HAND IN HAND report

DESIGN AND FABRICATION OF A

MECHANICAL WINDROW TURNER

A PROJECT REPORT

Submitted in partial fulfillment of the

Requirement for the award of the

Degree of

BACHELOR OF TECHNOLOGY

In

MECHANICAL ENGINEERING

By

GAUTAM MERWAN BALAGOPALA

10BME1045

S. SUROTHAM

10BME1086

THULASIRAM REDDY P.

10BME1106

VARUN MOORTHY

10BME1110

Under the Guidance of

Prof. C.P. Karthikeyan

SCHOOL OF MECHANICAL AND BUILDING SCIENCES

VIT University CHENNAI

(Tamil Nadu) 600127 (MAY 2014)

SCHOOL OF MECHANICAL AND BUILDING SCIENCES

CERTIFICATE

This is to certify that the project work titled “Design And Fabrication Of

A Mechanical Windrow Turner” that is being submitted by “Gautam

Merwan Balagopala (10BME1045), S. Surotham (10BME1086),

Thulasiram Reddy P. (10BME1106), Varun Moorthy (10BME1110)” is

in partial fulfillment of the requirement for the award of Bachelor of

Technology in Mechanical Engineering, is a record of bonafide work

done under my guidance. The contents of this project work, in full or in

parts, have neither been taken from any other source nor have been

submitted to any other Institute or University for award of any degree or

diploma and the same is certified.

Thesis submission date:

Guide Program Chair

Internal Examiner External Examiner

THIS PROJECT IS DEDICATED TO

THE NGO “HAND IN HAND” AND ITS CAUSE OF

PROMOTING SOLID WASTE MANAGEMENT

FOR A GREEN INDIA

i

ACKNOWLEDGEMENTS

The project has been an enriching experience for the four of us and we would like to

thank the people who have been pivotal in providing us with such an experience. Our

sincere gratitude to our project guide, Dr. C.P. Karthikeyan, whose inputs and support

have been crucial in guiding our efforts in the right direction throughout the entire

project’s progress from brainstorming to implementation. We thank Mr. Jalasayanan

(HIH) for proposing this project idea to us and for introducing us to the challenge of

finding an innovative and green solution for small scale solid waste management. We

would also like to extend our gratitude to all of the volunteers of HIH for helping us on

site at the HIH projects and for their kind cooperation in answering our doubts with

regard to the pragmatic aspects of our project. The University and the staff have been

very kind in providing us with the equipment and expertise necessary for the completion

of this project and we are very grateful for this valuable opportunity to do something

significant before becoming professionals.

(Gautam Merwan Balagopala)

Reg. No. 10BME1045

(S. Surotham)

Reg. No. 10BME1086

(Thulasiram Reddy P.)

Reg. No. 10BME1106

(Varun Moorthy)

Reg. No. 10BME1110

ii

ABSTRACT

The objectives of the work undertaken are to design a fully mechanical model

of a windrow turner to suit the capacity of windrow composting operations of HIH as

per requirements laid out by their officials. The requirements given are to turn a

windrow of approximate dimensions 1.5ft height, 3ft width. and 15ft length with a

machine which is powered manually by a pushing or pulling force with a suitable

transmission ratio from the wheels of the machine to the turning shaft. The transmission

system from the wheels to the shaft has to be designed without using a chain drive as it

would require much maintenance and is not properly suited for such a dirt-involving

operation. The size and weight of the transmission system are important factors of the

design since the entire machine has to be mobilized entirely by manual pushing or

pulling forces. This is because of wanting to adhere to HIH’s “green” philosophy. The

hardware prototype was tested against a heap of fine sand with properties comparative

to an equivalent heap of compost and design modifications were made based on the

observations from testing.

