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MCB3083

MECHANICAL ENGINEERING DESIGN

DESIGN PROJECT

SEPTEMBER 2013 SEMESTER

LECTURER : Dr Dereje Engida Woldemichael

AP Dr Chandan Kumar Biswas

GROUP : 15

DATE : 16 December 2013

TITLE : Motorized Treadmill Jogging Machine

GROUP MEMBERS : 1. LEE KIAN SENG (Leader) 14739

2. YIT MAN HENG 15984

3. KHAW YAO SHUN 18293

4. THAM WAI HUNG 15936

5. ALAN A. ALEXANDER 16036

1

EXECUTIVE SUMMARY

This project spans for one month from 16 of November 2013 to 16 of December 2013. From

planning, job dedication, marketing survey, conceptual design, sketching, mechanical engineering

design, detail calculation to execution, a splendid motorized treadmill was being prototyped from

stretch. This machine allows users to jog anytime they want. It is mostly suitable to those living in

the cities who rarely have time to find a suitable garden or natural park to jog. To the matter of

fact, no many suitable jogging spot is available in the big metropolitan without much pollutant to

be inhaled. It is suitable to young and old. Users allow to tune the machine to their desired speed

so to jog comfortably. It came with three speed modes which are 1km/h (0.2778m/s), 5km/h

(1.389m/s) and 10km/h (2.778m/s) and it can accelerate from 0 to 3m/s in 1 second. Thus it makes

much no tedious and much no easy to the users. With the deck of 1 meter, users can jog synchronize

the speed of conveyor belt so that they won't tip over. This report encompass the detail of the

machine. It has detail planning, calculation and a detail engineering drawing. Fault analysis and

costing were considered in the project as well.

2

TABLE OF CONTENTS

No. Title Page

1. Introduction 3

2. Market and User Need 3 - 4

3. Brief Product Design Specification 4

4. Literature Review 5 - 6

5. Methodology 7 - 16

6. Detailed Design Drawing 17 - 18

7. Fault Tree 19

8. Cost Evaluation of Design 20

9. Conclusion 20

10 References 21

11. Appendices 22 - 38

3

1.0 INTRODUCTION

There are 2 types of treadmill in the market which are the manual treadmill and automatic

treadmill. Manual treadmill is much simpler and lighter which passively resists the motion, moving

only when walkers push the belt with their feet. On the contrary, automatic treadmill provides the

moving platform with a wide conveyor belt driven by an electric motor. The belt moves to the rear

requiring the user to walk or run at a speed matching that of the belt. The rate at which the belt

moves is the rate of walking or running.

The first commercial motorized treadmill is developed by William Staub who is a mechanical

engineer born at Philadelphia. He got the inspiration from Dr. Kenneth Cooper who claimed that

people at that time love to excuse from jogging due to weather. Staub then challenged himself to

develop a relatively cheap treadmill to encourage people to jog regardless of when and where.

This further the cause of joining the inspiration to develop an affordable motorized treadmill so

that the people can jog to a healthy lifestyle.

2.0 MARKET AND USER NEED

1Treadmill utilizes a law of conservation of energy to convert rotational energy to potential energy

or vice versa. Human in the past used treadmill to circulate water or to move water to a higher

altitude (against gravitational potential energy). Currently electrical potential energy was turned

to rotational energy in order to run the conveyor belt in the treadmill.

These days, people use treadmill to exercise. The advantages of using a treadmill are:

a) Easy to use

b) Users can customize the speed, inclination, warm up period, cool down period and energy

spend easily.

c) Users can design custom programs to fit the time to exercise.

d) Multiple users can use the same equipment

e) Step counters and heart rate monitors to regulate fitness progress.

f) Burn calories faster.

Therefore, the product will be marketed to those who want to exercise effectively.

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Besides from the study done by national health and fitness research group:

i. 65% of people who own a treadmill lost a minimum of 7% of their body weight over the

first year of owning and using the machine.

ii. 90% of treadmill owners who use it at least 3 times a week report feeling more energized

and in better physical condition from using the machine.

iii. 75% of people who bought one believe that they made the right choice in the type of

workout machine they bought.

