preliminary design review. outline background information o team and motivation project focus o...
TRANSCRIPT
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PRELIMINARY DESIGN REVIEW
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Outline Background
Informationo Team and Motivation
Project Focuso Mission Statemento Design/Performance
Criteriono Goalso Inspiration
Design Overview - Primary
o Overall Concept and Generation
o Mechanism Design
Primary Analysiso Kinematicso Cam Profileso Gear Ratioo Torqueo Packagingo BOM
Controlso Hardware and Packagingo Software
Design Overview - Secondaryo Overall Concept and
Generationo Mechanism Design
Logisticso Costo Schedule
Speaker: Nick Schwartzers
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Team and Motivation
BACKGROUND INFORMATION
Speaker: Nick Schwartzers
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Team Composition
Speaker: Nick Schwartzers
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Objective5
To design and create an automatic Continuously Variable Transmission (CVT) for a bicycle, eliminating discrete steps in gear ratio in order to maintain the ideal human cadence, with no user input.
Speaker: Nick Schwartzers
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Motivation
For years bicycles have relied on the same basic transmission design.
While this is an efficient and light weight design, there could be massive improvements for the average recreational rider
The inexperienced casual rider is often bewildered by derailleur shifting
Increase human efficiency by continuously maintaining the ideal cadence
Make bicycling more user friendly in order to elevate bicycling as viable transportation and reduce emissions
Speaker: Nick Schwartzers
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Human Efficiency vs. Cadence7
Cadence: The pedaling speed in RPM’s
The optimum cadence for human efficiency is shown to be near 100 rpm
This will lead to lower fatigue and a more enjoyable experience
Taken from : Cycling Science Speaker: Nick Schwartzers
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Comparison to Current Designs8
0 20 40 60 80 100 120 140
Shift Points of Various Systems
Road DoubleRoad CompactMounatian TripleNexus 8Shift CVTLinear (Shift CVT)Linear (Shift CVT)
Gear Ratio (Gear Inches)
Dots Represent Shift Points
SHIFT CVT Has seamless gear free shifting
Gear Inches: the diameter of the drive wheel times the gear ratio
Speaker: Nick Schwartzers
You’ll have an infinite number of ratios within its range to seamlessly transition to exactly the right ratio for you and your personal riding style.
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Mission Statement, Goal, and Design Criteria
Project Focus
Speaker: Nick Schwartzers
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Mission Statement
TO PROMOTE THE ACTIVITY OF BICYCLING BY ENHANCING THE EXPERIENCE FOR THE CASUAL RIDER, BY DESIGNING, DEVELOPING, AND PROTOTYPING A DEVICE THAT WILL OPTIMIZE THE PEDALING SPEED OF THE USER THROUGH A CONTINUOUSLY VARIABLE TRANSMISSION WHILE REMAINING AESTHETICALLY PLEASING. BICYCLING WILL BECOME A MORE ENJOYABLE MEANS OF EXERCISE OR MODE OF TRANSPORTATION. WE AIM TO PROMOTE CLEANER TRANSPORTATION AND A HEALTHIER POPULATION.
“
”Speaker: Nick Schwartzers
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Goals
Requires minimal user input and easy to use. Contains a gear range suitable for average rider. Automated and maintains user-selected, constant
cadence. Automatically adjusts gears for riders preference,
position, and conditions. Compact, unobtrusive and light-weight.
Uses a standard interface to easily mount to any bike frame.
System is safe and low maintenance. Quiet and efficient
Speaker: Nick Schwartzers
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Design Criteria
Maximum of 10 net pounds of additional weight Q-factor < 12 inches Efficiency of 85% Gear ratio range of at least 1:1 to 3 ½: 1 Controls cadence to within 5 rpm while bike is in
gear range Retail Price Below $300 Maintenance of 1 year or 2,000 miles No more than 20% increase in noise (decibels)
Speaker: Nick Schwartzers
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Inspiration and Ideas
Concept Generation
Speaker: Nick Schwartzers
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House of Quality
Results:
Emphasis on Packaging, contact stress, torque capability
Speaker: Nick Schwartzers
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Previous CVT Work
Four Different Types of CVTs have been developed:
Variable diameter pulley systems
Toroidal or roller-based CVT
Hydrostatic CVTs
Ratcheting CVTs
Speaker: Nick Schwartzers
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Decision Matrix16
Ratcheting Roller Based
Hydrostatic
Variable Pulley
Efficiency
Rotational Speeds
Contact Stress
Weight
Controls= Optimal= Acceptable= Unacceptable
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Ratcheting CVT
Uses static friction ratchets as opposed to dynamic friction
Uses variable kinematics to change ratios.
