composite telescopic tower report

Department of Mechanical Engineering

Machine Design III

Composite Tower for Various Applications

October 2012

Declaration

This report has been submitted to the Durban University of Technology on the 26 of October

2012. The authors declare that the report entitled ‘Composite Tower for Various

Applications’ is a record of their work carried out by themselves. The content of this report in

full or in part has not been submitted to this institution for any award:

Signed: _____________________ Govender N 20907576

_____________________ Govender Y 20910089

_____________________ Harrichand T 20600597

_____________________ Horning S S 20918319

_____________________ Jagjivan N 21142523

_____________________ Kahulume T 20924220

_____________________ Khoosal A M 21142431

_____________________ Khumalo N 21010156

Acknowledgements

We have taken efforts in this design project, however this would not have been possible

without the kind support and help of colleagues, lecturers, friends and families. We would

like to extend our sincere thanks to all of them.

We would like to express our gratitude to Professor Kanny for his guidance and assistance

in successfully completing this project.

ABSTRACT

The present design consists of a composite tower mounted on a trailer for circumstances of a

temporary nature. The tower includes a number of retractable segments which extend to a

maximum height of 10.5m and nest to minimum height of 2.7m. It can be moved to an

inclined position, for storage and transportation, and a vertical position for use. The highest

segment of the tower supports a flange on which a mast rotator is mounted to provide a 4500

rotational range to a maximum payload of 200kg. Each of the succeeding segments is

gradually smaller in cross sectional area to enable the nesting of the individual sections. The

extension of the tower is pneumatically operated.

In terms of improvement, advanced composite material technology would be utilized in the

manufacture of the tower structure. This offers a lower maintenance cost in the long run and a

lower risk of environmental pollution. There are also reduced installation costs when

composites are used. As a result the higher material cost of the composite material as opposed

to steel is offset.

CONTENTS

CHAPTER 1

1. INTRODUCTION 1

� Horning S – Khoosal A – Jagjivan N

CHAPTER 2

2. LITERATURE REVIEW 3

2.1 ALTERNATE MATERIALS 3

2.2 PROCESSES OF MANUFACTURE 3

2.3 TOWER DESIGNS 4

2.4 PNEUMATIC POWERED TOWER 4

2.5 HYDRAULIC POWERED TOWER 5

2.6 CHAIN DRIVEN TELESCOPING TOWER 5

� Harichand T – Khumalo N

CHAPTER 3

3. DESIGN 6

3.1 PRODUCT REQUIREMENT SPECIFICATION 6

� Harichand T

3.1.1 DESIGN REQUIREMENTS 6

3.1.2 DESIGN CONSTRAINTS 6

3.1.3 DESIGN CRITERIA 7

3.2 CONCEPTUAL DESIGN 7

� Group

3.2.1 DESIGN CONCEPTS 8

3.2.2 CONCEPTUAL DESIGN SELECTION 9

3.3 FINAL DESIGN 10

� Kahulume T 3.3.1 TOWER SECTIONS (SEGMENT) 11

3.4 STRUCTURE ANALYSIS 13

� Kahulume T

3.5 PISTON AND SEALS 19

� Kahulume T

3.5.1 SELECTION OF PISTONS MATERIAL 19

3.5.2 PISTON AND SCRAPER SEAL MATERIAL SELECTION 21

3.5.3 WEAR RING 23

3.6 COLLAR or CYLINDER END CAP 24

� Kahulume T

3.7 LOCKING MECHANISM 25

� Kahulume T

3.8 TILTING MECHANISM 26

� Khoosal A – Horning S - Kahulume T – Govender N

3.8.1 REACTIONS ON TOWER 27

� Kahulume T

3.8.2 CLEVIS MOUNTING AND PIN CALCULATION 29

3.8.3 PNEUMATIC PISTON ROD CALCULATION 31

� Kahulume T

3.8.4 WING BOLT CALCULATION 32

� Horning S

3.9 COMPRESSOR SELECTION 35

� Govender Y

3.9.1 THE MAXIMUM OPERATING PRESSURE REQUIRED 35

� Kahulume T

3.9.2 COMPRESSOR DRIVE SYSTEM 36

� Kahulume T

3.9.3 SELECTED COMPRESSOR SPECIFICATIONS 37

� Kahulume T

3.9.4 PNEUMATIC SYSTEM DIAGRAM 38

� Kahulume T

3.9.5 MAST ROTATOR 39

� Jagjivan N – Govender Y

3.9.6 INVERTER 39

� Govender Y

3.9.7 ELECTRICAL WIRING 41

� Govender Y

3.9.8 BATTERY ISOLATOR 43

� Goverder Y

3.9.9 SODIUM ELECTRICAL WIRE 44

� Govender Y

3.10 UNIVERSAL CONNECTING ADAPTERS FOR

COMPOSITE TOWER 45

� Jagjivan N – Govender N

3.10.1 UNIVERSAL POLE MOUNT – DOUBLE SIDED 45

3.10.2 UNIVERSAL TILTING BRACKET 46

3.10.3 POLE MOUNT SIDE ARMS – DOUBLE SIDED 47

3.10.4 ATTACHMENTS FOR SIDE ARMS 48

3.10.5 POLE KIT WITH 2 INCH (5.08 CM) U - BOLTS 49

3.11 FINITE ELEMENT ANALYSIS 52

� Horning S – Kahulume T

3.12 MANUFACTURING PROCESS 74

� Harichand T – Khumalo N

3.12.1 SYNOPSIS 74

3.12.2 MATERIAL SELECTION 75

3.12.3 TOWER MANUFACTURING PROCESS 77

3.12.4 REVIEWED MANUFACTURING PROCESS 77

3.12.5 CHOSEN MANUFACTURING PROCESS 79

3.12.6 CHASSIS MATERIAL 84

3.12.7 CHASSIS AND PLATFORM CONSTRUCTION 85

3.12.8 STANDARD PARTS TO BE USED 87

3.12.9 TOWER BASE PLATE 87

3.13 ENGINEERING DRAWINGS 90

� Kahulume T – Govender N

CHAPTER 4

4. HAZARD AND OPERABILITY STUDIES 124

� Group

4.1 HAZARD STUDIES 124

4.1.1 TOWER EXTENSION HAZARD 124

4.1.2 LIFTING HAZARD 124

4.1.3 TRANSPORTATION HAZARD 124

4.1.4 MOVING PARTS HAZARD 124

4.1.5 CRUSH HAZARD 124

4.1.6 BURST HAZARD 124

4.1.7 WELDING ALUMINIUM 125

4.2 TOWER OPERATION 126

4.2.1 SAFETY INSTRUCTIONS 126

4.2.2 EXTENDING THE TOWER 126

4.2.3 RETRACTING THE MAST 127

4.3 MAINTENANCE AND SERVICE INSTRUCTION 127

4.3.1 SCHEDULED MAINTENANCE 127

4.3.2 CORRECTIVE MAINTENANCE 128

CHAPTER 5

5. COSTING 129

� Group

CHAPTER 6

6.1 CONCLUSION 131

� Harichand T – Horning S

6.2 RECOMMENDATION 132

� Jagjivan N

CHAPTER 7

7.1 REFERENCES 133

7.2 APPENDIX 135

Machine Design III – Composite Tower for Various Applications

CHAPTER 1

1. INTRODUCTION

Increasing reliability, transportability and cost savings… Our group has been assigned

the task of designing a composite tower for various applications. Our project 'Composite

Tower for Various Applications' is to create a lightweight cost effective mobile platform that

can have various components installed on it. Mobile broadcasting stations are usually

expensive converted vehicles driven to locations to broadcast signals to viewers. However

due to cost most companies send out one to two vehicles depending on the scale of the

televised event. With our mobile trailer we could have only one main vehicle but multiple

antennas/trailers to boost signal and quality of the broadcast due to the lower cost of our

trailers. Due to the mobility of the trailer we can avoid damaging property as well as renting

property nor is there a need to fell trees or excavate land. Our trailers are not only limited to

broadcasting, atop our tower is a universal attachment for various applications such as

satellites for weather information. Our goal is to make a tower that can be used for as many

applications as possible making the transition between applications as quick and as cost

effective as possible.

The general approach to this project was to do extensive research on portable telescopic

towers, finding various designs, and gaining sufficient knowledge to improve on those

designs or even generate an entirely new innovative design. Although there are already

numerous proposals available, not all are considered to be reliable, easily transportable and

affordable to maintain. Therefore, several concept plans were drawn up by members in the

group, taking into account the limitations of the design, costing, the manufacturing process,

etc. With the most promising concepts being selected through an evaluation process, a further

analysis was carried out on those selected designs. Materials and mechanical components

(bearings, bolts, etc.) were also selected for certain concept plans, thus giving us a cost

estimate, aiding us in the selection process.

Included in this report are all of the concept designs, together with the evaluation/selection

1


method used. The pros and cons are listed as well, indicating the reasons why certain

concepts will/will not work in this application.

Based on the knowledge acquired, through research, this report examines the imperfections in

other proposals and provides a new and improved composite tower design through an

organised process that will be seen throughout this report. Each and every issue that was

encountered was recorded and inserted into this text for easy viewing of how the design was

brought down to the finest, most elite concept chosen by this group.

Creating a design that is as intricate as this one is not an easy task. A lot of research and time

is required of those who are directly involved in the design. A tower with antenna-like

properties made out of composite material is a complex device that has numerous uses in

industry and life as we know it. Functionality and convenience are key factors when

designing any piece of equipment and this design comprises of both of the above key

characteristics.

2


CHAPTER 2

2. LITERATURE REVIEW

2. ALTERNATE MATERIALS

New and innovative materials for towers have been researched for many years as an

alternative to steel and concrete. The desire for cost effective and environmentally friendly

options is fast becoming a global trend. It also provides the advantage of reduced assembly

and logistics costs. The selection of carbon fibre over other considered materials was based

mainly on its strength to weight ratio and its tensile strength. Making the tower out of such

material will allow the tower to be able to handle many weather situations, in extreme heat

the carbon fibre will not catch fire easily but the carbon fibres may expand slightly due to its

low coefficient of thermal expansion. This slight expansion will not affect the overall

capabilities of the tower. In windy conditions the tower should have no problems due to the

high ultimate strength of the combined carbon fibre, i.e. the composite wound structure. In

extreme weather cases like hurricane winds the strength of the material may be exceeded and

failure may occur.

2.2 PROCESSES OF MANUFACTURE

There are many processes in manufacturing composite components which are cylindrical, but

the two manufacturing methods that were reviewed for this design project are the composite

pultrusion process and filament winding process. The most common and widely used method

of manufacturing cylindrical parts is the filament winding method.

The filament winding process is a simple and general process used to manufacture cylindrical

parts, but some modifications were made to the process to produce the desired final product.

The modifications done to the process will provide a good surface finish, without have to

machine, cut, or scrape the wound fibres.

3


2.3 TOWER DESIGNS

When conducting the needs analysis of our design, we have established that a telescopic mast

has the closest possible operational factors to our design task. Present designs of telescoping

masts are commonly pneumatically, hydraulically, or chain driven.

2.4 PNEUMATIC POWERED TOWER

Pneumatic drive motors need airtight seals sandwiched between telescopic mast sections to

function effectively. Currently the environment in which these masts are utilized makes

maintaining an airtight state between mast segments difficult. Impurities, or radial ice, left

between mast intersections will stop the mast from descending or may impair the mast

segments, and can certainly destroy the seal necessary for efficient operation of the

pneumatic drive. With the destruction of the seal the mast will fall due to gravity with

disastrous consequences.

Another disadvantage that current pneumatically powered telescoping masts contain is that

they can only hold one of two positions. The tower is fully extended otherwise fully retracted.

In many instances due to obstructions or other concerns, it is required to have the telescoping

mast segments in a restricted state of extension or retraction. Also such drives are costly to

manufacture, assemble, and maintain, which confines their appeal in uses where the device is

used on irregular terrain, pneumatic units are unable to work consistently on grades beyond

fifteen degrees and, if the loading at the peak is high. The cylinders on pneumatic masts on

gradients exceeding the limit may curve at the joint, triggering air leakage at the joint and a

corresponding failure. Thus a unit is needed which can safely preserve structural integrity on

inclines exceeding fifteen degrees.

4


2.5 HYDRAULIC POWERED TOWER

A hydraulic jacking system was our first considered option. We looked at many jacking

systems to discern whether or not we could incorporate it in the lifting mechanism of our

composite tower. Hydraulic systems for the purpose of raising masts suffer from several of

the same limitations as pneumatic powered systems. Hydraulic drives are quite heavy in

weight plus are expensive to manufacture, assemble, and maintain. Additionally, such drives

are susceptible to damage from environmental contact as hydraulic lines are exposed.

Furthermore, impurities can penetrate the hydraulic system and cause malfunction.

2.6 CHAIN DRIVEN TELESCOPING TOWER

Chain driven telescopic masts likewise suffer from the same deficiencies. The drive

mechanisms are relatively heavy in weight and are expensive to manufacture, assemble, and

maintain. The chain link mechanism is also exposed and susceptible to damage from contact

with environmental objects.

Other shortcomings common to the aforementioned conventional telescopic mast drives and

devices are that the wiring to the outboard end of the mast is exposed and can be damaged by

accidental contact with surrounding obstacles or suffer from damage from exposure to the

elements. Moreover, the masts are generally fabricated from conductive material from the

base to the top end. An electrical charge introduced into such, masts from inadvertent contact

with exposed overhead electrical lines will, accordingly, be transferred to the vehicle below,

causing a potential for danger to the operators on the ground. Available systems lack

effective means for preventing such a charge transfer, such as a fuse system. However, even

were fuses implemented into wiring of available units, because the wiring is exposed to the

elements, such fuses would be prone to damage and deterioration from exposure to the

elements and may not function as intended when they are needed.

5


CHAPTER 3

3. DESIGN

3.1 PRODUCT REQUIREMENT SPECIFICATION

3.1.1 DESIGN REQUIREMENTS

1. The design will be proficient in performing the following functions: supporting in a

stationary position, raising, lowering, and shielding the equipment

2. The tower must be constructed of composite materials as stated in the task statement

3. It must be possible to install and level the device on a flat surface having a gradient not

exceeding 5̊.