3.0 BRIEF PRODUCT DESIGN SPECIFICATION

No. Features Specifications

1. Drive Motor 4 HP AC Motor

2. Timing Belt Dimension: 20mm (w) X 3mm (t)

Material: Neoprene

3. Conveyor Belt Dimension: 475 mm (w) X 5mm (t) X 3960 mm (l)

Material: PVC

4. Rollers Dimension: 114.6mm (d) X 500mm (l)

Material: Steel

5. Shaft Dimension: 75mm (d) X 800mm (l)

Material: Steel 1020CD

5. Deck Dimension: 1400mm (l) x 850mm (w) x 18mm (t)

Material: MDF (Medium-Density Fiberboard)

6. Speed Range 1, 5, 10 km/h

7. Weight 100 kg

8. Max. User Weight 150 kg

9. Overall Dimension Height: 1.5m, Length: 2.28m, Width: 1m

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4.0 LITERATURE REVIEW

4.1 The Advancement of Treadmill

Top Treadmill Brand:

Lifespan Fitness

Nordic Track

Have 14 treadmills on the market that priced $1000 to $1299

Feature a Google Maps feature that simulates the inclines and declines of various

roadways as well as online fitness tracking and wireless pulse and heart tracking

tools.

Precor

The Ground Effects Impact Control System uses shock absorbers built into the deck

to cushion the foot and minimize the impact felt by the body.

Its Integrated Footplant Technology varies the belt speed to accommodate for when the foot pushes

off and lands, allowing you to run naturally and not with the pulling and dragging that happens

with other treadmills. 2

Treadmill lies with the "turnspit"used to turn meat cooking over a fire.

Treadmill was used for milling, churning or shelling, running by dogs, sheeps and horses

The Colby family make carpet mills for the purpose to keep dogs fit not just for the purpose of work

William Staub then invented the latest treadmill that we seen today for people to jog and walk

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4.3 Objective Tree & Evaluation of the Design Concepts

Reliable and Affordable Motorized Treadmill

Cheap (0.3)

Prototype cost less than $2000 (0.3)

Production cost less than $1500 per unit (0.7)

Supply Cost less than $700 per unit (0.5)

Overhead cost less than $400 per unit (0,2)

Profit more than $400 per unit (0.3)

Safe (0.3)

No sharp part (0.1)

No Slippery (0.1)

Moving parts shrouded (0.5)

Secure assembly (0.2)

No electrocution (0.1)

Reliable (0.4)

To be able to use 8hrs straight

(0.1)

Maintenance free (0.2)

Easy to get changeable parts (0.4)

Mechanical parts (motor, belt, sprockets)can sustain long

usage for years (0.2)

Easy to clean (0.1)

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5.0 METHODOLOGY

5.1 Selection of Motor

Jogging speed,

𝑣1 = 1 𝑘𝑚

ℎ×

1000 𝑚

1 𝑘𝑚×

1 ℎ

3600 𝑠= 0.2778 𝑚𝑠−1

𝑣2 = 5 𝑘𝑚

ℎ= 1.389 𝑚𝑠−1

𝑣3 = 10 𝑘𝑚

ℎ= 2.778 𝑚𝑠−1

Velocity ratio of the driving sprockets to the driver sprockets connected to roller is 3:1

Velocity ratio of the driver sprocket to the roller is 1:2

Hence velocity ratio of driving sprocket to roller is 3

1×

1

2 =1.5:1

Required velocity of driving sprocket is therefore,

𝑣𝑚𝑜𝑡𝑜𝑟 =𝑑𝑚𝑜𝑡𝑜𝑟 𝑛𝑚𝑜𝑡𝑜𝑟

𝑑𝑗𝑜𝑔𝑔𝑖𝑛𝑔 𝑛𝑗𝑜𝑔𝑔𝑖𝑛𝑔𝑣𝑗𝑜𝑔𝑔𝑖𝑛𝑔 ,

𝑛𝑚𝑜𝑡𝑜𝑟

𝑛𝑗𝑜𝑔𝑔𝑖𝑛𝑔=

𝑑𝑗𝑜𝑔𝑔𝑖𝑛𝑔

𝑑𝑚𝑜𝑡𝑜𝑟

𝑣𝑚𝑜𝑡𝑜𝑟 = 𝑣𝑗𝑜𝑔𝑔𝑖𝑛𝑔

𝑣𝑚𝑜𝑡𝑜𝑟 = 0.2778 𝑚𝑠−1, 1.389 𝑚𝑠−1, 2.778 𝑚𝑠−1

Loading capacity,

𝑊 = 𝑚𝑔 = 150 𝑘𝑔 (9.81 𝑚𝑠−1) = 1471.5 𝑁

When a person is running at speed about 3 m/s (more than 2.778 m/s), the force exerts o ground

or treadmill is,

𝐹 = 2𝑚𝑔 = 2(1471.5 𝑁) = 2943 𝑁

The coefficient of friction of the timing belt with MDF (medium-density fibreboard) deck is

