Advisor: Prof. Kishore Pochiraju

Group #10:Biruk Assefa

Lazaro Cosma

Josh Ottinger

Yukinori Sato

ME424 Senior Design

February 16th, 2006

2

Agenda

• Problem Statement

• Conceptual Design Re-cap

• Feedback from ME423 Panel

• Prototype Design

• Engineering Analysis

• Fabrication Plan

• Performance Testing

• Conclusion

3

Problem Statement• ME 423 Re-cap

– Design a device to harness wave energy at a remote location

– Innovative conceptual design with engineering analysis

• Goals for ME 424– Finalize prototype design– Fabricate a working prototype– Test prototype in wave tank– Analyze test data to improve original design

4

Major Issues• Original plan to purchase CoTS products

– Specifications of components– Scaling factor

• Optimal design versus fabrication constraints / issues

• Opening of Davidson Laboratory -scheduled alternative testing facility

• Optimizing current design with ME budget

5

Conceptual Design Re-cap (ME 423)

Full-Wave Rectification Device• Buoy – 6ft diameter, 2ft height• Reel – Drum diameter 3 inches• Shaft – AISI 1045 Steel (1” diameter)• Rectifier – 5 gears, 2 unidirectional clutches• Gearbox – 180 degree parallel shaft• Flywheel – Size determined through testing• Alternator – Optimal speed ~ 300 rpm• Battery – Deep cycle battery• Electronics – Control Alternator EMF

Estimated Budget = $ 1915

6

Actions from ME423 Feedback• Concerns about

excessive mechanical components – Simplified prototype design

• Alternator efficiency – Typical car alternator

efficiency of 50% at 300RPM

• Ambiguity of drag and natural frequency of the device – Will be determined through

testing

• Water-proofing Device

7

Considerations for Prototype

• Rectifier– Time and Cost constraint – Replaced with half-wave rectifier– Harvesting more kinetic energy on upstroke– Minimizes required spring torque– Simplicity

• Less mechanical components• Higher reliability and efficiency

• Scaling– Ease of transportation for testing– Time and Cost constraint

8

Considerations for Prototype

• Alternator– Low operational RPM

preferred– Budget constraints

• Custom-built Low RPM Alternator ~ $500

• Used car alternator (Higher operational RPM range) ~ $10

– Car alternator tested at AutoZone

• Charging• Discharging• Diodes

9

Clutch housingFlywheel

Reel

Gear Box

Alternator

Prototype Design

• Wooden base• Shaft mounted reel• Half-wave rectifier -

Unidirectional Clutch• Two-stage adjustable gear box• Car alternator

Batteries

Wooden Base

10

Prototype Design Cont.

Reel casing

Cone shaped hole

Buoy Main Casing

• Scaled Buoy (1:1.5)• Diameter = 4ft• Height = 1.5 ft

• Cone shaped hole• Allows freedom of cable movement

• Device centered on top of buoy

11

Gear Box

Gear box (gear ratio: 10)

Gear box (gear ratio: 20)

Two stage gear Box

• First stage (10 pitch gears):

• 60 teeth to 15 teeth ( 4:1 gear ratio)

• Second stage (12 pitch gears):

• 60 teeth to 24 teeth ( 2.5:1 gear ratio)

• 60 teeth to 12 teeth ( 5:1 gear ratio) Initially:Two gear ratios (10:1 and 20:1) will be tested

Adjustable gear box Design:

• Input and output shaft immovable

• Idler shaft will be adjusted to needed position

12

Gear Box Analysis

• Input Torque & RPM known • Primary failure mechanism

– Bending Stress of Spur Gear Teeth

• Utilized Design Modules– Size up gear

• Face width, pitch, maximum ratio possible for each stage

– Factor of Safety of 1.5– Due to high input torques,

Face width of ¾” and greater required

Design Equation forBending of Spur Gear Teeth

Given information that is common to both gears in the set: = 14.5 degrees Pressure angle P d = 12 teeth/in Diametral pitchF = 0.75 inches Face width Wt = 176.4 lbf Transmitted load

v t = 288 ft/min Pitch line velocity

SF = 1.50 Factor of safety

Given information that may be different for each gear in the set: Pinion Gear

N i = 60 24 teeth Number of teethMaterial = 1018 Steel 1018 Steel Material type

Values found from the above information and inserted by the designer:s at = 50,000 50,000 psi Allowable stressJ = 0.42 0.39 Geometry factor

Values computed using the above information:K v = 1.23 Dynamic factorK m = 2.3 Load distribution factors t = 18,869 20,321 psi Left-hand side of eqn.