4. The device must include a support platform

5. The device should allow comfortable admittance of the working zone through the

height range 0 to 12m.

6. The tower must be capable of supporting, lifting, and lowering a total payload quantity

of at least 200kg, including the mass of the platform.

7. The support platform and payload must be supported by means of a mechanism capable

of raising tower and loaded platform at a constant speed with an allowable tolerance of

0,001m/s

8. The tower must be capable of keeping the laden platform stationary with a precision of

30mm

9. The tower must be capable of lowering the laden platform at a constant speed of 0.4m/s

with an suitable tolerance of 0.01m/s

10. The tower must be capable of enduring, without toppling, bending or fracturing, winds

not exceeding 22m/s at sea level

11. The tower has to include a safety feature that will avert the platform from dropping, in

the event of a power failure.

3.1.2 DESIGN CONSTRAINTS

1. The construction material of the tower must be composite in nature

2. All applicable regulations and standards need to be adhered to.

3. The design should be non-hazardous and cause no environmental damage to the site of

use

4. The design should be as lightweight as possible.

6


3.1.3 DESIGN CRITERIA

1. The device ought to be easy to operate with no special training required.

2. Little or no maintenance should be required, if possible

3. The life expectancy of the design should exceed 10 years

4. The annual operational costs should be as little as possible

5. The tower should be transportable so as to be utilized where the selected application is

required.

6. The tower should be easily extended within 2 minutes by two people

3.2 CONCEPTUAL DESIGN

The purpose of conceptual design process is to determine the main components of the

design that will satisfy the market need, regulations and target specifications as stated in the

previous section. Different parts and sub-assemblies need to be researched to choose the best

options. Depicted below in figure 3.1.1 is the overall process flow used to determine the best

concept design concept.

Figure 3.2.1: Conceptual design flowchart

Market need and

specifications Basic configuration

Powering method

and source of

powerSafety

Final concept

7


3.2 DESIGN CONCEPTS

After intense information gathering and research on various methods and

configurations to meet the design specifications, the design team provided several ideas and

hand sketches of basic design concepts. The concepts provided can be seen in the following

page. Figure 3.2.1

Figure 3.2.1

8


Concept Configurations

1. Pneumatically erected tower: in this configuration the tower is made of hollow

cylindrical composite adjacent telescoping sections, with each section sliding

relatively to an adjacent section. The tower is erected by means of compressed air,

therefore requiring an Air compressor or a manual air pump.

2. Belt driven tower: this configuration is similar to the first except that instead of

compressed air, a belt is used to erect the tower. The belt can be manually driven or

coupled to an electric motor.

3. Lead screw driven tower: This design comprises a screw on its base section, and each

section has a nut which engages with the screw to raise and lower the tower. The

screw can be manually cranked or automatically driven by an electric motor through a

gear set.

3.2.2 CONCEPTUAL DESIGN SELECTION

Criterion Weighting

(Relative

importance)

Concept

(Max 5) Concept 2

(Max 5) Concept 3

(Max 5)

Easy to operate 25% 5 3 4

Maintenance 15% 4 1 1

Life expectancy 15% 3 1 3

Capital cost 10% 1 1 5

Transportable 35% 5 3 3

Total 100% 83 44 63

Table 1: Evaluation Chart

Based on the design criteria determined in the beginning of the design process a pneumatic

driven lifting mechanism is the most suitable design for the application and is thus the

selected/approved proposal.

9


3.3 FINAL DESIGN

The following design, as depicted in figure 3.4.1 shows the final assembly of the

product with all components and sub-assemblies in place. The telescopic tower is mounted on

a base plate that is hinged to the trailer frame to allow the tilting manoeuvre. A pneumatic

cylinder is mounted on clevis-mounting to tilt the tower into vertical and inclined position for

use and transportation respectively. A compressor is mounted on the trailer to supply

compressed air for the erection of the tower and the actuation of the air cylinder. Two 12V

batteries are secured to the chassis to supply power to the compressor.

Figure 3.3.1 Final assembly.

Most components were entirely designed by the team, yet some items were selected

from suppliers for time saving purpose. Items designed by the team include; telescopic tower,

tilting mechanism and trailer. Selected items include; Air compressor, batteries and the

universal connecting adapter for equipment securing. In the following sections, calculations

and parameters used for the design and selection of each item or sub-assembly will be

discussed in detail.

10


3.3.1 TOWER SECTIONS (SEGMENT)

As previously mentioned in the design specifications, the tower is to be no less

than 10m of extended height and no more than 3m of retracted height. The tower is to be

telescopic to reduce the storage space and ease the transportation, all telescoping sections of

the tower are to made of composite materials to achieve a strong but yet light in weight

structure, the tower is to be self-supported to reduce the time and number of people required

for deployment, the tower should not deflect more than 20mm when working at maximum

load.

To accomplish all the specifications earlier mentioned, intense research on different

composite materials were carried to select a suitable material for the application. The table

(table 3.3.2) below shows the properties of different fabrics used with epoxy resin.

11


Mechanical Properties of Carbon Fibre Composite Materials, Fibre / Epoxy resin (120°C Cure)

Fibres @ 0° (UD), 0/90° (fabric) to loading axis, Dry, Room Temperature, Vf = 60% (UD), 50% (fabric)

Symb

ol Units

Std

CF

Fabr

ic

HMC

F

Fabr

ic

E

glass

Fabri

c

Kevl

ar

Fabr

ic

Std

CF

UD

HM

CF

UD

M55

**

UD

E

glass

UD

Kevl

ar

UD

Bor

on

UD

Ste

el

S97

Al.

L6

5

Tit.

dtd

5173

Young’s Modulus

0° E1 GPa 70 85 25 30 135 175 300 40 75 200 207 72 110

Young’s Modulus

90° E2 GPa 70 85 25 30 10 8 12 8 6 15 207 72 110

In-plane Shear

Modulus G12 GPa 5 5 4 5 5 5 5 4 2 5 80 25

Major Poisson’s

Ratio v12

0.10 0.10 0.20 0.20 0.30 0.30 0.30 0.25 0.34 0.23

Ult. Tensile

Strength 0° Xt MPa 600 350 440 480 1500 1000 1600 1000 1300 1400 990

46

0

Ult. Comp.

Strength 0° Xc MPa 570 150 425 190 1200 850 1300 600 280 2800

Ult. Tensile

Strength 90° Yt MPa 600 350 440 480 50 40 50 30 30 90

Ult. Comp.

Strength 90° Yc MPa 570 150 425 190 250 200 250 110 140 280

Ult. In-plane Shear

Stren. S MPa 90 35 40 50 70 60 75 40 60 140

Ult. Tensile Strain

0° ext % 0.85 0.40 1.75 1.60 1.05 0.55

2.50 1.70 0.70

Ult. Comp. Strain

0° exc % 0.80 0.15 1.70 0.60 0.85 0.45

1.50 0.35 1.40

Ult. Tensile Strain

90° eyt % 0.85 0.40 1.75 1.60 0.50 0.50

0.35 0.50 0.60

Ult. Comp. Strain

90° eyc % 0.80 0.15 1.70 0.60 2.50 2.50

1.35 2.30 1.85

Ult. In-plane shear

strain es % 1.80 0.70 1.00 1.00 1.40 1.20

1.00 3.00 2.80

Thermal Exp. Co-

ef. 0°

Alpha

1

Strain

/K 2.10 1.10 11.60 7.40 -0.30

-

0.30 -0.30 6.00 4.00

18.0

0

Thermal Exp. Co-

ef. 90°

Alpha

2

Strain

/K 2.10 1.10 11.60 7.40

28.0

0

25.0

0 28.00 35.00

40.0

0

40.0

0

Moisture Exp. Co-

ef 0° Beta1

Strain

/K 0.03 0.03 0.07 0.07 0.01 0.01

0.01 0.04 0.01

Moisture Exp. Co-

ef 90° Beta2

Strain

/K 0.03 0.03 0.07 0.07 0.30 0.30

0.30 0.30 0.30

Density

g/cc 1.60 1.60 1.90 1.40 1.60 1.60 1.65 1.90 1.40 2.00

** Calculated figures

Fibres @ +/-45 Deg. to loading axis, Dry, Room Temperature, Vf = 60% (UD), 50% (fabric)

Symbol Units Std. CF HM CF E Glass Std. CF

fabric

E Glass

fabric

Steel Al

Longitudinal Modulus E1 GPa 17 17 12.3 19.1 12.2 207 72

Transverse Modulus E2 GPa 17 17 12.3 19.1 12.2 207 72

In Plane Shear Modulus G12 GPa 33 47 11 30 8 80 25

Poisson’s Ratio v12 .77 .83 .53 .74 .53

12


Tensile Strength Xt MPa 110 110 90 120 120 990 460

Compressive Strength Xc MPa 110 110 90 120 120 990 460

In Plane Shear Strength S MPa 260 210 100 310 150

Thermal Expansion Co-ef Alpha1 Strain/K 2.15 E-6 0.9 E-6 12 E-6 4.9 E-6 10 E-6 11 E-6 23 E-6

Moisture Co-ef Beta1 Strain/K 3.22 E-4 2.49 E-

4

6.9 E-4

Table 3.3.2 [10]

From the above table, standard carbon fibre epoxy resin was selected for its high

tensile and compressive strength and good young’s modulus at 0 and 90 degrees to the

loading axis. Also from this information it was determined to lay fibres at 0 and 90 degrees to

the loading axis to achieve maximum resistance to internal/external pressure and longitudinal

bending/buckling given that the tower will be subjected to internal pressure as it is

pneumatically erected and to compressive load.

Using the mechanical properties of standard carbon fibre epoxy resin highlighted in

the above table, the average outside and inside diameter of the tower will be determined and

later refined to satisfy the specifications. (NB: a very small deflection was taken to avoid any

kind of leakage at the tower sections joints).

3.4 STRUCTURE ANALYSIS

Tower Loading

Maximum axial load: 200kg

Maximum projected area: 1m2

Maximum operational wind speed: 100km/h, calculations will performed at a

wind speed of 150km/h to accommodate a safety factor of 1.5

Maximum allowable deflection 20mm

Maximum height: 10.5m

Material properties

Young’s modulus: 70GPa

Ultimate tensile strength: 600MPa

Ultimate compressive strength: 570MPa

13


NB: In the preliminary calculations of the tower diameter, the force induced by the air

pressure on the projected area of the tower itself will be neglected given that the size is not

known; it will be included later in the refinement calculations.

Assumptions

The tower is dealt with as a cantilever beam of circular hollow cross sectional

area; therefore the maximum stress is induced at the support where the beam is clamped.

Wind loading

Before determining the wind pressure we need to obtain the basic wind speed which is

adjusted for: Mean return period

Terrain category

Local effects

Height above ground

Class of structure

• The mean return correction factor for communications structures such this mobile

tower is kr=1.04 [Parrot]

• For safety reasons in the design process the terrain category 1 will be considered, in

this category it is assumed that structure is in an exposed open terrain with few or no

obstructions and in which the average height of any obstruction is 1.5m.[parrot]

• Local effects: not considered for this design given that the structure is mobile. [parrot]

• Height above the ground will be considered as the maximum level above the sea in

South Africa

• The tower is a structure of class A since there is no dimension exceeding 20m.

From these parameters the wind speed multiplier kz=1.09 was selected from the SANS

10160-3:2009 publication page 11-17(See appendix).

Characteristic wind speed: ��

Basic wind speed: �� = �� × � = 1.04 × 47 = 48.88�/� (3.1)

Air density: � = 1.20��/��

Altitude factor: �� = 0.60�� ℎ��500��

14


1m

A

B

�� 1.09 � 48.88 ≅ 53�/� (3.2)

Velocity pressure: �� (3.3)

�� 0.60 � 53� � 1685�/��

Force due to projected area: � � �� 1685 � 1 � �� (3.4)

Force due to axial load: � 200 � 9.81 � 1962"

Free body diagram representation of the tower assuming that the axial load is 1m offset from

the tower’s vertical axis

F

10.5m P

The anticlockwise moments and downward forces are considered as positive.

Force P will cause a moment MB equal to � 1 � 1962"�

∑$� � 0 � $� % &� � 10.5' % & � 1' (3.5)

→ $� � &1685 � 10.5' ) &1962 � 1' � 19654.5"�

∑�� ↓� %+�� ) � � 0 (3.6)

∴ +�� 1685"

∑� ←� %+� ) � 0 (3.7)

∴ +� � � 1962"

In the next section the moment of inertia of the beam will be determined using Macaulay’s

method, and later the beam diameters will determined from the Inertia equation.

./��

� �� $�⟨1 % 10.5⟩� %$�⟨1 % 0⟩� % +�⟨1 % 10.5⟩� % �⟨1 % 0⟩� (3.8)

./��

� � $�⟨1 % 10.5⟩� %$�⟨1 % 0⟩� %

��

�⟨1 % 10.5⟩� %

�

�⟨1 % 0⟩� ) 3 (3.9)

�

15


�� =��

�⟨� − 10.5⟩� −

��

�⟨� − 0⟩� −

��

⟨� − 10.5⟩� −

⟨� − 0⟩� + �� + � (3.10)

Boundary conditions: at point A (X=10.5) deflection and slope is 0

�� = 10.5��(3.9)

→ � = �1962 × 10.5 + (1685.4 × 10.5�)/2 = 113508.675 (3.11)

��3.11 ��3.10 ��!! ��ℎ��"�� 0 = −

#�

2⟨� − 0⟩� −

$6⟨� − 0⟩� + �� + �

→ � =1962 × 10.5�

2+

1685.4 × 10.5�

6− �113508.675 × 10.5 = −758508.975

As previously mentioned the maximum allowable deflection is to be 20mm, therefore using

this parameter the moment of inertia will be calculated from the deflection equation (3.10) at

x=0 (maximum deflection occurs at x=0)

�� = � (3.12)

� =�� =

| − 758508.975|

70 × 10� × 20 × 10 �= %. &'() × '* �+ �

The moment of inertia of a hollow cylindrical cross section is determined by the following

expression :

� =��

��

� (3.13)

t: thickness

d: outside diameter

Using error and trail method, different thickness values will be used in equation (3.13) until a

suitable diameter is found.

