Automa+`Ted Sepak Takraw Ball Throwing Mechanism for Training

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AUTOMA+`TED SEPAK TAKRAW BALL THROWING MECHANISM FOR TRAINING

Tanakorn Tony Ontam B. E., Khon Kaen University, 2000 B.S., California State University, Sacramento, 2008

THESIS

Submitted in partial satisfaction of the requirements for the degree of

MASTER OF SCIENCE

MECHANICAL ENGINEERING

CALIFORNIA STATE UNIVERSITY, SACRAMENTO

SUMMER 2010

AUTOMATED SEPAK TAKRAW BALL THROWING MECHANISM FOR TRAINING

A Thesis

Tanakorn Tony Ontam

Approved by:

______, Committee Chair Dr. Akihiko Kumagai

______, Second Reader Dr. Yong Suh

______Date

Student: Tanakorn Tony Ontam

I certify that this student has met the requirements for format contained in the University format manual, and that this thesis is suitable for shelving in the Library and credit is to be awarded for the thesis.

______, Graduate Coordinator______Dr. Kenneth Sprott Date

Department of Mechanical Engineering

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Abstract

AUTOMATED SEPAK TAKRAW BALL THROWING MECHANISM FOR TRAINING

Tanakorn Tony Ontam

This study of the first automated Sepak Takraw ball throwing mechanism presents the

design of a new mechanism which is able to generate common types of Sepak Takraw

ball motion. Sepak Takraw is a unique competitive ball sport where two teams of three

players kick the ball over a net with their feet. Kinematic data of ball motions were

acquired by measuring from actual Sepak Takraw games. Requirements of a Sepak

Takraw ball throwing mechanism were established and a prototype was designed,

manufactured and tested. Results showed that the Sepak Takraw ball throwing

mechanism is able to produce realistic Sepak Takraw ball motions and a reasonable

accuracy compared to expected projectile equations with a low standard deviation. The mechanism can be used to help develop skills of Sepak Takraw players.

______, Committee Chair Dr. Akihiko Kumagai

______Date

ACKNOWLEDGMENTS

I would like to thank Dr. Akihiko Kumagai, the advisor of this thesis, for guiding me throughout this study and the manufacturing process.

I would also like to thank Dr. Yong Suh who guided me in the designing process using Pro/ENGINEER software.

I am thankful to staff and students who work at Engineering and Computer

Science (ECS) Tech Shop at California State University, Sacramento including Michael

Bell.

I am grateful to Wat Sacramento Buddhavanaram, USA Takraw Association, and the U.S. Sepak Takraw team, who have been encouraging me to do this study. This work would not have been possible without their support.

Special thanks to my family for their great support and encouragement.

TABLE OF CONTENTS

Page

Acknowledgments ...... v

List of Tables...... viii

List of Figures ...... viii

Chapter

1. INTRODUCTION ...... 1

2. OBJECTIVES ...... 9

3. METHODOLOGY AND DESIGN ...... 11

Kinematic Data ...... 11

Design ...... 17

Testing Validation ...... 31

4. RESULTS AND DISCUSSION...... 37

Design Requirements Met ...... 37

Testing Results ...... 39

5. CONCLUSION ...... 49

Improve Design/Future Study ...... 49

Appendices ...... 51

Appendix A: Motor and Wheel Size Calculations for Ball Shooter ...... 64

Appendix B: Projectile Calculations Using Wolfram Mathematica 7 ...... 70

References ...... 80

vii

LIST OF TABLES

Page

1. Table 3.1 Basic Kinematic Data of Four Movements in Sepak Takraw ...... 15

2. Table 4.1 The Suitable Tire Pressure of Wheels ...... 39

3. Table 4.2 The Suitable Gap Between Two Wheels ...... 40

4. Table 4.3 Maximum Range ...... 40

5. Table 4.4 Maximum Ball Velocity ...... 41

6. Table 4.5 Ball Feeder Efficiency at 6 Balls per Minute (10 Second Time Interval) ...... 41

7. Table 4.6 Standard Deviations, Average Length, and Number of Balls Missing Target Area ...... 46

8. Table A.1 Ball Velocity of Four Movements Using a Speed Gun ...... 52

9. Table A.2 Velocity of the Wheels and Velocity of the Balls Given Different RPM ...... 53

10. Table A.3 How Final Mechanism Met Design Requirements ...... 55

11. Table A.4 Partial Automatic at 30 Degrees at a Launching Height of 3 Feet at 6 Second Time Interval (Tossing) ...... 56

12. Table A.5 Partial Automatic at 30 Degrees at a Launching Height of 3 Feet at 10 Second Time Interval (Tossing) ...... 57

13. Table A.6 Partial Automatic at 50 Degrees at a Launching Height of 3 Feet (Tossing) ...... 59

14. Table A.7 Automatic Feed at 11.5 Degrees at a Launching Height of 6.5 Feet (Serving & Spiking) ...... 60

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15. Table A.8 Automatic Feed at 11.5 Degrees at a Launching Height of 3.5 Feet (Tossing) ...... 62

16. Table A.9 Partial Automatic at 75 Degrees at a Launching Height of 2.5 Feet (Setting) ...... 63

LIST OF FIGURES

Page

1. Figure 1.1 Dimensions of Official Sepak Takraw Court ...... 2

2. Figure 1.2 Sepak Takraw Game in Action. There Are Three Players on Each Side...... 2

3. Figure 1.3 Test Ball. Sepak Takraw Ball Officially Approved by International Sepak Takraw Federation (ISTAF) for Men’s Events ...... 5

4. Figure 1.4 Four Main Types of Sepak Takraw Ball Movements Generated by Athletes Include: a) Tossing b) Serving c) Setting and d) Spiking...... 6

5. Figure 3.1 Illustration of Launching Point and Launching Angle of Sepak Takraw Ball Movement in: a) Tossing b) Serving c) Setting d) Spiking ...... 13

6. Figure 3.2 Illustration of Projectile Motion ...... 16

7. Figure 3.3 Block Diagram of Controllers ...... 24

8. Figure 3.4 Pro/ENGINEER Computer Model of Sepak Takraw Ball Throwing Mechanism Prototype Featuring Ball Shooter and Ball Feeder ...... 25

9. Figure 3.5 Pro/ENGINEER Computer Model of Sepak Takraw Ball Throwing Mechanism Prototype Showing Ball Shooter ...... 26

10. Figure 3.6 Pro/ENGINEER Computer Model of Rotating Carousel Design Inside Ball Feeder of Sepak Takraw Ball Throwing Mechanism...... 27

11. Figure 3.7 Base and Control Box of Sepak Takraw Ball Throwing Mechanism .. 28

12. Figure 3.8 Ball Feeder, Ball Hopper and Ball Shooter of Sepak Takraw Ball Throwing Mechanism ...... 29

13. Figure 3.9 Ball Shooter and Telescopic Pole of Sepak Takraw Ball Throwing Mechanism ...... 30

14. Figure 3.10 Ball Target Size Created in Pro/ENGINEER ...... 32

15. Figure 3.11 Experimental Set Up For Accuracy Testing of Ball Throwing Mechanism...... 35

16. Figure 3.12 Flow Chart of Sepak Takraw Ball Throwing Mechanism ...... 36

17. Figure 4.1 Number of Balls Missing Target Based on Angle and Feeder Mode of Mechanism ...... 46

18. Figure 4.2 Standard Deviation Based on Angle, Height, and Feeder Mode of Mechanism ...... 46

19. Figure 4.3 Sepak Takraw Players Interacting with the Sepak Takraw Ball Throwing Mechanism to Practice ...... 48

Chapter 1

INTRODUCTION

The purpose of this thesis is to design a novel automated ball throwing mechanism for training in the sport of Sepak Takraw. Sepak Takraw is a challenging, point-based competitive team sport that is played both outdoors and indoors. The sport is played by two opponent sides which have a 5.09 feet high net separating the court. The court is the same size as a badminton court, which is 20 x 44 feet (Figure 1.1).

There are three players in a Sepak Takraw team, as seen in Figure 1.2. The sport is similar to volleyball, except that the three players on each side cannot use their hands.

The game begins with one player tossing the ball by hand to the server (this is the only time that hands are allowed in the game), then the server uses their foot to kick the ball over the net (in Fig 1.1, the tosser is in position 1 and the server is in position 3). The opponent side is then allowed to use any part of their body, except the arms, to make contact with the ball and kick the ball over the net.

The rules of the game allow players to make contact to the ball up to three consecutive times per side [1]. During the Sepak Takraw game, both teams will make different powerful moves to kick and spike the ball to go to the opponent side and fall within the boundary line of the court. See Fig. 1.1 for Sepak Takraw court dimensions, as specified by the International Sepak Takraw Federation (ISTAF) [1].

Figure 1.1 Dimensions of Official Sepak Takraw Court

Figure 1.2 Sepak Takraw Game in Action. There Are Three Players on Each Side.