RHS 33,333 33,333 psi Right-hand side of eqn.

Status SAFE SAFE

RTF

NatBmdsvot KKS

Ys

J

KK

F

PKKKW

13

Shaft Analysis

Shaft Diameter (inches)

Max shear stress (Ksi)

Max Von - Mises stress (Ksi) Fos (Von - mises) Fos (Shear)

1/2 71.8 (XZ plane) 125 2 1.7

5/8 36.6 (XZ plane) 66.2 3.8 3.3

3/4 21.7 (XZ plane) 38.1 6.6 5.7

1 9.5 (XZ plane) 16.5 15 13

Shaft analysis of 5/8” diameter shaft

New shaft analysis carried out for modified prototype design

• Shaft material Chosen: AISI 1566 Steel

• Reason: Strong and cheap

• Factor of safety chosen: 2

• Max Torque applied: 137 lb-ft

• 5/8” shaft or greater meet design

requirements

14

Electronics

Input RPM Low?

Charging Voltage > 14.4V?

Decrease Rotor EMF

Increase Rotor EMF

Yes

Yes

No

No

MICROCONTROLLER LOGIC

Relay

Battery

PWM AlternatorRotor

Charging Voltage

Rotor Voltage

Legend: Signal Current

AlternatorStator

Encoder

RPM

• Control Rotor (Field) EMF• Feedback of RPM and Voltage• 3 approaches considered• Selected approach:

– PWM and relay

• Encoder and RelayBrainStem GP 1.0

Microcontroller Module

BrainStem

Charging Voltage

Need to figure out this reference RPM

15

Electronics

BatteryBrainStem

5V Power Source

Voltage Divider

+-

Stator

Rotor (Field)

Relay

Encoder

Alternator

16

Technical Specifications

Buoy Specifications• Buoy diameter 48” and height 18”• Buoy material: Urethane foamReel & Cable Specifications• Cable: nylon-coated galvanized steel• Total cable travel: 108”• Cable diameter: 3/32" • Maximum spring recoil strength: 35lbs• Reel outer diameter 6” and drum

diameter 3.5”Shaft Specifications• All shafts sized to withstand the max

input cable tension force of 942 lbs• Shaft diameters: 1.25”, 1”, 3/4” & 5/8”

Clutch Specifications• Maximum torque: 133lb-ft• Bore diameter: 1.18” (30mm)Gearbox Specifications• Two-stages• Adjustable gear ratio: 1:10 to 1:20• Maximum input torque: 137 lb-ft• Factor Of Safety 1.5Alternator Specifications• Bonneville ’90 automobile alternatorMicrocontroller• Brainstem GP 1.0• 5 channel, 10 bit A/D• 5 digital I/O lines• Runs up to 4 programs concurrently

Overall System Specifications• Estimated device weight: 235lbs• Overall Height: 28”

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Fabrication Plan• Important Considerations

– Shafts• Align to reduce bending and vibrations• Machine shafts to fit commercial products

– Components must be securely mounted– Waterproof casing

1.18” OD(Machine)

1 1/4” OD1” OD

3/4” OD

5/8” OD 5/8” OD (Machine) 3/4” OD

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Fabrication Plan

Stationary Mount

Connected to Drum

Clutch Bearing

• Stationary mount for spring reel• Shaft mounted directly to drum -

Allowing torque to be transmitted through device

• Mounted bearing supplies critical support to the reel

• Clutch connected to gearbox through custom housing

• Placement of couplers allows for easy maintenance

• Alternator mount is set up for simple exchanges of alternator

19

Fabrication Plan

• Casing is designed to keep all components away from the water except for the reel