� = ��

��

�

(3.14)

Thickness

Outside

Diameter

Inside

Diameter

10 516.7220958 496.7220958

12 486.2541091 462.2541091

14 461.8997081 433.8997081

16


16 441.7911775 409.7911775

18 424.7820906 388.7820906

20 410.1225992 370.1225992

22 397.297781 353.297781

24 385.9401421 337.9401421

26 375.7790669 323.7790669

28 366.6100413 310.6100413

Table 3.4.1 (copied from an excel spread sheet) see appendix

From table 3.4.1, 410mm outside diameter and 20mm thickness were selected as the suitable

size for the bottom section of the tower bearing in mind that the tower is telescopic.

For easy transportation and good telescopic functioning, it was decided for the tower to be

made out of 6 cylindrical sections of approximately 1.75m. The following are the 3D models

for each tower section.

First cylinder (bottom section) Second cylinder

Third cylinder Fourth cylinder

17


Fifth cylinder Sixth cylinder (Top section)

Figure 3.4.2 all models were drawn on Pro Engineer Wildfire 5.0

Each cylinder or segment of the tower will have a piston on its bottom end and a collar or

cylinder end cap on its top end, with exception of the first cylinder or bottom section of the

tower which does not require a piston, and the top section which is equipped with a six hole

flange on its top instead of a collar.

3.5 PISTON AND SEALS

The pistons are designed to convert the pressure into a lifting force, to bear the

piston seals that provide a sealing between the sections of the tower and to carry wear rings

that will provide a smooth contact surface and support between the tower sections.

To avoid any kind of leak around the pistons, it is crucial that the pistons are made of

a less or non-deformable material under extreme working temperatures and forces. Several

materials were considered, among them; Glass filled nylon, Glass filled epoxy, Aluminium,

steel and other thermoset composite…

And due to the complex shape of the piston, it was decided that the pistons should be

casted and later machined to provide dwelling grooves for piston sealing and wear ring. The

selection of a suitable material was carried taking into account all previously cited

18


characteristics.

3.5.1 SELECTION OF PISTONS MATERIAL

Below in table 3.5.1 is a list of considered material for the tower pistons. From the

properties of materials listed in the following table a suitable material for the pistons will be

selected.

Composites

Material

Density

- ρ -

(103 kg/m3)

Tensile

Modulus

- E -

(GPa)

Tensile

Strength

- σ -

(GPa)

Specific

Modulus

- E/ρ -

Specific

Strength

- σ/ρ -

Maximum

Service

Temperature

(oC)

Short-fiber

Glass-filled

epoxy

(35%)

1.9 25 0.3 8.26 0.16 80 - 200

Glass-filled

polyester

(35%)

2.0 15.7 0.13 7.25 0.065 80 - 125

Glass-filled

nylon

(35%)

1.6 14.5 0.2 8.95 0.12 75 - 110

Unidirectional

S-glass

epoxy

(45%)

1.8 39.5 0.87 21.8 0.48 80 - 215

Carbon

epoxy

(61%)

1.6 142 1.73 89.3 1.08 80 - 215

19


Material

Density

- ρ -

(103 kg/m3)

Tensile

Modulus

- E -

(GPa)

Tensile

Strength

- σ -

(GPa)

Specific

Modulus

- E/ρ -

Specific

Strength

- σ/ρ -

Maximum

Service

Temperature

(oC)

Kevlar

epoxy

(53%)

1.35 63.6 1.1 47.1 0.81 80 - 215

Metals

Material

Density

- ρ -

(103 kg/m3)

Tensile

Modulus

- E -

(GPa)

Tensile

Strength

- σ -

(GPa)

Specific

Modulus

- E/ρ -

Specific

Strength

- σ/ρ -

Maximum

Service

Temperature

(oC)

Cast Iron,

grade 20 7.15 100 0.14 14.3 0.02 230 - 300

Steel, AISI

1045 7.7 - 8.03 205 0.585 26.3 0.073 500 - 650

Aluminum

2045-T4 2.7 73 0.45 27 0.17 150 - 250

Aluminum

6061-T6 2.7 69 0.27 25.5 0.10 150 - 250

Table 3.5.1 list of different materials for pistons [10]

From the list of materials shown in table 3.6.1, Aluminium 6061-T6 was selected for its

highest castability, good stress strain ratio (3.91*10-9

) and high working temperatures. Steel

and cast iron were avoided for their high density and composite were dismissed for their high

deformation and low working temperatures.

The figure 3.5.2 bellow shows a piston 3D model created on Pro Engineer wildfire 5.0

20


The piston is casted and machined.

The blue highlighted grooves show the

piston seal dwelling, while the green

one shows the wear ring location.

Backup seal groove

Wear ring groove

Seal groove

Figure 3.5.2 piston model

3.5.2 PISTON AND SCRAPER SEAL MATERIAL SELECTION

The selection of the piston seals and scraper seals were based on the following criteria:

• Long wear life: The tensile strength of seal material is a commonly used indicator of

wear resistance. Material with high tensile strength offer superior performance

compared to low tensile strength material.

• Lifetime self-lubricating: self-lubricating seals offer the advantage of low

maintenance requirement reduces the friction, heat generation and wear in both seal

and cylinder.

• High strength and toughness: due to shock loads and high working pressures, seal lips

might nick or tear. To avoid this seals should be strong and tough but yet without

reinforcing fabric which can decompose and affect the system.

• Self-life: the seal should be able to perform correctly even after a long storage time

• Easily installed: the seal should be easily installable, and should retain its original

shape after installation.

21


As seen in the table 3.5.3 below the thorseal polymer offers the best tensile strength and is

self-lubricated, thus was selected for this application (see appendix for the design

information)

Table 3.5.3 Tensile strength of common elastomers.

3.5.3 WEAR RING

The wear ring will be used on the piston to guide the piston in the cylinder and in

collar to guide cylinder and provide more support at the joint. Glass filled nylon was selected

as the suitable material for its high compressive strength and load bearing capabilities

22


Figure 3.5.4 Thorseal polymer piston seal

Figure 3.5.5 Glass filled nylon wear ring

Figure 3.5.6 Thorseal polymer scraper seal

3.6 COLLAR or CYLINDER END CAP

The role of the collar in this design is to cover the cylinder, provide a stop for the

inner cylinder and accommodate a wear ring and seal. The collars will be made of the same

material as the pistons (casted aluminium alloy 6061 T6) and will fastened to the cylinders.

Base Plate for Risen Insert will be imbedded in the composite cylinders during the

manufacturing process of the later to fastening of collars. See more details in the

manufacturing process section.

Because of the complex shape of the collar and of course the piston, only finite element

analysis will be carried to determine the induced stresses in these components.

23


Scraper seal groove

Wear ring groove

Locking key way

Fastening holes

Figure 3.6.1 Collar model

3.7 LOCKING MECHANISM

The locking mechanism is a mean of locking each section of the tower after

extension or retraction. The locking mechanism is fitted in each collar and is operated

manually to allow the erection of the desired section the tower. The locking mechanism is a

spring loaded key with a wing nut which allows to engage or disengage the key by rotating it

3060 clockwise or anticlockwise respectively.

The locking mechanism is made of aluminium; a 3D model assembly of the locking

mechanism is shown in figure 3.8.1 see next page.

24


Wing Nut

Circlip

Spring (compressed)

Locking key

Figure 3.7.1 locking mechanism assembly.

3.8 TILTING MECHANISM

A tilting mechanism has been designed to ease the tilting of the tower to vertical or

inclined position for use and transportation purpose. Two conceptual designs were provided

by the team, one consisted of a winch system driven by an electric motor and the second is a

pneumatic cylinder. The second design was implemented because of its simplicity and use of

the same Air supply as the tower.

The whole tilting mechanism is composed of following sub-items; a tilting base plate on

which the tower is secured, a swing bolt that help secure the tower once in vertical position

and lastly a pneumatic cylinder fixed on a clevis mounting at one end and connected to clamp

around the tower’s bottom section. The figure 3.9.1 bellow shows the tilting assembly.

The pin and pneumatic cylinder sizing calculations will be demonstrated in the following

sections. Reactions at the tilting point and at the clamp connection will be determined in and

used as acting forces on the pins.

The weight, centre of gravity and dimensions of the tower were directly taken from the CAD

25


model, see appendix for references

Tower weight: 408kg

Tower centre of gravity along y axis: 1271.5mm

Payload: 200kg

Figure 3.8.1 tilting mechanism

3.8.1 REACTIONS ON TOWER

To facilitate calculations a free body diagram will be drawn to illustrate the

tower. From figure3.9.1 it can be seen that maximum reaction on the clamp pin and hinge pin

will occur when the tower starts moving from the inclined position. Therefore calculations

will be performed with tower inclined at 190 and the payload added on top of the tower.

26


Refer to dimensions on the previous page

Payload (P)

2.78m

Weight of tower (F)

Horizontal and vertical clamp pin reaction

Reaction at hinge

Figure 3.8.2 Tower representation

Force due tower weight: 408 � 9.81 � 4002"

• Vertical component= 4002 cos 19 � 3784"

• Horizontal component =4002 sin 19 � 1303"

Payload force: 200 � 9.81 � 1962"

• Vertical component= 1962 cos 19 � 1855"

• Horizontal component= 1962 sin 19 � 634"

From the diagram it can noticed that the horizontal clamp pin reaction is

1303 ) 634 � �:;<�

The vertical reactions will determined using Beam Boy2.0 see result on the next page.

Figure 3.8.2

27


Beam result screen shot

Figure 3.8.2

Reaction at hinge was found to be 13100N

Vertical component at clamp pin was found to be 18800N

Therefore the resultant reaction at clamp is given by √18800� + 1937��

= '-)**.

28


At angle:= tan��

�� 5.85°=A=B��=CD�EDA�FAG�

3.8.2 CLEVIS MOUNTING AND PIN CALCULATION

Force in the Piston rod

5.850

18900N 26.40

∴ �� 18900

cos50.45� ��

With this force the size of the Pin connecting the pneumatic cylinder to the clamp will be

calculated, knowing that it is more likely to fail under shear.

The following figure 3.8.3 shows the connection setup

29


Figure 3.8.3 detailed view of clevis joint. (Drawn on Pro Engineer Wildfire 5.0)

The pin is made of steel and the clevis mount is made of aluminium 6060 T6.

Steel yield strength =380MPa

Shear strength = 0.5×380=190MPa

Aluminium yield strength=270MPa

Shear strength=0.5×270=135Mpa

A factor of safety of 3 will be used in all calculations.

3.6.Shear in the Pin

� =�

�� (3.15)

Taking into account the factor of safety

/ =3�20 =

6�1��

∴ � = 2�

��= 2 ×��

�×��×��= 17.3��

For normalization purpose a pin of 20mm will be used

3.7.Tension in the double eye clevis mount

�

=

�� (3.16)

∴ �ℎ�"�� =3$�� − � 23 =

3 × 29682

(0.046 − 0.024) × 2 × 270 × 10= 7.5��

A minimum thickness of 8mm has been used in the design.

3.8.Tension in the singe eye clevis mount

�

=

�� (3.17)

∴ �ℎ�"�� =3$

(� − �)3 =3 × 29682

(0.044 − 0.024) × 270 × 10= 16.5��

A minimum thickness of 14mm with reinforcing rib

30


3.8.3 PNEUMATIC PISTON ROD CALCULATION

The pneumatic cylinder used in this design is a tie rod cylinder with stainless steel

piston rod, Aluminium cylinder and polyurethane seals. This type of Air cylinder was

selected for its light weight and maintenance simplicity.

The cylinder is mainly subjected to compressive load and hence tends to buckle. To avoid

this calculation are performed to choose the right size of the piston rod that carry the design

load with a safety margin and not buckle.

The cylinder stroke is 714mm.

Piston rod material 304 stainless steel - annealed condition

Yield strength: 215MPa

Modulus of elasticity: 190GPa

• Piston rod diameter

Buckling critical load formula (safety factor 3)

�� =��

�� (3.18)

Taking in account the factor of safety

34�� =1��5� ; ∴ � =

34��5�1�� =3 × 29682 × 0.714�

1� × 190 × 10�= 2.42079 × 10 ��

� = ��

�� (3.19)

� = 664�1�

= 664 × 2.42079 × 10 �

1�

= 26.5��

A standard 26mm piston rod was selected for the design

31


Figure 3.8.4 Air cylinder 3D model

3.8.4 WING BOLT CALCULATION

P=200kg

F: Force due to wind pressure on

projected Area= 380N

A wind speed of 25.16m/s or

80km/h was used as the speed

limit to avoid turn-over of the

tower. the same speed is used to

determine the reaction at the

swing bolt.

Pressure load F =0.6×25.162=380N/m

2

The 200kg is secured a meter from the tower. Wind direction

Force due to tower projected Area

Force due to gravity G=4002N

32


Rh: reaction at hinge Rb: reaction at bolt

The Projected Area of the tower is found by multiplying each section diameter to its length.

Section Length (m) Diameter (m) Area (m2)

1 2 0.410 0.82

2 1.7 0.364 0.62

3 1.66 0.318 0.53

4 1.63 0.272 0.44

5 1.62 0.226 0.37

6 1.55 0.180 0.28

Projected Area of the tower =3.06m2

Force due to projected Area is equal to wind pressure multiplied by the tower’s projected

Area.

Projected Area Force =3.06× 380=1163N

This force acts at the centroid of the tower’s projected Area ( �)

� =1 × 0.82 + 2.85 × 0.62 + 4.53 × 0.53 + 6.115 × 0.44 + 7.74 × 0.37 + 9.325 × 0.28

3.06

= &. 7+

Taking the sum of moment at the hinge reaction,

∑#�� = 8� × 0.666 − 4002 × 0.31 + 1136 × 4.3 + 1962 × 1 + 380 × 10.36 = 0∴ 9: = −'&7;-.