Although Sepak Takraw is a relatively new sport in the last thirty years in the

United States, the sport originated in Southeast Asia in the late 1500s. The sport is now

being played in many countries throughout the world, including the United States of

America, Canada, Brazil, India, China, Germany, Thailand, Malaysia, Switzerland,

Japan, and France, among other countries [1]. Sepak Takraw is also taught in schools and

universities in Physical Education and Kinesiology classes. There is a USA Takraw

Association, which is the organization that recruits players for the U.S. national team to compete in the world championship. This world championship tournament includes both men’s and women’s events, with teams participating from up to 30 countries. According to USA Takraw Association’s website [2], the organization is trying to develop the sport in this country by promoting Sepak Takraw through training, consulting, and hosting tournaments around the country. It is clear that Sepak Takraw is a sport of growing interest in the world market. In fact, Sepak Takraw is even featured in a new Nintendo

DS video game [3].

Although Sepak Takraw is a growing sport, there are a limited number of advanced athletes and coaches available to train new players in the USA. Since the game requires complex ball control skills, it is important for Sepak Takraw players to have sufficient and thorough training. This training can be a time and labor-intensive process.

For example, during practice sessions, the U.S. national team members are trained by coaches who use their labor and manual training techniques to generate a variety of ball motion to train players. Manual training might involve throwing the balls by hand, or

hitting the balls with a wooden paddle to athletes for defense and offence drills. It is a difficult and time consuming process because a Sepak Takraw coach’s arms will tire after

hitting 50 balls consecutively. For three hours per day of training sessions, a coach may

have to hit the ball repeatedly up to 300 times. In addition, the accuracy of human-

generated ball motion cannot be controlled, and this can effect development of athlete’s

kicking skills. Furthermore, kinematic data and analysis of this sport has not yet been

done to help Sepak Takraw athletes improve their skills.

One way to develop ball control and kicking skills and to address the other

training problems discussed above is to use an automated mechanism that generates

motion of the Sepak Takraw ball. Although there are ball throwing machines available

for other sports, such as baseball, volleyball, tennis, table tennis, and soccer, none of

these machines have been designed to specifically meet the needs of the unique sport of

Sepak Takraw. Sepak Takraw balls are very different in size, material, and structure from

others balls used in the sports described above. Sepak Takraw balls that are used to test in

this study are the official competition balls (Marathon Model MT 908) which are 0.39

pounds in weight. The balls have a hollow spherical shape 5 inches in diameter with

twelve pentagon-shaped holes around the ball surface (see Fig 1.3). The area of each hole

is 0.43 square inches. The ball is made from woven synthetic rattan material with a soft

rubber outer surface which has good bouncing characteristics and shock absorption [4].

diameter = 5 inches

Figure 1.3 Test Ball. Sepak Takraw Ball Officially Approved by International Sepak Takraw Federation (ISTAF) for Men’s Events

Furthermore, the types of motion involved in Sepak Takraw, which can be described as a unique blend of gymnastics, volleyball, soccer, hacky sack and martial arts, are specific to the sport of Sepak Takraw [2]. See Figure 1.4 for the four main types of ball motion generated in Sepak Takraw: tossing, serving, setting, and spiking. A ball throwing mechanism that meets the unique motion and ball specifications of Sepak

Takraw doesn’t currently exist and needs to be developed and tested.

Figure 1.4 Four Main Types of Sepak Takraw Ball Movements Generated by Athletes Include: a) Tossing b) Serving c) Setting and d) Spiking.

In order to find out what principles are used in other types of ball throwing

machines, research on the various types of commercially available ball machines was

done as a background of study. There are several ball throwing machines available on the

market. The most common principles involved with these machines are rotating lever arm, propulsion system and two counter rotating wheels [5-6].

Furthermore, there are several studies of ball pitching machines [5-9], including

research that tested baseball pitching machines using different kinds of balls. These studies showed that baseball pitching machines are being continuously improved to

imitate the desired motions of the baseballs. For example, Mish and Hubbard [5] found

that the pitching machine prototype that they studied could provide their required linear

and angular velocity of the ball with good accuracy and repeatable motions. Having a

machine throw balls to reproduce the throw of an adversary pitcher, can also be used to improve batting technique of players [6]. Similarly, tennis serve simulation machines have been developed and studied under repetitive and realistic serving conditions [9]. In addition to baseball pitching and tennis serving machines, there are also commercial mechanisms available for volleyball, football, cricket, and soccer ball throwing [10-12].

Currently there is no automatic training device for coaching and helping Sepak

Takraw players to improve their kicking skills commercially available on the market.

This study hopes to provide a new educational and training tool for youth and professional Sepak Takraw players to practice repeatable drills and a variety of

movements to improve their ball control skills. Furthermore, the mechanism, along with kinematic ball motion data, could be used to create Sepak Takraw training instructions for schools as well as for amateur and professional athletes.

Chapter 2

OBJECTIVES

The objective of this thesis is to build a prototype of a Sepak Takraw ball

throwing mechanism to simulate different kinds of ball motion in the sport of Sepak

Takraw. The study will gather kinematic data for ball motion (for example, ball velocity and ball launching position), which doesn’t currently exist for the sport of Sepak Takraw, and then design an automated Sepak Takraw ball throwing device and prototype not yet

commercially available, to aid in the training of athletes to develop ball control skills.

The study and measurement of kinematic data of ball motion in actual performance of

Sepak Takraw players will inform the design of a machine that is both accurate and

capable of producing realistic ball motions in order to effectively train and challenge

players.

The mechanism will be operable using automated means, with little need for

human operation while the mechanism is launching the balls. According to the Longman

Advanced American Dictionary, automated means “using machines to do a job or

industrial process” [13]. With an automated Sepak Takraw ball throwing mechanism, the

goal is for the machine to help do the job of the coach or player, and for Sepak Takraw

players to potentially be able to practice by themselves the four main types of ball motion

generated in the sport, including tossing, serving, setting, and spiking (see Fig. 1.4). Or,

as one Sepak Takraw player summarized, “One machine, one man, four movements.”

[14].

The automated Sepak Takraw ball throwing mechanism will be designed to shoot

a variety of realistic ball motions over a range of velocities seen in the actual sport. The

use of this device in tests will provide experimental data to evaluate the performance of

the prototype. Motion data will be compared between the automated mechanism

prototype and the expected results from mathematics equations.

Overview of This Thesis:

This thesis will detail and follow the design process of the automated Sepak

Takraw ball throwing mechanism. In Chapter 3, the detailed methodology, including

kinematic data used to inform the design, prototype design, and test set up process,

including the mathematical equations used, will be introduced and described. Chapter 4 will describe and evaluate the results of the final mechanism and experimental validation, and include a discussion of these results. Chapter 5 will make conclusions as well as

recommendations for future study and expansion, followed by Appendices.

Chapter 3

METHODOLOGY AND DESIGN

The scope of this thesis includes gathering kinematic data on the types of ball motion generated in Sepak Takraw and using this data and other research in order to design and build a novel automated Sepak Takraw ball throwing mechanism to be used for training athletes. The overall plan for the methodology and design of this study can be described in three main parts:

1. Kinematic Data: Study and measure kinematic data of ball motion in actual

performance of Sepak Takraw players.

2. Design: Describe design specifications and requirements and generate computer

model of a prototype mechanism. Build, assemble and iteratively adjust prototype

to ensure mechanism is in working order.

3. Testing Validation: Generate projectile equations. Collect and compare ball

motion data generated by the prototype to the expected results to ensure machine

is capable of creating realistic Sepak Takraw ball motion.

Kinematic Data

In order to ensure that the ball throwing mechanism reproduces the actual ball motion of Sepak Takraw players, kinematic data of ball motion in actual performance of

Sepak Takraw players was studied and measured by using a video camera and velocity

measuring devices at local Sepak Takraw games in Sacramento, California. The Sepak

Takraw players observed were intermediate in skill level; more advanced Sepak Takraw players were not available locally for this study. The players’ heights ranged from 5 to 6 feet. A JVC digital video camera (Model: Everio, JVC, Japan) was used to record the

nature of the game and movements of the ball with actual Sepak Takraw players.

The videos collected from local Sepak Takraw games in Sacramento, California

were analyzed frame by frame for ball launching positions, launching angles, and

velocity. By studying videos of Sepak Takraw games, different moves that are used in the

game were found. There are four major movements that cause the ball to move in the air

during the Sepak Takraw game. Those four movements are: tossing, serving, setting and

spiking. Moreover, the position of a launching ball in reference to the ground as well as

the angle of the launching ball with respect to a horizontal plane were observed. The ball

releasing points vary depending on the height of the players, kicking skills and different

moves. See Fig. 3.1 for an illustration of some kinematics involved in the four main types

of ball motion observed in Sepak Takraw players: tossing, serving, setting, and spiking

respectively.

a) b)

c) d)

Figure 3.1 Illustration of Launching Point and Launching Angle of Sepak Takraw Ball Movement in: a) Tossing b) Serving c) Setting d) Spiking

As seen in the above figure, the four movements can be described as follow:

• Tossing: Ball is tossed by the tosser position (position 1 in Fig. 1.1) from 2-3 feet

high with a positive angle (+θ) in reference to the horizontal plane, to the server

position on the same side of the court.