• The reel is encased so it is the only component exposed

• Sealed lid for easy accessibility

20

Performance Testing• Taguchi Method

– Orthogonal Array Matrix• Optimally perform tests

while minimizing runs– Current set-up consists of 4

variables with 3 stages• Full scale testing: 81 runs• Orthogonal Matrix: 9 runs

Experiment Number

Variables

Wave Height / Wave Period Alternator EMF Gear Ratio Flywheel Size

(inches) / (seconds) (Voltage) (ratio) (weight, inertia)

1 4 / 3 A 10:1 D

2 4 / 3 B 15:1 E

3 4 / 3 C 20:1 F

4 8 / 6 A 15:1 F

5 8 / 6 B 20:1 D

6 8 / 6 C 10:1 E

7 12 / 10 A 20:1 E

8 12 / 10 B 10:1 F

9 12 / 10 C 15:1 D

• Wave Tank Testing– Davidson Laboratory

• Currently under construction• ETOC: April – May 2006

– Webb Institute (Long Island, NY)• Scheduled for Mid-April 2006

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Recording Test Results• Variables:

– Wave Height– Heave– Input Power

• Alternator RPM• Alternator Torque

– Output Power• Charging Voltage• Charging Current

Prototype Test Equipments

DAQ

LabViewMonitor, Record &

Analyze

PC

Data

22

Conclusion• Tasks accomplished:

– Finalized prototype design– Ordered majority of parts– Workbench in Davidson Laboratory

• What’s Next:– Order remaining parts– Fabricate buoy– Begin assembly

23

Gantt chart

24

Part Name Description Quantity Total CostReelShaft Mount Reel Spring Loaded Reel 1 $ 110.58

GearsInput Gear 10 Pitch, 1" face, 60 Teeth 1144 Steel 1 $ 50.06 Idler Gear_1 10 Pitch, 1" face, 15 Teeth 1144 Steel 1 $ 20.62 Idler Gear_2 12 Pitch, 3/4" face, 60 Teeth 1144 Steel 1 $ 51.53 Output Gear_1 12 Pitch, 3/4" face, 24 Teeth 1144 Steel 1 $ 24.79 Output Gear_2 12 Pitch, 3/4" face, 12 Teeth 1144 Steel 1 $ 13.06

Shafts1.25" OD 12" in length, 1566 Steel 1 $ 22.00 1" OD 18" in length, 1566 Steel 1 $ 25.20 3/4" OD 36" in length, 1566 Steel 1 $ 36.31 5/8" OD 12" in length, 1566 Steel 1 $ 9.78 7/16" x 7/16" 12" in length, High Carbon Steel: Standard 1 $ 9.99

One-way ClutchCSK 30 Sprag clutch w/ 6200 series ball bearing Torque rating: 133 ft.lbs 1 $ 70.00

Mounts1 1/4"OD Base Aluminum Base Mounted Self-Lubricating Bronze Sleeve Bearings 1 $ 29.64 3/4"OD Base Aluminum Base Mounted Self-Lubricating Bronze Sleeve Bearings 1 $ 12.96 1"OD Flange Stamped steel Flange Mounted Ball Bearings 1 $ 12.77 3/4"OD Flange Stamped steel Flange Mounted Ball Bearings 2 $ 23.80 5/8"OD Flange Stamped steel Flange Mounted Ball Bearings 1 $ 11.33

CouplerSet Screw Coupler Steel One-Piece Set-Screw Coupling 3/4" Bore, 1-1/2" Od, 2" Length 1 $ 10.62 Set Screw Coupler Steel One-Piece Set-Screw Coupling 5/8" Bore, 1-1/4" Od, 2" Length 1 $ 9.39

BuoyUrethane Foam 1 $ -

CasingHDPE sheets High Density Polyethylene (HDPE) Sheet 1/4" Thick, 48" X 48" 2 $ 86.26

ElectronicsMicrocontroller Brainstem GP 1.0 1 -$ Serial Interface Connector Connects microcontroller to a PC 1 11.75$ Relay 12VDC/30A, solenoid 1 6.29$

Total $658.73

ME 424 Budget