Engine Hoist Cals

8/12/2019 Engine Hoist Cals

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DESIGN OF AN ENGINE HOIST

by

Lara SherefkinAlice Jakobsen

ME 09-599Fall 2003

Final Report

The following work has been done in an effort to find the optimal design of an enginehoist. Using an engineering model, the initial optimization was done with the goal ofminimizing the overall weight of the hoist. Subsequently, a microeconomic model wascreated to re-optimize the design problem, maximizing profit in production. To furthervalidate the economic model, a survey was given and conjoint analysis used to determineattribute elasticities. The attributes that were considered were those deemed to be themost important to potential consumers. These include the maximum feasible loadcapacity, the maximum height that the hoist can lift, and the price. Finally, three productfamilies were established. The objective of each of the models was weighted andcombined to give an overall score. This combined score was then maximized overdifferent sets of weights using two separate sets of commonality constraints. Inconclusion, for the economic model, the outcome of the survey showed that to consumersload capacity and price were the most important of the attributes. It was then found thatthe maximum profit that could be obtained, taking into consideration the costs associatedwith production, was $4,278,967 for a hoist that could lift just over two tons to a heightof 7.79 feet and would cost $277.


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Table of Contents

Table of Contents................................................................................................................ 2Nomenclature...................................................................................................................... 31. Introduction................................................................................................................. 5

1.1. The product design problem ............................................................................... 51.2. Product development process ............................................................................. 51.3. Design Requirements .......................................................................................... 61.4. Product decisions from the design phase ............................................................ 71.5. Design requirements that can be quantified........................................................ 71.6. Design requirements that can be quantified using engineering analysis ............ 7

2. Engineering Design Model ......................................................................................... 82.1. Design optimization problem.............................................................................. 82.2. Analysis model.................................................................................................... 92.3. Optimization model in negative null form........................................................ 112.4. Optimization results.......................................................................................... 11

3. Model Extension: Microeconomics .......................................................................... 123.1. Competitors....................................................................................................... 123.2. Maximization of profit...................................................................................... 153.3. Results............................................................................................................... 19

4. Model Extension: Marketing .................................................................................... 194.1. Market size........................................................................................................ 194.2. Determining betas ............................................................................................. 204.3. Linearized demand function, Qm ...................................................................... 224.4. Comparison of elasticities and intercept ........................................................... 234.5. Re-optimization of design decision model ....................................................... 234.6. Comparison of results ....................................................................................... 24

5. Product Family Design ............................................................................................. 255.1. Market segments ............................................................................................... 255.2. Design optimization models ............................................................................. 255.3. Separate design optimizations........................................................................... 26

a. Load capacity .................................................................................................... 26b. Lifting height .................................................................................................... 27c. Price (operating variable cost) .......................................................................... 28

5.4. Creating Pareto surface with first set of commonality constraints ................... 295.5. Pareto surface with second set of commonality constraints ............................. 31

6. Conclusions............................................................................................................... 337. Appendices................................................................................................................ 34

5.1. Appendix A: Patent images .............................................................................. 347.2. Appendix B: Initial fixed investment and variable cost.................................... 37

Business plan .................................................................................................................... 40A) Business opportunity............................................................................................. 40

a) Business objective................................................................................................. 40b) Product description ............................................................................................... 40c) Market analysis ..................................................................................................... 41

B) Financial data ........................................................................................................ 42


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a) Capital equipment and supply list......................................................................... 42b) Breakeven analysis................................................................................................ 43c) Pro-forma income and cost projections ................................................................ 44

I) Annual cost ....................................................................................................... 44II) Net profit after depreciation and taxes.......................................................... 44

C) Supporting documents .......................................................................................... 45a) Existing patents..................................................................................................... 45b) Technical analysis and benchmarking .................................................................. 47

8. Slut ............................................................................................................................ 48

Nomenclature

A Total length of boom

a Cross section area of tubing

C Cost

C0 Initial fixed investment

C1 Operating variable cost per hoist

d Diameter of hoist tubing (square)

