bike-o project report

32
1 Mechanical Engineering Design MBB3043 July 2010 Project Title: Bike-O (Magnetic Resistance Exercise Bike) Group 33 Team Leader: Cheng Lee Chon 11445 Team Members: Chen Ming Hui 11444 Chin Swee Miin 11446 Kan Sze Wei 11456 See Yun Chuan 11515 Tan Chee Sheng Tan Foo Piew 11522 11523 Tay Chuang Hwee Wong Ning 11524 11528 Approved for Submission: Dr Syed Ihtsham Ul-Huq Gilani 9 th November 2010

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Page 1: Bike-O Project Report

1

Mechanical Engineering Design MBB3043

July 2010

Project Title:

Bike-O (Magnetic Resistance Exercise Bike)

Group 33

Team Leader: Cheng Lee Chon 11445

Team Members: Chen Ming Hui 11444

Chin Swee Miin 11446

Kan Sze Wei 11456

See Yun Chuan 11515

Tan Chee Sheng

Tan Foo Piew

11522

11523

Tay Chuang Hwee

Wong Ning

11524

11528

Approved for Submission:

Dr Syed Ihtsham Ul-Huq Gilani

9th

November 2010

Page 2: Bike-O Project Report

2

Abstract

Exercise bicycle has been introduced to the market as a tool for exercise in the

convenient way. Cycling is considered as a good way to exercise but as an alternative to cycling,

exercise bicycle was designed to allow people to cycle in the comfort of their home. There are

already many types of designs for the exercise bicycle now. However, improvements are made

from time to time to fix the disadvantages of the previous design. Our design is to fulfil that

requirement too.

In this paper, we will present our design in detail. There will an essay on identification of

need or initial specifications. There will be sketches, and also a set of 2D or 3D drawings for the

design to allow a better picture of our design. Engineering calculations will be shown and

calculations of cost are done too. We also elaborate on the materials selected for the product, the

manufacturing process and the evaluation of the design.

The paper will give you the understanding of our product through the engineering aspect

and also the marketability aspect. Our aim for the product is to be able to fulfil the customers’

request and it will be able to compete with the other exercise bicycles in the current market.

Page 3: Bike-O Project Report

3

Table of Contents

Contents Page

Abstract 2

Table of Contents 3

Chapter 1: Identification of Needs

Chapter 2: Initial Specifications

4

4

Chapter 3: Sketches for Conceptual Design Stage 5

Chapter 4: Literature Survey 6

Chapter 5: Evolution of Design Concept

(a) 2D and 3D Modeling

(b) Functions of Each Part

(c) Flow of Mechanism

7-9

10

11

Chapter 6: Engineering Analysis 12-13

Chapter 7: Calculations 14-16

Chapter 8: Material Selection 17-19

Chapter 9: Manufacturing Process 20-22

Chapter 10: Evaluation of Design

(a) Failure Mode and Effect Analysis (FMEA)

(b) Ergonomics Analysis

(c) Economics Analysis

23

24

24-26

Chapter 11: Discussion 27

Chapter 12: Conclusion 28

Chapter 13: Project Management 29

Reference 30

Appendix 31-32

Page 4: Bike-O Project Report

4

Chapter 1: Identification of Needs

It is a bicycle exercise machine with the following criteria:

Operator: 1 person

Maximum Load: 100Kgs

Exercise Load: Variable

Height: 1.6256 m – 1.8796 m

Leg to height ratio = 0.61

Resistance Type: Magnetic

Chapter 2: Initial Specifications

1. Stability:

The bicycle shall be stable in a statically loaded condition and shall not tip forward, backward or

sideward. The bicycle base of support shall not tilt when force is applied. The bicycle structure to

which the horizontal force is applied shall not break or be permanently deformed.

2. Exterior Design:

All edges of parts accessible to the user or to bystanders shall be burr-free, rounded, or otherwise

guarded. The design of rotating and moving parts which are accessible to the user shall avoid

shear, pinch, or catch points. Dangerous points of drive train components shall be guarded.

3. Seat Post and Seat:

The seat shall be adjustable as prescribed by the manufacturer’s specifications. The seat post

shall have a permanent visual mark indicating a maximum extension. The seat shall be mounted

onto the post with a steel seat pan, shouldered seat post, capped seat bracket, or any other device

that protects the user from impalement in case of failure of the seat or seat post. When properly

adjusted according to the manufacturer’s specifications, the seat shall not tilt.