Using a factor of safety of 3 and taking steel yield strength to be 215Mpa, the wing bolt

diameter (d) will be calculated (The bolt is in tension)

�

=

�×��

�� ()

33


� = � 12 × 14328� × 215 × 10�= �.��

From calculations a 16mm wing bolt was used.

34


3.9 COMPRESSOR SELECTION

Selecting a compressor that is too small for the task will waste valuable time, yet

purchasing one that is too large will waste valuable resources. Therefore a calculated decision

needs to be taken to prevent either the waste of time or resources, to do so the following

criteria will be considered for the selection of an appropriate compressor to erect the tower

and actuate the tilting air cylinder.

3.9.1 THE MAXIMUM OPERATING PRESSURE REQUIRED

The maximum pressure required to erect the tower and actuate the tilting cylinder will be

calculated to decide whether a single or double acting cylinder is required. The pressure

required is found by dividing the total load to be lifted by the piston area.

Pressure required= (Payload + lifted tower section(s) mass) × 9.81/Piston Area (3.20)

The following data were acquired from the product CAD model properties (see appendix for

model properties)

• The second tower section mass is 75.3kg, the piston diameter is 370mm

• The third tower section mass is 63.8kg, the piston diameter is 324mm

• The fourth tower section mass is 54kg, the piston diameter is 278mm

• The fifth tower section mass is 44.2kg, the piston diameter is 232mm

• The sixth tower section mass is 32.2kg, the piston diameter is 186mm

� Pressure required to lift the tower second section P2

4� =(200 + 75.3 + 63.8 + 54 + 44.2 + 32.2) × 9.81 × 41 × 0.37�

= &;-7<. ;=> � Pressure required to lift the tower third section P3

4� =(200 + 63.8 + 54 + 44.2 + 32.2) × 9.81 × 41 × 0.324�

= &<)*7. %=> � Pressure required to lift the tower fourth section P4

4� =(200 + 54 + 44.2 + 32.2) × 9.81 × 41 × 0.278�

= %77)-. %=> � Pressure required to lift the tower fifth section P5

4� =(200 + 44.2 + 32.2) × 9.81 × 41 × 0.232�

= <&'&'. -=> � Pressure required to lift the to lift tower sixth section

35


4 =(200 + 32.2) × 9.81 × 41 × 0.186�

= -7-77. '=> � Pressure require by the tilting Air Cylinder Pt

=� =$�"��ℎ�!��4��0�� =

8900 × 41 × 0.082�= '. <-?=>

From the pressure results obtained in the previous page, it can be seen that the highest

required pressure is the Tilting Air Cylinder pressure (1.68MPa). Thus the Compressor

pressure should be a little above the maximum required pressure.

3.9.2 COMPRESSOR DRIVE SYSTEM

The most common type of compressor drive system is either electric motor or

gasoline engine. In this design the electric motor drive system was selected for its low

pollution to the environment and the possibility of using batteries as power source, thus

making the mobility of the compressor much easy.

36


3.9.3 SELECTED COMPRESSOR SPECIFICATIONS

The compressor that was selected from relevant calculations is a 38 litre ASME

tank mounted. It is primarily used for industrial applications and in the automotive industry

for the inflation of truck tyres. This specific ASME motor is fan cooled which allows it to

operate for many continuous hours. The compressor will be purchased from Oasis

Manufacturing item # XDT10-4000-24. The product information below was provided on

request by Oasis Manufacturing.

Table 3.9.1 compressor specifications

Compressor Model XD4000-24

Nominal Operating Voltage 24 Vdc

Dimensions in meters (L x W x H)

1.016×0.254×0.6096

Net Weight (kg) 49.895

Motor Type Series Wound

Motor Thermal Protector Not Required

Max Pressure 250 PSI

Max Restart Pressure 150

Horsepower 2.2

Current at Max Load (Amps) 90

Power at Max Load (Watts) 2160

Duty Cycle @ 689.475 Kpa @ 70 deg

100%

Features • 38 litre Tank

• Fan cooled motor

• Fan cooled compressor

37


3.9.4 PNEUMATIC SYSTEM DIAGRAM

This section illustrates the pneumatic system diagram for the control of the tower

and that of the tilting cylinder. The system is set in such a way that only one actuator can be

operated at a time to avoid lowering or lifting the tower while moving it to the horizontal or

inclined position.

The system consists of the following components:

1) Telescopic tower

2) Tilting cylinder

3) Three position four way spring-centred, lever operated valve

4) An Adjustable pressure relief valve

5) Air line lubricator

6) Air Compressor

7) Air filter

8) Pressure gauge

9) Three position 3way spring-centred, lever operated valve

38


3.9.5 MAST ROTATOR

The composite tower is designed to be utilised for various applications in the

telecommunications field. In this field a major challenge is to achieve a constant and reliable

signal .The tower is fitted with a mast rotator which be operated by remote, this allows a vast

rotation range for best signal. The mast rotator operates at a low rpm thus allowing a minute

change for optimum quality to be achieved. This will be purchased from Will Burt item

G800S Mast Rotator.

Figure 3.9.2 mast rotator

3.9.6 INVERTER

An inverter is an electrical device that converts Direct current to Alternating current. DC

power is steady and continuous, with an electrical charge that flows in only one direction.

When the output of DC power is represented on a graph, the result would be a straight line.

AC power, on the other hand, flows back and forth in alternating directions so that, when

represented on a graph, it appears as a sine wave, with smooth and regular peaks and valleys.

A power inverter uses electronic circuits to cause the DC power flow to change directions,

making it alternate like AC power. An inverter is silent and virtually maintenance free.

The inverter will be used to power a compressor and a mast rotator .The inverter will run of a

separate 12 volt battery mounted on the trailer , this battery will be charged by the vehicles

39


alternator. The electronic components require 90 amperes and 1000 watts of power.

A Schematic circuit diagram of a 1 kw inverter :

Figure 3.9.3 inverter circuit

A table of parts required to build the circuit

Part Total Qty. Description C1, C2 2 68 uf, 25 V Tantalum Capacitor

R1, R2 2 10 Ohm, 5 Watt Resistor

R3, R4 2 180 Ohm, 1 Watt Resistor

D1, D2 2 HEP 154 Silicon Diode

Q1, Q2 2 2N3055 NPN Transistor

T1 1 24V, Center Tapped Transformer

MISC 1 Wire, Case, Receptical (For Output)

Table 3.9.4

The inverter will incased in lightweight aluminum housing. This casing would have

40


perforations in it to permit ventilation.

3.9.7 ELECTRICAL WIRING

Electrical wire is the medium through which electricity is carried to the associated devices. It

consists of a metal that easily conducts electricity, such as copper, aluminium and gold. The

conductor or metal is covered by a plastic sheath called an insulator. There are various

different types of electrical wire, each suited to certain loads and conditions.

The electrical wire to be used to the charge the batteries from the alternator would consist of

a single core multi strand copper wire, this wire was selected due to it being lightweight,

cheap, the plastic insulation has a high melting point and is SABS approved for car wiring.

The requirements for battery cable:

• 12 Volts

• 90 Amperes

• 1000 Watts

• 5 % Ampere rating

• 7.7 meters or 25.2625 in length

Table 3.9.5

Wire Gauge WG Maximum length in feet for car wiring

Current load in Amps @ 12 Volts DC

1 2 4 6 8 10 12 15 20 50 100 200

10 908 454 227 151 113 90 75 60 45

8 1452 726 363 241 181 145 120 96 72 29

6 2342 1171 585 390 292 234 194 155 117 46 23

4 3702 1851 925 616 462 370 307 246 185 74 37

2 6060 3030 1515 1009 757 606 503 403 303 121 60 30

1 7692 3846 1923 1280 961 769 638 511 384 153 76 38

41


From the table a No. 6 gauge copper was selected. This gauge of wire is most often used in

high temperature electrical devices such as stoves, some furnaces, and in air conditioners.

The insulation coating of this gauge can withstand temperatures of 150 degrees, which makes

it ideal for engines bays.

A No 6 wire will have a cross sectional area of 16 ��

WG mm2

6 16

4 25

2 35

Above table represents the cross sectional of a wire gauge

Electrical wiring for lights on the trailer:

Table 3.9.6

42


3.9.8 BATTER ISOLATOR

A battery isolator protects alternator circuit against heavy voltage surge and prevents engine

from excess strain. It can control a circuit up to 500 amps, with an initial load of 100 amps

and a continuous load 12 - 24v.

The isolator incorporates two pairs of terminals as well as the main battery lead terminals.

One of these pairs of contacts opens when you turn off the switch and kills the engine by

either interrupting the ignition supply or closing the fuel solenoid (diesel). The second pair of

contacts closes when the switch is turned off and this diverts the power from the alternator

(which is still producing power until it stops turning) and diverts this power through a ballast

resistor to earth thereby protecting the alternator.

Table 3.9.7

43


3.9.9 SODIUM ELECTRICAL WIRE

The composite tower required a unique electrical cable, this cable needed to supply power to

a turn table motor and to facilitate fast data transfer for telecommunications. It also had to be

flexible so that it could wrap around the tower without interfering with the lifting mechanism

of the tower.

Such a cable was designed by Dr David Levine; it was called sodium electrical wire. This

cable has a springy flattened micro tube tempered beryllium copper and aluminium alloy

chemically isolate with sodium which is covered with a reinforced insulating material. The

micro tube enables the wire to be pre stressed around almost any shape it also gives the wire a

significantly greater melting point of 550��. The bimetallic thermal stresses compensate

while maintaining spring force near elastic limit.

The sodium electrical wire has a self-repairing feature, when cut the atmospheric pressure

pushes sodium deep into the micro tube causing it to expand radially outwards.

Simultaneously, pressurized liquid extrudes from cut micro channels. Some of the liquid

covers the hole, smothering retreating oxidizing sodium. The cable can easily be recycled

with less energy than aluminium or copper, because sodium is also more biodegradable.

44


3.10 UNIVERSAL CONNECTING ADAPTERS FOR COMPOSITE TOWER

The composite tower is designed for various applications; therefore a universal

adapter is required for the numerous functions that the telescopic tower can be used for. It

needs to be simple yet functional, and efficient. These adapters and accessories were selected

for their functionality and simplicity. It does not require a great amount of effort to assemble

and fit as all the accessories are ready for application and pre manufactured to specification

by BlueSky® Masts elevating solutions.

3.10.1 UNIVERSAL POLE MOUNT – DOUBLE SIDED

The pole mount is the foundation of all the accessories to be utilised as it is

essential for the facilitation of all other connections. It is built to specific diameter and then

fastened into place on the tower connecting mast via two screw type swivel clips that apply a

tension that holds the pole mount into place. This part is fully height adjustable by just

loosening the clips slightly and then raising or lowering it to the required height. It is

advisable to adjust the height before other connections are fitted. Approximate weight is 0.4

kg. The universal pole mount is illustrated in the picture below.

45


3.10.2 UNIVERSAL TILTING BRACKET

The tilting bracket works hand in hand with the universal pole mount above. It

connects directly onto the pole mount and allows for 60 degrees of vertical tilting allowing

for accurate positioning of satellites and antennas to provide the best possible results for

transmission of signal and reception etc. This bracket could also be customised to be fitted

with cameras and/or lights. It facilitates angle adjustment by a screw type fastener, loosening

to allow movement and then tightening once the correct angle is selected. This part weighs

approximately 0.4 kg and is easily fitted onto the pole mount.

(Picture: http://www.blueskymast.com/images/stories/MasterDocs/Datasheets)

Extension arms are to be utilised in order to attach a satellite or antenna mounting. These

arms are adjustable and can vary in length. Shown below are more attachments necessary for

various applications.

1. Universal Pole mount - double sided (Part number: BSM2-P-A352-T00-000)

2. Universal tilting bracket (Part number: BSM2-P-A349-BRK-000)

46


3.10.3 POLE MOUNT SIDE ARMS – DOUBLE SIDED

These side arms are used in conjunction with the universal pole mount and

tilting brackets. They have lengths varying from 15.24 cm to 111.76 cm with respective

weights starting from 1.2 kg and ranging to 2.7 kg. The lengths and weights increase in

various increments that can be chosen at will. These arms will be attached onto the tilting

bracket simply with a pin connection holding it in place at whatever angle the tilting bracket

is set to.

(Picture: http://www.blueskymast.com/index.php/accessories-main/pole-mount-side-arm-kits)

Illustration showing the shortest available side arm kit. Custom made connections, could

deviate from illustrations shown as satellites will vary in size and nature, requiring different

adapter settings, lengths and angles necessary for maximum efficiency of product and the

best results required from tower and relevant equipment.

3. Pole Mount side arm kit (Part number: BSM2-K-A352-TXX-100)

47


3.10.4 ATTACHMENTS FOR SIDE ARMS

• Bolster Plate

The bolster plate is an add-on attachment that slots into the end of the side arm fitting. It

comprises of a 180 degree tilt feature with 22.5 degrees adjusting spaces which allows this

accessory to be mounted either upright(vertically) or flat(horizontally). It has universally

spaced bolt holes for easy fitting of satellites. The total weight of the item is 0.4 kg and is

held in place with a pin and slots.

(Picture: http://www.blueskymast.com/images/stories/MasterDocs/Datasheets/BSM2-P-A101-BOL-EM0.pdf)

• Adjustable Cup Holder

Easily adjustable cup holder for most radio and cell phone antennas allows part to be fixed

vertically or horizontally with the aid of a 22.5 degree spaced, 180 degree tilting feature that

can be pinned at any angle in 22.5 degree increments. This part can hold an antenna of

diameter 3.175 cm - 5.08cm with an adjustable screw type fastening bolt for the purpose of

keeping antenna firmly slotted in place at any angle selected. Total depth of the cup is

4. Side Arm Mount- Bolster plate (Part number BSM2-P-A101-BOL-EM0)

48


equivalent to 16.51 cm and the total weight of the fixture is approximately 0.41 kg.

Illustration of part mounting shown below.