0.15. Hence, when a 150 kg person is running at 3 m/s, the friction is

𝐹𝑓 = 𝜇𝑁 = 0.15(2943𝑁) = 441.5 𝑁

If the belt should be able to drive the running track from 0 m/s to 3 m/s with 150 kg user jogging

on it is 1 s, then the acceleration should be

𝑎 = 𝑣 − 𝑢

𝑡=

3 − 0

1 𝑠= 3 𝑚/𝑠2

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So, the belt needs a pulling force, 𝐹𝑝𝑢𝑙𝑙

Σ 𝐹 = 𝑚𝑎;

𝐹𝑝𝑢𝑙𝑙 − 𝐹𝑓 = 𝑚𝑎

𝐹𝑝𝑢𝑙𝑙 = 150 𝑘𝑔(3 𝑚𝑠−2) + 441.45 = 891.45 𝑁

The maximum power needed from the motor to drive running track with acceleration of 3 m/s2 to

3 m/s is

𝐻 = 𝐹𝑝𝑢𝑙𝑙𝑣𝑚𝑜𝑡𝑜𝑟 = 891.45 𝑁(2.778 𝑚𝑠−1) = 2476.45 𝑊 ×1 ℎ𝑝

745.7 𝑊= 3.32 ℎ𝑝

The torque exerted by the motor is 𝑇 = 𝐻𝑃 (63025)

𝑛

When the motor is turning to give rise to maximum treadmill speed at 10 km/h, 𝐻𝑃 = 3.32 ℎ𝑝

and 𝑛 = 694.42 𝑟𝑝𝑚 as shown in part 3

𝑇 = 3.32(63035)

694.42= 301.32 𝑙𝑏 𝑖𝑛 ×

4.448 𝑁

1 𝑙𝑏×

0.0254 𝑖𝑛

1 𝑖𝑛= 34.04 𝑁𝑚

Horsepower required at different speed, 𝐻𝑃 = 𝑇𝑛

63025

𝐻𝑃1 = 301.32(69.44)

63025= 0.332 ℎ𝑝

𝐻𝑃2 = 301.32(347.21)

63025= 1.660 ℎ𝑝

𝐻𝑃3 = 301.32(694.42)

63025= 3.32 ℎ𝑝

Which 𝑛1 = 69.44 𝑟𝑝𝑚, 𝑛2 = 347.21 𝑟𝑝𝑚 and 𝑛3 = 694.42 𝑟𝑝𝑚 (verified in part 3)

The specification of motor required for the treadmill is

Horsepower, 𝐻𝑃 = 3.32 ℎ𝑝,

Torque, 𝑇 = 34.04 𝑁𝑚,

Rotational speed, 𝑅𝑃𝑀 = 694.42 𝑟𝑝𝑚 adjustable to lower RPM

9

5.2 Design of the Timing Belt

PowerGrip® Timing Belt is used

From Table of Basic PowerGrip® Service Factors, for service up to 8 hours per daily for treadmill

purpose, service factor required is 1:1

Design 𝐻𝑃 = 3.32 × 1.1 = 3.65 ℎ𝑝

Assumption 1: The RPM of motor shaft is less than 700 RPM (verified in part 4)