iii

TABLE OF CONTENTS

LIST OF TABLES v

LIST OF FIGURES vi

LIST OF ABBREVIATIONS viii

LIST OF GRAPHS ix

1 INTRODUCTION 1

1.1 Motivation 1

1.2 Scope 1

2 BACKGROUND THEORY 3

2.1 Windrow Composting 3

2.2 Market Survey 3

3 DESIGN 4

3.1 Study of Windrows 4

3.2 study of commercial Windrow Turners 5

3.3 Theoretical calculations 7

3.3.1 Power input 7

3.3.2 Shaft load 9

3.3.3 Heap load 10

3.4 Design of mechanisms 12

3.5 Design of transmission system 12

3.6 Design of Blade Shaft 14

3.7 Design of Frame 16

4 FABRICATION AND ASSEMBLY 19

4.1 Fabrication of blade shaft 19

4.2 Fabrication of shaft-end flanges 20

4.3 Fitting of driver pulleys 20

4.4 Plummer block mounts 21

4.5 Assembly on frame 22

5 ANALYSIS AND TESTING 23

5.1 Analysis 23

5.1.1 Blade shaft 23

5.1.2 Flange shaft 24

iv

5.2 Testing and observations 25

5.2.1 First test 25

5.2.2 Second test 26

5.2.3 Third test 27

6 CONCLUSIONS 29

REFERENCES 30

BIO DATA 31

v

LIST OF TABLES

SL.NO NAME PAGE.NO

1 sizes and power variations of various windrows for MENART windrow turners 5

2 Data from table 1 converted to standard units 5

3 possible combination of mechanisms 12

4 Hit and trial mass optimization data for blade shaft 15

vi

LIST OF FIGURES

SL.NO DESCRIPTION PAGE.NO

1 Commercial Windrow Turner and windrow 3

2 studying the compost material 4

3 Analyzing a windrow at HIH biogas plant, Mamallapuram

4

4 Dimensions of windrow to be operated upon 5

5 Schematic of a cross-belt pulley drive 7

6 push cart wheel with measured outer diameter 8

7 Schematic of blade shaft rotating through the heap (side view)

11

8 Flow chart of transmitted torque from source to blade shaft

11

9 Schematic of a cross-belt pulley drive 13

10 RP CAD Model and Finished Prototype 14

11 Two-dimensional representation of shaft with respect to heap

14

12 Revised CAD Model of shaft and finished shaft 15

13 Two-dimensional representation of revised shaft with respect to heap

15

14 Initial design of frame; Custom made Chassis 16

15 depiction of common push cart 17

16 Finalized design; CAD model of the machine developed using the common push cart frame

18

17 Drawing of blades with notched profile 19

18 Gas welding of blades to shaft 20

19 Flange fitting with shaft 20

20 Shaft-end Flange 20

21 Pulley press-fitted with MS sleeve

20

22 Fine Internal Threads on sleeve

20

23 fine threads on wheel hub 21

24 Pulley fastened onto the wheel hub 21

25 Plummer block mounts 21

26 Deformation analysis of shaft in ANSYS 23

vii

27 Equivalent stress analysis of shaft in ANSYS 24

28 Simulated result; plot of factor of safety for flange shaft

24

29 simulated result; plot of factor of safety for the shaft portion of the flange shaft

25

30 First test setup 25

31 Schematic of straight belt drive 26

32 Straight belt drive testing 26

33 Test setup 3 27

viii

LIST OF ABBREVIATIONS

SL.NO ABBREVIATION EXPANSION

1 HIH Hand-In-Hand

2 NGO Non-Government Organization

3 MS Mild Steel

ix

LIST OF GRAPHS

SL.NO DESCRIPTION PAGE.NO

1 Variation of height Vs power on commercial

windrows 6

2 Variation of Cross Section Vs Power on commercial windrows

6

3 Variation of Section Vs Power on commercial windrows

7

1

CHAPTER 1

INTRODUCTION

1.1 MOTIVATION - Two major factors have influenced the decision of the final

year project. The project had to be contributive towards the environment and towards

society as well. With these motives in mind, brainstorming began for problems

concerning the environment which could be tackled by the group. An NGO, Hand In

Hand (HIH), based in Chennai whose mission is to maximize solid waste management

attracted the attention of the group. HIH has 16 projects taking care of the waste of

various town and panchayat level administrations across Chennai and a few in other

parts of Tamilnadu as well. HIH tries to reduce the amount of waste reaching the

landfills by reusing as much of it as possible through various processes like biogas

generation, composting, recycling, etc. After seeing a few of their projects and talking

with officials of HIH, the group was able to identify a few opportunities for contribution

concerning solid waste management among the various projects. The idea of design and

fabrication of a fully mechanical model of a turning machine for the windrow

composting process was proposed by one of the NGO officials, Mr. Jalasayanan. It was

a proposal for creating a “green” model of a machine for a particular process of

composting and it also had the most direct social impact among the other ideas which

made it well suited for the group’s motives of doing a project which is contributive

towards the environment and the society.