(Picture: http://www.blueskymast.com/images/stories/MasterDocs/Datasheets/BSM2-P-A100-CUP-EM0.pdf)

3.10.5 POLE KIT WITH 2 INCH (5.08 CM) U - BOLTS

This antenna fixture is aluminium and 5.08 cm in diameter. Its length is 30.48 cm and

connects onto the bolster plate by means of two, 2 inch stainless steel U-bolts. The

illustration below shows how the pole kit assembles onto the bolster plate fixture.

Approximate weight is 0.4 kg.

49


• Cross pattern plate

20.32 X 25.4 cm aluminium plate with cross shaped cut out for fixing of heavy duty

antennae. Approximate weight is 0.76 kg.

(Picture: http://wwww.blueskymast.com/images/stories/MasterDocs/Datasheets/BSM2-A-M408-MPP-

EM0.pdf)

5. Side Arm Mount - Adjustable Cup holder (Part number: BSM2-P-A100-CUP-EM0)

7. Side arm mount - Cross pattern plate (Part number: BSM2-A-M408-MPP-EMO)

50


• Solid Aluminium plate

Square plate with 27.94 cm sides and approximate weight of 0.43 kg.

• Lighting and Camera fittings

All lighting and camera fitting are custom made by BlueSky® Masts elevating solutions, to

specifications required.

(Picture: http://www.blueskymast.com/index.php/vertical-markets)

51


3.11 FINITE ELEMENT ANALYSIS

Mechanical components in form of bars, beams, and so on can be easily analysed

by basic method of mechanics that provide closed-form solutions. Actual components,

however, are rarely so simple, and the designer is forced to less effective approximations of

closed form solutions, experimentation, or numerical methods. There are great numerical

techniques used in engineering applications for which the digital computer is so useful.

Where Computer Aided Design software is heavily employed, the analysis method that

integrates with CAD is finite element analysis (FEA) [Richard, G. and Keith J. 2008.

Shigley’s Mechanical Engineering Design. Singapore: McGraw-Hill]. and. This method was

used to analyse complex components of our design such as the collar the piston etc.., the

finite element analysis mode used in this design is the static analysis and the application used

is Pro Engineer mechanica 5.0.

The analysis process consist of assigning the right material to the component,

applying loads and constraint to much the working conditions of the components, meshing

the component and then selecting a type of analysis to run.

The following pages present the von Mises and maximum principal stress

obtained from the finite element analysis. All maximum stresses were found to be three or

four times less than the yield strength of the particular material.

52


Figure: 3.11.1. Maximum principal stress obtained in cylinder 2: 267.8MPa

53


Figure: 3.11.2. Maximum principal stress obtained in collar 1: 58.4MPa

54


Figure 3.11.3: Maximum displacement in collar 1: 0.0130mm

55


Figure 3.11.4: Maximum principal stress in Piston 2: 15.8MPa

56


Figure: 3.11.5. Von Mises stress in piston 2: 14.2Mpa

57


Figure: 3.11.6. Maximum principal stress in lock key: 33.86Mpa

58


Figure: 3.11.7. Von Mises stress in lock key: 77.87MPa

59


Frame Analysis Report

Analyzed File: chasis 2.iam

Version: 2012 (Build 160160000, 160)

Creation Date: 10/22/2012, 6:03 PM

Simulation Author: Stefano Horning

Summary: Simulation run with a factor of safety of 2.

Project Info (iProperties)

Summary

Author Group 3

Project

Part Number Chasis

Designer AutoCad

Cost R1500

Date Created 8/21/2012

Status

Design Status Completed

Physical

Mass 124.019 kg

Area 120776.360 mm^2

Volume 45763.315 mm^3

Centre of Gravity

x=-1583.311 mm

y=-901.433 mm

z=-0.000 mm

Simulation:1

General objective and settings:

Simulation Type Static Analysis

Last Modification Date 10/22/2012, 6:00 PM

60


Material(s)

Name Aluminum-6061

General

Mass Density 2.710 g/cm^3

Yield Strength 275.000 MPa

Ultimate Tensile Strength 310.000 MPa

Stress Young's Modulus 68.900 GPa

Poisson's Ratio 0.330 ul

Stress

Thermal

Expansion Coefficient 0.0000236 ul/c

Thermal Conductivity 167.000 W/( m K )

Specific Heat 1.256 J/( kg K )

Part

Name(s)

ISO 80x80x8 00000062.ipt, ISO 80x80x8 00000066.ipt, ISO 80x80x8 00000069.ipt, ISO

80x80x8 00000063.ipt, ISO 80x80x8 00000064.ipt, ISO 80x80x8 00000065.ipt, ISO

80x80x8 00000068.ipt, ISO 50x50x5 00000042.ipt, ISO 50x50x5 00000043.ipt, ISO

50x50x5 00000041.ipt, ISO 80x80x8 00000061.ipt, ISO 80x80x8 00000067.ipt

Cross Section(s)

Geometry

Properties

Section Area (A) 2084.248 mm^2

Section Width 80.000 mm

Section Height 80.000 mm

Section Centroid (x) 40.000 mm

Section Centroid (y) 40.000 mm

Mechanical

Properties

Moment of Inertia (Ix) 1683770.111 mm^4

Moment of Inertia (Iy) 1683770.111 mm^4

Torsional Rigidity Modulus (J) 3070000.000 mm^4

Section Modulus (Wx) 42094.253 mm^3

Section Modulus (Wy) 42094.253 mm^3

Torsional Section Modulus (Wz) 66600.000 mm^3

Reduced Shear Area (Ax) 999.871 mm^2

Reduced Shear Area (Ay) 999.871 mm^2

Part Name(s)

ISO 80x80x8 00000062.ipt, ISO 80x80x8 00000066.ipt, ISO 80x80x8 00000069.ipt,

ISO 80x80x8 00000063.ipt, ISO 80x80x8 00000064.ipt, ISO 80x80x8 00000065.ipt,

ISO 80x80x8 00000068.ipt, ISO 80x80x8 00000061.ipt, ISO 80x80x8 00000067.ipt

Geometry Properties

Section Area (A) 835.619 mm^2

Section Width 50.000 mm

Section Height 50.000 mm

Section Centroid (x) 25.000 mm

Section Centroid (y) 25.000 mm

Mechanical

Properties

Moment of Inertia (Ix) 270377.484 mm^4

Moment of Inertia (Iy) 270377.484 mm^4

61


Torsional Rigidity Modulus (J) 475000.000 mm^4

Section Modulus (Wx) 10815.099 mm^3

Section Modulus (Wy) 10815.099 mm^3

Torsional Section Modulus (Wz) 16600.000 mm^3

Reduced Shear Area (Ax) 394.684 mm^2

Reduced Shear Area (Ay) 394.684 mm^2

Part Name(s) ISO 50x50x5 00000042.ipt, ISO 50x50x5 00000043.ipt, ISO 50x50x5

00000041.ipt

Beam Model

Nodes 36

Beams 12

- Square/Rectangular Tubes 12

Rigid Links

Name

Displacement Rotation Parent

Node Child Node(s) X -

axis

Y -

axis

Z -

axis

X -

axis

Y -

axis

Z -

axis

Rigid

Link:1 fixed fixed fixed fixed fixed fixed Node:15 Node:9, Node:35

Rigid


Rigid

Link:3 fixed fixed fixed fixed fixed fixed Node:18

Node:10, Node:29,

Node:14

Rigid


Rigid


Rigid

Link:6 fixed fixed fixed fixed fixed fixed Node:34

Node:12, Node:13,

Node:28

Rigid

Link:7 fixed fixed fixed fixed fixed fixed Node:37 Node:26

Rigid

Link:8 fixed fixed fixed fixed fixed fixed Node:38 Node:25

Operating conditions

Gravity

Load Type Gravity

Magnitude 9810.000 mm/s^2

Direction Z-

62


Force:1

Load Type Force

Magnitude 12000.000 N

Beam Coordinate System No

Angle of Plane 0.00 deg

Angle in Plane 180.00 deg

Fx 0.000 N

Fy 0.000 N

Fz -12000.000 N

Offset 1010.340 mm

Selected Reference(s)

63


Results

Reaction Force and Moment on Constraints

Constraint

Name

Reaction Force Reaction Moment

Magnitude Components

(Fx,Fy,Fz) Magnitude

Components

(Mx,My,Mz)

Fixed

Constraint:2 883.413 N

0.000 N

663008.155 N mm

-306703.756 N mm

-0.000 N -587803.215 N mm

883.413 N 0.000 N mm

Fixed


0.000 N

659144.566 N mm

307316.919 N mm

0.000 N -583119.088 N mm

876.855 N 0.000 N mm

Fixed


-0.000 N 2723413.131 N

mm

1943414.253 N mm

-0.000 N 1907909.883 N mm

5702.862 N -0.000 N mm

Fixed


0.000 N 2754129.016 N

mm

-1959895.363 N mm

0.000 N 1934951.369 N mm

5801.109 N 0.000 N mm

Static Result Summary

Name Minimum Maximum

Displacement 0.000 mm 4.058 mm

Forces

Fx -50.951 N 50.903 N

Fy -5702.862 N 5801.109 N

Fz -0.000 N 0.000 N

Moments

Mx -1908584.463 N mm 1959895.363 N mm

My -39674.778 N mm 7546.539 N mm

Mz -1934951.369 N mm 1907909.883 N mm

Normal Stresses

Smax 0.000 MPa 46.560 MPa

Smin -46.560 MPa -0.000 MPa

Smax(Mx) 0.000 MPa 46.560 MPa

Smin(Mx) -46.560 MPa -0.000 MPa

Smax(My) -0.000 MPa 3.668 MPa

Smin(My) -3.668 MPa 0.000 MPa

Saxial -0.000 MPa 0.000 MPa

Shear Stresses Tx -0.129 MPa 0.129 MPa

Ty -5.802 MPa 5.704 MPa

Torsional Stresses T -28.647 MPa 29.053 MPa

Figures

64


Displacement

Fx

65


Fy

Fz

Mx

66


My

Mz

67


Smax

68


Smin

Smax(Mx)

69


Smin(Mx)

Smax(My)

70


Smin(My)

Saxial

71


Tx

Ty

T

72


T

73


3.12 MANUFACTURING PROCESS

3.12.1 SYNOPSIS

The filament winding process has become a primary process in manufacturing composite

circular or oval shaped components, this is mainly because of its low cost and it being an

automated process. This process requires few workers on it as it is a process where the speeds

of the moving parts are programmed.

Image 1: image briefly illustrate filament winding process

Image from: www.cadfill.com/filamentwindingprocess.html

The fibre in this process has three different types of winding that can be used. There is

helical, circumferential and polar winding. These different types of winding have their own

advantages but in designing this tower the helical winding has been chosen. The filament

winding process, in order produce the desired product with the desired surface finish, has had

to be modified slightly to facilitate the desired purpose.

Prior to choosing the filament winding process to manufacture the tower another method of

manufacturing the tower was considered. This considered process was the filament pultrusion

process. In this pultrusion the fibres are pulled from roving racks, passed through a resin, and

then passed through a heating die to cure the resin on the fibres.

74


3.12.2 MATERIAL SELECTION

• Tower Material

The tower will be made several composite materials. Each cylindrical section of the tower

will be made of two parts; a filament wound cylinder section and a short collar that covers the

top. These short collars which cover the top section of the tower will have scraper which will

keep the dirt from entering the inside of the tower and interfering with the air system. The

short collar also supports the smaller section of the tower, which will rise from inside the

larger section as air is pumped into the tower.

The cylindrical section of the tower will be made of wound carbon fibre. Carbon fibre was

chosen because of the impressive properties, which is why carbon fibre is so widely used.

These properties are:

Properties Description

High strength to weight ratio This is the force per unit area, divided by density.

Carbon fibre has a value of 2457 kN.m/kg compared

to fibre glass which has 1307 kN.m/kg

Good tensile strength The maximum stress a material can withstand before

failing, compressive or tensile stress. Carbon fibre

has a tensile strength of 4127 MPa compared to

3450 MPs for E-glass fibres

Corrosion resistance Carbon fibre itself does not corrode, the epoxy and

other substances that carbon fibre is combined with

that corrode away. Epoxy is sensitive to the sun and

is protected from it.

Good rigidity Rigidity is measured by the young’s modulus value

and measures a materials deflection under stress.

Fire resistance Carbon fibre does not burn easily, this property also

depends on the manufacturing process and the

material its combined with.

Low coefficient of thermal expansion A measure of the amount of expansion or

contraction of a material when there is an increase in

temperature.

Fatigue resistance An ability to oppose failure due to continued use.

Non poisonous Carbon fibre is not toxic; which is why it is used for

medical applications.

Relatively expensive Because carbon fibre has excellent advantages,

especially weight saving. It has a higher cost

compared to fibre glass.

Needs specialist equipment and

workers

To take full advantage of carbon fibre’s properties,

the fibre have to have a high level perfection must

be achieved. This means no imperfections.

75


Table 3.12.1: Properties of carbon fibre

In selecting the material for the two materials were considered, carbon fibre and fibre glass.

With further refinement in the material selection carbon fibre was chosen. Carbon fibre AS4

was chosen over carbon fibre T700S.

Fibre Properties Carbon Fibre T700S Carbon Fibre AS4

Tensile strength (MPa) 4.9 4.433

Tensile modulus (GPa) 230 231

Electrical resistivity (ohm-cm) 1.6×10-3

1.7×10-3

Composite Properties

Tensile strength at 0° (MPa) 2.55 2.205

Tensile Modulus at 0° (GPa) 135 141

Flexural strength at 0° (MPa) 1.67 1.889

Tensile strength at 90° (MPa) 69 81

Table3.12.2 carbon fibre T700S vs AS4

In the manufacturing process and for the final product, the tower, the type of resin used is

very important. This is because the resins probably degrade before the carbon fibre due to

exposure to the natural elements, i.e. sunlight, cold air, wind or even rain. The below

properties will show why epoxy liquid resin has been selected over vinyl ester liquid resin.