4. Handlebars:

No mark is required if the minimum insertion depth is already provided by the design. The

handlebars shall not rotate around its horizontal axis. The handlebar stem shall not rotate around

its vertical axis (excepting when the handle is purposely in motion as part of the exercise).

5. Pedals:

Pedals shall have right hand/left hand symmetry. A nonslip tread surface shall be present on the

surface presented to the rider’s foot. A minimum clearance of 3.81cm shall be provided below

the pedals when they are in a horizontal position at the lowest level. The pedals shall not

permanently deform under use.

6. Resistance Mechanism

Resistance mechanism allows users to adjust to change the level of resistance and therefore, to

increase or decrease the difficulty of workout. The type of mechanism shall influence the

smoothness of the ride and the cost of the bike. Therefore, reasonable cost and smooth transition

through levels of resistance level shall be the considerations. The noise produced by the

mechanism is another concerning matter.

Page 5: Bike-O Project Report

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Chapter 3: Sketches for Conceptual Design Stage

Page 6: Bike-O Project Report

6

Chapter 4: Literature Survey

There are many exercise bicycles existing in the current market. It is always going

through improvisation and changes in order to come out with a better exercise bicycle. We need

to look for the existing designs that are out in the market for further understanding about the

flaws and advantages of the existing designs. Then, we will know where to apply improvisation

and further improve the design from the existing designs. We looked up at two existing designs

as our reference.

First, the Exercise Bicycle invented by Charles F. Cones(Appendix 1). It is an exercise

bicycle including a flywheel assembly mounted on the driveshaft of a hydraulic pump and a load

resistance control mechanism for variably controlling the load resistance on the hydraulic pump.

A pressure gauge means is also provided to measure the pressure between the load resistance

control mechanism and the hydraulic pump so as to serve as an indicator of the exercise bicycle.

A linkage means connects the handlebars to the driveshaft in such a manner that the drive-shaft

may be driven by pivotal movement of the handle-bars or rotation of foot pedals mounted to the

flywheel assembly. This design has a load resistance control valve and it operates in such a

manner. This invention eliminates the need for brake pads or friction straps in order to control

the load resistance by employing a flow control valve arrangement in combination with a

hydraulic pump. The advantage lies in the load resistance control valve is much less subject to

wear than are brake pads or similar type friction means. Thus, the level of load resistance can be

accurately set and maintained at a particular load setting over long periods or use.

Second is the Stationary Exercise Bicycle invented by Johnny Forcillo(Appendix 2). The

invention is directed to a stationary bicycle which has load-providing components alllowing for

fine-tuned adjustment of the selected load. This stationary bicycle comprises a design which

allows for ergonomic fine tuning of the relative positioning between the varioius components

thereof so as to provide ergonomic adjustments thereby reducing the risk of injury to the body of

the individual and allowing for a more efficient workout. This design of exercise bicycle uses

belt and gears as the drive mechanism. It is an improvement to the common chain type. Belt was

chosen because it is more resistant to wear, is rust proof and is relatively unbreakable, thus,

reducing the required amount of maintenance and repairs associated with conventional chains of

prior art decices. Furthermore, it has a specifically designed load of varying means for varying

the load or the amount of force necessary to turn the flywheel. As for the materials for the frame,

instead of the standard forged steel with welds that are used for most of the conventional

stationary bicycles, a stainless and cold forged, semi-tempered, seamless steel is used. Then, it is

coared with electronic paint instead the usual powder coat paint. This provides a stronger, sweat

resistant and chip resistant finish.

These two inventions both had its changes as an improvement of the older designs. We

refer to these both as a guidance on which aspect shall we change to improve the design. The

figures will be attached in the appendix as references.

