P14042: Una -Crutch
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Transcript of P14042: Una -Crutch
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P14042: UNA-CRUTCHRight Move, Right Place, Right Time
Subsystems Design ReviewAna AllenJoanna Dzionara-NorsenBeverly LirianoDan Sawicki
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AgendaReview (Weeks 1-6)
• Background• Problem Definition• Additional Project Deliverables
Identifying Critical Subsystems• Engineering Requirements• Risk Assessment• Functional Decomposition• System Architecture
Proof Of Concept• Overview of Prototypes / Prototype Test Plan• User Feedback• Second- Order Analysis
Feasibility• Manufacturing Analysis
Detailed Design Preview (Weeks 10-12)
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REVIEW (WEEKS 1-6)
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Current Product
Many designs all revolving around two SEPERATE crutches.
Una-Crutch is a design that can combine from 2 separate pieces into
1 universal device
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P14042 Problem Statement
Current State
• Standard axilla crutches• A prototype was developed by Kyra, but
the product is non-load bearing and has no effective connective mechanism
Desired State
• A functional product which is ergonomically friendly, has a quick and intuitive method of connection, and can be marketed to companies
Project Goals
• Perform analysis of standard axilla crutches, crutch patents, and assistive technologies used specifically for lower body injuries
Constraints• Consider Intellectual Property for the
connective mechanism
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Additional Project Deliverables
Functional prototype which will be targeted
towards the majority of crutch users and will be
available as a household item.
The product will have an aesthetic
appeal and will have the potential
to be manufactured
right away.
Patent Documentation• Logbook• Prove the concept –
prototyping• Protection of
Intellectual Property• Conduction of
market research
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Prototypes Introduced Week 6A B C
D E F
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IDENTIFYING CRITICAL SUBSYSTEMS
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Risk Assessment
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Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
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Functional Decomposition
Support independent user with lower extremity injury walking
from point A to point B in multiple types of environments.
Position Crutches
Access crutch
assembly
Permit height
adjustment
Permit connective versatility
Transport User
Support user weight
Maintain contact with the ground
Stabilize user in vertical position
Mobilizes user
Release UserDisengage from
crutch-user interface
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Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
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Engineering Requirements
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Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
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System Architecture
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Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
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Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg1. Connective Mechanism
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Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg1. Connective Mechanism
2. Axilla Pad/ Handles
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Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg1. Connective Mechanism
2. Axilla Pad/ Handles
3. Frame
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Critical Subsystems Defined
Connective Mechanism Frame Axilla Pad/
Handles
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PROOF-OF-CONCEPT
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Prototypes Introduced Week 6A B C
D E F
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Prototypes Introduced Week 6
REVISED
A B C
D E F
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Prototype G
• Pros:• Compact Design• Usable for all ages• Stable
• Cons:• Not necessarily aesthetically
pleasing• Two separate bases• Pad is in contact with the ground
Male/female mold
Pin
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Prototype H
• Pros:• Lightweight • Easy to manufacture• Sliding button connective
mechanism• Cons:
• Design resembles standard axilla crutch
Sliding button
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Prototypes to CreateB C
G H2.
Fra
mes
and
Con
nect
ive
Mec
hani
sms
1. A
xilla
Pad
s an
d H
andl
es
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Axilla Pads and HandlesPrototypes Created
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C
B
Frames and Connective MechanismsPrototype B and C
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Frames and Connective MechanismsPrototype G
G
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H
Frames and Connective MechanismsPrototype H
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Prototype Test Plan
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User FeedbackAxilla Pads and Handles
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User FeedbackAxilla Pads and Handles
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User FeedbackFrames and Connective Mechanisms
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Second-Order Analysis
Connective Mechanism Analysis
• Magnetic Analysis• Bike Clamp Analysis
B/C Prototype Analysis
• CAD Model• Spring Analysis• Deflection Analysis
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Magnetic Analysis
Magnet to a Steel Plate Example
Magnet to Magnet Example
Two configurations:
Magnet to MagnetMagnet to Plate
Two shapes:
Square/ RectangularCylindrical/ Disk
Analyzing Grade 42 magnets
Interfacing mechanism does not unlock due to user weight.Ideal value: 3 lbs.Marginal Value: 5 lbs.