From belt pitch selection guide graph, 3.65 hp, 700 rpm give rise to 8 mm PowerGrip GT2 to be

chosen

Pitch, 𝑃 = 8𝑚𝑚

From Table of 8mm Pitch PowerGrip®GT® 2 Belt Drive Selection, for speed ratio of 3.000 and

center distance of 6.36 in

Belt Pitch length = 33.071 𝑖𝑛 = 840 𝑚𝑚

Belt length factor = 0.90

Number of teeth the belt has is 840 𝑚𝑚

8 𝑚𝑚= 105 𝑡𝑒𝑒𝑡ℎ

To choose an appropriate belt width, 8 mm Pitch PowerGrip®GT® 2 Power Rating Table is

referred. For RPM of motor shaft 700 rpm and groove number of 30, the base rated horsepower

for smallest width of 20 mm is about 5.32,

The maximum horsepower that the belt can withstand

= 𝐵𝑎𝑠𝑒 𝑅𝑎𝑡𝑒𝑑 ℎ𝑜𝑟𝑠𝑒𝑝𝑜𝑤𝑒𝑟 × 𝐵𝑒𝑙𝑡 𝑙𝑒𝑛𝑔𝑡ℎ 𝑓𝑎𝑐𝑡𝑜𝑟 > 5.32 × 0.90 = 4.788 𝐻𝑃 > 3.32 𝐻𝑃

Hence, width of 20 mm is sufficient

Specifications of the timing belt,

Pitch = 8mm

Pitch length = 840 mm

No. of teeth of the belt = 105 teeth

Belt width = 20 mm

Material = Neoprene

Advantages of timing belt:

Does not stretch significantly or slip and consequently transmits power at a constant

angular-velocity ratio.

No initial tension is needed.

Have efficiencies in the range of 97 to 99 percent

Requires no lubrication

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5.3 Design of Driving and Driven Sprocket

As specified earlier the speed ratio of driving and driven sprocket is 3:1

From 8 mm Pitch PowerGrip®GT® 2 Belts Drive Selection Table, for speed ratio of 3.000 and

center distance of 6.36 in

Driver sprocket will have 30 number of grooves, whereas, Driven sprocket will have 90 number

of grooves

Hence, the pitch diameter sprocket, 𝑑 = 3.008 𝑖𝑛 (Assumption 2 is verified) and pitch diameter

for driven sprocket, 𝐷 = 9.023 𝑖𝑛

The minimum recommended Sprocket Outside Diameters for Horsepower of 3.32 hp and motor

RPM of 700 rpm is 2.7 in which less than 𝑑 = 3.008 𝑖𝑛,

Hence, the selected pair of sprockets is acceptable

Assumption 2: The sprocket diameter of driving sprocket is 3.0008 in (verified in part 3)

Speed of the belt is fpm is

𝑉 < 3.008𝑖𝑛 × 700 𝑟𝑝𝑚

3.82= 551.20 𝑓𝑝𝑚

Since the belt speed is less than 6500 rpm, the sprocket size is acceptable

From Table of 8 mm Pitch PowerGrip®GT® 2 Sprocket Specifications,

Driver sprocket requires 1210 bushing whereas, Driven sprocket requires 2517 bushing.

Bore diameter for the driving sprocket should be more than 0.500 in and less than 1.250 in, 0.75

in is chosen.

Bore diameter for the driven sprocket should be more than 0.500 in and less than 2.688 in, 1.5 in

is chosen

Width of both sprockets are 1.13 in

Sprockets Selections:

1–840–8MGT – 20 PowerGrip®GT® 2 belt

1–P30–8MGT – 20 Driver Sprocket 1210 0.500 1.1250 AF-1 1.13in

1–1210 Bushing with a 0.75 in bore

1–P90– 8MGT – 20 Driven Sprocket 2517 0.500 C-2 1.13in

1–3020 Bushing with a 1.5 in bore

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Specifications of Sprocket

Specifications Driver Driven

Number of groove 30 90

Pitch diameter 3.008 in 9.023 in

Bushing 1210 2517

Bore diameter 0.75 in 1.5 in

Width 1.13 in 1.13 in

Outside Diameter 2.954 in 8.969 in

5.4 Other Calculations of Timing Belt Drive

Center-to-center distance of the two sprockets,

𝐶 = 0.25 {𝐿𝑝 −𝜋

2 (𝐷 + 𝑑) + √[𝐿𝑝 −

𝜋

2 (𝐷 + 𝑑)]

2

− 2(𝐷 − 𝑑)2}

= 0.25 {33.071 −𝜋

2 (9.023 + 3.008)

+ √[33.071 −𝜋

2 (9.023 + 3.008)]