• Serving: Ball is kicked by the server (position 3 in Fig. 1.1) from 3-6 feet high

with a positive (+θ) or negative (-θ) angle in reference to the horizontal plane, to

the opposing side of the court.

• Setting: Ball is kicked from 1.5-2.5 feet high with a positive angle (+θ) in

reference to the horizontal plane, to another player in the spiker position (position

2 in Fig. 1.1) on the same side of the court.

• Spiking: Ball is spiked by spiker from 5-8 feet high with a positive angle (+θ) and

negative angle (-θ) in reference to the horizontal plane, over the net to the

opposing side of the court.

By observing the ball motion during the game it was also determined that the

Sepak Takraw ball can spin when it is kicked. There are two types of spin: top spin (ball spins towards the same direction of ball travel) and under spin (ball spins in opposite direction of ball travel). The ball spin characteristics vary by each movement. Table 3.1 details the ball spin characteristics, ball launching angle, ball travel distance, and ball

release height and end height for each of the four movements as acquired by analyzing the video frame by frame.

Table 3.1 Basic Kinematic Data of Four Movements in Sepak Takraw

Ball position Ball travel Ball launch Ball spin (ft) distance (ft) angle (degree) characteristic Movements Releasing End Top Under height height min max min max spin spin Tossing 2-3 3-6 12.2 16.2 0 60 No Yes Serving 3-6 3-6 13 36.7 -30 60 Yes Yes Setting 1.5-2.5 5-8 2 22 30 80 Yes Yes Spiking 5-8 5-8 5 44 -30 30 Yes Yes

A Bushnell speed gun (Bushnell Speedster II Radar Gun Model #10-1900) was used to measure the speeds of each of the four main ball moves that are generated in

Sepak Takraw games. The speed gun used a digital signal to capture the speed of the moving Sepak Takraw ball. The speed gun provides accuracy at +/-1 mile per hour

(MPH) for measured speeds. The observer stood behind a Sepak Takraw player, aimed the speed gun and pressed the trigger at the ball when the player released the ball (i.e. tossed or kicked the ball). The speed gun was pointed to the ball in the same plane of ball direction of travel. Table A.1 in the Appendix shows the ball velocities for tossing, serving, setting and spiking motions. As seen in Table A.1, velocities of tossing and setting were similar to each other, and they were lower in range than velocities of serving and spiking. On the other hand, the velocities of serving and spiking were closer to each

other, but higher in value than tossing and setting velocities. Identifying the proper velocities, angles, ranges of releasing heights, and types of motion seen in actual Sepak

Takraw games is important in determining the functional requirements needed for a realistic ball throwing mechanism for Sepak Takraw.

The basic principles involved in each of the ball movements are based on projectile motion. See Figure 3.2 for an illustration of projectile motion.

h y

x Figure 3.2 Illustration of Projectile Motion

Knowing the basic kinematic data from the actual study of Sepak Takraw games

will help to determine the trajectory of the ball by using projectile principles. The

equations for calculating projectile motion are as follows:

y = h + (u sinθ) t – (gt2)/2 (3.1)

x= u (cosθ) t (3.2)

The equation calculates the motion of the ball, where h is initial height, y is target

height, g is gravitational acceleration, t is time of flight, x is distance between releasing point and target, u is initial velocity of the ball and θ is ball launching angle. The desired

end height to kick the balls is varied. Equations will be helpful to set up testing targets to

validate ball accuracy. Equations will be created with Wolfram Mathematica 7.0 [15].

Further detail on testing set up will be discussed later.

Design

The kinematic data from the previous section and requirements from the Sepak

Takraw players guided the design specification of the first prototype for the Sepak

Takraw ball throwing mechanism. Feedback from Sepak Takraw players in the USA was

also an important way to define requirements. In the USA, most Sepak Takraw games are

played outdoors and this prototype was designed to meet these conditions. To design a

ball throwing mechanism capable of being used for Sepak Takraw training it is important

that design specifications are identified.

Design Requirements

The prototype must be:

1) Portable: Transportable from one location to another location by vehicle.

2) Weight under 50 pounds: easy to take apart and assemble.

3) Partially Automatic: operating by itself or by using only a few controls.

4) Sufficient Ball Capacity: Able to contain up to 10 balls.

5) Battery powered: able to run the machine without electrical outlet.

6) Able to generate ball speeds from 10- 60 MPH.

7) Able to shoot the ball from 2-45 feet in distance.

8) Able to adjust ball release point from 2.5-8 feet high from the ground.

9) +/- 30 degree ball launching angle adjustable along a horizontal plane

10) +80 and -30 degree ball launching angle adjustable along a vertical plane.

11) Able to provide various time intervals of ball release: 6-10 balls/minute.

Principles and Design Overview

1. Ball Shooter

In reviewing the basic Sepak Takraw kinematics, a basic principle that needs to be

considered in the design of the Sepak Takraw ball throwing mechanism is projectile

motion. After observing Sepak Takraw ball motion in live matches and videos of the games, observers also saw that the ball exhibits both translational and rotational motions.

The characteristic of these motions led to the decision to use the principle of the two counter rotating wheels as the main ball shooter component of the mechanism. The two

wheels rotate in different directions, generating speed on the wheels’ surface which imparts speed on a ball propelled between these wheels. Equation 3.3 is used to calculate

velocity of the wheel’s surface (v) where ω is angular velocity (rpm) of the wheel and

is radius of the wheel.

v= ω (3.3)

According to Mish and Hubbard [5], the following equation can be used to calculate ball linear velocity ( ) based on the velocities of the two points of contact

( and ) between the wheels and the ball:

= ( + )/2 (3.4)

Table A.2 in the Appendix shows velocity of the wheels and velocity of the balls

given different RPM.

A spin may also be produced when the two wheels spin at different speeds. This spin is imparted about an axis which is perpendicular to the ball linear velocity vector,

; the following equation [5] can be used to calculate the magnitude of this spin based on the two linear velocities and , radius of the ball:

ω = ( - )/2 (3.5)

The radius of the Sepak Takraw test ball is 2.5 inches. As seen in Table 3.1,

several Sepak Takraw movements impart spin on the ball; to create this type of spinning

ball motion using the Sepak Takraw ball throwing mechanism, the counter rotating

wheels need to spin at two different speeds; if the top wheel spins faster than the bottom

wheel it will create a top spin on the ball. On the other hand if the bottom wheel spins

faster than the top wheel, the ball will produce an under spin.

Since the Sepak Takraw ball is hollow with 12 holes around its synthetic rubber

surface, the two counter rotating wheels need to provide some cushion of the ball to help

propel the ball out; furthermore a hard solid wheel could break the ball; thus pneumatic

rubber wheels were selected as the wheel type so that the air pressure could cushion the

ball and help avoid ball damage. The two rubber wheels selected for the ball shooter were

9 inches in diameter and 1.5 inches in width. The diameter was based on the wheel

calculations found in Appendix A. The wheel surface is black, grooved and curved. The

two wheels should have a gap size between them that is a little less than the diameter of

the Sepak Takraw ball (5 inches) to allow for the wheels to press the ball out when it is received in between the two wheels.

Since the mechanism must be portable, a 12 volt rechargeable battery (Fisher

Price, 12 V Power Wheels Battery, 9.5 Ah) was selected as the power source. The two wheels are driven by two separate DC motors connected to this battery. See Appendix A for the motor calculations used to determine the size of the motor that is suitable to produce the required ball speeds of up to 60 miles per hour. The revolutions per minute for a suitable motor to generate ball speed at 60 MPH is 3360 RPM (see Appendix A for

motor calculations). The motor commercially available that best meets these

requirements is the Protech DC motor (Protech 1/7 HP 12 VDC 3785 RPM PM Motor).

This motor has amperage of 13.1 amps and voltage 12 DC, with a speed of 3785 RPM.

Because the design requirements specify the need to adjust the launching angle along a vertical plane, the mechanism of a rotating fixed axis between the frame and the ball shooter was applied. Changing the launching angle is important because the different Sepak Takraw movements, such as serving and setting, depend on a variety of angles, as seen in Table 3.1. This mechanism also allows horizontal angle adjustment.

This horizontal angle changing feature is mounted to a U shaped base which freely moves along a vertical axis.