1.2 SCOPE - Upon successful completion of the design and fabrication of such a

small-scale and manually powered windrow turner, not only would it help HIH

undertake windrow composting operations with greater ease and efficiency but also it

would be seen as an attractive implement for such small-scale windrow composting

operations taken up by government bodies in rural areas as well as other private

institutions in the cities as well. Thus, the call for such a machine extends much beyond

just that of one NGO and has a potential to attract the attention of government bodies

as well. They would be able to undertake composting operations more efficiently and

within a reasonably cheap budget as well when compared to the cost of commercial

windrow turners available in the market. Although not a commercial market, providing

a useful tool for this niche market can be seen as a start to the means of an easier and

2

cheaper composting process and in turn encourage a consumer market of Earth-

conscious individuals who could start practicing such windrow composting even on

their own terraces perhaps. It would be easy, cheap, and suitably hygienic considering

one has to simply push or pull the machine across a row of organic waste. More and

more waste could be efficiently recycled. Encouraging solid waste management

activities i.e. converting waste to useful forms of energy at the smaller and smallest

levels is a strong undertone of this project.

3

CHAPTER 2

BACKGROUND THEORY

2.1 WINDROW COMPOSTING - Windrow composting is a process of

composting organic waste by piling organic matter or biodegradable waste in long rows,

called windrows. These rows are generally turned periodically to improve porosity and

oxygen content, mix in or remove moisture and redistribute cooler and hotter portions

of the pile. It is a commonly used farm scale method of composting for large volume

compost production from windrows which are 4ft or higher and as much as 12ft wide.

It is also carried out just as efficiently in smaller volumes and that’s what HIH is trying

to implement with the waste from particular panchayat towns. Since the volume of

waste generated by such small towns is not nearly as high as that of a farm, they cannot

use the huge windrow turners commonly available in the market. These are both too

expensive and unreasonably oversized for HIH’s operations or any government solid

waste management projects as well. They require a much smaller machine for turning

their windrows and require it to be fully mechanical as per the NGO’s “green”

philosophy as well. This is the group’s contribution towards HIH through this project.

2.1 MARKET SURVEY – In order to get a better idea about how to go about the

design, a study of commercially available windrow turners was taken up along with a

market survey to better determine the kind of materials and services available locally

at our disposal. Successive site visits to the HIH projects in Mamallapuram and St.

Thomas Mount Cantonment were taken up to better understand the essence of windrow

composting and the ambience involved for the operation and maintenance of the

windrow turner to be designed by the group. Interaction with the volunteers of HIH

gave much insight towards the development of the preliminary design.

Figure 1: Commercial Windrow Turner and windrow

4

CHAPTER 3

DESIGN

3.1 STUDY OF WINDROWS – The design process was initiated by first studying

small windrows for which the design was being

done. These heaps were available for our study at

HIH’s solid waste management plant in

Mamallapuram. The windrows were carefully

analyzed for important parameters such as mass,

density, porosity, moisture content, toughness, etc.

It was found that there is no standard density for organic compost material in the

windrows as they are a mixture of different kinds of organic waste. The heterogeneous

mixture consists of vegetable peels, egg shells, coconut shells, slurry, etc. This mixture

is first shredded by passing it through an organic shredder before being piled up into

windrows. The shredding process is important because it converts coarse material into

finer particles and enables easy mixing of the windrows. It essentially reduces the

toughness of the organic material which in turn reduces the effort required to carry out

the mixing. Each and every windrow will have varying densities depending on the

porosity and the amount of moisture absorbed by the heap. Thus, more specific

information on the density and the porosity of the material of the windrows was

required to proceed with the design.