Liquid Resin Properties Epoxy Vinyl ester

Specific Gravity 1.1 1.046

Tensile Strength (MPa) 344 86

Tensile Modulus (GPa) 17.4 3.2

Flexural Strength (MPa) 235 150

Flexural Modulus (GPa) 6.1 3.4

Glass Transition Temperature

(°K)

423 393

Dynamic Viscosity (MPa/s) 600 100

Table 3.12.3: resin properties, Epoxy vs vinyl ester

• Collar Material

The material which was chosen for the short collar is aluminium. The material chosen for the

collar has to be a material which will not deflect or deform easily. The material must not

deform in any conditions, such as extremely hot or cold weather. The material considered

material was a thermoset polymer. The thermoset polymer softens when heat is applied and

therefore deforms too much for the desired application, it also is weak compared to

aluminium and therefore does not provide the support that is required of the collar.

76


Thermosets Polymer

Aluminium Melamine formaldehyde Phenol formaldehyde

Density (kg/m3) 2700 1800-2000 1600-1900

TensileStrength (N/mm2) 310 50-90 38-50

Young’sModulus (GPa) 69-70 7 17-35

Table 3.12.4: Collar material, Aluminium vs Thermoset Polymer

3.12.3 TOWER MANUFACTURING PROCESS

There are many processes in manufacturing composite components, but the two

manufacturing methods that were reviewed for this design project are the composite

pultrusion process and filament winding process. The most common and widely used method

of manufacturing cylindrical parts, which was chosen for this project, is the filament winding

process.

3.12.4 REVIEWED MANUFACTURING PROCESS

Pultrusion

The pultrusion process is similar to the filament winding process, except for the sections of

the fibre winding. The pultrusion process is a process of pulling the composite fibres through

a resin bath and a heating die.

Image 3.12.5: Image illustrates the pultrusion process

Image from: www.sparecomposite/pultrusion

77


This process of manufacturing begins with racks containing rolls of the composite fibre/ fibre

rovings or composite fibre mats. The fibres or mat is then guided from the racks through the

resin bath. The fibres are now completely impregnated with the resin so that the fibres are

completely saturated.

The resin soaked fibres leave the resin impregnation system. The soaked fibres, uncured

fibres are guided to design shaping tools that organize and correctly align the fibres into the

desired shape. The excess resin is also removed, squeezed from the fibres. This is known as

debulking. This tool that pre-shapes the fibres is known as the pre-former. To improve the

surface finish of the final product the composite mats are added at this point of the process.

The fibres, which now contain no excess resin, then pass through a heated die. The heating

die is generally chromed steel. In this heating die the temperature is kept constant, though it

may have several temperature zones throughout the length. This part of the process cures the

thermosetting resin as the fibre pass through the heat produced. The final product is then a

pultruded fibre reinforced polymer or FRP composite.

The final product is pulled through by the pulling mechanism, which could be callipers tracks

or hydraulic grips. The product is a long continuous part. This long continuous piece now

enters the final stage where it is cut by the cut off saw into specified lengths and then stacked

as finished products.

Image 3.12.6: Putrusion process in the form of a production line, producing pipes

Image from: www.libertypultrusions.com/pulturusion-process

78


3.12.5 CHOSEN MANUFACTURING PROCESS

Filament Winding

Filament winding has become a primary process for manufacturing cylindrical composite

components. In filament winding threads are wound around a mandrel. The properties of the

composite product are dependant not only on the properties of the fibres and the resin, but

also on the way the carbon fibres are processed and laid for the manufacturing of the

structure.

Image 3.12.7: Shows the angle at which fibres are laid

Image from: www.sciencedirect,com

The threads are wound at a specific angle, � which is the angle from the horizontal; which

best suits the purpose of the product and the required properties of the final product.

Tower Filament Winding Process

The composite tower will consist of six sections, with each section tapering towards the top.

The filament winding process will be used to manufacture the composite cylinder part of each

section.

Before the filament winding process begins there are some preparations to be made. The first

preparation involves degreasing the mandrel, which allows contaminates to build up on the

wound tube. The next preparation is to spray or apply a releasing agent to the mandrel, which

79


makes the removal of the hollow cylindrical section an easy job. The final preparation is to

improve the rough surface finish of the wound cylinder, by lining the mandrel with a

thermosetting plastic so the smooth, polished surface finish of the mandrel will transfer to the

polymer. The threads will be wound on this this polymer.

The filament winding process begins with reels of dry carbon fibre, placed on a creel. The

carbon fibre threads will make their way around tensioner bars. These tensioner bars may

have sensors on them; the sensors send signals to the control unit. This is so the tensioner

bars can keep a constant tension on the carbon threads while the reel is unwinding for the

process. If the tension of the applied threads is high the resulting product will have a higher

strength and rigidity. If the tension is low the result will be a flexible final product. If not

enough attention is paid to the tension of the carbon threads, this may result in an increase in

the amount of voids or cavities in the volume of the wound final product.

Image 3.12.8: Illustration of reels of Carbon fibre

Image from: www.zoltek.com

Voids in the wound products are a factor which influences the strength and stiffness of the

final product.

80


Image 3.12.9: Shows a single tensioner bar

Image from: www.compositesworld.com

From the tensioners the carbon threads are directed to a resin bath, where the threads get a

coating or impregnated with the resin. The fibre will then pass under a spreader, this spreader

will spread the carbon threads flat on the surface of the feedeye carriage and also remove the

extra resin. The access resin will then be recycled back into the rein bath. From the spreader

the carbon threads will pass under a thread comb, this untangles the threads. The untangled

threads then pass through a guide or eye, this bring the threads very to close each other. From

the guide the threads are ready to be wound on the mandrel.

Before the threads are wound on the mandrel, the mandrel will be covered with a sleeve of a

composite thermoset plastic. The sleeve is added to improve the inner surface finish and so

the grooves and indentations which are required can be produced on it rather than the fibre

wound sections. The sleeves will be drilled where the hole will be and special inserts will be

placed. The holes that will be used for the locks will be threaded and so will the inserts. The

inserts will be the same length as the combined thickness of the sleeve and the wound

section.

Image 3.12.10: Shows threaded hole inserts

Image From: ww.specialinsert.com

This sleeve, with the inserts placed on it will be placed over the mandrel and the filament

81


winding will take place on top of the sleeve. The threads will wind around the hole inserts.

The carbon threads from the guide on the feedeye carriage are to be wound on the mandrel.

There are three methods of winding threads that will be looked at, first will be the polar

winding method, the second will be the circumferential winding and finally the helical

winding method.

Polar Winding

Image 3.12.10: illustrates polar filament winding

Image from: www.sciencedirect.com

In this form of winding (polar) the threads are wound tangentially across the mandrel. The

threads are wound from one pole to the other, from left to right. This results in the angle of

the threads being an acute angle, the angle approaches zero degrees, the mandrel is rotated

about the longitudinal axis by the arm. This method of winding is generally used for domed

end pressure vessels.

• Circumferential Winding

Image 3.12.11: Shows circumferential winding method

Image from: www.sciencedirect.com

82


In circumferential winding the threads are wound tightly and close together around the

mandrel. Each rotation of the mandrel moves the feedeye carriage one bandwidth in the

direction of its horizontal movement. The angle at which the fibres are wound approaches

90°.

• Helical Winding

Image 3.12.12: Shows Helical winding

Inage from: www.sciencedirect.com

In this winding method the threads are wound at 90° to each other, 45° from the horizontal.

As the mandrel rotates and the feedeye carriage moves horizontally, the threads leave gaps

between each of the threads laid per revolution of the mandrel. These gaps will be closed by

the multiple layers of threads to be wound. The horizontal movement of the feedeye and the

rotary motion of the mandrel make the machine used here a 2 axis winding machine.

The helical winding method was chosen in manufacturing the tower because the threads laid

in this manner will cope well with the forces. When blown by the wind the tower may bend

or deflect, this method of winding will be able to cope with the compressive stresses of the

inner fibres and the tensile stresses of the outer fibre. The stresses will be distributed across

the fibres

Once the threads have been successfully wound on the mandrel the resin needs to be

hardened or cured. The curing of the resin will affect the overall performance of the final

product’s structure. Special attention is paid to the temperature of curing the resin. When

curing the wound product the amount of layers and the thickness of the cylindrical section

have to be taken into account when setting the temperature of the oven.

83


Image3.12.13: Shows a large curing oven

Image from: www.addax.com

Advantages of Filament Winding

� It’s a process which can be automated, reduced labour

� Can produce high quality components and is repeatable

� There is no pollution or environmental concerns

� Water based, transfer left on the mandrel can be washed with water

� The cylindrical sections will have a smooth inner surface finish

� Easy removal of the mandrel

� The use of continuous fibres produces very good properties, such as high strength and

stiffness.

� The fibres can be laid in many ways to suit the product and its uses

� The material can be used in its simplest form, which saves cost

3.12.6 CHASSIS MATERIAL

For the construction of the chassis and some of its components we decided to go with an

aluminium alloy as it now ranks second to steel in standings of worldwide quantity and

expenditure. It has achieved prominence in nearly all sectors of the economy with foremost

uses in transportation.

There are numerous unique and attractive properties that account for the engineering

significance of aluminium such as workability, corrosion resistance, light weight etc.

Aluminium has a specific gravity of 2.7 whilst that of steel is 7.85 making it a third of the

84


weight of steel at the same volume.

It can also be recycled repeatedly with no harm in quality. This saves 95% of energy required

to produce aluminium from ore [5]. The only serious flaw that aluminium has from an

engineering perspective is a fairly low modulus of elasticity.

For the trailer which forms the base of the tower we have selected aluminium alloy 6061-T6

over the 7075 series which are both from the wrought alloy classification. These are shaped

as solids therefore have attractive forming characteristics. Whilst stronger than 6061, 7075 is

nearly impossible to weld due the high copper content.

Composition and Properties of some wrought aluminium alloys in various conditions

7075-T6 6061-T6

% Composition Cu 1.6 0.28

% Composition Si 0.6

% Composition Mn 0.2

% Composition Mg 2.5 1.0

% Composition Others 5.6 Zinc 0.20 Cr

Tensile strength (MPa) 552 290

Yield Strength (MPa) 483 276

Elongation in 2 inch % 6 12

Brinell Hardness 150 95

Uses and Characteristics Strongest alloy for extrusions Strong, Corrosion resistant

Table: 3.12.13 Yield strength taken at 0.2% permanent set, information is taken from

reference [5]

3.12.7 CHASSIS AND PLATFORM CONSTRUCTION

The chassis will be a fully welded aluminium 6061-T6 rolled sheet and the platform consists

of a skeletal top deck to accommodate the load.

• Welding

Aluminium 6061 is highly weldable. For the purpose of the trailer construction tungsten inert

gas welding (TIG) has been selected as the most appropriate; however the weld has to be heat

85


treated and age harden to the T6 temper due to a loss of strength of nearly 80% [13].

The heat treatment must adhere to the standards stated by the Structural Engineering

Division cited in reference [3].

Equipment needed:

• A TIG Welder

• Welding gloves

• A good welding helmet (Gold plated is best)

• Argon gas (an argon/helium mix is the only suitable mix allowable for use)

• Aluminium welding rod

• Stainless steel brush dedicated for use on aluminium only

• A metal work bench

• A squirt bottle filled with water to put out minute fires

• Fire extinguisher

• Vice grips/clamps

• Blocks of aluminium or copper for use as heat sinks

Precautions:

• Clean the aluminium- use 100% acetone, rinse with water, and once dry scrub with

the stainless steel brush.

• Clamp the part being welded to a heat sink to keep the work from warping

• Preheat the aluminium before welding

• Fit the parts as tightly together as possible

Many of the components of the chassis, such as the wheel hub assemblies etc. will be

standard parts that can be purchased at any local store. The designed parts were done so to

accommodate the tower as current components do not meet the design standards. Any local

engineering firm can put the trailer together.

86


3.12.8 STANDARD PARTS TO BE USED:

Steering:

A single ball bearing lock which is restricted to 45 degrees can be used as well as single or

twin Ackerman steering.

Axles/Hubs:

Solid steel axle (diameter 50mm) beams fitted with taper roller bearings (diameter 115mm).

The beam and stud configurations that are determined by load capacity are:

Wheels and tyres:

Selection influences take account of load capacity and the surface condition of the

environment. On that basis 15 inch was selected.

Drawbar/Towing eye:

A hinged frame construction with a T handle for manual operation

3.12.9 TOWER BASE PLATE

The composite tower rests on a base plate made of cast aluminium to enable easy storage and

movability. Aluminium is a lightweight alternative to using steel and has the added bonus of

non-rusting features. It does however have the tendency to develop stress cracks in high

stress regions. Our casted aluminium base plate is designed from one piece. The connection

of the base plate to the column is realized by a crimping process. This ensures a seamless,

completely sealed construction.

We decided to use an alloy with a higher strength than that which we used in the construction

of the trailer. Aluminium 2014-T6 has an ultimate tensile stress of 485 MPa, which exceeds

that of many grades of steel. Forging is porosity free therefore permitting straight forward

heat treatment processes that considerably improve selected mechanical characteristics. A

wide range of finished can be achieved by forging

87


2014-T6 6061-T6

Bulk Modulus (GPa) 71 67

Density (g/cm3) 2.80 2.70

Elastic (Young’s) Modulus

(Gpa)

73 69

Electrical Conductivity (%

IACS)

40 43

Elongation at Break:

Typical (%)

4 14

Elongation at Break:

Minimum (%)

6 4

Fatigue Strength

(Endurance Limit) (Mpa)

125 97

Hardness: Brinell 135 95

Maximum Temperature:

Onset of Melting (Solidus)

(°C)

507 582

Poisson’s Ratio 0.33 0.33

Shear Modulus (Gpa) 290 207

Shear Strength (Mpa) 160 150

Stiffness-to-Weight Ratio:

Bulk (MN-m/kg)

25 25


Shear (MN-m/kg)

10 12


Tensile (MN-m/kg)

26 25

Strength-to-Weight Ratio:

Fatigue (kN-m/kg)

44 35


Shear (kN-m/kg)

100 76


Tensile, Ultimate (kN-

m/kg)

170 110


Tensile, Yield (kN-m/kg)

140 100

Tensile Strength: Ultimate

(Mpa)

485 310

88


Tensile Strength: Yield

(Proof) (Mpa)

415 276

Thermal Conductivity:

Ambient (W/m-K)

154 167

Thermal Expansion: 20 to

100°C (µm/m-K)

22.5 23.6

Table3.12.14: information is taken from reference [14]

89


3.13 ENGINEERING DRAWINGS

This section includes all relevant engineering drawings of the final product design and

the winch tilting mechanism option drawings. All drawings dimensions are in millimetre

unless otherwise specified on the drawing.