Capacity to handle larger torques without slipping
Speaker: Nick Schwartzers
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Ratcheting CVT Example18
Speaker: Nick Schwartzers
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Primary Design: Non Variable Cam
DESIGN OVERVIEW19
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Assembly Models
Speaker: Nick Schwartzers
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Assembly Models
Speaker: Nick Schwartzers
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Assembly Models
Speaker: Nick Schwartzers
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Sub Systems
Cam and input shaft Follower assembly Moving output shaft Motion Control
Speaker: Nick Schwartzers
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Assembly Models24
Speaker: Nick Schwartzers
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Assembly Models
Speaker: Nick Schwartzers
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Primary Design: Non Variable Cam
Design Analysis26
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Desired Characteristics
Constant output torque Constant follower velocity vs cam angle At least 1 follower in this segment at all
positions Continuous displacement and velocity Requirements for cam:
Constant Velocity segment Smooth return Low pressure angle No undercutting
Speaker: Tom Gentry
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Lift Curve
Speaker: Tom Gentry
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Cam
Lift
(in)
Cam Angle (Degrees)
Lift
Follower 1 Lift
CycloidalHalf Rise Constant Velocity Rise Cycloidal
Half RiseCycloidal
Fall
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Lift Curve
Speaker: Tom Gentry
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-0.2
0
0.2
0.4
0.6
0.8
1
1.2
0 50 100 150 200 250 300 350 400
Cam
Lift
(in)
Cam Angle (Degrees)
Lift
Follower 1 Lift Follower 2 Lift
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Kinematic Analysis of the Cam/Follower System
Speaker: Tom Gentry
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Kinematic Analysis of the Cam/Follower System
Speaker: Tom Gentry
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Design Inputs
Variable Value Unit Data type RangeSmooth Lift (in) 0.11 inches real 0,1
Chain ring (tooth) 106 tooth integer 11,106Input Gear (tooth) 11 tooth integer 11,53
Cam Rises 2 integer integer 1,10Followers 2 integer integer 2,2
Base circle diameter (in) 3.5 inches real 0,5Planet Shaft to Cam Clearance (in) 0.1 inches real 0,3
Output Gear (tooth) 30 tooth integer 11,53Back wheel Gear (tooth) 11 tooth integer 11,53
Quick Return 3.7 ratio real 1.01,10Eccentricity (in) 0 inches real -1,1
Roller Diameter (in) 0.5 inches real .25,1.5Output Shaft Travel (in) 6 inches real 0,15
Preload (lbf) 8 lbf real 0,200Follower Type Roller N/A N/A Roller
Rise Constant V N/A N/A Constant VFall 1 Cycloidal/SHM integer 1,2
alpha (rad/s^2) 0 rad/s^2 real -100,100Single/Variable Profile Single N/A N/A Single
Input Shaft Torque (ft-lb) 114.8293963 ft-lb real 0,120Follower Mass 0.2 lbm real 0,200Cadence (rpm) 110 rpm real 0,150
Speaker: Tom Gentry
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Kinematics
0 50 100 150 200 250 300 350 400
-4
-3
-2
-1
0
1
2
3
4
5
0
0.2
0.4
0.6
0.8
1
1.2
Velocity
Follower 1 Velocity Follower 2 Velocity Follower 1 Lift Follower 2 Lift
Cam Angle (Degrees)
Follo
wer
Vel
ocity
(ft/s
)
Lift (i
n)
Speaker: Tom Gentry
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Kinematics
0 50 100 150 200 250 300 350 400
-2000
-1500
-1000
-500
0
500
1000
1500
2000
0
0.2
0.4
0.6
0.8
1
1.2
Acceleration
Acceleration Follower 1 Acceleration Follower 2 Lift Follower 1
Cam Angle (Degrees)