Upon critically discussing with the HIH officials, significant information was extracted

regarding the characteristics of the heap as far as our design requirements were

concerned. Instead of using actual organic compost, the officials approved that the

Figure 2: studying the compost material

Figure 3: Analyzing a windrow at HIH biogas plant, Mamallapuram

5

behavior of dry sand with certain given properties is analogous to the behavior of

organic compost, i.e. Sand could be used to design and test the machine. Dry sand has

a density of 1700 Kg/m3 and

when moist it has a density of

1920 Kg/m3 [1].

HIH’s required heap

dimensions were 3ft width, 1.5

ft height and 15 feet length.

3.2 STUDY OF COMMERCIAL WINDROW TURNERS – Having obtained

a fair idea about the characteristics of the matter to be turned (dry sand), the next step

was to study existing commercial windrow turners. Companies like Menart and

Aerosmith are experts in manufacturing large-scale windrow turners. The technical

details of such machines were borrowed to draw a scaled-down analogy for the

specifications of our own machine [2].

height(m) height

(ft) section (m) section(ft)

cross Section(sq.m)

cross section (sq.ft)

Power (HP)

1.4 4.592 1.5 4.92 0.5 5.3792

1.5 4.92 1.8 5.904 1 10.7584

1.6 5.248 2 6.56 1.5 16.1376

1.7 5.576 3.3 10.824 2.7 29.04768 80

1.8 5.904 4.3 14.104 4.5 48.4128 100

1.9 6.232 4.8 15.744 5.5 59.1712 125

2 6.56 5.3 17.384 6.6 71.00544 140

Figure 4: Dimensions of windrow to be operated upon

Table 2: sizes and power variations of various windrows for MENART windrow turners

Table 2: Data from table 1 converted to standard units

6

Based on the figures in the above table, various graphs were drawn and the trend lines

were extrapolated to help estimate the power requirement for our scaled-down machine.

0

20

40

60

80

100

120

140

160

0 1 2 3 4 5 6 7

Po

wer

(HP

)

Height (ft)

Height Vs Power

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60 70 80

Po

wer

(HP

)

Cross Section (sq.ft)

Cross Section Vs Power

Graph 1: for a height of 1.5 ft the power is around 2 HP

Graph 2: for a cross section of 2.25 ft the power is around 20 HP

7

Observing the extrapolated results from the above graphs, it can be seen that

there is a lot of deviation arising between the results for the scaled-down required power

based on various parameters of the heap. Thus, the extrapolations were seen to be

inconclusive and unreliable as a reference for determining the scaled-down input

power. So, theoretical method have been adopted in calculating the input power which

will be discussed in the next section.

3.3 THEORETICAL CALCULATIONS –

3.3.1 Power input - Since the Machine is mechanically operated, the input power comes

from the pushing action of the operators. It has been deducted that an average human

can produce a power output in the range of 100 to 120 W [3].

0

20

40

60

80

100

120

140

160

0 2 4 6 8 10 12 14 16 18 20

Po

wer

(HP

)

Section (ft)

Section Vs Power

Graph 3: for a section of 3 ft the power is around 17 HP

Figure 5: Schematic of a cross-belt pulley drive

8

Power output by an Average Human (Ptotal) = 120 W

Total no.of. humans = 2

Diameter of the wheel (dwheel) = 406.4 mm

Distance travelled by one rotation of the wheel (Srotation) = 3.14xdwheel

= 3.14x406.4x10-3

= 1.276 m

Chosen time for the wheel to cover Srotation m (trotation) = 3.5 s

Selected speed of the cart

(speed at which the cart is to be pushed) Vcart = 0.3645 m/s

R.P.M of the wheel (Nwheel) = Vcart x 60/(3.14xdwheel)

= 0.36x60/(1.276)

= 17.14 R.P.M

The torque produced on the wheels by the pushing action is calculated as follows.