Page 7: Bike-O Project Report

7

Chapter 5: Evolution of Design Concept

(a) 2D and 3D Modeling

Detail 3D drawing

3D Model

3D model rendered with material define

Seat Handle

Body Frame

Crank

Flywheel Casing

Pedal

Page 8: Bike-O Project Report

8

Detail Design for 3D Drawing of Magnetic Flywheel

Electromagnet Magnet

Coil embedded on casing

Flywheel

Casing

Page 9: Bike-O Project Report

9

2D View

Page 10: Bike-O Project Report

10

(b) Functions of Main Components

1. Main frame

• Main body of the exercise bicycle that supports most of the user’s weight

• Includes structural inserts for seat post, handle bars, and casing of flywheel and

pedals

2. Saddle, Seat Post & Bracket

• A supportive structure for user to sit while riding

• Provides height adjustment

• Provides user comfort

3. Flywheel Casing

• A structure to hold in the magnetic flywheel mechanism and the pedal shafts

• Can be disassembled at one side for maintenance purposes

• Attached to the bottom of main frame

4. Magnetic Flywheel Mechanism

• To provide different resistance levels for exercising purpose

5. Pedals & Crank

• To be assembled to the flywheel

• Pedals are attached with rubber straps to provide user comfort

6. Handle Bars & Frame

• A structure for user to grip with while riding

• Assembled to main frame through an aluminium sleeve seat

• Handles are attached with rubber grips to provide user comfort

• Frame are to hold the monitor

7. Monitor

• To provide a graphical user interface where user can select different levels of

exercising

• To display important electronic feedback such as speed, heart beat rate etc

Page 11: Bike-O Project Report

11

(c) Flow of Mechanism

* As flywheel moves through the induced magnetic field from electromagnets, eddy currents are

generated in the disc. These currents create magnetic fields which oppose the changing

magnetic flux from electromagnets through the flywheel, thus, resist the rotation of flywheel

by dissipating some of the disc’s energy.

User sits on bicycle

and starts pedaling

Power generated and

supplied to control system

User sets program to get

desired resistance level.

Specified current flows to

solenoid which induces

magnetic field. Eddy current created

in flywheel.*

Movement of user resisted

and more pedaling force is

required.

More calories burnt until

user achieves objective.

User stops pedaling and

no power generated. System shuts down.

Page 12: Bike-O Project Report

12

Chapter 6: Engineering Analysis

Engineering Analysis:

All test are simulated using COSMOSXpressStudy in SolidWorks.

Displacement Test

Result: Maximum displacement ≈ 3.882 x 10-3cm

Stress Test

Result: Maximum stress ≈ 5.246 MPa

Page 13: Bike-O Project Report

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Stability Test

Result: The center of mass is within the length of the base area when a load of 100kg is

put on it. Therefore, it will not topple and confirm the stability of the design.

Page 14: Bike-O Project Report

14

Chapter 7: Calculations

Mechanical Energy

We define the following variables:

- r d = Radius of disc (m) = 0.1m

- r = crank length = 0.25m

- ����� = Mass of disc (kg) = 13kg

- �� = Moment of Inertia of disc about the shaft (kg.m2)

- ω = ����� ������ �������� = Revolutions per minute (rpm) of rider

The following relations are used:

- ������ �� ������� ��� ����, �� =�

���

- Kinetic Energy of Rotating Flywheel = �

��!

The following assumptions were made in the calculation.

- Weight of flywheel is evenly distributed.

- Average angular velocity !"#$ is 60 rpm

A mathematical analysis was done to calculate the inertia of the flywheel and to obtain the initial

force required on the pedal with zero resistance level. The initial torque is achieved when the

pedal is 900 from the vertical axis (maximum force applied).

Force Flywheel

Connecting Rod

Page 15: Bike-O Project Report

15

Kinetic Energy in Flywheel

%& =�

�! = '. � ; where � = 2 *�!, ω in rev/s

�� =1

2���

= 1

2,13.,0.10. = 0.0652� • �

1

2�! = '. �

' = 1

2

�!

= 1

2

,0.065.,60 × 2 × * ÷ 60.

,2 × * × 0.25 × 1.

= 0.81687

������ 8��9� ��9���� �::� �� :��� = ' × �

= 0.8168 × 0.25

= 0.2 7 ∙ �

Electrical Energy

When the flywheel is rotating, the magnetic fields of the magnet inside the flywheel are being

cut through by the coil attached cover of the flywheel. When the coil passes between the poles

of the magnet, the field induces current in the coil, and this phenomenon is explain by the

Faraday Law.

%��������<� ����� = 7 � ∅>

��

N is the number of turns of wire and ∅> is the magnetic flux in Webbers through a single loop.