2

− 2(9.023 + 3.008)2}

= 6.36 𝑖𝑛

Driver speed, 𝑛 = 𝑣

𝜋𝑑

𝑛1 = ( 0.2778 𝑚𝑠−1)(

60 𝑠1 𝑚𝑖𝑛)

𝜋 × 3.008 𝑖𝑛 (0.0254 𝑚

1 𝑖𝑛)

= 69.44 𝑟𝑝𝑚

𝑛2 = ( 1.389 𝑚𝑠−1)(

60 𝑠1 𝑚𝑖𝑛)

𝜋 × 3.008 𝑖𝑛 (0.0254 𝑚

1 𝑖𝑛)

= 347.21 𝑟𝑝𝑚

𝑛3 = ( 2.778 𝑚𝑠−1)(

60 𝑠1 𝑚𝑖𝑛)

𝜋 × 3.008 𝑖𝑛 (0.0254 𝑚

1 𝑖𝑛)

= 694.42 𝑟𝑝𝑚 < 700 𝑟𝑝𝑚

(Assumption 1 verified)

12

All the rotational speed of driving sprockets are lower than 1100 rpm used in the design analysis

of sprockets and belt. Therefore, our design is safe under the three speeds.

5.5 Designation for Running Belt and Rollers

Speed of the roller calculation

Assume:

Belt width = 500 mm

Centre distance = 1800 mm

Roller Length = 500 mm

Calculate Speed of the roller, 𝑛 = 𝑣

𝑑𝜋

𝑛1 = (0.2778 𝑚𝑠−1) (60 𝑚𝑖𝑛)

4.5115 𝑖𝑛 × 0.00254 𝑚

1 𝑖𝑛 × 𝜋

= 46.298 𝑟𝑝𝑚

𝑛2 = (1.389 𝑚𝑠−1) (60 𝑚𝑖𝑛)

4.5115 𝑖𝑛 × 0.00254 𝑚

1 𝑖𝑛 × 𝜋

= 231.494 𝑟𝑝𝑚

𝑛3 = (2.778 𝑚𝑠−1) (60 𝑚𝑖𝑛)

4.5115 𝑖𝑛 × 0.00254 𝑚

1 𝑖𝑛 × 𝜋

= 462.988 𝑟𝑝𝑚

Calculate the velocity of the conveyor belt which attach to the roller, 𝑣 = 𝜋𝑑𝑛

𝑣1 = 𝜋 (9.023 𝑖𝑛 ×0.00254 𝑚

1 𝑖𝑛) (

23.149

60 𝑚𝑖𝑛) = 0.2778 𝑚𝑠−1

𝑣2 = 𝜋 (9.023 𝑖𝑛 ×0.00254 𝑚

1 𝑖𝑛) (

115.747

60 𝑚𝑖𝑛) = 1.389 𝑚𝑠−1

𝑣3 = 𝜋 (9.023 𝑖𝑛 ×0.00254 𝑚

1 𝑖𝑛) (

231.494

60 𝑚𝑖𝑛) = 2.778 𝑚𝑠−1

The power supply from the is able to reached the speed of 10km/h

(proven)

13

It is proven that the velocity of the conveyor belt is

Front roller diameter = Back roller diameter = 𝜋

𝜃𝑑 = 𝜃𝐷 = 𝜋

Calculate the length of the conveyor belt

𝐿 = [4𝐶2 − (𝐷 − 𝑑)2]0.5 +1

2(𝐷𝜃𝐷 + 𝑑𝜃𝑑)

= [4(1.8)2 − (0)2]0.5 +1

2(0.1146𝜋 + 0.1146𝜋)

= 3.96 𝑚

5.6 Designation for Shaft

Calculation for the tension of the motor belt

Calculate the Centrifugal tension

𝐹𝑐 = 𝐾𝑐(𝑣

2.4)2

𝐾𝑐 = 0.965 (Select the position B from Table 17.16)

𝑣 = 4.167 𝑚/𝑠 (velocity of motor belt)

𝐹𝑐 = 0.965 (4.167 𝑚𝑠−1

2.4)