2. Ball Feeder

Since the mechanism must provide Sepak Takraw balls to the ball shooter automatically, a ball feeder component was designed. The ball feeder needed to vary the individual drop rate of balls by set time intervals. The design of the ball feeder also needed to meet the size requirements of the Sepak Takraw ball, and hold a capacity of 10 balls at the smallest feeder size possible. Based on the principle of uniform rotation, a rotating carousel was used as the mechanism to transport single balls in different time intervals to the ball shooter. This component is what automatically rotates and drops the

Sepak Takraw balls at regular intervals (i.e. every 10 seconds) to the ball shooter. The carousel is designed to hold four balls per rotation about a fixed axis, and consists of four ball pockets; each pocket is 5.5 inches in diameter to allow the closest fit of the balls and thus the most compact size.

The ball feeder also consists of a ball hopper where the balls are inserted into a basket, with a diameter of 20 inches at the top and a diameter of 6 inches at the bottom, to allow the balls to drop into the carousel one at a time. The rotating carousel is driven by an 18.33 RPM 12 VDC Gear Motor with running torque 35 in-lb, amperage of 1.5 amps and 12 volt DC. This motor was selected based on carousel motor calculations as seen in

Appendix A. The ball feeder can be taken apart from the ball shooter for ease of transportation of the mechanism and for flexibility in using the mechanism.

3. Control box

Controllers are needed to switch the motors on, change the speed, and set ball

release time intervals. The mechanism design should be as simple as possible using only

a few controls. Three MX033 DC motor speed controls were selected for the mechanism

– two to control the ball shooter motor and one to control the ball feeder motor. These

controllers met the specifications for the motors used in the ball feeder and ball shooter,

and feature 12 VDC, 15 amp max, and Pulse with Modulation (PWM). In order to vary the time interval of the ball release from the ball feeder, the DC motor speed controller is

used to modify time intervals of dropping balls in the ball feeder. Similarly the

controllers for the ball shooter are used to change the motor speed of the ball shooter and

in turn impact the launch speed of the ball. The three speed controllers are housed in a

control box with speed dials controlling their range. See Figure 3.3 for a block diagram of

the motor speed controllers for the Sepak Takraw ball throwing mechanism.

Figure 3.3 Block Diagram of Controllers

4. Base

Since the mechanism must be portable and needs to hold steady while the balls are released, the base was designed with four lockable caster wheels that can swivel at full 360 degrees of rotation. The top of the base is a 2.5 inch steel square tube 10 inches in length, with four different holes along the length of the tube. The height can be adjusted by lifting and placing a telescopic pole into the tube and inserting a bolt into the hole to support the bottom of the telescopic pole. The telescopic adjustable pole is attached to the base to further adjust the height of the mechanism, allowing for the range of required ball releasing heights as seen in Table 3.1.

A computer model of the prototype mechanism was designed using

Pro/ENGINEER Schools Edition software which provides 3D design functions. See

Figures 3.4, 3.5, and 3.6 for Pro/ENGINEER software screenshots of the computer drawings of the prototype design, featuring the ball feeder and ball shooter.

Figure 3.4 Pro/ENGINEER Computer Model of Sepak Takraw Ball Throwing Mechanism Prototype Featuring Ball Shooter and Ball Feeder

Figure 3.5 Pro/ENGINEER Computer Model of Sepak Takraw Ball Throwing Mechanism Prototype Showing Ball Shooter

Figure 3.6 Pro/ENGINEER Computer Model of Rotating Carousel Design Inside Ball Feeder of Sepak Takraw Ball Throwing Mechanism.

The design of the prototype included detailed computer models, followed by manufacturing and assembly. Fabrication was performed in the ECS Tech Shop at

California State University, Sacramento. Figures 3.7, 3.8 and 3.9, respectively, show

photographs of the automated Sepak Takraw ball shooting mechanism built, including the

base and control box, ball feeder, and ball shooter.

control box

base

Figure 3.7 Base and Control Box of Sepak Takraw Ball Throwing Mechanism

ball hopper

ball feeder

ball shooter

Figure 3.8 Ball Feeder, Ball Hopper and Ball Shooter of Sepak Takraw Ball Throwing Mechanism

ball shooter

telescopic pole

Figure 3.9 Ball Shooter and Telescopic Pole of Sepak Takraw Ball Throwing Mechanism

Testing Validation

In order to test the accuracy of the machine in shooting out balls and the ability to

reproduce ball motion seen in Sepak Takraw, the following procedure was used:

1. Projectile equations:

Projectile equations were calculated by using Wolfram Mathematica (see

Appendix B), to predict the ball motion to simulate the motion of various moves involved in a Sepak Takraw game. See Equations 3.1 and 3.2 for the projectile formulas. The equations will help test the machine if it meets the predicted values. Figure 3.11

represents the experimental set up used to validate the accuracy of the ball throwing

mechanism in generating projectile motion that compares to these equations.

2. Set up target:

After the projectile equations were generated using the given data, the equation

should be able predict the target position. A target was created and placed on a stand

along the trajectory line of the ball. The target size was 25 inches in diameter (see Figure

3.10 below). The size of the ball (5 inches in diameter, represented by pink zone in Fig.

3.10) determined the target size. Ideally the ball should land within 7.5 inches of the

target (represented by the red and pink zones in Fig. 3.10), which is two ball widths away

from the center of the target. Landing in this zone will help to ensure that the player can

receive the ball to make effective movements.

Figure 3.10 Ball Target Size Created in Pro/ENGINEER

3. Set up mechanism:

After the target is set up, the mechanism will need to be set up based on the projectile equations generated in Mathematica (see Appendix B). First, place the mechanism at specified distance (x) with the ball shooter in line with the target. Second, adjust the initial launching height (h) of the ball shooter. Third, adjust the launching angle

(θ). The angle of each test is set up by using an angle finder (Swanson, Magnetic C Angle

Finder) on the ball shooter between the two counter rotating wheels at the releasing point.

Fourth, adjust the initial speed (u) for the ball shooter by changing the RPM of the top and bottom counter rotating wheels. A digital photo tachometer (DT-2234C+) is used to measure the RPM of the counter rotating wheels. A speed gun is used to measure the ball

velocity. The basic experimental set up can be illustrated in Figure 3.11. See Appendix B for details for each test’s projectile calculations. A video camera was placed behind the ball throwing mechanism to observe if the machine replicates the ball motion and to assist with data gathering. The following tests were set up:

• Partial automatic at 30 degrees at a launching height of 3 feet at 6 second time

interval (tossing)

• Partial automatic at 30 degrees at a launching height of 3 feet at 10 second time

interval (tossing)

• Partial automatic at 50 degrees at a launching height of 3 feet (tossing)

• Automatic feed at 11.5 degrees at a launching height of 6.5 feet (serving &

spiking)

• Automatic feed at 11.5 degrees at a launching height of 3.5 feet (tossing)

• Partial automatic at 75 degrees at a launching height of 2.5 feet (setting)

4. Insert ball into mechanism:

There are two ways to insert a ball into the ball shooter mechanism. See Fig. 3.12.

First, the ball can be inserted by ball feeder (automated). The ball will be placed into the

hopper by a human and then fall into the rotating carousel and dropped by gravity at the bottom of the ball feeder into the ball shooter.

Second, the ball can be inserted into the mechanism by a human placing the ball into the ball shooter directly (partial automated). A wood lever can be used by a human to direct the ball into the ball shooter to keep the insert consistent.

5. Record ball position:

Record the location where the ball hit the target. The observer used a marking pencil to mark the position where the ball places on the 25 inch diameter target area.

6. Repeat for consistency:

Repeat 50 times for each test to ensure a sufficient sample size and increase precision in estimates.

ball

ball throwing mechanism

video camera target

initial height

target height target stand

target distance

Figure 3.11 Experimental Set Up For Accuracy Testing of Ball Throwing Mechanism. Not to Scale.

Figure 3.12 Flow Chart of Sepak Takraw Ball Throwing Mechanism

Chapter 4

RESULTS AND DISCUSSION

Design Requirements Met

After design and testing, the design requirements were reviewed and showed that

the Sepak Takraw ball throwing machine is capable of meeting 10 out of 11 design requirements. See Table A.3 in the Appendix for details on how the mechanism met the requirements. In summary, the final Sepak Takraw ball throwing mechanism was:

• portable and fit in a car.

• partially automatic for the ball shooter, automated for the ball feeder.

• sufficient in ball capacity, fitting up to 10 balls.

• battery powered.

• able to generate ball speeds from 10-53 mph.

• able to shoot the ball from 2-45 feet in distance.

• able to adjust ball release point from 2.5-8 feet high from the ground.

• +/- 30 degree ball launching angle adjustable along a horizontal plane

• +80 and -30 degree angle adjustable along a vertical plane.

• able to generate various time intervals of ball release.