Follo
wer
Acc
eler
ation
(ft/s
^2)
Lift (i
n)
Speaker: Tom Gentry
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Kinematics
0 50 100 150 200 250 300 350 4000
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Follower Angle
Follower 1 high gear Follower 1 low gear Follower 2 low gear Follower 2 High gear
Cam Angle (deg)
Angle
(ra
d)
Speaker: Tom Gentry
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Cam Profile
-3 -2 -1 0 1 2 3
-3
-2
-1
0
1
2
3
Cam Profile
Pitch Curve Base Circle Cam Surface Roller
X ( in)
Y (
in)
Speaker: Tom Gentry
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Output Analysis
0 50 100 150 200 250 300 350 4000
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0
0.2
0.4
0.6
0.8
1
1.2
Output Velocity
Equivalent Follower Output Velocity Lift Follower 1
Cam Angle (Degrees)
Out
put F
ollo
wer
Vel
ocity
(ft/s
)
Lift (i
n)
Speaker: Tom Gentry
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Output Analysis
0 50 100 150 200 250 300 350 4000
20
40
60
80
100
120
140
160
180
Clutch Torque
High Gear Low Gear
Cam Angle (Degrees)
Torq
ue (ft
-lbf)
Speaker: Tom Gentry
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Output Analysis
0 50 100 150 200 250 300 350 400
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Inertial Force on Cam
Follower 1 Follower 2
Cam Angle (deg.)
Forc
e (
lbf)
Speaker: Tom Gentry
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Design OutputsVariable Value Unit
Total Lift (in) 0.985925926 inchesMinimum Case Height 11.0726239 inches
w 111.0029404 rad/sOutput Travel per rise (high) (deg) 0.466063428 degOutput Travel per rise (low) (deg) 0.140719761 deg
Final ratio (high) 4.678624042 ratioFinal ratio (low) 1.412629302 ratio
Total Ratio 3.311997023 ratioMax Lead Screw Force (lbs) 36.37085325 lbs
Speed (mph) (low) 12.08386649 mphSpeed (mph) (high) 40.02172982 mph
Gearbox Input Torque (Low) (ft-lb) 11.91625811 ft-lbOutput Gear Torque (Low) (ft-lb) 170.0913578 ft-lb
Rear Wheel (Low) (ft-lb) 103.9447186 ft-lbGearbox Input Speed (low) (rpm) 110 rpmOutput Gear Speed (low) (rpm) 1060 rpmRear Wheel Speed (low) (rpm) 94.96008084 rpm
Gearbox Input Torque (high) (ft-lb) 11.91625811 ft-lbOutput Gear Torque (high) (ft-lb) 47.89929041 ft-lbRear Wheel Torque (high) (ft-lb) 29.27178858 ft-lb
Gearbox Input Speed (high) (rpm) 110 rpmOutput Gear Speed (high) (rpm) 1060 rpmRear Wheel Speed (high) (rpm) 314.507505 rpm
Minimum Spring Constant (lbf/in) 2.893935408 lbf/inConcave Profile? 1 boolean
Maximum Pressure Angle (deg) 1.504222056 degAllowable Radius of Curvature? (roller) 1 boolean
Minimum Concave Radius of Curvature (in) 9999 inSpring Force % 3.843095842 %
Spring Compression (in) 3.750327639 in
Speaker: Tom Gentry
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Efficiency
Major Contributions: Kinematics ~94% (High), ~99.8% (low) 2 Chains ~98% each Follower Sliding Friction ~7.5% (High),
~1.8% (Low) Roller Follower Rolling Resistance ~3.2% Spring Energy ~3.2%
High Gear Efficiency – 80% Low Gear Efficiency – 86%
Speaker: Tom Gentry
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Losses
Speaker: Tom Gentry
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0.00%
1.00%
2.00%
3.00%
4.00%
5.00%
6.00%
7.00%
8.00%
9.00%
0 50 100 150 200 250 300 350 400
Loss
%
Cam Angle
Major Losses
Chain Losses Spring Losses Cam Pressure Angle Losses Follower Pressure Angle Losses Friction and Rolling Resistance Losses
- Friction and Rolling
- Chain
- Spring
- Cam Pressure Angle- Follower Pressure Angle
Due To:
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Efficiency
Speaker: Tom Gentry
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0 50 100 150 200 250 300 350 4000.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