The number next to a part name on the drawing indicates the section of the tower on

which that part is fitted or belongs. Drawings were generated using Pro Engineer Wildfire

5.0.

90

SHEET

SCALE:

METRIC

PROJECT

SIZE

ORIGINATOR ORIGINATION DATE CHECKED BY CHECK DATE

REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER

DURBAN UNIVERSITY OF TECHNOLOGY Faculty of Engineering and Built Environment


TOUT EST GRACE

1 92 Air_cyl_Base_mount 13 AIR_CYL_PIN 14 air_cylinder1.asm 15 Animated_tower_4 16 Pin_lock_plate 17 stand_frame 18 stop_timber 19 Swing_bolt 110 Tilting_base_mounting 111 Trailer_plate 112 Wing_nut1 1ITEM

PART NAME QTY1 OF 1

0,040

A3 A

KAHULUME T 2012/10/19 PROF. KANNY 2012/10/26 GROUP 3

COMPOSITE TELESCOPIC TOWER

TOWER001

mm-kg-s

MDES302

1

3

5

7

8 9

10

11

12

2 4 6

WELDING SPECIFICATION : AWS D14.3

MASS EXCL. WELDING

1200 kg

PROCESS STANDARD FOR

TOLERANCE SEE 700997 U.O.S

SECONDARY PROCESSES

DO NOT SCALE FROM PRINTED DRAWING 91

SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

2763

610

1023

1,5

180

410

470

1 Section_1 12 Section_2 13 Section_3 14 Section_4 15 Section_5 16 Section_6 1ITEM

PART NAME QTY1 OF 1

0,075

A3 A


TELESCOPIC TOWER

TOWER002

mm-kg-s

MDES302

SCALE 0,060

SCALE 0,025

1

2

3

4

5

6

SCALE 0,025SECTION B-B

A

A(0,200)

SCALE 0,060

MASS EXCL. WELDING

408.88 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

470

2078

450

370

1 42 Air_cyl_towerclamp 13 base_cap.prt 14 Base_ORing 15 Bolt_Ring 16 collar01 17 Cylinder_1 18 M12_Socket_Cap_Screw 69 Support_pin 210 Tower_support 1ITEM

PART NAME QTY1 OF 1

0,020

A3 A

KAHULUME T 2012/10/20 PRO. KANNY 2012/10/26 GROUP 3

SECTION 1

TOWER003

mm-kg-s

MDES302SCALE 0,075

1

2

3

4 5

6

7

8

9 10

SCALE 0,075SECTION A-A

SCALE 0,060

MASS EXCL. WELDING

118.39 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

2043

,38

1543

,5

369

148

1 Base_Ring2 12 Collar02 13 cylinder_2.prt 14 M10_HEX_SCREW 65 M12_Cap_Screw 66 Oring 17 Piston_2 18 seal_1.prt 29 Wear_ring_1 1ITEM

PART NAME QTY1 OF 1

0,034

A3 A


SECTION 2

TOWER004

mm-kg-s

MDES302

SCALE 0,075

1

2

3

4

5

6

7

8

9

SCALE 0,075

SCALE 0,080MASS EXCL. WELDING

75.3 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

2002

,22

1508

,5

358

1 Base_Ring3 12 Collar03 13 cylinder_3.prt 14 M10_Hex_Socket_Screw 65 M12_Socket_Cap_Screw 66 oring03.prt 17 piston_3.prt 18 seal_2.prt 29 wear_ring_2.prt 1ITEM

PART NAME QTY1 OF 1

0,060

A3 A


SECTION 3

TOWER005

mm-kg-s

MDES302

SCALE 0,075

1

2

3

4

5

6

7

8

9

SCALE 0,075

SCALE 0,075

MASS EXCL. WELDING

63.77 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

1973

,06

1485

,5

312

1 Base_Ring4 12 Collar04 13 cylinder_4.prt 14 M10_Hex_Sockel_Screw 65 M12_Socket_Cap_Screw 66 oring04.prt 17 piston_4.prt 18 seal_3.prt 29 wear_ring_3.prt 1ITEM

PART NAME QTY1 OF 1

0,026

A3 A


SECTION 4

TOWER006

mm-kg-s

MDES302

SCALE 0,080

1

2

3

4

5

6

7

8

9

SCALE 0,080

SCALE 0,075

MASS EXCL. WELDING

54.1 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

266

1478

,5

1959

,89

1 Base_Ring5 12 Collar05 13 cylinder_5.prt 14 M10_Hex_Socket_Screw 65 M12_Socket_Cap_Screw 66 oring05.prt 17 piston_5.prt 18 seal_4.prt 29 wear_ring_4.prt 1ITEM

PART NAME QTY1 OF 1

0,028

A3 A


SRCTION 5

TOWER007

mm-kg-s

MDES302

SCALE 0,080

1

2

3

4

5

6

7

8

9

SCALE 0,080

SCALE 0,080

MASS EXCL. WELDING

44.18 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

240

300

1873

,73

185

1 cylinder_6.prt 12 M10_Hex_Socket_Screw 63 M12_Socket_Cap_Screw 64 oring06.prt 15 piston_6.prt 16 seal_5.prt 27 Top_Flange 18 wear_ring_5.prt 1ITEM

PART NAME QTY1 OF 1

0,030

A3 A


SECTION 6

TOWER008

mm-kg-s

MDES302

SCALE 0,085

1

2

3

4 5

6

7

8

SCALE 0,085SECTION A-A

SCALE 0,085

MASS EXCL. WELDING

32.26 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

B

B

A

A

410

1990

42,3

430

176,6

100

428

40

90400

1950

256

80

5

1 OF 1

0,080

A3 A


CYLINDER 1

TOWER023

mm-kg-s

MDES302

SECTION B-B

SECTION A-A

M12x1.75 ISO - H TAP 20,000 10.2 DRILL ( 10,200 ) 20,000 -( 6 ) HOLE

MATERIAL DESCRIPTION

MATERIAL No. MAT. QUANTITY ITEM MASS

Carbon Fibre Epoxy Resin

75.58 kg 75.58 kg


SECONDARY PROCESSES

DO NOT SCALE FROM PRINTED DRAWING

1,1

99

SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

B

B

A

A

11

26

369 32418

501698

,5

1698

,5

1644

,5

1519

,5

101 40

30

364

1 OF 1

0,100

A3 A


CYLINDER 2

TOWER024

mm-kg-s

MDES302

SECTION B-B


SECTION A-A



Carbon Fiber Epoxy Resin

52.3 kg 52.3 kg


SECONDARY PROCESSES


1,1

100

SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

B

B

A

A

26

323 278

1663

,5

1609

,5

1484

,5

101

40

30

1815

11

318

1 OF 1

0,100

A3 A


CYLINDER 3

TOWER025

mm-kg-s

MDES302

SECTION B-B

M12x1.75 ISO - H TAP 24,480 10.2 DRILL ( 10,200 ) -( 6 ) HOLE THRU

SECTION A-A



Carbon Fibre Epoxy Risen

44.45 kg 44.45 kg


SECONDARY PROCESSES


1,1

101

SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

B

B

A

A

232

30

1792

1640

,5

1586

,5

1461

,5

40

101

26 11

277

272

1 OF 1

0,100

A3 A


CYLINDER 4

TOWER026

mm-kg-s

MDES302

SECTION B-B


SECTION A-A




37.1 kg 37.1 kg


SECONDARY PROCESSES


1,1

102

SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

B

B

A

A

26

231

11

186

1633

,5

1579

,5

1454

,5

40101

1785

30

226

1 OF 1

0,100

A3 A


CYLINDER 5

TOWER027

mm-kg-s

MDES302

SECTION B-B


SECTION A-A




30.19 kg 30.19 kg


SECONDARY PROCESSES


1,1

103

SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

B

B

A

A

185 140

26

1603

,5

1549

,5

1444

,5

30

81

1755

30

180

1 OF 1

0,100

A3 A


CYLINDER 6

TOWER028

mm-kg-s

MDES302

SECTION B-B


SECTION A-A



Carbon Fibre Epoxi Resin

23.04 kg 23.04 kg


SECONDARY PROCESSES


1,1

104

SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

AA

4

410+0,14 0

148

80

379

385

36

13

365+0,007-0,029

118

40

1 collar_test1.prt 12 Lock_mechnism 23 Scraper_1 14 wear_ring_01.prt 1ITEM

PART NAME QTY1 OF 1

0,200

A3 A


COLLAR 1

TOWER017

mm-kg-s

MDES302

1

2

3

4

SECTION A-A



Al 6061 T6

15.92 kg 15.92 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

AA

4

14

60°

364+0,14 0

319+0,007-0,029

404339323

333

80

148

11840

18

1 collar_test2.prt 12 Lock_mechnism 23 scraper_2.prt 14 wear_ring_02.prt 1ITEM

PART NAME QTY1 OF 1

0,200

A3 A


COLLAR 2

TOWER018

mm-kg-s

MDES302

1

2

3

4

SECTION A-A



Al 6061 T6

14.22 kg 14.22 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

AA

4

14

287

273+0,005-0,027

318+0,13 0

148

11840

358

293

277

60°

80

68 63 43 177,

5


PART NAME QTY1 OF 1

0,250

A3 A


COLLAR 3

TOWER019

mm-kg-s

MDES302

1

2

3

4

SECTION A-A



Al 6061 T6

12.51 kg 12.51 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

AA

4

14

241

80

60°

272+0,115 0

227+0,005-0,024

148

11840

312

231

24768 63

43

177,

5

18


PART NAME QTY1 OF 1

0,250

A3 A


COLLAR 4

TOWER020

mm-kg-s

MDES302

1

2

3

4

SECTION A-A



Al 6061 T6

10.8 kg 10.8 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

AA

4

14

185

201

266

181+0,005-0,024

226+0,115 0

40

118 14

8

7,5

1743

6368

18

60°

80

195


PART NAME QTY1 OF 1

0,300

A3 A


COLLAR 5

TOWER021

mm-kg-s

MDES302

SECTION A-A

1

2

3

4



Al 6061 T6

9.09 kg 9.09 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

AA

95

25

43

62,25

17,6

79,6

3,5

12 11

1 14

11,6

19,6

35,732,7

1 Circlip 12 Locking_Key 13 spring 14 Wing_Nut 1ITEM

PART NAME QTY1 OF 1

0,500

A3 A


LOCKING MECHANISM

TOWER016

mm-kg-s

MDES302

SCALE 0,600

1

2

3 4

SECTION A-A

MASS EXCL. WELDING

0.412 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

A A

210

180+0,10-0,01

18

23,4 13

60

300

15

240

1 OF 1

0,400

A3 A


CAP FLANGE

TOWER022

mm-kg-s

MDES302

SECTION A-A

6 HOLES



Al 6061 T6

4.8 kg 4.8 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

A A

291,66

324 +0,005-0,094

369 +0,06 0

185,

38

152

142

124 11

6968870

87,6°

14

1 Oring 12 Piston_2 13 seal_1.prt 24 Wear_ring_1 1ITEM

PART NAME QTY1 OF 1

0,111

A3 A


PISTON 2

TOWER030

mm-kg-s

MDES302

SCALE 0,200

1

2

3

4

SECTION A-A




Al 6061 T6

8.27 kg 8.27 kg


SECONDARY PROCESSES


6

112

SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

889

20

46,24

46

1 122 Air_cyl 13 Air_cyl_cap 14 Air_cyl_head 15 AIR_CYL_PIN 16 Air_cyl_pistonrodmount 17 Air_cyl_piton_rod 18 M12_NUT 49 Pin_lock_plate 110 Tie_rod 4ITEM

PART NAME QTY1 OF 1

0,050

A3 A


TILTING CYLINDER

TOWER009

mm-kg-s

MDES302

SCALE 0,150

1

2

3

4

5 6 7 8

9

10

SCALE 0,200

MASS EXCL. WELDING

12.18 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

0,5

24 +0,015+0,002

20 +0,02 0

16

2

1 OF 1

4,000

A3 A


20×16 BUSH

TOWER013

mm-kg-s

MDES302



Brass

0.0183 kg 0.0183 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

24 +0,015+0,002

20+0

,013

0

0,5

28

2

1 OF 1

3,000

A3 A

KAHULUME T 2012/10//20 PROF. KANNY 2012/10/26 GROUP 3

20×28 BUSH

TOWER014

mm-kg-s

MDES302



Brass

0.0322 kg 0.0322 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

79

46

106

680

720

14

44

1717

15

537,4

1 bush_16_brass.prt 22 tilting_base_plate1.asm 13 Tiltiting_hinge 24 Tliting_pin 2ITEM

PART NAME QTY1 OF 1

0,200

A3 A


TILTING PLATE ASM

TOWER010

mm-kg-s

MDES302

SCALE 0,150

1

2

3

4

MASS EXCL. WELDING

19.92 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

1

24 +0,002 0

79

46

16

1 OF 1

1,500

A3 A


TILTING HINGE MOUNT

TOWER012

mm-kg-s

MDES302



Al6061 T6

0.156 kg 0.156 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

68

1

17

1,2

64

20 0-0,0013

1 OF 1

2,000

A3 A


TILTING PIN

TOWER011

mm-kg-s

MDES302SURFACE FINISH: YELLOW-ZINC



Steel

0.166 kg 0.166 kg



SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

S 32

100

22

82,11

5018

16

1 Eyebolt_mount 22 Eyebolt_pin 13 Swing_Bolt 1ITEM

PART NAME QTY1 OF 1

1,000

A3 A


SWING BOLT

TOWER032

mm-kg-s

MDES302

1

2

3



Steel

0.325 kg 0.325 kg


SECONDARY PROCESSES


SHEET

SCALE:

METRIC

PROJECT

SIZE


REVISION

SUBMITTING TEAM

PART NAME

PART NUMBER



TOUT EST GRACE

44

267

160

51,3

517,98

102,

7

100

16

409,99

479,98

28

6 1 Air_cyl_towerclamp 12 air_cyl_towerclamp_1.prt 13 bush_28_brass.prt 14 M12_35BOLT 65 M12_NUT 66 M12_WASHER 6ITEM

PART NAME QTY1 OF 1

0,200

A3 A


TOWER CLAMP

TOWER015

mm-kg-s

MDES302

1

2

3 4

5

6

MASS EXCL. WELDING

8.02 kg



SECONDARY PROCESSES


DRAWNCHECKED

UNLESS OTHERWISE SPECIFIEDDIMENSIONS ARE IN MILLIMETERS

NAMENishalJ

DATEDurban University of Technology

Mechanical Engineering DepartmentTITLE

SIZEA4

REV

SCALE: WEIGHT: SHEET 1 OF 1

Universal Pole Mount

TOWER 031

0.4 kg1 : 2

Prof. Kanny 26/10/201222/10/2012

110

160

150

80

50 100

40

121


CHAPTER 4

4. HAZARD AND OPERABILITY STUDIES

4.1 HAZARD STUDIES

4.1.1 TOWER EXTENSION HAZARD

Extending the tower into overhead obstructions could result in death or serious injury

and could damage the tower. Therefore before actuating the tower, make sure there is enough

space above and to all sides of the expected required space of the full extended tower and

payload. People must be kept clear of the tower and never lean directly over the tower.

