presentation 3 full corrected red one final

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Towing Extension Mechanismfor Flatbeds

Team Members:Victor Marte Rosario 52945Rafael Romero Santiago 50416

Carlos Alvarado Phd.Hector Rodriguez Phd.

2/23/2011


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Agenda

Subsystem Trade Studies Subsystem Architecture into Components Trade Studies for Critical Components Sub-System Risk Assessment Project Planning


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Subsystem 1 Frame & Mobility

Owner Victor J. Marte


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Alternatives: Frame & Mobility

1. Two frame connected lifters withmanual expansion and contractionwith threaded screw casters

underneath a U shaped barperpendicular to the frame, screwthreaded caster provide themechanism a 360mobility. Frameand lifters will be resting on the Ushaped bar while the screw threaded

casters will be attached with nuts.


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Alternatives: Frame & Mobility

2. Two frame connected lifters with manualexpansion and contraction with tires,underneath a straight bar perpendicular tothe frame. Frame and lifters will be resting

on the straight bar while the pivotingmechanism providing a 30 mobility will beattached to the frame.


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Rating & Weighting: Mobility Alternatives

Criteria MOPs Weight Alt#1 Alt#2

Cost 0.3 3 0.9 1 0.3

Load Support 0.2 1 0.2 2 0.4

Movement 0.2 (360) 3 0.6 (30) 1 0.2

Portability 0.2 2 0.4 1 0.2

Weight 0.1 2 0.2 2 0.2

Sum=1 2.3 1.3

Alternative #1 Alternative #2


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Subsystem Sub-subsystem Components

Structure Breakdown

Subsystem Architecture intocomponents


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Interface Requirements - Subsystem integration

Roller

FrameU Shape Bar

Wheels

Tire load 1500 lb

Load on wheelsLoad on wheels


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Alternatives: Tires/Wheels

1.Polyolefin Caster: Price $15.69 each Load rating 700lbs Weight 3.09lbs Load height 4-1/4

Manufacturer: Apollo Caster


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Alternatives: Tires/Wheels

2. PolyurethaneCaster: Price $26.97 Load rating 600lbs Weight 6lbs Load height 4-1/4

Manufacturer: Caster City

R ti & W i hti


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Rating & Weighting:Tires/Wheels


Cost (each) 0.3 ($15.69) 3 0.9 ($26.97) 1 0.3

Design Adaptability0.2 2 0.6 2 0.6

Weight 0.2 3 0.6 1 0.2

Load 0.3 (700lbs) 2 0.9 (600lbs) 1 0.6

Sum=1 3.0 1.7

1. Polyolefin Caster 2. Polyurethane Caster


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Alternatives: Bearings

1. Ball Bearing 2. Roller Bearings

In a ball bearing, the load istransmitted from the outer race to

the ball, and from the ball to theinner race. Since the ball is asphere, it only contacts the innerand outer race at a very smallpoint, which helps it spin verysmoothly.

In these bearings, the roller is acylinder, so the contact between

the inner and outer race is not apoint but a line. This spreads theload out over a larger area,allowing the bearing to handleheavy loads.

Manufacturer: The Timken Company


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Rating & Weighting: Bearings


Supports axial and

radial loads

0.6 1 0.6 3 1.8

Durability 0.4 2 0.8 2 0.8

Sum=1 1.4 2.6

1. Ball Bearing 2. Roller Bearing

*Cost would have been a factor but in this case price is included

in wheels/tires components.


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Alternatives: ImmobilizationDevice

1. Floor Lock. Steel matching regular

caster tops for easyinstallation

.

Large brake shoe, non-skid, molded rubber forsolid, no-slip contact

. Adjusted by slight footpressure for simple,

instant locking. Corrosion resistant zinc

plate for long-use

Manufacturer: House Of Wheels, Inc.


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Alternatives: ImmobilizationDevice

Caster BrakeTread-gripping action lockswheel and prevents rolling.Simple cam mechanism hasno connecting linkage towear or misalign. Installationis quick and easy. Directionallock is an option as well.

