P14042: Una -Crutch

P14042: UNA-CRUTCHRight Move, Right Place, Right Time

Detailed Design ReviewAna AllenJoanna Dzionara-NorsenBeverly LirianoDan Sawicki

AgendaReview of Preliminary Detailed Design Review

Review of Final Design• Features of Crutch• Materials• Cost Analysis

Feasibility of Design• FEA Analysis• Buckling Analysis

Review of Test Plan

Project Plan MSD II

REVIEW FROM PRELIMINARY DDR

Crutch A

• Pros:• Lightweight • Easy to manufacture• Sliding button connective

mechanism• Cons:

• Design resembles standard axilla crutch

Sliding button

Crutch B

• Pros:• Aesthetically different from

standard axilla crutch• Pads tested during user

feedback

• Cons:• Complicated to connect• Hard to Manufacture

Notes from Preliminary DDR

Notes from Preliminary DDR

REVIEW OF FINAL DESIGN

Revised Features of Connective Mechanism

More Durable than Nylon

Higher Strength Material such as SteelAlternate Connective Mechanism

Postponement

Bill of MaterialsBill of Materials

Axilla Pad FrameAxilla Pad Frame Pad

Screws to connect Axilla Pad frame to shaftShafts

Handle FrameHandle Frame Pad

Female Button BlockMale Button Block

Pin to connect/adjust handle frame to shaftScrews to connect shaft to Base connection

Base ConnectionHeight Adjustment Shaft

Button for Height AdjustmentTip

Brinkman Lab Parts









Bar Stock









Pins/ Screws/ Buttons

FEASIBILITY OF DESIGN

The Six Key Components of the Una-Crutch

Item Number Part1 Shaft

2 Axilla Pad Frame

3 Adjustment Shaft

4 Tip

5 Handle

6 Base Connection3

6

1

4

5

2

Engineering Requirements

Rqmt. #

Importance

Source Function

Engr. Require

ment (metric)

Unit of

Measure

Marginal

ValueIdeal Value

Comments/Status

Desired

Direction

S1 9 CR3, CR4Minimizes deflection under maximum

user weight for any crutch configuration (single and double)

Deflection in 0.1 0.05 -

S2 9 CR3, CR4Do not fracture or break under user load when weight is concentrated on one crutch or both crutches as a unit.

User Weight lbs 200 300 215 lbs is average: +

S3 9CR4, CR6, CR12

User will be able to use the Una-Crutch without compromising comfort Comfort scale 2 1

Based off Comfort Pain Scale (1-Best, 5-Worst)

-

S4 9 CR8, CR12

High coefficient of friction on normal surfaces

Slip Resistance N/A 0.75 1 +

S5 9 CR1, CR13

Interfacing mechanism does not unlock due to user weight Connectivity lbs 5 3 -

S6 9 CR1, CR13 Short disconnect time Separability seconds 30 15 -

S7 9 CR7 Crutch combination is not too heavy Weight lbs < 7 < 5 -

S8 3CR5, CR6, CR10

Appealing to the majority Design Appeal yes/no yes yes +

S9 9 CR9, CR11 Adjust to fit users of varying heights Adjustability ft 5.2<h<5.8 4.8<h<6.4 -

Item 1: Shaft

Shaft Characteristics

Shaft Static FEA• Assume and no friction.• Material: 1060 Al Alloy

• YS = 27.6 MPA• Load at Point 1, P=150lb due to

E.R. #2.• Constraints:

• Fixed at Point 2• Roller at Point 1

1

1

2

Shaft Von Mises Stresses

Max stress < YS, Thus no failure.

Shaft Displacement

Item 2: Axilla Pad Frame

Axilla Pad Frame CharacteristicsMagnets TBDAnalysis to be completed by Gate Review

Axilla Pad Frame Static FEA• Assume and no friction.• Material: Nylon 6/10.

• YS = 139 MPA• Distributed load of P=300 lb

split across surface 1 due to E.R. #2.

• Constraints:• Fixed at Holes 2 and 3.

1

2

3

Axilla Pad Frame Von Mises Stresses


Axilla Pad Frame Displacement

Item 3: Adjustment Shaft

Adjustment Shaft Frame Characteristics

Adjustment Shaft Static FEA • Assume and no friction.• Material: Al 1060.

• YS = 27 MPA• Distributed load of P=300 lb

at hole 1 due to E.R. #2.• Constraints:

• Roller at Surface 2.• Fixed at Surface 3.

12

3

Adjustment Shaft Von Mises Stresses


Adjustment Shaft Displacement

Item 4: Tip

Tip Characteristics

Note: FEA Analysis neglected for Tip since part rests on Adjustment Shaft

Item 5: Handle

Handle Characteristics

Handle Static FEA• Assume and no friction.• Material: Nylon 6/10.

• YS = 139 MPA• Distributed load of P=300

lb along Surface 1 due to E.R. #2.

• Constraints:• Fixed at Shaft Surface 2.• Roller at Shaft Surface 3.

12

3

Handle Von Mises Stresses


Handle Displacement

Item#6 Base Connection

Base Connection Characteristics

Base Connection Analyses• Material: Nylon 6/10.