F1 Force on boom from the load at edge of boom

F2 Force on boom where jack is attached

F3 Force on boom where attached to back

F4 Vertical force on back where attached to bottomG Gravity

t Thickness of hoist tubing

I Moment of inertia of tubing

h1 Height of boom when jack fully compressed

h2 Height of boom when in horizontal position

h3 Height of boom when jack fully extended

h3 Height of boom when jack fully extended

l1 Distance from front edge, on boom, to where jack is mounted

l2 Distance from hoist body, on boom, to where jack is mounted

l5 Horizontal distance from back top to back were jack is attachedl6 Distance along hoist back between top and point of jack attachment

l9 Horizontal distance from back top to back bottom

lj,e Length of the jack fully extended

lj,c Length of the jack fully compressed

M2 Moment on back where attached to bottom

Mmaxback Maximum moment in back

Mmaxboom Maximum moment in boom


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p Price of hoist

q Quantity

t Thickness of tubing

Vback Volume of back

Vboom Volume of boom

Vtotal Total volume of back and boomwload Weight load

y Distance from center axes of tubing to the edge

Angle of hoist body form verticalr

Vector of product attributes

Angle between boom position in vertical and maximum height

Sum of angles: , , and

ar

Vector of attribute elasticities

p Price elasticity

Profit

Intercept with quantity axes on demand curve (economic model) Angle between boom when in minimum height position and back (engineering model)

Density

maxback Maximum stress in the back

maxbackM Maximum stress in back caused by the moment

backT Stress in back caused by the tension

maxboom Maximum stress in boom

y Yield strength Angle between boom position in vertical and minimum height


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1.Introduction

Figure 1 below shows an example of a standard engine hoist.

Figure 1: Engine hoist

1.1. The product design problemThe intended user of this product is both commercial garages and private at-homemechanics. For these users, the engine hoist should have the following characteristics.

These include choosing dimensions that minimize weight so the hoist is easy to movearound, but which also maintain the required functionality in weight capacity. Enaddition the design must have an acceptable range of operating angles toaccommodate the change in vertical height required by the user. The product shouldalso fold up into a more compact form and should be easy to operate. Also importantis the need for the product to be inexpensive and for the load capacity to be able to bechanged by adjusting the length of the boom.

1.2. Product development processThe product development process of an engine hoist is illustrated below.

InitializationThere is market demand forsomething that can liftengines easily out of car.

The company wants tobegin producing a productthat fills the market demand.

Marketing analysisWhat is the goal of thecompany in the market?

The market segment will becommercial garages and theat-home mechanic. The goalis to reach these segmentsby producing a product that

will satisfy the designrequirements.


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1.3. Design Requirements

Product definition

The market is for a productthat can easily lift heavyloads and fit into tightspaces.

Product must be able tosupport required loads, notexceed a specified size, andbe of minimum weight.

Idea generation

The product should fold upfor space savings in storage,and it should be possible toadjust the length of theboom (and thereby loadcapacity). The productshould also be able to beeasily moved around. Theoperating height shouldhave a sufficiently largerange of motion using anexisting hydraulic ram.

General product goals havebeen established andexisting technologyexamined.

Concept evaluationThe desired productcharacteristics have beendetermined.

Criteria such as materialavailability and cost havebeen applied to thegenerated ideas.

Design optimization

Concepts that fulfill allbasic requirements.Functional designconstraints.

Final design.

PrototypeDesign specifications.

Does the model work? Amodel for evaluation, fortesting, and for consumer

focus groups.

TestingHow robust is the product?Life cycle durability.Determine warranty issues.

Physical model

Sales

Marketing

strategy

Results fromconsumerfocus groups.

Plan for amarketingcampaign.

Production

planning

How the product will be

mass-produced, whatfacilities will be used, whothe suppliers will be, andhow the product will bedistributed.

Changes aremade todesign.

Production Final productFinal designspecifications


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The product must be able to lift a specified range of loads. The boom must be long enough to reach and support the load (clearance issues). Using an existing hydraulic ram, the product must be able to move through a

specified range of operating heights. The total weight should be minimal such that it can easily be moved around. The appearance of the product must be appealing. The cost of the produce must be minimal. The product should be able to fold up into a smaller volume for ease of storage

and transportation. The load capacity of the hoist should be able to be changed by adjusting the

length of the boom.

1.4. Product decisions from the design phaseThe design phase, which encompasses product definition through designoptimization, the product decisions that can be made include: Topology Load capacity Appearance Size (in use) Ability to move around Durability Manufacturing considerations

1.5. Design requirements that can be quantified The design must be able to lift a specified range of loads. The boom must be long enough to reach and support the load. The hoist must be tall enough to reach into standard size cars and trucks. The product must be able to move through a specified range of operating heights. The product should be light enough to easily move around. The product must have minimal cost. The hoist must be durable.