Engineering Requirement S5:
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Magnetic Analysis
Magnetism Physics on a Crutch
• Pull Force: quantity required to separate two attracting magnets.• Pull Force Equations: The Lorentz Equations• Pull Force Increases as Area Increases.• Pull Force Decreases as Distance Increases.
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Magnetic Analysis
Configurations AnalyzedSquare Magnets Chosen
Easier to embed in material.Proper amount of Pull Force.
Square Magnet Grouping:Length (in) 1 1 1 1 1 1 1 1 1 5 5Width (in) 0.5 0.75 1 0.5 0.75 1 0.5 0.75 1 1 1
Surface Area (in^2) 0.5 0.75 1 0.5 0.75 1 0.5 0.75 1 5 5Thickness (in) 0.1875 0.1875 0.1875 0.1875 0.1875 0.1875 0.1875 0.1875 0.1875 0.1875 0.1875
Distance Between Magnets (in) 0 0 0 0.125 0.125 0.125 0.25 0.25 0.25 0.125 0.25
Pull Force Magnet to Magnet (lb) 17.06 21.93 24.65 5.45 7.66 9.12 2.67 3.97 4.9 19.92 12.24Pull Force Magnet to Plate (lb) 17.06 21.93 24.65 3.6 5.41 6.74 1.36 2.26 3 18.71 11.06
Current Magnets in Prototypes
1 2 3 4
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Magnet Overview
Prototype Design Tested
Note: If used in final design, magnets will have a small distance separating them.
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Bike Clamp Analysis• Split-Ring Clamp Type Shaft Collar• Analysis:
• Torque necessary to achieve pre-load• Axial holding force of seat post collar• Hoop Tension in collar
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Bike Clamp Analysis
Torque in Cap Screw• Assume:
• Cap screw is coarse pitch• Low or medium carbon• Non-permanent connection• Screw diameter = 6 mm
• Torque = 6.11 Nm
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Bike Clamp Analysis
Axial Holding Force• Assume:
• Coefficient of friction = 0.61• Fx = 13,000 N
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Bike Clamp Analysis
Hoop Tension• Assume:
• Collar width = 12 mm• Internal radius 6.35 mm• Internal pressure = 7.08 MPa
• Fh = 540 Pa
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Cheetah Leg Connection Mechanism
Grip Connection Mechanism
CAD Model: B/C Prototype
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Spring Analysis
• Analyzing Spring at Base of Crutch.• Normal Force = Spring Force• N = user load• Two Stresses on Spring:
• Torsion Shear Stress• Direct Shear Stress
N
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Spring Analysis
Results
• Stress absorbed by the springs results in a large stress.
• May give user more endurance to use crutches longer.
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 462.00E+05
2.20E+05
2.40E+05
2.60E+05
2.80E+05
3.00E+05
3.20E+05
3.40E+05
3.60E+05
3.80E+05
4.00E+05
2.000
2.200
2.400
2.600
2.800
3.000
3.200
3.400
Spring Analysis w/ k=100lb/in & kw=1.25 Spring Shear Stress [lb/in^2]
Spring Displace-ment [in]
θ[deg]
Sher
a St
ress
(psi
)
Sprin
g Di
spla
cem
ent (
in)
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Deflection of Cheetah Leg Base• Assume:
• Carbon fiber material• Circular cross-section
• r = 0.75in = 1.91x10-2m• R2 = 0.3 m
• Deflection = 0.08in = 0.002m
R2
M
D
P
P
P
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FEASIBILITY
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Manufacturing Processes
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Brinkman Lab Resources
3D Printing (Connective
Mechanisms)
Water Jet (Frames)
RTV Mold (Axilla Pads/ Hand grips)
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DETAILED DESIGN PREVIEW
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Detailed Design Phase (Weeks 10-12)
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Detailed Design Phase (Weeks 10-12)
Cost and Material Analysis (Friction Analysis)
Connective
Mechanism
Prototypes from
Brinkman Lab
Focus Group for
New Prototype
s
FEA and Detailed Design
Analysis
Bill of Materials
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QUESTIONS?Thank you!
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BACKUP SLIDES
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Customer Requirements
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Final Product Test Plan