The only one design requirement that wasn’t met was the weight of the machine

(lighter than 50 pounds). This requirement wasn’t met because the researcher selected the

material of steel for the ball shooter and adjustable pole parts of the prototype design due

to cost and experience of the researcher in working with the material. In the future, more

lightweight materials such as aluminum might be considered for the ball shooter to

minimize weight. Also some of the steel parts could be cut into smaller, lighter sizes with more time and availability of the machine shop. The ball feeder was made out of wood, which may have added weight. This material was picked due to availability of tools for cutting and researcher experience using the tools. The researcher chose wood since it was easier to cut into shape needed for the feeder box. In future designs, plastic could be used to decrease weight of the ball feeder.

The manufacturing process took longer compared to the other process in this study due to lack of tools, limited hours of the ECS Tech Shop, limited equipment, limited tool experience, and other challenges of the hands-on manufacturing process for the researcher. During the manufacturing process, the design was iteratively adapted to ensure the machine worked in the desired way. For example, connecting the motor shaft to the counter rotating wheels of the ball shooter and getting the wheels to spin without vibration was a big challenge because the shaft was designed to be supported on one side of the wheel. For future designs, the motor axis support must be more balanced with the wheels and the shaft should be supported on both sides of the wheels to ensure stability and increase performance and accuracy of the mechanism.

Overall the mechanism met the needs of Sepak Takraw players. The Sepak

Takraw ball throwing mechanism as designed can generate the tossing, serving, setting and spiking ball motions which are needed to practice the unique sport of Sepak Takraw.

Testing Results

The following tests were done prior to the accuracy testing to determine suitable pressure for the wheels, gap between the wheels, maximum velocity, maximum range, and time interval of ball release to produce the most efficient ball motion.

Table 4.1 The Suitable Tire Pressure of Wheels

Tire Launching Average Initial speed Spin/ Distance pressure angle distance (mph) No spin (ft) (psi) (degree) (ft) 45 20 spin 41 10 45 20 spin 38 41.47 45 20 spin 45.4 45 20 spin 41.3 15 45 20 spin 47 44.60 45 20 spin 45.5 45 20 spin 38.5 20 45 20 spin 36.7 38.23 45 20 spin 39.5

The most suitable pressure of the two tires was 15 psi, which propelled the ball to the longest average distance, 44.60 feet. Thus the rest of the tests used this tire pressure.

Table 4.2 The Suitable Gap Between Two Wheels

Average Wheel gap Tire pressure Initial speed Spin/ Distance distance (inch) (psi) (mph) No spin (ft) (ft) 15 20 spin 43.5 4.5 15 20 spin 37 40.17 15 20 spin 40 15 20 spin 18.5 4.75 15 20 spin 27 22.00 15 20 spin 20.5

The most suitable gap between two wheels was 4.5 inches, which shot the ball the longer average distance, 40.17 feet, compared to a gap at 4.75 inches, which only shot the ball to 22.0 feet.

Table 4.3 Maximum Range

Tire Launching Average Initial speed Spin/No Distance pressure angle distance (mph) spin (ft) (psi) (degree) (ft) 45 49 spin 45.75 15 44.88 45 49 spin 44

The maximum range found when tested at a 45 degree launching angle was 45.75 feet.

Table 4.4 Maximum Ball Velocity

Maximum ball velocity Ball release point (ft) Launching angle (degree) (mph) 5 0 53

The maximum ball velocity recorded was 53 miles per hour.

Table 4.5 Ball Feeder Efficiency at 6 Balls per Minute (10 Second Time Interval)

Number of balls passed Ball total Number of balls stuck through 50 48 2

At a feeding rate of 6 balls per minute, 48 out of 50 balls passed through the rotating carousel of the ball feeder, which is 96% feeding efficiency.

The researcher used Wolfram Mathematica 7 as a tool to calculate projectile

equations used to predict target height for given angles and initial heights. Six tests

representing the various types of movements found in Sepak Takraw were done to

validate the accuracy of the ball motion generated by the mechanism. The experiment

showed that the Sepak Takraw ball throwing mechanism could meet the targets of

projectile equations by having reasonable standard deviation from calculated results.

The standard deviation method and equation were used to justify the accuracy of the

mechanism based on average length from target. The equation for standard deviation is as

follows:

(3.5)

σ: standard deviation x: individual sample

: average

N: number of samples

As discussed in the methodology section, a 7.5 inch radius is acceptable distance

from the center of the target. The test results can show accuracy and consistency of the

ball motion generated by the throwing mechanism by using average values of the ball

distance from the target and standard deviation.

If the number for standard deviation is high it shows that the distribution of the

average values of the ball accuracy testing is spread all over and inconsistent. On the

other hand if the standard deviation is low then the results are close to the average values

and accuracy is consistent and acceptable. Assuming normal distribution of data (i.e. bell

curve), the standard deviation method [16] can be used to validate the expected landing

position of the balls in relation to the target. Using average length ( ) plus or minus

three standard deviation (σ) units, the lowest and highest lengths from the target can be

calculated, and 99.73% of all balls shot should fall within that range. In other words, 99

out of 100 balls will fall within the expected range.

The Tables with results of the standard deviation accuracy tests can be found in the Appendix in Tables A.4, A.5, A.6, A.7, A.8 and A.9. The first two projectile accuracy tests, seen in Tables A.4 and A.5, were run to establish the best time interval to use for the rest of the projectile accuracy tests. See Tables A.4 and A.5 for the standard deviations for the tests for the following conditions:

• 30 degrees at 20 mph at 6 second time interval

• 30 degrees at 20 mph at 10 second time interval

According to the results of the tests, the machine performed better at the 10 second time interval (6 balls per minute) set up compared to the 6 second time interval

(10 balls per minute). This can be demonstrated by a lower standard deviation and

average value of length from target for the 10 second time interval (σ = 3.29 and 6.79 inches respectively) as compared to the 6 second time interval (σ = 4.67 and 8.3 inches respectively). Assuming normal distribution, we can expect that 99.73% of the balls shot to the target will fall within plus and minus three standard deviation (3σ) units of the average length from the target, or within a range of 0 to 16.66 inches and 0 to 22.3 inches for the 10 second time intervals and the 6 second time intervals, respectively. These results are acceptable for professional players who have more kicking skills and are able to kick the ball at 2-3 times the ideal range (7.5 inches). The results show that the 10 second time interval has a smaller average range compared to the 6 second time interval.

In addition, the 10 second time interval had fewer errors (2 out of 50 throws) compared to the 6 second time interval (19 out of 50 throws) with the same experimental conditions.

Thus it was determined that the rest of the tests would be run using the 10 second time interval. The researcher found that the 10 second time interval worked better and this may be because the motor needs more recovery time to get speed back after a ball is ejected from the two wheels.

Tables A.6, A.7, A.8 and A.9 outline the results of tests for the following conditions:

• 50 degrees at 16 mph at 10 second time interval at initial height of 3 feet

• 11.5 degrees at 20 mph at 10 second time interval at initial height of 3.5 feet

• 11.5 degrees at 21 mph at 10 second time interval at initial height of 6.5 feet

• 75 degrees at 18 mph at 10 second time interval at initial height of 2.5 feet

Table 4.6 shows the standard deviations, average length from the target, range based on plus and minus three standard deviations, and number of balls missing the target area for those four tests. As seen in Table 4.6, the tests showed that lower ball launching angles had a lower average length and standard deviation than the higher angles. Overall, the results for standard deviation seen in Table 4.6 are acceptable for professional who can kick the ball at double the ideal range (7.5 inches). In addition, the number of balls missing the target were lower for the lower angles than the higher angles. See Figures

4.1 and 4.2 for bar graphs of these comparisons. Moreover, the standard deviation and average lengths from the target of the balls dropped by automatic ball feeder mechanism were lower compared to the results for balls using partial auto mode. This may be due to the error from the human feeding the ball in partial auto mode.

Table 4.6 Standard Deviations, Average Length, and Number of Balls Missing Target Area

Angle (˚) Standard Average length Number of 3σ deviation (σ) from target, balls missing (inch) (inch) target area 11.5 (auto ball feeder, 2.51 5.93 4 13.46 3.5 ft) 11.5 (auto ball feeder, 2.36 6.99 14 14.07 6.5 ft) 50 (partial auto – 3 ft) 2.93 7.81 18 16.6 75 (partial auto – 2.5 2.65 8.95 28 16.9 ft)

30 11.5° (auto ball feeder, 3.5 ft) 25 20 11.5° (auto ball feeder, 6.5 ft) 15 10 50° (partial auto, 3 ft) 5 0 75° (partial auto, 2.5 ft) number of balls that missed target

Figure 4.1 Number of Balls Missing Target Based on Angle and Feeder Mode of Mechanism

3 11.5 ° (auto ball feeder, 3.5 ft) 2.5

2 11.5 °(auto ball feeder, 6.5 ft) 1.5 1 50 ° (partial auto, 3 ft) 0.5 0 75 ° (partial auto, 2.5 ft) standard deviation

Figure 4.2 Standard Deviation Based on Angle, Height, and Feeder Mode of Mechanism

The causes of the variations may have been from:

• Human – in partial auto mode (at angles above 11.5 degrees), the human pushed

the ball into the ball shooter using a wood lever

• Machine – wheels’ vibration, wheel surface not flat, contact area, etc.