100.00%
Total Efficiency
High GearLow Gear
Cam Angle
Syste
m E
fficie
ncy
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Design Optimization
Parametric Model Optimization method
Gradient based Non gradient based
Inputs Ranges/types
Outputs Maximize/Minimize/Target
Speaker: Tom Gentry
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Excel Parametric System Model
Speaker: Tom Gentry
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Isight Capabilities47
Speaker: Tom Gentry
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Isight Capabilities
http://www.simulia.com/download/products/Fiper_Isight35_web.pdf
Speaker: Tom Gentry
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Gear Ratio
Speaker: Andrew Shaw
High Gear (3.5:1) Low Gear (1:1)
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Output Analysis – Gear Ratios and Torques
Gear Ratios: High Gear Low Gear UnitStart angle 0.0 0.0 radEnd Angle 0.5 0.1 rad
Output Travel per rise 0.5 0.1 radOutput Travel per rise 26.7 8.1 deg
Output Travel per crank 1029.3 310.8 degBack wheel per crank 1684.3 508.5 deg
Final ratio 4.7 1.4 :1Total Ratio 3.3
Shaft Torque (low Gear) (ft-lb)Input Shaft 114.8293963
Gearbox Input 11.9Output Gear 170.1Rear Wheel 103.9
50
Speaker: Andrew Shaw
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Follower Type
Pros: Flexibility with cam
profile (positive radius of curvature)
Multiple rises Less wear
Cons: More Parts Slightly more contact
stress
Pros: Lower number of
parts Pressure angle is
always 0 Cons:
Wear Friction Losses Spring Packaging
Translating Roller Follower
Oscillating Flat Faced Follower
Speaker: Andrew Shaw
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Roller Follower Selection
Max Allowable stress of 100 kpsi given by manufacturer
Stud Bending Stress
Cam Contact Stress
Follower Bearing Fatigue
Speaker: Andrew Shaw
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Contact Stress
Max Contact Pressure
Principle Stresses
Speaker: Andrew Shaw
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Contact Stress cont.
Speaker: Andrew Shaw
σx= -34922.175525717 PSIσy= -23696.480153326 PSIσz= -96310.995880065 PSI
taumax= 36307.257863370 PSI
Cam Roller
AISI 4140 AISI 52100
Processing Quenched & Tempered @ 425°C
Quenched & Tempered
Tensile Strength(kpsi) 181 325
Yield Strength(kpsi) 165 295
Brinell Hardness 370 518
Factor of Safety 1.87 3.73
Normally contact strength is a factor of 2 more than Sut
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Contact Stress cont.
To reduce the contact force: Change the transmission kinematic parameters
Increase cam rotation speed Increase amount of rise Increase number of cam rises
To reduce contact stress: Reduce the contact force Increase the diameters of the contacting bodies Reduce the modulus of elasticity of the materials
involved Change the geometry of the contact region
Speaker: Andrew Shaw
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Contact Fatigue
1000 1200 1400 1600 1800 20000.4
0.6
0.8
1
1.2
1.4
1.6Factor of Safety The-
oretical
Factor of Safety
Hours
Facto
r of
Safe
ty
•This is with an experimental K = 9000 for 4150 steel. Our calculated K needed is 108.
•Take away is we can use a weaker material but for yielding we are using a harder material, which gives an infinite life for contact fatigue.
1000 1500 20000
5E+016
1E+017
1.5E+017
Factor of Safety Needed K
Factor of Safety
Hours
Facto
r of
Safe
ty56
Speaker: Andrew Shaw
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Follower Arm Stress
,a f a nomK
,m f m nomK
11
1
tf
KK
ar
0.5e utS S
ba utk aS
1
/ /fa e m ut
nS S
( )
yy
a M
Sn
e a b c d e f eS k k k k k k S
Critical plane at the end near fillet.