Torque produced (Ttotal) = Ptotal x 60(2x3.14xNwheel)

= 120 x 2 x 60/(2x3.14x17.14)

= 133.75 Nm

Total weight of the cart = 27 Kg

Acceleration required acart – Srotation = u trotation +0.5acart t2

rotation

1276.096 = 0 + 0.5xacart x 3.52

Acart = 0.208m/s2

Figure 6: push cart wheel with measured outer diameter

9

Force required to push the cart (Fcart) = 27xacart

= 27x0.208

= 5.635 N

Power required to push the cart through a distance

Srotation metres in trotation seconds (Pcart ) = Fcart x Vcart

= 5.625 x 0.364

= 2.05 W

Power available to drive the blade shaft (Pshaft) = Ptotal - Pcart

=240 – 2.05

= 237.94 W

Torque available from this power (Tdriver) = Pshaft x 60/(2x3.14xNwheel)

= Pshaft x 60/(2x3.14x17.14)

= 132.61 Nm

This is the torque available that can be used to drive the blade shaft.

3.3.2 Shaft Load - Since the shaft is a rotating element, certain resistance has to be

overcome and this resistance is called mass moment of Inertia. The torque available

from the wheels, after transmission reduction, must be great enough to do two jobs:

one, Overcome the mass moment of inertia and two, overcome the resistance caused

by the heap.

Total mass of the shaft (Mshaft) = 6.66 Kg

Mass of cylinder (Mcylinder) = 3.54 Kg

Mass of one Blade (Mblade) = 0.176 Kg/blade

No.of blades = 18

Outer Radius of cylinder (rcylinder out) = 50.8 mm

Inner radius of cylinder (rcylinder in) = 44.8 mm

10

Mass Moment of inertia of Cylinder (Icylinder) = (½)Mcylinder x (rout2

- rin2)

= 3.8x(50.8 – 44.80) 2 x10-6/2

= 0.0010152 Kgm2

Distance of blade center of gravity

from cylinder axis (rblade) = 107.1 mm

Mass Moment of inertia of one blade (Iblade) = Mblader2

blade

= 2.018792 kgm2

Total mass moment of inertia (Itotal) = Icylinder + 16xIblade

= (4.9 + 16x57.72)x10-3

= 36.3392 kgm2

Selected transmission ratio (rtrnsmission) = 1:4

Ndriven = 4xNwheel

= 417.4

= 68.57 R.P.M

Angular velocity of driven pully (wdriven) = 7.177 rad/s

Angular Acceleration of the Driven pully (αdriven) = 2.050 rad/s2

Torque required to rotate the shaft from rest (Tshaft) = Itotal x αdriven

= 0.0765 Nm

3.3.3 Heap Load - The heap load is calculated in analogy to completely lifting a

particular volume of heap having a certain mass through a distance which is equal to

the tip to tip distance of the blade shaft. Though this is not the exact case, scope for

margin of safety is allowed.

Density of heap material = 1600 Kg/m3

Volume of heap through which the

shaft rotates at any point of time (Vheap) = 457.2x914.4x138x10-9/2

= 0.0288m3

Mass of the volume Vheap (Mheap) = 0.0209x1600

= 33.44 Kg

11

It is considered that at any point of time the blade shaft is in effective contact with the

heap for a distance of 100 mm in the direction parallel to the heap.

The torque required to rotate the shaft through

the heap (Theap) = 33.44x10x138x10-3

= 32.77 Nm

Total torque required at driven pully (Trequired driven) = Theap + Tshaft

= 32.85 Nm

Torque available at the Driven pulley

after reduction (T available driven) = Tdriver/2

= 33.15Nm

Tavailable driven > Trequired driven

Figure 7: Schematic of blade shaft rotating through the heap (side view)

Figure 8: Flow chart of transmitted torque from source to blade shaft

12

3.4 DESIGN MECHANISMS – The basic principle is that when the machine is

moved over the heap, the windrow should be mixed underneath. So, the machine should

essentially consist of the following parts:

1) A frame

2) Wheels

3) Transmission System

4) Blade Shaft

With these parts, different combinations of mechanisms were developed. They are

depicted in the following table.