• Measurement – since a human had to measure the distance from the target and

mark when the ball hit the target

• Wheel surface - the contacting area between the wheels and the ball, since the

wheels are in a curve shape

• Windy conditions – the conditions were windy on the day of the testing

• Battery ran out of power - when the battery was low, the speed of the motor was

low too, and that reduced the ball speed

• Drag force – drag force was neglected in the projectile equation motion analysis

• Method – initial speed of the ball thrown may not have been the initial speed

when we used the speed gun

Even though there were some issues, overall when using the mechanism for training, Sepak Takraw players were excited with the results of the first Sepak Takraw ball throwing mechanism and the motions that could be created to do different moves. A video screenshot of Sepak Takraw players testing the machine is found in Figure 4.3.

Figure 4.3 Sepak Takraw Players Interacting with the Sepak Takraw Ball Throwing Mechanism to Practice

Feedback of Sepak Takraw players after trying the machine was positive. For example, one player said that the machine can help him improve his kicking skills. In a short period of time he said he was able to kick so many balls and the mechanism could

shoot the balls both to repeating spots and also randomly to challenge him. Another

player mentioned that when he practiced kicking the ball after it was served by the

mechanism, he felt like he received the Sepak Takraw ball from a professional player

because the ball was fast and had spin.

Chapter 5

CONCLUSION

The objective to build the first prototype for a Sepak Takraw ball throwing

mechanism was met. Results showed that the new Sepak Takraw ball throwing

mechanism is capable of recreating realistic Sepak Takraw ball motion and can even be

used by one person. Accuracy of the ball motion generated by the mechanism was

validated. The study also aimed to gather kinematic data that doesn’t currently exist for the sport of Sepak Takraw, and the study met this objective.

The kinematic data and the principles used in this study can be useful for research. Since an engineering study about Sepak Takraw has never been done before, this study can be used as base standard information for future reference for others interested in this kind of ball motion, ball mechanism, and the study of developing kicking skills in Sepak Takraw.

Improve Design/Future Study

Since the maximum angle that can be used on automatic ball feeder mode is only

11.5 degrees, for future study, researcher needs to insert a part such as a counter weight lever that can automatically push the ball in between the two counter rotating wheels.

This would allow more automated movement for all angles by not requiring "gravity" to drop the balls from the ball feeder into the ball shooter. In addition, for serving and

spiking ball throwing, which are at heights of 5-8 feet tall, the mechanism’s ball hopper is too tall for loading the balls into the feeder. In the future, ball feeder feeding efficiency can also be improved by ensuring stability of the rotating carousel. For the adjustable height telescopic pole, there can be an improvement by developing the pulley system to make it easier to adjust the height of ball release.

Also, as mentioned earlier there needs to be better motor shaft support since now it's only attached to one side of the wheel, and this can cause vibration on wheels.

Another improvement on the wheels would be to change the color of the wheels to a light color, to avoid marking on the Sepak Takraw ball surface. In addition, increase the width of the two counter rotating wheels and contact area of the ball to increase the area of friction and grip needed to increase consistency to shoot the ball out of the ball shooter.

In the future prototype the researcher could also work with Sepak Takraw coaches to create user training and a user manual on how to use the Sepak Takraw ball throwing mechanism to improve athlete’s skills.

Appendices

Table A.1 Ball Velocity of Four Movements Using a Speed Gun

Ball velocity (mph) Number Tossing Serving Setting Spiking 1 11 28 10 34 2 12 32 14 36 3 13 36 13 36 4 10 33 11 30 5 10 34 11 26 6 12 31 12 23 7 12 30 14 28 8 12 32 15 21 9 13 34 12 28 10 12 28 14 30 11 14 25 13 35 12 13 26 16 32 13 12 26 15 30 14 15 25 14 30 15 13 24 13 37 16 12 17 12 37 17 13 18 14 40 18 10 31 15 31 19 15 26 13 44 20 13 28 14 42 21 14 27 16 27 22 13 28 14 31 23 12 25 12 33 24 12 24 15 44 25 13 25 13 40 Average 12.62 26.86 13.67 32.81

Table A.2 Velocity of the Wheels and Velocity of the Balls Given Different RPM

ω1 ω2 vball (rpm) r1 (in) v1 (in/s) (rpm) r2 (in) v2 (in/s) vball (in/s) (mph) 1 300 4.5 141.3 300 4.5 141.3 141.3 8.03 2 350 4.5 164.85 350 4.5 164.85 164.85 9.37 3 400 4.5 188.4 400 4.5 188.4 188.4 10.70 4 450 4.5 211.95 450 4.5 211.95 211.95 12.04 5 500 4.5 235.5 500 4.5 235.5 235.5 13.38 6 550 4.5 259.05 550 4.5 259.05 259.05 14.72 7 600 4.5 282.6 600 4.5 282.6 282.6 16.06 8 650 4.5 306.15 650 4.5 306.15 306.15 17.39 9 700 4.5 329.7 700 4.5 329.7 329.7 18.73 10 750 4.5 353.25 750 4.5 353.25 353.25 20.07 11 800 4.5 376.8 800 4.5 376.8 376.8 21.41 12 850 4.5 400.35 850 4.5 400.35 400.35 22.75 13 900 4.5 423.9 900 4.5 423.9 423.9 24.09 14 950 4.5 447.45 950 4.5 447.45 447.45 25.42 15 1000 4.5 471 1000 4.5 471 471 26.76 16 1050 4.5 494.55 1050 4.5 494.55 494.55 28.10 17 1100 4.5 518.1 1100 4.5 518.1 518.1 29.44 18 1150 4.5 541.65 1150 4.5 541.65 541.65 30.78 19 1200 4.5 565.2 1200 4.5 565.2 565.2 32.11 20 1250 4.5 588.75 1250 4.5 588.75 588.75 33.45 21 1300 4.5 612.3 1300 4.5 612.3 612.3 34.79 22 1350 4.5 635.85 1350 4.5 635.85 635.85 36.13 23 1400 4.5 659.4 1400 4.5 659.4 659.4 37.47 24 1450 4.5 682.95 1450 4.5 682.95 682.95 38.80 25 1500 4.5 706.5 1500 4.5 706.5 706.5 40.14 26 1550 4.5 730.05 1550 4.5 730.05 730.05 41.48 27 1600 4.5 753.6 1600 4.5 753.6 753.6 42.82 28 1650 4.5 777.15 1650 4.5 777.15 777.15 44.16 29 1700 4.5 800.7 1700 4.5 800.7 800.7 45.49 30 1750 4.5 824.25 1750 4.5 824.25 824.25 46.83 31 1800 4.5 847.8 1800 4.5 847.8 847.8 48.17 32 1850 4.5 871.35 1850 4.5 871.35 871.35 49.51 33 1900 4.5 894.9 1900 4.5 894.9 894.9 50.85 34 1950 4.5 918.45 1950 4.5 918.45 918.45 52.18

ω1 ω2 vball (rpm) r1 (in) v1 (in/s) (rpm) r2 (in) v2 (in/s) vball (in/s) (mph) 35 2000 4.5 942 2000 4.5 942 942 53.52 36 2050 4.5 965.55 2050 4.5 965.55 965.55 54.86 37 2100 4.5 989.1 2100 4.5 989.1 989.1 56.20 38 2150 4.5 1012.65 2150 4.5 1012.65 1012.65 57.54 39 2200 4.5 1036.2 2200 4.5 1036.2 1036.2 58.87 40 2250 4.5 1059.75 2250 4.5 1059.75 1059.75 60.21 41 2300 4.5 1083.3 2300 4.5 1083.3 1083.3 61.55 42 2350 4.5 1106.85 2350 4.5 1106.85 1106.85 62.89 43 2400 4.5 1130.4 2400 4.5 1130.4 1130.4 64.23 44 2450 4.5 1153.95 2450 4.5 1153.95 1153.95 65.57 45 2500 4.5 1177.5 2500 4.5 1177.5 1177.5 66.90 46 2550 4.5 1201.05 2550 4.5 1201.05 1201.05 68.24 47 2600 4.5 1224.6 2600 4.5 1224.6 1224.6 69.58 48 2650 4.5 1248.15 2650 4.5 1248.15 1248.15 70.92 49 2700 4.5 1271.7 2700 4.5 1271.7 1271.7 72.26 50 2750 4.5 1295.25 2750 4.5 1295.25 1295.25 73.59 51 2800 4.5 1318.8 2800 4.5 1318.8 1318.8 74.93 52 2850 4.5 1342.35 2850 4.5 1342.35 1342.35 76.27 53 2900 4.5 1365.9 2900 4.5 1365.9 1365.9 77.61 54 2950 4.5 1389.45 2950 4.5 1389.45 1389.45 78.95 55 3000 4.50 1413.00 3000 4.50 1413.00 1413.00 80.28 56 3050 4.5 1436.55 3050 4.5 1436.55 1436.55 81.62 57 3100 4.5 1460.1 3100 4.5 1460.1 1460.1 82.96 58 3150 4.5 1483.65 3150 4.5 1483.65 1483.65 84.30 59 3200 4.5 1507.2 3200 4.5 1507.2 1507.2 85.64 60 3250 4.5 1530.75 3250 4.5 1530.75 1530.75 86.97 61 3300 4.5 1554.3 3300 4.5 1554.3 1554.3 88.31 62 3350 4.5 1577.85 3350 4.5 1577.85 1577.85 89.65 63 3400 4.5 1601.4 3400 4.5 1601.4 1601.4 90.99 64 3450 4.5 1624.95 3450 4.5 1624.95 1624.95 92.33 65 3500 4.5 1648.5 3500 4.5 1648.5 1648.5 93.66 66 3550 4.5 1672.05 3550 4.5 1672.05 1672.05 95.00 67 3600 4.5 1695.6 3600 4.5 1695.6 1695.6 96.34 68 3650 4.5 1719.15 3650 4.5 1719.15 1719.15 97.68 69 3700 4.5 1742.7 3700 4.5 1742.7 1742.7 99.02 70 3750 4.5 1766.25 3750 4.5 1766.25 1766.25 100.35 71 3800 4.5 1789.8 3800 4.5 1789.8 1789.8 101.69