Speaker: Andrew Shaw
Factor of safety=2.55
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Spring Force
A spring is used to keep the follower in contact with cam and must be capable of applying a force equal to inertia force.
F - mfg - S(X - xo) = mf Af
F = contact force, mf = mass of the follower, Af = acceleration of the follower.
Neglect gravity
Speaker: Andrew Shaw
Spring Constant Preload 8 lbfFollower Mass 0.00621118 slug
Minimum Spring Constant 2.893935408 lbf/inMinimum Net Force 282.4 lbf
Spring Force/min net force % 3.8Spring Compression 3.8 in
0 50 100 150 200 250 300 350 400
-0.4
-0.2
0
0.2
0.4
Inertial Force on Cam
Follower 1 Follower 2
Cam Angle (deg.)
Forc
e (
lbf)
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Sprag Clutch
Selected based on torque, speed and axial load
Transmits high torque compared to other devices
Similar to a bearing but allows only one way rotation
Speaker: Andrew Shaw
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Bearing Selection
60 D DL L n rpmDn hrsDL
10D
Lx
L
10L RatingLife
1/
10 1/0 0( )(1 )
a
DD b
D
xC F
x x R
0.9DR 0 , , and x b Wiebull Parameters 3a
•No Axial Load•Sealed single row deep groove ball bearings•Bearings are available in suitable sizes for this project
Speaker: Andrew Shaw
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Material Selection
Cam RollerAISI 4140 AISI 52100
Processing Quenched & Tempered @ 425°C
Quenched & Tempered
Tensile Strength(kpsi) 181 325
Yield Strength(kpsi) 165 295
Brinell Hardness 370 518
Endurance Limit Strength (kpsi)
90.5 100
Modulus of Elasticity(106 psi)
29.2 29.5
Poisson’s Ratio .29 .3
Machinability .65 .40Speaker: Andrew Shaw
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Packaging
Mounts to existing bike frame with clamps
Provides adequate clearances Aluminum case Chain tensioner Translucent side to see operation Low center of gravityFollower length 8.3 inches
Minimum Case Height 5.6 inchesIncluding Followers 11.1 inches
Speaker: Andrew Shaw
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BOM
CONCEPT 1 BOM
ITEM COMPANY PART # QUANTITY Price Line Cost
RBC Follower Bearing Engineering S16LWRBC 2 $13.80 $27.60 Rail Guide Grainger 2CRR8 2 $19.25 $38.50 Carriage Grainger 2RLE4 2 $27.80 $55.60
Sprag Clutch VXB Kit8182 2 $19.95 $39.90 Shaft 8x1/2 McMaster-Carr 6061K103 2 $4.33 $8.66
Bearing McMaster-Carr 6384K49 4 $8.33 $33.32 Sprocket McMaster-Carr 6280K661 2 $11.05 $22.10
Chain Price Point 25068 2 $12.98 $25.96 Aluminum for Housing Metal Depot S318 1 $37.40 $37.40
Follower Arms AL 6061 1'x1.5"x.5" McMaster-Carr 6023K251 1 $15.92 $15.92
Springs McMaster-Carr 9657K128 (12ct.) 1 $6.97 $6.97
Retainer Clips for 1/2" Shaft McMaster-Carr 9590A122 (10ct.) 1 $8.94 $8.94
Aluminum Carriage 5"x2"x2" Metal Depot SQ32 1 $26.94 $26.94 Woodruff Key Home Depot 79758 2 $0.25 $0.50
4140 Steel for Cam McMaster-Carr 8960K61 2 $23.96 $47.92 Miscellaneous 1 $100.00 $100.00
Total = $496.23 Speaker: Andrew Shaw
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Control System-Concept Selection-Functional Diagrams-Equipment Selection
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System Control Concept Selection
Mechanical Electro-Mechanical
Electrical
Weight High Medium Medium
Output Force Very Low High High
Adjustability Very Low Medium Very High
Accuracy High Low Very High
Cost Medium Low High
Power Source Rider Battery Battery
Position Control Difficulty
Medium High Very Low
Speaker: Brian Pigman
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Functional Diagram
Wheel Speed
Optimal Cadence
Desired Gear Ratio/Position
Gear Position
PLC Controller
Drive and Motor
Encoder
Power Source
Speaker: Brian Pigman
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Electrical Control Components