DEPENDENT INDEPENDENT

1-man transmission system motor/engine

2-men transmission system pedalling

3-men transmission system hand cranking

Dependent or independent refers to the connection between the wheels and the blade

shaft. The rotation of the blade shaft can be either dependent or independent of the

rotation of the wheels. If the system is dependent then there has to be a transmission

system to transfer the power from the wheel to the blade shaft. Independent systems

can have separate operators for pushing the cart and rotating the shaft. Upon proposing

these combinations to HIH, they selected the 2-men dependent system as they wanted

to promote green technology by avoiding electricity and fossil fuels.

3.5 DESIGN OF TRANSMISSION SYSTEM – A 2-men dependent system

requires a transmission system so that when two operators are pushing the cart, the

power from the two is effectively transferred to the blade shaft. The following

conventional systems are available:

1) Belt Drive

2) Chain Drive

3) Gear drive

Table 3: possible combination of mechanisms

13

After carefully considering, belt drive has been chosen to develop the transmission

system owing to the following factors:

1) Belt drives are the simplest of the three and involves lesser moving parts. Since

the design is a low powered application, belt drive is just enough to handle the

load.

2) Chain drives involve more moving parts and need to be lubricated and HIH

recommends minimal maintenance. Also, there will a lot of dirt and fine

particles suspended in the surrounding space while mixing the heap and this dirt

might settle on the sprockets that could lead to jamming of the drive.

3) Gear drives are not cost effective. They cannot be used in systems where there

is a longer center distance involved as idler gears need to be installed to cover

the entire distance. Also, the same dirt jamming problem may arise.

Figure 3 Cross belt drive diagram

The direction of rotation of the wheel and the direction of rotation of shaft are to be

opposite to each other. This is a must because only in this arrangement the windrow

process proceeds efficiently i.e. proper mixing of the heap happens. Accordingly, A-

type pulleys were selected based on the torque requirements, the center distance was

selected (9 x ds)[4] and the belt length for cross belt drive is calculated by,

[4]

Where,


14

dL = 8 in

dS = 2 in

C = 9 x 2 x 25.4 = 456 mm

LC = 53 in

3.6 DESIGN OF BLADE SHAFT – Simultaneously, rapid prototyping of the shaft

was undertaken in the college itself. Since it was only the chassis that was asked to be

revised, the shaft design became finalized and in order to test its effectiveness in

transporting material from the outside edges to the inside to maintain the heap shape, it

was deemed necessary to go for rapid prototyping of a scaled down model of the shaft.

Figure 10: RP CAD Model and Finished Prototype

The observations from the rapid prototype testing led us to believe that there was too

much vertical drop in between the blades of the shaft and that material would get

dropped in these gaps instead of getting fully mixed.

Figure 11: Two-dimensional representation of shaft with respect to heap

15

The design of the shaft was then re-iterated to have more blades and less vertical drop

between the successive blade edges. A second rapid prototype was not taken up due to

economic constraints.

Figure 12: Revised CAD Model of shaft and finished shaft

Figure 13: Two-dimensional representation of revised shaft with respect to heap

The weight of the shaft plays an important role is effective power transmission. The

power required to rotate the shaft should be as minimum as possible. So, the number

of blades and the type of shaft have been optimized from the following trials:

shaft

diameter

(inch)

material blade

thickness

(mm)

blade

width

(mm)

total weight

(Kg)

shaft type

4" AISI 1010 2 50 64.946 solid

4" AISI 1010 2 50 3.629 hollow(1mm)

4" AISI 1010 2 50 6.067 hollow(2mm)

4" AISI 1010 2 50 8.45 hollow(3mm)

2" AISI 1010 2 50 17.505 solid

2" AISI 1010 2 50 2.785 hollow(1mm)

2" AISI 1010 2 50 3.967 hollow(2mm)

Table 4: Hit and trial mass optimization data for blade shaft

16

Finally, a hollow shaft of 4 inch outer diameter has been chosen to be the optimal

design based on strength, stress and required size conditions

3.7 DESIGN OF FRAME –

Based on the initial market survey and study of commercial windrow turners, a rough

design concept was modelled in SolidWorks. As the blade shaft was the main

component affecting the quality of operation, the chassis was completely redesigned

according to the market survey conducted. Based on our understanding of the

problem, a steering system was incorporated and a highly unique chassis design was

made which could not use standard parts but used much less material by avoiding

unnecessary appendages for achieving light weight design. Other commonly available

parts like bicycle forks and wheels were also used in order to achieve a very cheap

design.