The Faraday Law can be written in another form,

%�� = 7?@� !@ cos ,!@�.

Where ,

N = Number of turns of wire

?@ = The peak flux density of the rotor magnetic field

A = Area of cross section cutting the magnetic field by the coil

!@ = Mechanical rotation around the stator

t = Time

Page 16: Bike-O Project Report

16

Magnetic energy

Retarding force associated with the braking

' = �D E ?

Where, I is the current and L is the same vertical height of the effective magnetic field.

Cadwell equation:

F =DG

H � E =

DG

H�

Where,

DG = Effective length

� = Thickness of metal plate

E = Width of the plate

H = Conductivity of the metal

< = Velocity of the plate

Eddy current can be written in,

� = ∈

G=

JKL>M

MN <

The magnetic field strength B,

?@"L = OPOQ

7�

OP = 4*E 10STHm-1

OQ = Permeability of the core

?�UU =?@"L

2

Rewrite the equation of retarding force.

'G =H�E?�UUD

DG

<

From this equation, by adjusting the current that flows through the electromagnet, it will increase

the magnetic field, ?@"L , and hence will increase the retarding force, 'G . The greater the

retarding forces, the higher the resistance needed to be overcome by the user, which in turn can

burn more calories. In this case, H, �, E , D, ��� DG are held constant, since the dimension of the

magnet and flywheel are constant.

Page 17: Bike-O Project Report

17

Chapter 8: Material Selections

Material selection is a key step as it is a crucial decision that links computer calculations

and lines on an engineering drawing with a working drawing. There are several criteria that taken

into consideration in the process of choosing materials for different parts of the project. Selecting

the best material will provide us with the best properties and necessary performance in service.

Cost and availability of raw materials, as well as processed materials, and manufactured

components are major concerns in manufacturing. The economic aspects of material selection

are as important as technological considerations of the properties and characteristics of materials.

So, it is favorable to choose a material with a lower cost and good availability. Poorly chosen

material can add to manufacturing cost and unnecessarily increase the cost of the parts.

The manufacturing cost of the finished product is the most important factor determining

the selection of the manufacturing process and material. There are several manufacturing

processes that have different costs such as the solidification (casting) process, powder processing,

joining processing, and assembly process. Choosing a suitable manufacturing process with a

lower cost can assure a cheaper product.

Often, materials are subjected to forces (also known as loads) when they are used.

Mechanical properties determine the usability of a material in a mechanical application, an

application that requires the material to sustain a force, resist deformation, or perform some

structural task. For this product, we consider the ultimate tensile strength and the tensile modulus.

Ultimate tensile strength is the maximum stress observed in a tensile test. It is important as

necking begins when this value is reached and cause failure to the product. The tensile modulus

signifies the relative stiffness of material which signifies the load that the material can sustain

before plastic deformation. Choosing a material with a higher ultimate tensile strength and

tensile modulus can ensure the material quality of the product.

The durability of the material and the corrosion resistant both depend on the grade of the

material, environment and surface finish. There are different grades and surface finishes of

materials to suit the environment to which the material will be subjected in its lifetime. The best

material for our product is a material that provides a good corrosion resistance which leads to a

high durability. The density of the material is another vital aspect of material selection. A

suitable density will provide stability for the product as stability is another main concern that

affects the safety of our consumer when using the product.

Hence, to compare and select the best material for every part of our product, we use the

Weighted Decision Matrix method to decide the most suitable material.

Page 18: Bike-O Project Report

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Material Selection for Each Part

1. Frame

For the material of frame, stainless steel is chosen because it possesses a very good mechanical

properties and corrosion resistance. Corrosion resistance should be taken into consideration as

the customer’s hands are subjected to sweat (due to work out). Sweat has salt and salt could

speed up the corrosion process of metal. Stainless steel with a minimum 10.5% to 11% of

chromium content by mass can increase the corrosion resistance. It also increases the durability

of the machine which is the main concern of the customer while choosing the product. High

ultimate tensile strength and tensile modulus of the frame assure the safety of product.

Alternative Material: Carbon Fiber (Zoltek Panex35) and Aluminum Alloy

2. Flywheel

A flywheel is a mechanical device with a significant moment of inertia used as a storage device

for rotational energy. Aluminum alloy is chosen as the material for the flywheel because it’s low

density and good durability. A material with good durability should be chosen to have a longer

life time so it does not need to be changed frequently. Although the material cost is slightly

higher than steel alloys, aluminum steel is still the most suitable material for flywheel due to the

more suitable properties.