- Optical Encoder- Transduces wheel speed to pulse
- PLC- Produces output voltage based on programmed input signal conditions
- Motor Drive- Delivers power to motor- Motor- Provides output position- Lead Screw- Converts Rotary Positioning
to Linear
Speaker: Brian Pigman
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Motor Selection
Stepper Servo
Holding Torque X
Price X
Encoder Required X
Continuous X
Accuracy X X
Speaker: Brian Pigman
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Lead Screw Force
http://www.smallmotors.com/html/lead_screws.html
Fcam
Fx
Fy
Tout
Ѳ*sin( )x camF F
0xF
The follower arm and output shaft are supported by a track. There are no moments and Fx is the only force on the lead screw
Speaker: Brian Pigman
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Lead Screw Force
Speaker: Brian Pigman
0
0.2
0.4
0.6
0.8
1
1.2
0
5
10
15
20
25
30
35
40
0 50 100 150 200 250 300 350 400
Forc
e (lb
f)
Cam Angle (deg)
Lead Screw Force
Lead Screw Force
Lift Follower 1
Lift Follower 2
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Motor Torque
η- Efficiency P- screw pitch (revolutions/inch) F- axial load on lead screw T – required motor torque
Speaker: Brian Pigman
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Motor Torque
Typical lead screw efficiency – around .4 Screw Pitch – 10rev/1in Axial Load – 50lb
Gives a required T = 20.7 oz-in
Speaker: Brian Pigman
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Maximum Torque RPM
Assume Maximum acceleration or deceleration will
occur when braking from full speed (~35mph) to zero
Braking within 6 seconds Neglect inertia of motor and shaft
At Maximum, carriage needs to travel 6” in 6 seconds
Speaker: Brian Pigman
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Maximum Torque RPM
6 in/6sec = 1 in/sec 1 in/sec * (10 rev/in) = 10 rev/sec Maximum Torque of 20.7oz-in needed at
10rps
At the given parameters the motor produces around 42 oz-in of torque
24Vdc at 10rps
Speaker: Brian Pigman
74
http://www.omega.com/Auto/pdf/2035.pdf
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Hardware
Motor – Stepper Motor OMHT17-275 Drive – 2035 Programmable Logic Controller - ELC-
PB14NNDR Encoder - RB-Cyt-39
http://www.hurst-motors.com/hybridstepper.html http://www.omega.com/pptst/2035.html
http://www.omega.com/pptst/ELC_PLC.html
http://www.robotshop.com/cytron-simple-rotary-encoder-kit.html Speaker: Ernie Stoops
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Lead Screw Buckling Analysis
F – Force to cause buckling
E – Modulus of Elasticity
I – Area Moment of Inertia
K – End Conditions
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
100002000030000400005000060000700008000090000
100000
Buckling Force vs. Diameter
F
Diameter (in)Forc
e (
lb)
At .5”, 5,800 lbf is needed to buckle
Max force is just over 40 lbf
Speaker: Ernie Stoops
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Power & Weight
24 V System Running 56 W Battery is 5 A-h
Gives a battery life of just over 1.7 hours
Weight of major componentsObject Weight (lbs)
PLC 0.348Battery 4Motor 0.79
Motor Drive 0.56255.7005 TOTAL
Speaker: Ernie Stoops
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Controls BOM
ITEM COMPANY PART # QUANTITY PRICEStepper Motor Omega OMHT17-275 1 $49.50
Motor Drive Omega 2035 1 $170.10 PLC Omega ELC-PB14NNDR 1 $181.80
Rotary Encoder Cytron Technologies RB-Cyt-39 1 $11.29 24 V Rechargeable Battery All-Battery 11809 1 $99.99
Battery Charger All-Battery 1007 1 $12.87 DIN Rail McMaster-Carr 8961K13 1 $4.74
Lead Screw McMaster-Carr 93255A431 1 $8.96 Platform Nut Fine Line Automation GRP108-00 1 $16.50 PLC Software Omega ELCSOFT 1 $247.50 PLC-PC Cable Omega ELC-CBPCELC1 1 $38.70