Manufacturer: Tente


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Rating & Weighting: ImmobilizationDevice


Cost 0.5 ($18.95) 1 0.5 ($7.92) 3 1.5Durability 0.5 3 1.5 3 1.5

Sum=1 2.0 3.0

1. Floor Lock 2. Caster Brake

*Directional lock can be added to alternative 2 for anadditional $2.85


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Caster-Brake Assembly


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Alternatives: Frame Retractionand Expansion

Two side sliding devices Tube within a tube


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Rating & Weighting: Frameretraction and expansion

1. Sliding device 2.Tube within a tube

Criteria Weight Alternative 1 Alternative 2

Failure Probability 0.5 Requires screws and/or soldiering and otherelements that could fail with continuous useand moment and torsion loads.(1)

0.5 Tubes are part of the structure. Design ofthe structure must be able to handle thevehicles loads.(3)

1.5

Cost 0.2 Additional elements that are used to attach

the device raise the budget cost.(1)

0.2 Does not require additional elements to

do the sliding.(3)

0.6

Retraction andexpansion

0.3 Allows Smaller elements to move parallel tothe main frame to allow easy expansion orretraction for larger distances.(3)

0.9 Requires long tubes and limits how muchcan frame retract or expand.(1)

0.3

Sum 1 1.6 2.4


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Alternatives: Locking Elements

1.Pigtail Locking Pin 2.Screw


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Rating & Weighting: Locking Elements1.Pigtail locking pin 2.Screw


Stability 0.35 Can slip with movementand vibration(1)

0.35 Stays fixed unlessincredible vibrations areexperimented.(3)

1.05

LoadCapacity

0.50 Around 500-lb wouldhave to be designed and

fabricated to better fitneeds.(1)

0.5 Assuming bolt with 20pitch 700 lb size can be

chosen.(3)

1.5

Elements 0.15 1 element(3)

0.45 2 elements (bolt and nut)(2)

0.3

0.85 2.85


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Group Risk Matrix

Pro

babilityofOccurrence

5

4

3 1 4 3

2 2

11 2 3 4 5

Impact of Occurrence

Criticality ApproachLow Mitigate (M)

Medium Watch (W)

High Research (R)

Mobility Subsystem Risk Assesment

Rank Risk Strategy Approach

1

Cost Overrun Material and componentselection should bedone in a very carefulmanner

W,R

2

Stress Failure Use materials that canbe highly loaded, havingin mind manufacturers

safety factors. W,M

3

Deadline Execute project planeffectively

W

4

Producibility Manufacturingprccedures shall beadecuate. R. M


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Subsystem Risk Assessment Factors of safety

Frame expansion/retraction device 3.0 better-known materials in uncertain

environments, loads and/or stresses.

Locking element 2.0 Average materials operated in ordinary

environments and subjected to loads and stressesthat can be determined.

Lifting System 2.0 Average materials operated in ordinary



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Subsystem 2 Lifting and

securingOwner Rafael Romero


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Alternatives: Concepts ofOperations

Alternative 1: Foot pedal tire lifter with securing

straps and hollow cylinder rollers.

Alternative 2: Car jack lifters.


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Rating Weighting


Complexity of mechanism 0.04 (1) 0.04 (3) 0.012

Cost 0.12 (2) 0.24 (2) 0.24

Weight 0.06 (3) 0.18 (2) 0.12

Low probability of failure 0.14 (2) 0.28 (1) 0.14

Tire coverage 0.15 (3) 0.45 (0) 0Load capacity 0.23 (3) 0.69 (3) 0.69

Time consuming 0.26 (3) 0.78 (1) 0.26

SUM 1 2.66 1.462


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Subsystem Architecture intocomponents

Structure breakdown

Subsystem Sub-subsystem Components


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Interface Requirements andSubsystem Integration

T d St di f C iti l


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Trade Studies for CriticalComponents

Ratchet System

Hydraulic Cylinder


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Rating Weighting


Load Capacity 0.4 3000 lbs(3)

1.2 3,000 lbs(3)

1.2

Cost 0.3 Up to 40 USD(3)

0.9 Around 200USD(1)

0.3

Durability 0.3 Does notrequire fluids(3)

0.9 Requires use ofoil (pressurized)(1)

0.3

Sum 1 2.8 1.8


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ConOps Rolling Bars

Alternative 1 Bar withinCylinder using roller racewaysfor rotation.