The design must be able to be produced easily and with as few parts as possible.

1.6. Design requirements that can be quantified usingengineering analysis

The design must be able to lift a specified range of loads. The boom must be long enough to reach and support the load. The hoist must be tall enough to reach into standard size cars and trucks.


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The product must be able to move through a specified range of operating heights. The product must have minimal cost. The hoist must be durable. The product must have minimal weight.

2.Engineering Design Model

2.1. Design optimization problemAssumptions:In this model the hoist will be represented as the hoist body andattached boom, the legs not being considered. The material for the hoist body andboom will be AISI 1018 steel square tubing and both will have the same crosssectional area. Cost will not be considered. For the jack used in the design it is

assumed that it is sufficiently strong enough to support all loads without buckling,deforming, or otherwise affecting the performance of the hoist (including a factor ofsafety).

Objective:Minimize weight.

Parameters:Hydraulic ram operating capacities; density an strength of material; loadcapacity.

Variables: Height of boom when jack is perpendicular to ground; length of jacksextension at boom horizontal position; distance from hoist body where the jack is

mounted to the boom; angle of hoist body form vertical; thickness of boom and hoistback; width of outer boom and hoist back.

Constraints:Height of boom when jack fully compressed must be less than theheight of the boom in horizontal position which must also be less than the height ofthe boom at jack full extension. The length of the jack fully compressed must be lessthan when the jack is at boom horizontal position which must also be less than whenthe jack is fully extended. The mounting point at the jack on the boom can be nolonger than the length of the boom itself. The maximum stress that the boom I seeingform the load must be no more than the yield strength of the material. The angle ofthe hoist back can be between 0 to 90 degrees. The location of the jack on the hoist

body must be at or above the total length of the hoist. The thickness of the materialmust be at least 1mm and the outer diameter must be between 2mm and 15cm.Finally, the angles that the boom makes at the various positions must each be lessthan 90 degrees.


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2.2. Analysis modelThe variables, parameters, and functions used to calculate the objective equation andconstraints are given below:

Variables:h2= height of boom from ground when in horizontal position

= angle of hoist body form verticall2= distance form hoist body, on boom, where jack is mountedl6= distance along hoist back between top and point of jack attachmentt= thickness of hoist tubingd= diameter of hoist tubing (square)

Parameters:

= densitywload= weight loadg= gravityA= total length of boom

y= yield strengthlj,e= length of the jack fully extendedlj,c= length of the jack fully compressedh1= height of boom when jack fully compressedh3= height of boom when jack fully extended

Figure 2: Boom FBD and moment forces

F1F2F3

l2 l1

-F1*l1

M


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Equations:

Figure 3: Hoist body and boom through range of angles

2

1 2

5 6

9

2 2

4 4

3 2

2 1

,

6

1

1

2

2

3 2 1

4

cos( )

sin( )sin( )

( )

2

( 2 )

12 12

arcsin( )

arccos( )

arcsin( )

b

b

boom

back b

total boom back

j h

load

hl

l A l

l ll l

a d d t

V A a

V l a

V V V

dy

d d tI

h h

A

h h

A

l

l

F w g

F AFl

F F F

F

=

=

= =

=

=

=

=

=

=

=

=

=

= + +

=

=

=

=3 2

2 2 5 4 9

max 1 1

max 2

max

max

max

max

4

max max

( ) ( )

cos( )

boom

back

boom

boom

back

backM

backT

back backM backT

total

F F

M F l F l

M F l

M M

M y

I

M y

I

F

a

w V

= +

=

=

=

=

=

= +

=

d

t

d

Figure 4: Cross-sectional area of tubing


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2.3. Optimization model in negative null formF3

F2

F4

l6

l7

M2

Figure 5: Hoist body FBD

1 max

2 max

3

4

5 2

6 2

7

8 6

9 2

10

2 2 2

1 2 6 2 6 ,

2 2

2 2 6 2 6

min

subject to

00

0.0016 0

0.01 0

0.127 0

02

0.2 0

0.127 0

1.219 0

2 0

2 cos( ) 0

2 c

back y

boom y

b

j c

w

gg

g t

g d

g l

Ag l

g

g l l

g h

g d t

h l l l l l

h l l l l

= =

= +

=

= +

=

= +

= +

= + =

= + =

= +

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Engine Hoist Cals