• YS = 139 MPA• Constraints location 1,1a, and 2

are fixed • Load of 300lb were places

locations 3 and 3a

1

2

1a

33a

Base Connection Von Mises Stresses


Base Connection Displacement

Buckling• Components and Materials:

• Shafts: Aluminum • Base Connection: Nylon 6/10• Adjustment Shaft: Aluminum

• Assumptions:• Half round cross-section and half round hollow cross-section• Pin-pin

• Use Euler formula:

Buckling Results• For no buckling to occur, load applied must be less than

the critical load• Shafts:

• Base Connection:

• Adjustment Shaft:

Load Applied (lb) Critical Load (lb) Buckle? Yes/No150 283 No



PROJECT PLAN

Gate Review

Updated BOM

Further Review of Axilla Pads• Magnet

Analysis• Material

Revised Handle Frame

Cost Analysis

Further Review of

Failure Modes

MSD II Project PlanTask Name Duration Start Finish Subsystem Level Prep/Build 11 days Mon 1/27/14 Mon 2/10/14 Subsystem Level Build/Test 15 days Tue 2/11/14 Mon 3/3/14 Subsystem & System Level Build/Test/Integrate 14 days Tue 3/4/14 Fri 3/21/14 System Level Build/Test/Integrate 16 days Mon 3/24/14 Mon 4/14/14 Verification & Validation 16 days Tue 4/22/14 Tue 5/13/14

Innovation Challenge

Grant Application

CAD Design and Analysis of

Alternate Connective Mechanism

Prototype of Alternate

Connective Mechanism

Prototype of Crutch A

User Feedback of Altered

Connective Mechanism

and Crutch A Prototype

QUESTIONS?Thank you everyone!

BACK UP SLIDES

Engineering Requirements

Rqmt. #

Importance

Source Function

Engr. Require

ment (metric)

Unit of

Measure

Marginal

ValueIdeal Value

Comments/Status

Desired

Direction

S1 9 CR3, CR4Minimizes deflection under maximum

user weight for any crutch configuration (single and double)

Deflection in 0.1 0.05 -

S2 9 CR3, CR4Do not fracture or break under user load when weight is concentrated on one crutch or both crutches as a unit.

User Weight lbs 200 300 215 lbs is average: +

S3 9CR4, CR6, CR12

User will be able to use the Una-Crutch without compromising comfort Comfort scale 2 1

Based off Comfort Pain Scale (1-Best, 5-Worst)

-

S4 9 CR8, CR12

High coefficient of friction on normal surfaces

Slip Resistance N/A 0.75 1 +

S5 9 CR1, CR13

Interfacing mechanism does not unlock due to user weight Connectivity lbs 5 3 -

S6 9 CR1, CR13 Short disconnect time Separability seconds 30 15 -

S7 9 CR7 Crutch combination is not too heavy Weight lbs < 7 < 5 -

S8 3CR5, CR6, CR10

Appealing to the majority Design Appeal yes/no yes yes +

S9 9 CR9, CR11 Adjust to fit users of varying heights Adjustability ft 5.2<h<5.8 4.8<h<6.4 -

Customer Requirements

Customer Rqmt. # Importance Description Comments/Status

CR1 9Comfort

Is adjustable to users of various heights

CR2 9 Ergonomically friendly to the user

CR3 9Durability

A single crutch can support the load of a user

CR4 9 Design product to last

CR5 3

Marketability

Low cost of production is absolute

CR6 3 Commercially marketable

CR7 3 Aesthetically appealing

CR8 9Versatility

An interfacing mechanism allows for easy coupling and uncoupling of the two independent crutches

CR9 9 Can be used outdoors and indoors

CR10 3

Ease of Use

Lightweight crutch assembly

CR11 9 Accommodate user daily functions

CR12 3 Intuitive assembly and disassembly

Risk Analysis# Risk L S I Action to Mitigate Action to Remediate

1Crutches (used individually

or connected) will not support the user

2 3 6 Perform stress analysis for many different materials Deformed crutch piece can be easily accessed and replaced

2 Connective mechanism failure 2 3 6 Perform stress and dynamic analysis for different

load configurations Redesign connective mechanism

3Crutch will lack slip resistance on some

surfaces1 3 3 Simulate possible force distribution Choose material with higher coefficient of

friction

4 Crutches will cause discomfort to the user 2 2 4 Conduct surveys with multiple prototypes Redesign including ergonomic issue

5 User load will force crutch to buckle 1 3 3 Design and computationally test the crutch with a

material with a high elastic modulusCreate a back-up design or a means of

strengthening the crutch frame

6 User treats crutch as a toy 2 2 4 High factor of safety - test crutch in all combinations of loading Strengthen the material

7 Handle snaps due to user force 2 2 4 Make handle with high elastic modulus

New handle can be placed on unit (adjustable handles will be

interchangeable)

8 The device will be too expensive to manufacture 1 2 2 Design Una-Crutch with common manufacturing

techniques - research manufacturingReturn and reconsider to manufacturing

process analysis

9 A team member leaves the team 1 3 3 Team communication to resolve issues Reconsider the customer requirements

and deliverables

10 Design is not patentable 3 1 3 Patent research and brainstorming Reconsider project deliverables

11User cannot connect the

two crutches while immobilized on one leg

2 3 6 Conduct surveys with prototypes while standing on one foot (simulate injury)

Reconsider product concept idea / discuss with customer to refocus the target group

12 User gets pinched when connecting crutches 1 2 2 Reduce sharp surfaces in connective mechanism Reconsider connective material/design

13User does not feel

comfortable using crutch on stairs

2 3 6 Test stair clearance Redesign to accommodate small spaces

Prototype Test Plan

Final Model Test Plan

Final Model Test Plan (continued)

Backup Slide: Shaft Strain

Backup Slide: Axilla Pad Strain

Backup Slide: Adjustment Shaft Strain

Backup Slide: Handle Strain

Documents

P14042: Una -Crutch