Alternative Material: Copper and Steel Alloys

Page 19: Bike-O Project Report

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3. Handlebar & Fly Wheel Casing

Handlebar is the steering mechanism for bicycles. The design of our handlebar is the bullhorn

handlebar. We chose aluminum alloy as our material because of its good durability and high

corrosion resistance. Handlebar is the steering of the bicycle where users will be holding while

cycling. User’s hands are subjected to sweat due to workout. So, aluminum will be a good

material for this part as its corrosion resistance is high (as mentioned before, sweat assist in

occurrence of corrosion). Handlebar will be one of the parts to support the load of the users

riding on the machine. It has to be made by materials with good ultimate tensile strength and

tensile modulus.

Alternative materials: PVC, Steel Alloys

4. Seat Post & Seat Post Bracket

Seat post is the part where it connects the bicycle frame to the saddle. It is a small part that has to

support the weight of user sitting on the bicycle. Considering the ease of manufacturing process

of this part, we choose aluminum alloy as the material of seat post and seat post bracket because

aluminum alloy requires a lower manufacturing cost using die casting and less surface finishing

compared to other materials.

Alternative Material: Carbon Fiber (Zoltek Panex 35) & Steel Alloy

Page 20: Bike-O Project Report

20

Chapter 9: Manufacturing Process

This product is mainly manufactured by four processes:-

1. Permanent Mold Casting

Permanent mold casting is a manufacturing process which the molds can be reused for several

thousand cycles, which is suitable to produce commercial products. A metal mold made from

steel or cast iron is used to cast non-ferrous metals, whereas graphite mold is used to cast iron

and steel metal. In this case, graphite mold is used to cast the stainless steel main frame. It

shares similarities to both sand casting and die casting. The molten metal is poured into a mold

which is clamped shut until the material cools and solidifies into the desired part shape.

Permanent mold casting is also referred to as gravity die casting because the molten metal is

poured into the die and not forcibly injected.

2. Die Casting

Die casting is a manufacturing process which the molds also can be reused many times. The

typical metal used is a non-ferrous alloy such as aluminium or zinc, is melted in the furnace and

then injected into the dies in the die casting machine. In this product, we use die casting to

manufacture smaller parts to be assembled to the main frame, i.e. seat post, seat post bracket,

handle bars and frame, flywheel and its casing, and pedal crank. Cold chamber machines are

used for this process because aluminium alloy is used and it has a high melting point. The casting

process is similar as permanent mold casting, except the molten metal is injected forcibly into the

mold and clamped shut for the metal to cool and solidified.

Page 21: Bike-O Project Report

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The table below shows the comparison between the capabilities, advantages and disadvantages

for both casting methods, and thus aid in identifying manufacturing processes that are compatible

with the parts’ design requirements.

Die Casting Permanent Mold Casting

Shapes Thin-walled: Complex, Solid:

Cylindrical, Solid: Cubic,

Solid:

Complex

Thin-walled: Complex, Solid:

Cylindrical, Solid: Cubic,

Solid:

Complex

Part Size Weight: 15 g – 200 kg Weight: 60 g – 300 kg

Materials Metals, Aluminium Alloy,

Lead,

Magnesium, Tin, Zinc

Alloy Steel, Carbon Steel,

Cast Iron, Stainless Steel

Surface Finish – Ra (um) 0.8 – 1.6 1.6 – 3.2

Tolerance +/- 0.5mm +/- 0.5mm

Max. Wall Thickness* 15.0 mm 50 mm

Quantity 100000 - 1000000 1000 – 10000

Lead Time Months Months

Advantages Can produce large parts, Can

form complex shapes, High

strength parts, Very good

surface finish and accuracy,

High production rate, Low

labour cost, Scrap can be

recycled

Can form complex shapes,

Good mechanical properties,

Many material options, Low

porosity, Low labour cost,

Scrap can be recycled

Disadvantages Trimming is required, High

tooling and equipment cost,

Limited die life, Long lead

time

High tooling cost, Long lead

time possible

Parts Manufactured Seat Post, Seat Post Bracket,

Handle Bars & Frame,

Flywheel & Casing, Pedal

Crank

Main frame

Parts Shape Thin walled & complex Solid & Complex

Parts Material Aluminium Alloy Stainless Steel

Parts Requirement Good accuracy and high

strength

Good mechanical properties

and good strength

*The thickest wall or feature of a part.