Table A.3 How Final Mechanism Met Design Requirements

Design Requirements Design How did the mechanism meet the requirements 1 Portable: Transportable from one Transported machine in medium location to another location by  sized car vehicle. 2 Weight under 50 pounds: easy to Did not meet but each component take apart and assemble.  weighs under 50 pounds and mechanism can be taken apart. 3 Partially Automatic: operating by Ball feeder is automatic and itself or by using only a few  mechanism only has 3 controls. controls. 4 Sufficient Ball Capacity: Able to  Able to hold 10 balls at a time. contain up to 10 balls. 5 Battery powered: able to run the  Used 12 Volt rechargeable machine without electrical outlet. battery power. 6 Able to generate ball speeds from Speeds up to 53 MPH were  10- 60 MPH. observed using a speed gun. 7 Able to shoot the ball from 2-45 Ball distances up to 45 feet were  feet in distance. observed. 8 Able to adjust ball release point Ball release points found at these from 2.5-8 feet high from the  heights using telescopic ground. adjustable pole. 9 +/- 30 degree ball launching angle Used four swivel wheels to adjust adjustable along a horizontal  horizontal rotation. plane

10 +80 and -30 degree angle  Tilted ball shooter to adjust adjustable along a vertical plane. vertical angles. 11 Able to generate various time Ball release time intervals of 6 intervals of ball release.  seconds and 10 seconds were observed.

Table A.4 Partial Automatic at 30 Degrees at a Launching Height of 3 Feet at 6 Second Time Interval (Tossing)

No. Length from target (in) x-xbar (x-xbar)^2 1 4 -4.31 18.5761 2 4.5 -3.81 14.5161 3 2.5 -5.81 33.7561 4 5.5 -2.81 7.8961 5 4.25 -4.06 16.4836 6 3.75 -4.56 20.7936 7 5.25 -3.06 9.3636 8 0.5 -7.81 60.9961 9 11 2.69 7.2361 10 5.25 -3.06 9.3636 11 2.5 -5.81 33.7561 12 12 3.69 13.6161 13 11.5 3.19 10.1761 14 12.5 4.19 17.5561 15 10.5 2.19 4.7961 16 6 -2.31 5.3361 17 5.5 -2.81 7.8961 18 17 8.69 75.5161 19 1 -7.31 53.4361 20 9.5 1.19 1.4161 21 12 3.69 13.6161 22 9.75 1.44 2.0736 23 11.5 3.19 10.1761 24 8.5 0.19 0.0361 25 22 13.69 187.4161 26 9.5 1.19 1.4161 27 8.5 0.19 0.0361 28 9.5 1.19 1.4161 29 12.5 4.19 17.5561 30 6.5 -1.81 3.2761 31 12.5 4.19 17.5561 Average 8.30 sum = 677.0566 σ = 4.67

Table A.5 Partial Automatic at 30 Degrees at a Launching Height of 3 Feet at 10 Second Time Interval (Tossing)

No. Length from target (in) x-xbar (x-xbar)^2 1 6.5 -0.29 0.0841 2 2 -4.79 22.9441 3 4 -2.79 7.7841 4 11.25 4.46 19.8916 5 11.25 4.46 19.8916 6 9.25 2.46 6.0516 7 9.75 2.96 8.7616 8 1.5 -5.29 27.9841 9 6 -0.79 0.6241 10 2.25 -4.54 20.6116 11 9.75 2.96 8.7616 12 11 4.21 17.7241 13 11.5 4.71 22.1841 14 8.75 1.96 3.8416 15 8 1.21 1.4641 16 11.5 4.71 22.1841 17 11 4.21 17.7241 18 8.5 1.71 2.9241 19 11.5 4.71 22.1841 20 12 5.21 27.1441 21 11 4.21 17.7241 22 9 2.21 4.8841 23 7.5 0.71 0.5041 24 9.5 2.71 7.3441 25 5 -1.79 3.2041 26 6 -0.79 0.6241 27 9.25 2.46 6.0516 28 5.5 -1.29 1.6641 29 2.25 -4.54 20.6116 30 11.75 4.96 24.6016 31 4 -2.79 7.7841 32 2.5 -4.29 18.4041 33 6.5 -0.29 0.0841 34 5.25 -1.54 2.3716 35 3.5 -3.29 10.8241

No. Length from target (in) x-xbar (x-xbar)^2 36 5 -1.79 3.2041 37 6 -0.79 0.6241 38 2.5 -4.29 18.4041 39 2.5 -4.29 18.4041 40 4.5 -2.29 5.2441 41 9.75 2.96 8.7616 42 4.5 -2.29 5.2441 43 5 -1.79 3.2041 44 2.5 -4.29 18.4041 45 3.5 -3.29 10.8241 46 7 0.21 0.0441 47 3 -3.79 14.3641 48 4.5 -2.29 5.2441 Average 6.79 sum = 519.4168 σ= 3.29

Table A.6 Partial Automatic at 50 Degrees at a Launching Height of 3 Feet (Tossing)

No. Length from Target (in) x-xbar (x-xbar)^2 1 9.5 1.69 2.8561 2 6 -1.81 3.2761 3 6 -1.81 3.2761 4 2 -5.81 33.7561 5 9.5 1.69 2.8561 6 7.5 -0.31 0.0961 7 7.25 -0.56 0.3136 8 6 -1.81 3.2761 9 9.5 1.69 2.8561 10 11.75 3.94 15.5236 11 11 3.19 10.1761 12 10 2.19 4.7961 13 10.05 2.24 5.0176 14 10.25 2.44 5.9536 15 5 -2.81 7.8961 16 5.25 -2.56 6.5536 17 12 4.19 17.5561 18 11 3.19 10.1761 19 12 4.19 17.5561 20 10.25 2.44 5.9536 21 9 1.19 1.4161 22 10 2.19 4.7961 23 5 -2.81 7.8961 24 5.5 -2.31 5.3361 25 4.5 -3.31 10.9561 26 2.5 -5.31 28.1961 27 2.25 -5.56 30.9136 28 7 -0.81 0.6561 29 6 -1.81 3.2761 30 12 4.19 17.5561 31 6 -1.81 3.2761 32 8.5 0.69 0.4761 Average 7.81 sum = 274.4717 σ = 2.93

Table A.7 Automatic Feed at 11.5 Degrees at a Launching Height of 6.5 Feet (Serving & Spiking)

No. Length from Target (in) x-xbar (x-xbar)^2 1 6 0.07 0.0049 2 8 2.07 4.2849 3 5.5 -0.43 0.1849 4 7 1.07 1.1449 5 6 0.07 0.0049 6 4 -1.93 3.7249 7 7.5 1.57 2.4649 8 3.25 -2.68 7.1824 9 3.5 -2.43 5.9049 10 3.5 -2.43 5.9049 11 4 -1.93 3.7249 12 2 -3.93 15.4449 13 6 0.07 0.0049 14 4.5 -1.43 2.0449 15 6 0.07 0.0049 16 10.5 4.57 20.8849 17 3 -2.93 8.5849 18 4.5 -1.43 2.0449 19 7.75 1.82 3.3124 20 10 4.07 16.5649 21 11 5.07 25.7049 22 11 5.07 25.7049 23 8 2.07 4.2849 24 3.25 -2.68 7.1824 25 2 -3.93 15.4449 26 10 4.07 16.5649 27 10.5 4.57 20.8849 28 5 -0.93 0.8649 29 7 1.07 1.1449 30 8.5 2.57 6.6049 31 3.75 -2.18 4.7524 32 7 1.07 1.1449 33 8.5 2.57 6.6049 34 4 -1.93 3.7249