2

= 2.909 𝑁

Calculate difference in tension ∆𝐹 of the motor belt, where

∆𝐹 =𝐻𝑑/𝑁𝑏

𝜋𝑛𝑑

𝐻𝑑 = 5.48 ℎ𝑝 = 4086.436 𝑊

𝑁𝑏 = 1

𝑛 = 1041.63 𝑟𝑝𝑚

𝑑 = 3.008 𝑖𝑛

∆𝐹 =4086.436 𝑊

𝜋(1041.63 𝑟𝑝𝑚)(3.008 𝑖𝑛)(0.0254 𝑚)= 16.334 𝑁

14

Calculate the tension 𝐹1, where

𝐹1 = 𝐹𝑐 +∆𝐹 exp (𝑓𝜙)

exp(𝑓𝜙) − 1

𝜙 = 𝜃𝑑 = 𝜋 − 2𝑠𝑖𝑛−1𝐷 − 𝑑

2𝐶= 𝜋 − 2𝑠𝑖𝑛−1

(9.023 𝑖𝑛 − 3.008 𝑖𝑛)(0.0254 𝑚)

2(6.36 𝑖𝑛)(0.0254 𝑚) = 2.1526 𝑟𝑎𝑑

𝑓 = 0.5123 (Coefficient of friction for grooves)

𝐹1 = 2.909 𝑁 +16.344 𝑁 exp [(0.5123)(2.1565)]

exp[(0.5123)(2.1565)] − 1= 27.35 𝑁

Calculate the tension 𝐹2, where

𝐹2 = 𝐹1 − ∆𝐹

𝐹2 = 27.35 − 16.344 𝑁 = 11.006 𝑁

5.7 Analysis of Tension in Conveyor Belt

Calculate the Centrifugal tension, where

𝜔 = 𝛾𝑏𝑡 = (3.32)(745.7)(0.5)(0.0016) = 1.981 𝑁/𝑚

𝐹𝑐 =𝑤

𝑔𝑣2 =

1.981

9.81(2.7782)2 = 1.559 𝑁

Calculate the torque

𝑇 =𝐻𝑛𝑜𝑚𝐾𝑠𝑛𝑑

2𝜋𝑛=

(3.32)(745.7)(1.25)(1.1)

2𝜋 (462.998

60)

= 70.2097 𝑁

Calculate the initial tension of the conveyor belt

𝑓 = 0.7 (Table 17-2)

𝐹𝑖 =𝑇

𝑑

exp(𝑓𝜙) + 1

exp(𝑓𝜙) − 1= (

70.21

9.023 𝑖𝑛2

(0.0254 𝑚)) [

exp(0.7𝜋) + 1

exp(0.7𝜋) − 1] = 765.54 𝑁

Calculate the tension 𝐹1and 𝐹2

𝐹1 = 𝐹𝑐 + 𝐹𝑖

2 exp(𝑓𝜙)

exp(𝑓𝜙) + 1= 1.559𝑁 + 765.54

2 exp(0.7𝜋)

exp(0.7𝜋) + 1 𝑁 = 1379.79 𝑁

𝐹2 = 𝐹𝑐 + 𝐹𝑖

2

exp(𝑓𝜙) + 1= 1.559𝑁 + 765.54

2

exp (0.7𝜋) + 1 𝑁 = 154.41 𝑁

15

5.8 Analysis for the Maximum Moment of Shaft

By considering the tension of conveyor belt and motor belt, calculate the maximum moment

experience by the shaft.

Refer to the Figure 1, 2, and 3

In x-y plane,

+↺ Σ𝑀𝐴 = 0; (11.006 + 27.35)(cos 28.235)(75) − (308.82 + 2759.58)(0.5)(400) − (𝐹𝐸)𝑦

= −763.93 = 763.93 𝑁 ↑

+↑ Σ𝐹𝑦 = 0; −(𝐹𝐴)𝑦 + (11.006 + 27.35)(cos 28.235) − (308.82 + 2759.58)(0.5)