Page 22: Bike-O Project Report

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3. Finishing

Finishing process is applied to certain parts which require better surface finish after

casting.

a. Trimming is done usually to remove excess material formed at parting lines out of

casting.

b. Polishing is used to enhance the smoothness of the surface of the mainframe, as

permanent mold casted product is has less surface finish than die casted products.

4. Parts assembly

Lastly, the main frame and the parts are assembled using sleeves, guards, bolts and nuts

through labour or automation.

Other minor manufacturing process includes injection molding to produce parts as follows:-

1. Saddle

The main structure of a saddle is made by hard nylon plastic using injection molding. It is

then covered with a thin layer of cell foam which is non absorbent and durable – a

desirable quality for a bicycle saddle that may get wet from damp from human

perspiration, and lastly affixed with an easily-cleaned leather cover using spray adhesives.

It also constructed with a stainless steel hollow metal tubing to be attached to the bicycle

frame.

2. Pedals

The pedals are made by composite plastic using injection molding. Then they are

attached with rubber pedal straps.

Injection molding is chosen because it can form complex shapes and fine details, excellent

surface finish, good dimensional accuracy, high production rate, and low labour cost. Scraps

formed by injection molding are also recyclable.

Page 23: Bike-O Project Report

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Chapter 10: Evaluation of Design

(a) Failure Mode and Effect Analysis

Item & Function Failure

Mode

Effects of

Failure

S Causes of

Failure

O Detection D RPN Recommended

Corrective Action

Responsibility

and Deadline

1. Pedal – user

applies force to

drive product

Torsional

stress failure

Product no

longer functions

8 Inadequate

welding

2 Inspection 3 48 -Higher quality

welding

-Welder in

manufacturing

process

2. Handlebar

Assembly – User’s

hands support and

comfort

Loose

screwing

Uncomfortable

for consumer

3 Vibrations from

use of product

9 Inspection 1 27 -Revision of

assembly

dimensions

- Handlebar

assembly

designer

- Frame

designer

3. Seat Assembly –

User weight

support and

comfort

Loose

casing

Uncomfortable

for consumer

3 Vibrations from

use of product

9 Inspection 1 27 -Revision of

assembly

dimensions

- Seat assembly

designer

- Frame

designer

4. Magnetic

Resistance Braking

System – Provide

different resistance

level for cycling

No

magnetic

field

induced

No resistance

level available

6 No current

from power

supply

3

Testing 4 27 -Revision of

wiring connection

and circuit

- Revision of the

functionality of

power generator

- Electrical

circuit designer

- Braking

System

Designer

5. Power generator

– Produce electric

power for control

system, LED, and

braking system.

No power

supplied

Consumer

cannot set

resistance

5 Magnets fail 2 Testing 4 40 -Change magnets - Power

generator

designer

5 Wiring

connection

problem

3 Inspection 5 75 -Revision of

wiring connection

- Electrical

circuit designer

-Power

generator

designer

6. Frame

- Support user

weight

Frame

broken/has

crack

Product failure 9 Insufficient

strength of

frame’s

material to

support

2 Inspection 3 54 -Weld on the part

with crack

-Change the new

frame

-Frame designer

Page 24: Bike-O Project Report

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Comparing failure mode for power generator and other failure modes, failure

mode of power generator due to wiring connection error has highest value of RPN.

However, this RPN value should not be blindly based on to select the “vital few”

problems. This is because failure mode of frame has a severity failure with rating of 9

which could cause safety risk and complete product failure. Failure of wiring

connection would cause only the power supply to electronic display and resistance

availability. It achieves high value because it is quite hard to detect the defect.

Certainly, failure of frame is more critical than the wiring failure and should be given

prompt attention for design of the product. Followed by is the pedal failure which

may cause the product not functioning, shall be paid more concern than other

remaining failures. It has higher RPN value as its severity rating of 7 which means it

would cause the product not operable and possible injury if it fractures suddenly.