Coupler Servo City CSC-.250-.375 1 $12.99 Thrust Bearing McMaster-Carr 5909K31 1 $2.76
Total = $857.70
Speaker: Ernie Stoops
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Secondary Design: Variable Cam
DESIGN OVERVIEW79
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Assembly Models
Speaker: Andrew Shaw
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Assembly Models
Speaker: Andrew Shaw
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Assembly Models – Low Gear82
Speaker: Andrew Shaw
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Assembly Models – High Gear83
Speaker: Andrew Shaw
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Assembly Models
Speaker: Andrew Shaw
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Assembly Models
Speaker: Andrew Shaw
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Cam Profile
Produce single profile and shrink down by factor
Speaker: Tom Gentry
86
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Secondary Design: Variable Cam
Design Analysis87
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Cam Profile
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
v (i
n)
u ( in)
Cam Profile
Pitch Curve Base Circle Cam Surface Roller
-3
-2
-1
0
1
2
3
-3 -2 -1 0 1 2 3
v (i
n)
u ( in)
Cam Profile
Pitch Curve Base Circle Cam Surface Roller
Low Gear High Gear
Speaker: Tom Gentry
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Kinematics
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
0 50 100 150 200 250 300 350 400
Angl
e (r
ad)
Cam Angle (deg)
Follower Angle
Follower 1 high gear Follower 2 High gear
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 50 100 150 200 250 300 350 400
Angl
e (r
ad)
Cam Angle (deg)
Follower Angle
Follower 1 high gear Follower 2 High gear
Low Gear High Gear
Speaker: Tom Gentry
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Output Analysis
0
50
100
150
200
250
300
0 50 100 150 200 250 300 350 400
Torq
ue (ft
-lbf)
Cam Angle (Degrees)
Clutch Torque
High Gear Low Gear
0
50
100
150
200
250
300
0 50 100 150 200 250 300 350 400
Torq
ue (ft
-lbf)
Cam Angle (Degrees)
Clutch Torque
High Gear Low Gear
Low Gear High Gear
Speaker: Tom Gentry
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Output Analysis
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
0 50 100 150 200 250 300 350 400Forc
e (lb
f)
Cam Angle (deg.)
Inertial Force on Cam
Follower 1 Follower 2
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 50 100 150 200 250 300 350 400Forc
e (lb
f)
Cam Angle (deg.)
Inertial Force on Cam
Follower 1 Follower 2
Low Gear High Gear
Speaker: Tom Gentry
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Output Analysis – Spring Rate
Preload 8 lbfFollower Mass 0.00621118 slug
Minimum Spring Constant 3.750161675 lbf/inMinimum Net Force 270.9 lbf
Spring Force/min net force % 4.3Spring Compression 3.1 in
8 lbf0.00621118 slug
0 lbf/in1263.4 lbf
0.60.0 in
Low GearHigh Gear
Speaker: Tom Gentry
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Output Analysis – Gear Ratios
Gear Ratios: High GearStart angle 0.0End Angle 0.3
Output Travel per rise 0.3Output Travel per rise 19.2
Output Travel per crank 766.8Back wheel per crank 1254.8
Final ratio 3.5
Low Gear Unit0.0 rad0.1 rad0.1 rad6.0 deg
241.8 deg395.6 deg
1.1 :1
Speaker: Tom Gentry
93
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Output Analysis – Torques
Shaft Torque (low Gear) (ft-lb)Input Shaft 114.8293963
Gearbox Input 11.5Output Gear 66.8Rear Wheel 40.8
Torque (High Gear) (ft-lb)114.8293963
11.566.840.8
Torque (low Gear) (ft-lb)114.8293963
11.5219.3134.0
Speaker: Tom Gentry
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BOM