Alternative 2 Cylinder withinCylinder


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Rating Weighting


Cost 0.3 Less materialrequired(3)

0.9 +-50% morematerial(1)

0.3

Construction 0.1 Single parts areplaced withscrews.(3)

0.3 Requiressoldiering and/orscrews(1)

0.1

Load Capacity 0.6 Hollow materialrequires thickercylinder wall.

(2)

1.2 Solid bar canwithstand heavyloads without

deforming.(3)

1.8

SUM 1 2.4 2.2


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Alternative 1 Single strap

Can hold the vehicle downbut can slip to the sides andlet the vehicle fall from the

mechanism.

Alternative 2 Basketstrap

Typically used for towdollies, this kind of

strapping system grabsthe tire firmly coveringmore area but still couldallow sideways moving.

ConOps -

Straps

Alternative 3 Tie downstrap

Fitting most tire sizes, thisstrap prevents movement in

any direction pressingtightly on the tire.


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ConOps Ratchets

Alternative 1 Standard Strap Ratchetwith wide handle

These ratchets feature a double securitylocking mechanism that makes it moredifficult for the ratchet to loosen or openwhile in service. The trap would have togo around an interfering fixed object inorder for this ratchet to be able to wraparound and tighten.

Alternative 2 - Ratchet(W/Finger Hook)

Hooks in ratchets allow us toplace the hook in any supporthole or ring available in themechanism frame in order totighten the strap.

Alternative 3 - Ratchet (W/SnapHook)

Ratchets with finger hooks allowus to tighten the strap fromextensions fixed to the frame.These extensions could be metalchains which would provedurable and would not createtare and wear on the strap soeasily.


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Rating WeightingCriteria Weight Alternative 1 Alternative 2 Alternative 3

Load capacity 0.5 3,670 lbs(3)

1.5 1,665 lbs(1)

0.5 2,000 lbs(2.5)

1.25

Cost (each) 0.2 Around 45 USD(1)

0.2 Around 21 USD(2)

0.4 Around 21 USD(2)

0.4

Method durability 0.3 (2) Tare due tofriction

0.6 (1) Deformationdue to shape withrepetitive use

0.3 (3) Deformationdue to shapewith repetitiveuse

0.9

Sum 1.0 2.3 1.2 2.55

Subsystem Risk Assessment


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Subsystem Risk Assessment

Factors of safety Frame expansion/retraction device

3.0 better-known materials in uncertainenvironments, loads and/or stresses.

Locking element 2.0 Average materials operated in ordinary


Lifting System 2.0 Average materials operated in ordinary



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Factors of safety Straps

Material factor Braking load vs load capacity = 10,000/3,000 (lb) =

Approx. 4 Takes in account wear and tare.

Load stess factor 1.3 for overloads that are difficult to analyze

Failure analysis 1.3 for non well developed analysis

Geometry factor 1.2 for no defined tolerances Reliability factor

1.2 for average reliability since straps wont handle thefull load individuallyTotal SF = 9.73


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Factors of safety Ratchets

2.0 Average materials operated in ordinaryenvironments and subjected to loads and stressesthat can be determined.


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Risk Assessment for Sub System 3

Rank Risk Strategy Approach

1

Vehicle securingfails causing itto fall frommechanism.

Verify method andselect an alternative.

M,R

2

Vehicle is

damaged by tiresecuringmethod.

Verify method and

select an alternative.M,R

3

Duration oftowingprocedure

Reduce the time inwhich the vehicle ismade towable

W,M

4

Producibility Select low cost/goodquality materials R,M

5

Liftingmechanismmalfunctions orbreaks

Perform a practicaland theoretical loadanalysis M,R

Risk Matrix

Pro

babilityofOccurrence

5

4

3 4

2 3

12 1 5

1 2 3 4 5

Impact of Occurrence

Criticality Approach

Low Mitigate (M)

Medium Watch (W)

High Research (R)

presentation 3 full corrected red one final

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