4.1.2 LIFTING HAZARD

The tower is designed to lift a payload of no more than 200kg at a wind speed less than

80km/h only. Any other use without confirmation from the designing team is strictly

prohibited. The tower should not be used to lift personnel under any circumstance.

4.1.3 TRANSPORTATION HAZARD

Moving the tower during operation of after extension could result in death or serious

injury. Do not relocate the tower while in use or extended. Operate the tower only when the

trailer is stationary and all for stabilizers lowered.

4.1.4 MOVING PARTS HAZARD

Moving parts can crush and cut resulting in death or serious injury. Always keep clear

from moving parts such as collars or tilting plate during operation.

4.1.5 CRUSH HAZARD

Do not stand directly beneath the tower or payload as this could result in death or

serious injury in case of sudden failure of the tower. Make sure the payload is safely secured

to the tower.

4.1.6 BURST HAZARD

Over pressurizing the tower will damage pressure relief valves and cause death or

serious injury. Do not exceed the maximum operating pressure of 100kPa for the tower and

1600kPa for the tilting cylinder. Keep personnel clear of safety valve exhaust direction.

124


4.1.7 WELDING ALUMINIUM

The success of the assembly depends on the control of many variables, such as

the training knowledge of the welder, as well as the use of proper materials and welding

processes. This is to ensure that reliable joints are produced in the equipment, due to the

importance of this various codes and standards exist. Unsound welds can result in failure in

service. Regardless of the procedure used, the welded joints must pass qualification tests. To

meet the welding criteria the joints that have been welded must be verified for tensile strength

and ductility. The welding characteristics of steel don’t exactly apply to welding aluminium.

For example, aluminium’s high thermal conductivity and low melting point can certainly lead

to burn through and warping complications if proper techniques aren’t followed.’

A copper alloy is generally difficult to weld due to heat cracking, however alloy 2014 can be

welded easily using a 2319 filler wire.

Image taken from http://www.lincolnelectric.com/en-us/support/process-and-

theory/Pages/aluminum-application-detail.aspx

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4.2 TOWER OPERATION

4.2.1 SAFETY INSTRUCTIONS

Before operating the tower, always ensure that:

� The tower is free of obstruction

� All electrical cables are undamaged

� The operator must have full view of the tower during use

� The trailer is not moving and the stabilizers are engaged

� The pneumatic system has no leaks

4.2.2 EXTENDING THE TOWER

� Select an area free of power lines or other overhead obstructions. The tower

location should not be closer to 12m from any overhead obstructions.

� The trailer transporting the tower should be located on a level ground and the

stabilizer engaged.

� Switch on the Air compressor, make sure the pressure gauge reading does not

exceed the maximum operating pressure. Move the tower to vertical position

using the tilting control valve. When the tower is at vertical position lock the

tilting plate using the swing bolt and wing nut provided. Then unlock the top

section of the tower by rotating both wing nut on the collar 3600 anticlockwise,

pressurize the tower using the tower control valve to extend the top inner section

of the tower. When the section is fully extended, release the control valve lever

and lock the extended section in place by rotating the same wing nut this time

clockwise. Exhaust the tower to confirm that the section is locked. If the section

is not locked repeat this step.

� Follow the same procedure for each subsequent tower section going from

smallest to largest.

� Any combination of sections can be extended if the full height is not required.

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4.2.3 RETRACTING THE MAST

� Pressurize the tower to lift the load until the base section locking mechanism can

be disengaged by rotating the wing nut anticlockwise. Once the section is

unlocked exhaust the tower until the section is fully retracted then lock it in place.

Repeat the same procedure for all remaining sections going from largest to

smallest. Keep hands clear of the retracting sections and collars.

� Once the tower is completely retracted remove the payload and tilt the tower to

inclined position using the tilting control valve.

4.3 MAINTENANCE AND SERVICE INSTRUCTION

This section provides instructions for maintaining and servicing the tower.

4.3.1 SCHEDULED MAINTENANCE

The tower should be cleaned and lubricated on a regular basis to insure smooth

operation and long life. The maintenance should be performed once per month depending up

on the frequency of use and the environmental conditions. The following signs indicate that a

cleaning and lubrication is required:

• Noisy operation of the tower

• Sticking of tower sections

� Retract the tower completely; remove the payload from the tower. Keep the tower in

vertical position, and then extend the top section very slowly by controlling the control

valve.

� While one person is controlling the section rising, the other may wrap a rag dampen in

a non-abrasive cleaner to wipe the surface of the tower.

� Same steps may be used for the remaining sections, going from smallest to largest.

� Inject lightweight machine oil into the weep hole of the exposed tower section. The

weep hole is located slightly below each collar.

� After lubricating, lower the tower completely and allow several minutes for the

lubricant to spread around the wear ring and seal.

� Care should be taken to avoid the penetration of any other liquid through the weep hole

during maintenance.

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4.3.2 CORRECTIVE MAINTENANCE

In this section step by step instruction are provided for the replacement of the

tower seal and wear ring both on the piston and in the collar.

� Lower the tower completely and tilt it to the inclined position.

� Use a mobile shop crane or any other safe lifting equipment should be used to hold

the tower at 190. The crane strap should be secure in the middle of the base section.

� With the tower safely held by the crane, remove the tilting air cylinder and lower the

tower horizontally on the trailer.

� To remove the top section, unlock the top collar locking mechanism and unfasten all 6

bolts on the top collar (see engineering drawings for better understanding).

� Gently pull the top section and secure it horizontally on supports to remove seals and

wear ring.

� Insure the area is free of dust. Remove old seal and wear ring, apply grease to the new

seal and wear ring and fit them back to the piston or in the collar.

� Repeat the three previous steps for the remaining sections.

� Slide back the last removed section, make sure the locking mechanism is still

unlocked then slide the collar around the appropriate cylinder and fasten the bolt into

the insert imbedded in each cylinder.

� Repeat step six to assemble back the remaining sections of the tower.

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CHAPTER 5

5. COSTING

ITEM PART NAME QTY ESTIMATED

PRICE/UNIT

TOTAL

PRICE

1 Section_1 1

2 Air_cyl_towerclamp 1 R1600 R1600

3 base_cap.prt 1 R1700 R1700

4 Base_ORing 1 R5 R5

5 Bolt_Ring 1 R2 R2

6 collar01 1 R1600 R1600

7 Cylinder_1 1 R4000 R4000

8 M12_Socket_Cap_Screw 6 R5 R30

9 Support_pin 2 R100 R200

10 Tower_support 1 R2000 R2000

11 Section_2 1

12 Collar02 1 R1500 R1500

13 cylinder_2.prt 1 R3500 R3500

14 M10_HEX_SCREW 6 R5 R30

15 M12_Cap_Screw 6 R5 R30

16 Oring 2 R5 R10

17 Piston_2 1 R1600 R1600

18 seal_1.prt 2 R130 R260

19 Wear_ring_1 1 R120 R120

20 Section_3 1

21 Base_Ring3 1 R5 R5

22 Collar03 1 R1400 R1400


24 M10_Hex_Socket_Screw 6 R5 R30


26 oring03.prt 1 R5 R5

27 piston_3.prt 1 R1500 R1500

28 seal_2.prt 2 R120 R240

29 wear_ring_2.prt 1 R110 R110

30 Section_4 1


32 Collar04 1 R1300 R1300


34 M10_Hex_Sockel_Screw 6 R5 R30



129


37 piston_4.prt 1 R1400 R1400

38 seal_3.prt 2 R110 R200


40 Section_5 1


42 Collar05 1 R1200 R1200





47 piston_5.prt 1 R1300 R1300

48 seal_4.prt 2 R100 R200


50 Section_6 1





55 piston_6.prt 1 R1200 R1200

56 seal_5.prt 2 R90 R180

57 Top Flange 1 R500 R500


59 Trailer 1 R17000 R17000

60 Air cylinder 1 R1500 R1500

61 Compressor 1 R4500 R4500

62 Battery 2 R850 R1700

TOTAL COST R66162

Table 2.1 Bill of material and cost.

Prices listed in the above table were acquired from supplier’s websites and some were

estimated based on the available product, therefore the total cost may be a little bit offset.

Based on this estimated price, it was concluded that if the product is rented for R100 an hour,

and operates at a minimum of four hours a day, then the payback period will be

approximately 10 months.

130


CHAPTER 6

6.1 CONCLUSION

As seen in our project there are many benefits to having a light weight carbon fibre tower for

various applications. Our tower aims to streamline operations, from transport to usability.

There is definitely a market for light, cost effective towers in industry today. By having a

universal attachment on top of our tower a broad array of industries could benefit from our

design.

The final design meets all our specified requirements. Every feature of the tower is intended

to accommodate safe erecting and resist external forces. Where previously pneumatic driven

towers were uncommon due to the inability to maintain the pressure once the compressor has

been turned off resulting in the descending of the tower due to gravity, the placing of a

locking mechanism in each segment of the tower prevents this. There is also a slight overlap

between tower segments to give the structure added stability.

At the base of the tower on the trailer, adjustable stabilizers have been mounted. This

provides for the maximum load condition.

131


6.2 RECOMMENDATION

Trailer canopy – When the tower is in the inoperative position (retracted and tilted), it lies

on the trailer for easy transport and low wind resistance when driving. Adding a canopy-like

cover that fits over the trailer and tower would be a major upgrade and would enhance the

sophistication of the design and would also keep all the minor mechanical parts and

mechanisms out of sight, resulting in a better appearance. The canopy would also add more

storage space for any necessary tools and equipment required for the operation and

maintenance of the tower.

Keeping the tower up to date – The portable structure has to be handled with care in order

for it to meet its life span expectations. Improved parts and little innovative technological

advancements would help in keeping the tower up to date with all the latest and most elite

mechanical and electronic parts. The pneumatic system will also be upgraded when the need

arises or when it ceases to function.

Replacement of moving parts – Constant usage of the tower will cause joints, connections

and friction between sliding faces to become worn out. The replacement and proper

maintenance of the essential parts will result in a composite materials have a very long life

span. As the parts get older the payload will have to decrease due to the strength of the

connections. For the most efficient tower, all necessary parts should be kept in good

condition in order to receive the maximum output.

132


CHAPTER 7

7.1 REFERENCES

1. Richard, G. and Keith, J. 200. Shigley’s Mechanical Engineering Design. Singapore:

McGraw Hill.

2. Drostsky, JG. 2008. Strength of Materials for technicians. 3rd ed. South Africa:

Heinemann.

3. Figert, John D, Process Specification for the Heat Treatment of Aluminium Alloys,

structural Engineering Division, NASA, August 2009

4. Ullman, David G, The Mechanical Design Process, McGraw-Hill, 2008

5. Black, J T and Kohser, Ronald A, DeGarmo’s Materials & Processes in

Manufacturing, John Wiley and Sons, USA, 10th Edition, 2007, pp 144-152

6. http://www.contactcorp.net/faq.html

7. http://www.boschrexroth.com/pneumatics-

catalog/Pdf.cfm?Language=EN&file=en/pdf/PDF_g5923_en.pdf

8. http://www.ashwinrshah.com/catalogs/Selection%20Guidelines.pdfhttp://www.perfor

mance-composites.com/carbonfibre/mechanicalproperties_2.asp

9. http://www.wisetool.com/fit.htm

10. [ttp://www.engineeringtoolbox.com/engineering-materials-properties-d_1225.html

11. [http://www.allsealsinc.com/pdf6/Thompson.pdf]

12. http://www.oasismfg.com/dc-air-compressors.html

13. http://en.wikipedia.org/wiki/6061_aluminium_alloy , Wikipedia: the free

encyclopaedia, 3rd September 2012

14. http://www.makeitfrom.com/compare-materials/?A=2014-T6-Aluminum&B=6061-

T6-Aluminum, makeitfrom.com: Materials property database, 3rd October 2012

15. http://www.lincolnelectric.com/en-us/support/process-and-theory/Pages/aluminum-

application-detail.aspx, Lincoln Electric Welding Experts,

16. http://www.magpulse.co.in/crimping.html

17. http://garzatelecom.com/Garza_Hardware.htm

18. http://www.blueskymast.com/index.php/accessories-main/universal-pole-mount-and-

brackets)

19. http://wwww.blueskymast.com/index.php/accessories-main/side-arm-mounts#,

133


20. http://wwww.blueskymast.com/images/stories/MasterDocs/Datasheets/BSM2-K-

A200-POL-EM0.pdf

134


7.2 APPENDIX

135

composite telescopic tower report

Documents