CONCEPT 2 BOMITEM COMPANY PART # QUANTITY Price Line Cost
RBC Follower Bearing Engineering S16LWRBC 2 $13.80 $27.60
Cam McMaster-Carr 9034K69 1 $149.04 $149.04 Bevel Gear Set Grainger 3ZP64 1 $115.15 $115.15 Lead Screw Nut McMaster-Carr 6350K42 1 $23.58 $23.58
Sprag Clutch VXB Kit8182 2 $19.95 $39.90 Shaft 8x1/2 McMaster-Carr 6061K103 2 $4.33 $8.66
Ball Spline Shaft Gridline Industrial SSP6S150mm 1 $102.58 $102.58 Ball Spline Nut Grainger 3HVC3 1 $101.00 $101.00
Bearing McMaster-Carr 6384K49 6 $8.33 $49.98 Sprocket McMaster-Carr 6280K661 2 $11.05 $22.10
Chain Price Point 25068 2 $12.98 $25.96 Aluminum for Housing Metal Depot S318 1 $37.40 $37.40
Follower Arms AL 6061 1'x1.5"x.5" McMaster-Carr 6023K251 1 $15.92 $15.92 Springs McMaster-Carr 9657K128 (12ct.) 1 $6.97 $6.97
Retainer Clips for 1/2" Shaft McMaster-Carr 9590A122 (10ct.) 1 $8.94 $8.94 32 Tooth Spur Gear McMaster-Carr 6325K85 3 $23.98 $71.94 65 Tooth Spur Gear McMaster-Carr 6325K73 1 $37.14 $37.14 Aluminum 2"x1"x1" McMaster-Carr 9008K141 1 $10.41 $10.41 Aluminum 3"x5"x1" McMaster-Carr 8975K313 1 $23.16 $23.16 Aluminum 1'x2"x2" Metal Depot SQ32 1 $26.94 $26.94
Woodruff Key Home Depot 79758 2 $0.25 $0.50 Miscellaneous 1 $100.00 $100.00
Total = $1,004.87
Speaker: Ernie Stoops
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Final Results
Design Comparison96
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Comparison of Concepts
Pros: -Easier to Machine-More efficient-Lighter weight-Cheaper ($1360)Cons:-Moving output shaft
Pros:-Possible neutral gear-Multiple input and
output configurationsCons:-More Shift Force-Heavier-Larger Package-Cost ($1870)
Non- Variable Cam Variable Cam
Speaker: Ernie Stoops
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Schedule
Legend
SHIFT GANTT CHART On Time ScheduledA Approval
Task Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 12 Week 13 Week 14
Organization Team Name A Team Logo A
Mission Statement A Goals A
Concept Design Design Criteria A
Concept Sketches A Preliminary Design Review
Critical Design Review Fabrication
Assembly & Integration Testing
Delivery
Speaker: Ernie Stoops
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Risk
Gearbox Time Machining Packaging
Control System Time New
Programming Language
Electrical failure
Speaker: Ernie Stoops
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Conclusion
SHIFT’s CVT will provide fully automatic, continuously variable gearing system that will improve experience for all riders
Team SHIFT has skills, dedication and drive to complete the development of the Bicycle CVT in allotted time
Request approval to continue with design process and begin Prototyping and preparing for Critical Design Review
Speaker: Ernie Stoops
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Acknowledgements
Professor StarkeyProfessor PennockProfessor SadeghiMike Moya
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Speaker: Ernie Stoops
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Questions?
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Problems encountered
Variable diameter pulley:
Low Efficiency Requires High Rotational
Speeds Hard to Control Unable to Shift while
Stationary
Hydrostatic: Heavy
Inefficient
http://cmgonline.com/content/view/2489/57/
http://auto.howstuffworks.com/cvt4.htm
Speaker: Nick Schwartzers
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Problems encountered cont.
Toroidal: High Contact Stress Requires Traction Fluid Tight Tolerances
required Balance of
Friction(wear), Normal Force(contact stress), Radius(size), and Angular Velocity(losses)
P T
P Fr
P Nr
http://www.nsk.com/products/automotive/drive/hcvt/
Speaker: Nick Schwartzers
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