+ 763.93𝑁 = 0

(𝐹𝐴)𝑦 = −736.48 = 736.48 ↑

In x-z plane,

+↺ Σ𝑀𝐴 = 0; (27.35 − 11.000)(sin 28.235)(75) + 800(𝐹𝐸)𝑍 = 0

(𝐹𝐸)𝑍 = −0.725 𝑁 = 0.725 𝑁 ↓

+↑ Σ𝐹𝑦 = 0; (𝐹𝐴)𝑦 + (27.35 − 11.000) sin 28.235 − 0.725 = 0

(𝐹𝐴)𝑦 = −7.007 𝑁 = 7.007 𝑁 ↓

In x-y plane,

𝑀𝑚𝑎𝑥 = 209.69 𝑁𝑚, 𝑥 = 401.4 𝑚𝑚

In x-z plane,

𝑀𝑚𝑎𝑥 = 0.525 𝑁𝑚, 𝑥 = 75.36 𝑚𝑚

Since the moment in x-z plane is very small as compared to x-y plane, the maximum moment is

209.69 Nm at 401.4 mm

16

5.9 Shaft Design

Maximum Moment, 𝑀𝑎 = 209.69 𝑁𝑚

Steady Torsion Moment, 𝑇𝑚 = 𝑊 (𝑑

2) = 1534.2 𝑁 (

0.1146 𝑚

2) = 87.91 𝑁𝑚

From Table 7-1,

Choose retaining groove, where 𝐾𝑡 = 5, 𝐾𝑡𝑠 = 3.0 = 𝐾𝑓𝑠

Choose material 1020 CD steel, 𝑆𝑢𝑡 = 470 𝑀𝑃𝑎, 𝑆𝑦 = 390 𝑀𝑃𝑎 (Table A-20)

Calculate the endurance limit

𝑆𝑒 = 𝐾𝑎𝐾𝑏𝐾𝑐𝐾𝑑𝐾𝑒𝐾𝑓𝑆𝑒′

Where 𝐾𝑎 = 𝑎𝑆𝑢𝑡𝑏

From Table 6-2, 𝑎 = 4.51, 𝑏 = −0.265

𝐾 = 4.51(470)−0.265 = 0.883

Assume, 𝐾𝑏 = 0.9, 𝐾𝑐 = 1 (𝑏𝑒𝑛𝑑𝑖𝑛𝑔), 𝐾𝑑 = 0.9(400 ℃), 𝐾𝑒 = 1, 𝐾𝑓 = 1

𝑆𝑒 = (0.883)(0.9)(0.9)(470 𝑀𝑃𝑎) = 336.581 𝑀𝑃𝑎

Calculate the diameter for the shaft, where

𝑑 = {16𝑛

𝜋(

2 𝐾𝑓𝑀𝑎

𝑆𝑒+

[3(𝐾𝑓𝑠𝑇𝑚)2

]0.5

𝑆𝑢𝑡)}

13

𝑑 = {16(462.998/60)

𝜋(

2(5)(209.69)

336.1581 × 106+

[3(3 × 87.91)2]0.5

470 × 106)}

13

= 0.066 𝑚

This minimum diameter to support the load of the motor pulley and the roller is 66 mm.

17

6.0 DETAILED DESIGN DRAWINGS

Figure 6.1: The whole treadmill

Figure 6.2: The whole treadmill with dimensions

18

Figure 6.3: Power transmission system

Figure 6.4: Power transmission system with dimensions

Please refer to Appendix 3.

19

7.0 FAULT TREE

7.1 Failure Mode and Effect Analysis

20

8.0 COST EVALUATION OF DESIGN

No. Part/Component Cost (US $)

1. 4 HP AC Motor 40.00

2. 1–840–8MGT – 20 PowerGrip®GT® 2 Neoprene

Timing Belt

4.75

3. PVC Conveyor Belt 40.00

4. Steel Drive Rollers 10.00

5. MDF Deck 6.00

6. 1–1210 Bushing with a 0.75 in bore 0.90

7. 1–3020 Bushing with a 1.5 in bore 2.00

8. 1–P30–8MGT – 20 Driver Sprocket 19.00

9. 1–P90–8MGT – 20 Driven Sprocket 20.00

Total 142.65

9.0 CONCLUSION

1 months of tedious planning, marketing survey, conceptual design, detail calculation and detail

prototype drawing, the hard-work has paid off. A brand new motorized treadmill has been

produced to meet the market demand, readily to be mass produced to spur a new business venture.

The new motorized treadmill will meet the requirement depicted in the objective tree. It must be

reliable, affordable and secure. In order to troubleshoot the possible dismay of the machine, a fault

tree analysis has been done. It will pass on to the respective technical department for further

warranty claim and repair job.

