expand, then simplify”
![Page 10: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/10.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Weight
I FIRST has a weight limit
I Very easy to exceed theweight limit without noticing
I Drilling holes can only getyou so far
I Think twice before usingsteel parts, large bolts, orthick plate
I Lighten parts as you go
I Weight is bad; weight uphigh is much worse
I Consider alternate materials:Lexan, nylon, HDPE/LDPE,or wood
![Page 11: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/11.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Outline
General PrinciplesSimplicityDisassemblyMultifunctionalityTheoryIterationWeight
How To. . .Power TransmissionChainsMotorsCAD
![Page 12: Mechanical Design · 2019-12-23 · Mechanical Design Ian Mackenzie General Principles Simplicity Disassembly Multifunctionality Theory Iteration Weight How To... Power Transmission](https://reader033.vdocuments.site/reader033/viewer/2022053006/5f0a61307e708231d42b59ed/html5/thumbnails/12.jpg)
MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Power Transmission
I Common problem: how to transmit power between ashaft and something attached to it
I GearI SprocketI Wheel
I High stresses, so easy to break
I Often hard to fix
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Power TransmissionSet Screws
I “Set screws inhale audibly”. . .
I Weak
I Prone to coming loose
I Sometimes the only choice for small shafts
I Use a dimple on the shaft
I Use Loctite or similar to slow down loosening
I Check/tighten every match
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Power TransmissionPins
I Stronger than set screwsI Fairly easy to use
I Can be tricky to get holecentred
I Weakens shaftI Hard to remove
I Tapered pins can be used,but they’re hard to findand tricky to use
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Power TransmissionKeys
I Very strong
I Does not significantlyweaken shaft
I Keying shaft requires specialcutter
I Can buy standardpre-keyed shaft
I Still need some way to holdgear and key from slidingalong shaft
I Often a good idea to haveset screw hold key in place
I Can have some backlash ifnot done properly
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Power TransmissionBolts
I Often underrated
I Very simple and easy to build
I Very strong
I Easily disassembled
I Most often used to attachsprocket/gear to wheel
I Can also be used betweensprockets/gears
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Chains
I StrengthI Switch to 3/8”?I Power argument: P = Fv
(power = force × velocity)I Power P is a constantI We want to reduce the
tensile force FI So. . . ?
I TensioningI Sprung tensioner or simple
block/rollerI Reduce backlashI Reduce probability of
chain becoming derailed
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
MotorsMotor Curves
FP801-005 Motor
MOTOR PERFORMANCE
0 50 100 150 200 250 300 350 400 450 500 550 600
Spe
ed (r
pm)
0
400
800
1200
1600
2000
2400
2800
3200
3600
4000
Effic
ienc
y (%
)
0
10
20
30
40
50
60
70
80
90
100
Pow
er O
ut (w
atts
)
0
40
80
120
160
200
240
280
320
360
400
Cur
rent
(am
ps)
0
10
20
30
40
50
60
70
80
90
100Constant Voltage: 12.0 V
Torque (oz-in)
Current (a)
Power Out (watts)
Efficiency
Speed (rpm)
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
MotorsMultiple Motors
I Only way to increase actualpower in drivetrain
I “But won’t the motors fighteach other?”
I As long as each motor isnot running faster thanfree speed, it iscontributing power
I Some motors mightcontribute more powerthan others
I Need to (roughly) matchmotor speeds if usingdifferent motors
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Computer Aided Design
I Usually used for complexand/or high-precision parts
I Not just a drafting tool – usefor design as well!
I See how parts go togetherI Check clearances between
componentsI Calculate mass of
subassembliesI Visualize mechanism
motionI Edit, restructure, and
redesign parts andassemblies
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Computer Aided Design
I Get familiar with a CADprogram before the buildseason
I InventorI SolidWorksI Pro/ENGINEER
I Think about “design intent”I Make sure you can modify
the design easily (becauseyou will)
I Use version control for CADfiles
I Peace of mindI Allow sharing of dataI Subversion, Autodesk
Vault
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Resources
I Mechanism Galleries, workshop presentationshttp://www.firstroboticscanada.org/site/resources
I White Papers, image galleries, discussion boardshttp://www.chiefdelphi.com
I Subversion (free, high-quality version control system)http://subversion.tigris.orghttp://tortoisesvn.tigris.org
I SDP/SIhttp://www.sdp-si.com
I McMaster-Carrhttp://www.mcmaster.com
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Resources (cont.)
I Boston Gearhttp://www.bostongear.com
I Use BostSpec 2 to search for gears (need to create freeaccount)
I Canadian Bearings (find local store)http://www.canadianbearings.com
I Metal Supermarkets (find local store)http://www.metalsupermarkets.com
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Questions?
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MechanicalDesign
Ian Mackenzie
General Principles
Simplicity
Disassembly
Multifunctionality
Theory
Iteration
Weight
How To. . .
Power Transmission
Chains
Motors
CAD
Resources
Questions
Exercise
Exercise
Some ideas of things to look for:
I Simple solutions to complex problems
I Disassembly
I Multifunctionality
I Theoretical calculations required
I Physical principles
I Why a certain method of power transmission was used
I Chain design
I Why a certain material was used
I Why a certain type of component was used
I Why a certain type of structure was used
I Design tradeoffs (usually weight and something else)
I Why pneumatics used instead of motors, or vice versa
I BONUS: Design leftovers