Even though failures of magnetic resistance system, handle bar, and seat assembly

have the same RPN, the failure of magnetic resistance will have higher priority also

due to its severity which will causes immediate customer dissatisfaction and violate

the design. From this, it can be seen that the high probability occurrence of the handle

bar and seat assembly failures gains less priority when comparing with severity of the

resistance system’s failure.

(b) Ergonomics Analysis

Every design must obey the ergonomic conditions while taking economics

condition into consideration too. Customers would want to purchase a product that not

only is durable and worthwhile, but also safe to use and ergonomically well.

Ergonomic conditions depend on the design and the materials chosen for the product.

We want to ensure that the exercise bicycle is comfortable for the users and we

express through the design and materials selected.

The bicycle is stable in a statically loaded condition and shall not tip forward,

backward, or sideward. The bicycle base is designed to support load up to 100kg and

it will not tilt when such a load or force is applied. Not only does it support the

vertical force, it will not break or permanently deformed when horizontal force is

applied. The stability of the bicycle is assured and users will not need to worry that it

will fall when using it. The seat on the bicycle is important as the user will be sitting

on the seat while utilizing the bicycle. The seat is adjustable and it will have a

permanent visual mark indicating a maximum extension. It has devices to support it

that will protect the user from impalement in case of failure of the seat or seat post.

The seat will not tilt when it is properly adjusted to the manufacturer’s specifications.

The pedals will have a nonslip tread surface so that the user’s foot will not slip while

riding the bicycle. The exterior design will be burr-free, rounded, or otherwise

guarded. This will ensure that the user or bystanders will not be harmed or

accidentally injured by the edges of the bicycle.

Page 25: Bike-O Project Report

25

For the materials part, the materials selected need to be durable, suitable, and

obey the economic conditions as well. The right material will ensure less chances of

failure. For the frame, we chose stainless steel as it possesses the suitable mechanical

properties. The high ultimate tensile strength and tensile modulus of the frame assure

the safety of product. The flywheel is used as a storage device for rotational energy. It

is quite the main part of the bicycle and it must have good durability to ensure the

bicycle does not fail too easily. Thus, aluminium alloy is chosen. The seat post is

important as it supports the seat. It must be good enough to support the weight of the

user to ensure good stability. Aluminium alloy is chosen to make the seat post and

seat post bracket.

(c) Economic Analysis

Economic conditions are an important aspect when it comes to designing and

producing a product. A product that is build perfectly but high in cost is not

considered a successful product. A product needs to meet the required quality but

marketable at the same time. The main factors to the economic conditions are the

manufacturing process, labour cost, and material selection. The cost must be

justifiable and reasonable; whether the cost is low or high.

The table below shows the estimated cost of materials per unit product, which is about

RM 1500.00.

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After including estimation of labour cost and manufacturing cost, our product

costs around RM2000-RM3000 - an average price when compared to the existing

exercise bicycles in the market. The present bicycle uses magnetic resistance as the

concept for our driving mechanism. There are existing exercise bicycles in the market

that are using this concept. The price range of these existing bicycles in the market is

within RM1000-RM5000; depending on the quality, features, design, and materials.

Permanent mold casting is chosen as a manufacturing process for the main

frame because we selected stainless steel. Permanent mold casting is more expensive

in terms of tooling and equipment but it will provide better mechanical properties.

This is also same for die casting to produce the other supporting parts. This will

support our aim to achieve high durability and stability. Our labour cost is in the

average level. However, our maintenance cost will be lower as we utilize the

magnetic resistance concept for the flywheel mechanism. This concept has a better

resistance to wear so it does not require frequent maintenance. This help to reduce

cost maintenance. Overall, the cost of this product is reasonable and can be further

reduced when it is mass produced.

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Chapter 11: Discussion

1. The exterior design of the product is based on a large wheel shape which is very

different from traditional exercise bicycle appearance. This wheel shape

provides several benefits:

(a) More attractive which increases the aesthetics value.

(b) Stress can be distributed to more area which is good for support purpose.

2. The seat, handlebar and pedaling assembly are adjustable in order to provide

maximum comfort for user during pedaling.

3. The stability of the design is assured. As from the analysis of center of gravity

before and after user with maximum 100kgs sits on it, the center of gravity is

within the area of base support which means that it will not topple.