Detail calculation on stress and strain whereabouts has been done to locate the weak spot on the

machine so that further enhancement can be done. Choosing of the material must be scrutinized

tightly to fulfil the following requirement:

Must be easily be located. Supply can be obtained easily.

Material itself must be strong.

Can support and enhance the weak spot on the machine

Follow the ASTM standard (worldwide recognition)

With the detail calculation and required material in hand, we can sketch out the design and further

modify it using engineering drawing. AUTOCAD is used to make the drawing more explicit and

detail. With 3D modelling, clients will have the ideas of the look of the machine. As the technology

progressed, amendment can be made on the technical drawing based on the fault tree analysis. It

made it possible for the manufacturers to manufacture the product easier and faster using the

prototype printer in the future using .dwg files

21

10.0 REFERENCES

[1] J.L Hanson. Home Treadmill Benefits – Statistics. Retrieved on 6th December 2013 from

http://ezinearticles.com/?Home-Treadmill-Benefits---Statistics&id=3367034

[2] Top Treadmill Brands. Retrieved on 6th December 2013 from

http://www.livestrong.com/article/392132-top-treadmill-brands/

[3] Medium Density Fibreboard. Retrieved from http://www.makeitfrom.com/material-

data/?for=Medium-Density-Fiberboard-MDF

[4] Habasit Product Data Sheet NAO-10ELAV. Retrieved from

http://www.habasit.com/HNET/proden.nsf/(LuAllByUNID)/975E9E65CB3D3D72C1256A7D00

4ED432?openDocument

[5] Richard G. Budynas, J. Keith Nisbett, Shigley’s Mechanical Engineering Design, Ninth

edition in SI Units, McGraw-Hill.

[6] Fault Tree Analysis (FTA):Concepts and Applications by Bill Vesely at NASA HQ.

[7] “Fault Tree Handbook with Aerospace Applications" Version 1.1, NASA Publication,

August 2002.

[8] "History of the Treadmill" by J Whatmore from J W'S K9 TREADMILL MAKER

[9] http://www.cad.sun.ac.za/catalogs/MachineComponents/powergripdesignmanual17195.PDF

22

APPENDICES

Appendix 1: Conceptual Design Sketch

23

Figure 1 Force distribution on the roller and shaft

Figure 2 Moment Diagram for x-y plane

Appendix 2: Diagrams for Shaft Analysis

24

Figure 3 Moment Diagram for x-z plane

25

Figure 1: The whole treadmill

Figure 2: Display, control and support of treadmill

Appendix 3: Detailed Drawings

26

Figure 3: Support of the upper part

Figure 4: Cover for the power transmission system

27

Figure 5: The power transmission system

Figure 6: Motor

28

Figure 7: Sprockets and timing belt

Figure 8: Shaft

29

Figure 9: Rollers and conveyor belt

Figure 10: Deck of treadmill

30

31

32

Appendix 4: PowerGrip Timing Belt Tables

33

34

35

Table 6.1 Conservative Value of Factor C and Exponent m

Table 7-1 First Iteration Estimates for Stress Concentration Factor Kr and Kts

Appendix 5: Shigley’s Mechanical Engineering Design Tables

36

Table 17-2 Properties of some Flat and Round-Belt Materials

Figure 17-16 Some V-Belt Parameters

37

38

Appendix 6: Break down of the jobs done by each member

No. Name Job

1. Lee Kian Seng

(Design)

I. Calculations of timing belts and sprockets

II. Calculations of motor and shaft

III. Drawing of sprockets and timing belts

IV. Drawing of upper portion of treadmill

V. Literature Review

VI. Fault Tree analysis

VII. Compilation

2. Khaw Yao Shun

(Research)

I. Summary

II. Introduction

III. Identification of Market and User Need

IV. Literature Review

V. Conceptual Design

VI. Fault Tree analysis

3. Alan A. Alexander &

Yit Man Heng

(Research)

I. Methodology

II. Overall Set of Calculations & Design Calculations

III. Cost Evaluation of Design

IV. Fault Tree analysis

V. References

VI. Compilation

4. Tham Wai Hung &

(Design)

I. Detailed Design & Calculations

II. Fault Tree analysis

III. Selection of Components