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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
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.
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
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.
5
Chapter 3: Sketches for Conceptual Design Stage
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.
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
8
Detail Design for 3D Drawing of Magnetic Flywheel
Electromagnet Magnet
Coil embedded on casing
Flywheel
Casing
9
2D View
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
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.
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
13
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.
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
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
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.
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.
18
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
19
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
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.
21
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.
22
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.
23
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
24
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.
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.
26
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.
27
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.
28
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.
29
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
30
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/
31
Appendix 1
32
Appendix 2