4. Magnetic resistance braking system is chosen as the resistance mechanism due

to following advantages:

(a) Very smooth and quiet compared to ordinary belt/fan/friction pad operated

exercise bike.

(b) More variable of resistance level by only pushing the button (+)/(-) which

the magnitude of current.

(c) Do not need any external power supply as there is a power generator built

in.

(d) Less heat produced as the eddy current brake belongs to surpass distance

force which generates less friction as compared to contact force.

(e) Mechanical wear can be avoided because this system does not require

contact resistance and prolong the life cycle of the system.

(f) Environment friendly as electrical supply is not needed and thus reduce

carbon footprint.

(g) Allow pre-programmed routes

By the way, the drawbacks of this system are:

(a) Expensive cost as control systems are needed to adjust the resistance level

and the materials involved are costly.

(b) Less realistic and satisfying ride

4. Future Added Features:

(a) Touch screen display

(b) Built in music player

(c) Charger device for hand phone, IPod etc.

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Chapter 12: Conclusion

In a nutshell, this magnetic resistance exercise bicycle fulfills the initial needs

and specifications. It is tailored to support user with maximum weight up to 100kg

and it provides variable exercise load by using magnetic resistance braking system

technology. The frame design proved to be stable, strong and durable from the

engineering analysis which has been discussed in the report. Materials have been

chosen carefully to give the best characteristics and purposes of each component of

the bicycle such as stainless steel for the main frame, aluminium alloy for flywheel

and so on. Manufacturing processes including permanent mold casting, thermal

plastic injection molding and die casting are selected after considering several factors

such as melting point of the material, dimension tolerance, complexity of shape etc.

The magnetic resistance mechanism brings several advantages which add to the value

of this exercise bicycle compared to ordinary belt/fan exercise bicycle. It solves the

noise and mechanical wear problems, thus provides comfortable ride and longer life

cycle time. Besides, the power generator eliminates the need of external power supply,

which indirectly reduces carbon footprint. All in all, this exercise bicycle is affordable

which has the range of RM2000-RM3000.

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Chapter 13: Project Management

Task Allocation

No Tasks Assigned member(s)

1. Abstract Kan Sze Wei

2. Specification Chen Ming Hui, Tay

Chuang Hwee

3. Sketches Wong Ning

4. Literature Survey Kan Sze Wei

5. Detailed Design – 3D, 2D Cheng Lee Chon

6. Flow of Mechanism Chin Swee Miin

7. Function of Each component See Yun Chuan

8. Engineering Analysis Tan Foo Piew

9. Calculation Tan Chee Sheng, Chin Swee

Miin

10. Material Selection Chen Ming Hui, Tay

Chuang Hwee

11. Manufacturing Process See Yun Chuan

12. Evaluation Chin Swee Miin

13. Conclusion Cheng Lee Chon

14. Appendixes, References and compiling Wong Ning

16. Slides Compilation Tan Foo Piew

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Reference

1. 3D CAD Browser-3D Model Preview-Bike Machine, Retrieved at October

28th

, 2010, from

http://www.3dcadbrowser.com/preview.aspx?modelcode=31489

2. 3D MAX Models, Retrieved at November 1st, 2010, from

http://www.freeitsolutions.com/3ds/3dmodels.aspx?search=gym%20bike

3. 3D Model Gym Equipement, Retrieved at November 2nd

, 2010, from

http://www.turbosquid.com/3d-models/3d-model-gym-equipment-v3/517477

4. Cidotte Modern Exercise Bike, Retrieved at October 29th

, from

http://design-milk.com/ciclotte-modern-exercise-bike/#more-43226

5. Die Casting, Retrieved at October 28th

, 2010, from

http://www.custompartner.com/

6. Injection Molding, Retrieved at October 26th

, 2010, from

http://www.custompartnet.com/

7. Mechanical Engineering Design in SI Units, Author: Budynas R.G.&Nisbett,

K.J (2008), 8th

Edition, New Cork, Publisher: Mc Graw Hill

8. Metal Prices, Retrieved at October 25th

, 2010, from

http://www,metalprices.com/

9. Material Properties, Retrieved at October 25th

, 2010, from

http://www.matweb.com/

10. Permanent Mold Casting, Retrieved at October 27th

, 2010, from

http://www.custompartnet.com/

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Appendix 1

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Appendix 2