No. Length from Target (in) x-xbar (x-xbar)^2 35 8.25 2.32 5.3824 36 6 0.07 0.0049 37 4.5 -1.43 2.0449 38 3 -2.93 8.5849 39 6 0.07 0.0049 40 3.5 -2.43 5.9049 41 8.5 2.57 6.6049 42 5.25 -0.68 0.4624 43 3.5 -2.43 5.9049 44 3.5 -2.43 5.9049 45 4.5 -1.43 2.0449 46 4.5 -1.43 2.0449 Average 5.93 sum = 288.9304 σ = 2.51

Table A.8 Automatic Feed at 11.5 Degrees at a Launching Height of 3.5 Feet (Tossing)

No. Length from Target (in) x-xbar (x-xbar)^2 1 6 -0.99 0.9801 2 9 2.01 4.0401 3 6 -0.99 0.9801 4 6 -0.99 0.9801 5 5 -1.99 3.9601 6 8.5 1.51 2.2801 7 7.25 0.26 0.0676 8 4 -2.99 8.9401 9 7 0.01 1E-04 10 11 4.01 16.0801 11 4.5 -2.49 6.2001 12 11 4.01 16.0801 13 8.5 1.51 2.2801 14 4 -2.99 8.9401 15 4.5 -2.49 6.2001 16 6 -0.99 0.9801 17 3.5 -3.49 12.1801 18 4.5 -2.49 6.2001 19 8 1.01 1.0201 20 6 -0.99 0.9801 21 8.5 1.51 2.2801 22 2.75 -4.24 17.9776 23 12 5.01 25.1001 24 8 1.01 1.0201 25 5 -1.99 3.9601 26 5.5 -1.49 2.2201 27 7 0.01 1E-04 28 6.75 -0.24 0.0576 29 4 -2.99 8.9401 30 7 0.01 1E-04 31 11.5 4.51 20.3401 32 9 2.01 4.0401 33 10 3.01 9.0601 34 8.5 1.51 2.2801 35 9 2.01 4.0401 36 7 0.01 1E-04 Average 6.99 sum = 200.6861 σ = 2.36

Table A.9 Partial Automatic at 75 Degrees at a Launching Height of 2.5 Feet (Setting)

No. Length from Target (in) x-xbar (x-xbar)^2 1 11 2.05 4.2025 2 5.5 -3.45 11.9025 3 4 -4.95 24.5025 4 9.5 0.55 0.3025 5 11.25 2.3 5.29 7 11 2.05 4.2025 8 6.5 -2.45 6.0025 9 2.5 -6.45 41.6025 10 10 1.05 1.1025 11 12 3.05 9.3025 12 9.5 0.55 0.3025 13 6 -2.95 8.7025 14 8.5 -0.45 0.2025 16 7.5 -1.45 2.1025 17 10 1.05 1.1025 18 12 3.05 9.3025 19 5 -3.95 15.6025 20 11 2.05 4.2025 21 11 2.05 4.2025 22 8 -0.95 0.9025 Average 8.59 sum = 155.0375 σ = 2.65

Appendix A

Motor and Wheel Size Calculations for Ball Shooter

Assumptions:

1) Ejecting 10 balls/minute

2) Maximum ball velocity is 60 MPH or 26.8 m/s

3) Powered by 12 volt battery

Given:

1) Ball mass is 177 grams or 0.39 lb

2) Shooting wheel diameter is 9 inches or 0.2286 m

3) Shooting wheel mass is 0.5 kg or 1.1 lbs

Free body diagram:

Solution

= ( )/2 r = =

= v = ωr r = 4.5 in or 0.1143 m

ω= = 234.5 rad/s

Convert to RPM: = 37.32 revolutions/second

= 37.32∗60 revolutions/minute

= 2240 RPM

Motor without load requires RPM = 2,240

Assume that safety factor of load acting on motor shaft is 1.5.

∴ Suitable motor to generate ball speed at 60 mph is:

= 2240*1.5

= 3360 RPM or 351.8 rad/s

Calculate amount of kinetic energy for ejecting the ball at 60 MPH:

= m

= (0.177 kg)

= 63.56 J

Power to eject 10 balls per minute:

P1 = ( )/t

= 10* 63.56 J

= 635.6 J/min

= J/s

P1 = 10.6 watts

There are two flywheels, so each wheel takes

∴one flywheel needs power of 5.3 watts

Energy stored in a shooting wheel:

= I

I = m = (0.5 kg) = 0.00326 kg.

∴ = I

= (0.00326)

= 201.73 J

Power needed to store enough energy to eject 10 balls per minute (P2):

P2= (10*201.73 J)/ 60s

P2= 33.62 watt

= P1+P2

5.3 + 33.62 = 38.92 watt or 0.052 hp

Assume that the safety factor is 3

∴ = 3*0.52 = 0.156 hp

∴ Motor specifications needed for shooting balls at 60 MPH and 10 balls per minute are:

0.156 hp with 3360 rpm

Motor calculations for carousel of ball feeder

Assumptions:

1) The slowest ball feeding rate is every 10 seconds (6 balls/min) or 1.5 RPM. The maximum ball feeding rate needed is 6 seconds (10 balls/min) or 2.5 RPM.

2) A maximum of 10 balls are contained in the ball feeder, and 4 balls can be contained in the carousel at a time.

3) Time required for carousel to reach the desired angular velocity from resting position is 0- 0.2 seconds (after turning on the switch).

4) Powered by 12 volt battery

Given:

1) Ball mass is 177 grams, or 0.39 lbs

2) Carousel diameter is16 inches, 5 inches thick

3) Carousel mass is 0.55 lbs

4) There are 4 ball pockets in the carousel, at 90 degree angles to each other (Figure 3.6)

Solution

)

= Angular acceleration (rad/ )

Moment of inertia of solid disk is m when r=radius of the disk

I= (0.55+(4 ))

I=67.52 lb.

1.5 RPM = 0.157 rad/s

.157 0.2 rad/

= 0.785 rad/

= 67.52 0.785

= 53 lb.in

Safety factor = 1.5

The desired motor should have torque that falls within the range of 53 to 79.5 lb.in and provides at least 2.5 RPM.

Appendix B

Projectile Calculations Using Wolfram Mathematica 7

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References

[1] International Sepak Takraw Federation, “Laws of the Game SepakTakraw” in The

24th King’s Cup Sepaktakraw World Championship 2009 Program, Bangkok,

Thailand, July 2-7, 2009.

[2] USA Takraw Association [Online], Available: http://www.takrawusa.com.

[3] Hudson Soft Co. Ltd., “Deca Sports DS” Video Game, Nintendo DS, 2009.

[4] B. Lorhpipat and B. Lorpipatana, “Mkv Takraw Ball,” Patent No. 20070254754,

Patented Date November 1, 2007, U.S. Patent and Trademark Office.

[5] S.P. Mish and M. Hubbard, "Design of a full degree-of-freedom baseball pitching

machine” in Sports Engineering, vol. 4, pp.123-133, 2001.

[6] S. Sakai, J. Oda, S. Yonemura, K. Kawata, S. Horikawa, and H. Yamamoto,

“Research on the development of baseball pitching machine” in Journal of System

Design and Dynamics, vol. 1 no. 4, pp. 682-690, 2007.

[7] S. Daigh, Shooting device for free-surface impact studies, Bachelor of Science Thesis,

Massachusetts Institute of Technology, 2004.

[8] L.W. Alaways, Aerodynamics of the curve-ball: an investigation of the effects of

angular velocity on baseball trajectories, PhD Dissertation. University of

California, Davis, 1998.

[9] J. Kotze and S.R. Mitchell, “A tennis serve impact simulation machine” in The

Engineering of Sport 4, pp. 477-484, 2002.

[10] Sports Attack [Online]. Available: http://www.sportsattack.com.

[11] S. Morgan and D. Reese, “Ball Throwing Machine Useful in Practicing the Game of

Volleyball,” Patent No. 4254755, Patented Date March 10, 1981, U.S. Patent and

Trademark Office.

[12] S.S. Roy, S. Karmakar, N.P. Mukherjee, U. Nandy, and U. Datta, “Design and

development of indigenous cricket bowling machine” in Journal of Scientific &

Industrial Research, vol. 65, pp. 148-152, 2006.

[13] Pearson Education Limited, “Automated Definition”, in Longman Advanced

American Dictionary, p. 78, 2005.

[14] T.T. Ontam (private communication), 2010.

[15] Wolfram, Mathematica 7.0 [software]. Champaign, IL: Wolfram Research, Inc.,

2010.

[16] A. Kumagai, “Control Charts and Machine Capability” Handout, from Department

of Mechanical Engineering, California State University, Sacramento, Received

May 13, 2010.