The frame part of the machine was custom designed to easily accommodate the center

distance of the driver and the driven pulleys. This design was then presented as a

proposal to the concerned NGO officials. Upon review and discussion with their

Figure 14: Initial design of frame; Custom made Chassis

17

officials, certain suggestions were made and constraints were laid upon the design

wherein the total design had to be re-iterated to meet these specifications.

1) The main concern of the NGO

was that instead of designing a

totally new chassis for the

machine, an actual and

commonly available

‘pushcart’ had to be used as

the base chassis. Accordingly

changes had to be

incorporated into the design and subsequent calculations and analysis were done.

2) A search for procuring used ‘pushcarts’ for the fabrication was unsuccessful and it

was decided to purchase and use the necessary parts for making a new pushcart,

The concept being unchanged: Recycling a used push cart. But Instead of actually

using a used push cart, a new push cart would play the same role in defining the

solution and is solely used for the purpose of proper demonstration.

3) The basic under frames of the pushcart (C-bends) were purchased in order to keep

the base chassis as that of a typical pushcart. The rest of the parts (Wheels) of the

pushcart were left out for later purchase to cater more specifically to the needs of

our design. Thus, certain parts (lateral Rods) which would have otherwise had no

role in our design were left out. This allowed us to keep to the constraint of using a

normal pushcart while at the same time giving us the flexibility to change out a few

parts for ones more suitable for our design; for example using smaller 16” wheels

instead of standard 26” wheels.

Taking all of these constraints and suggestions into account, a fresh design was made

based on the purchased standard parts like the c-bends. The aim of the second design

was to achieve as much standardization as possible in at least the parts and components

used even if it were slightly more costly. Standardization meant easier purchase and

maintenance for the NGO as well. The second design was then presented to the officials

of the NGO and the project progressed forward only after their approval of the same.


18

This was a very important part of the project as the end user of our unique product was

going to be the NGO and it was essential that those client requirements be met on par

with their expectations.

Figure 16: Finalized design; CAD model of the machine developed using the common push cart frame

19

CHAPTER 4

FABRICATION AND ASSEMBLY

The main stages of fabrication are:

1) Fabrication of Blade Shaft

2) Fabrication of Shaft-End Flanges

3) Fitting of Driver Pulleys

4) Plummer Block Mounts

5) Assembly of Frame

4.1 FABRICATION OF BLADE SHAFT – The blade shaft proved to be the

largest and most critical part of the fabrication phase. An MS pipe and MS sheet metal

pieces were purchased according to dimensions laid out in the final design. According

to the design, a certain profile had to be cut into one side of the blade sheets so that they

could sit perfectly on the MS pipe for welding. Necessary notching was done in the MS

sheet metal pieces by means of gas cutting and subsequent grinding.

Figure 47: Drawing of blades with notched profile

These notched blades were then positioned onto the MS pipe shaft in a specific spiral

orientation as per the final design. This step required a lot of time in order to get the

maximum precision possible in maintaining the perfect spiral shape of the blades being

welded onto the shaft. The blades were carefully tacked into place with a simple metal

arc welding electrode. They were then tweaked after tacking into the appropriate

angular orientations and positions and then the blades were completely welded into

position with a gas welding torch. Gas welding was decided upon as the most suitable

option for this operation as it would have minimal heat exposure to the blades since

they are of very little thickness (2mm) and at the same time ensure the strength of the

20

welded joints would be sufficiently strong. The welding was performed on both sides

of the blades for ensuring maximum strength of the blade-shaft joints as they would be

bearing most of the load from the resistance of the heap being turned.

Figure 18: Gas welding of blades to shaft Figure 19: Flange fitting with shaft

4.2 FABRICATION OF SHAFT-END FLANGES – Flanges were included in

the design in order to connect the blade shaft to the chassis through the smaller pulley.

A standard flange of 1.5inch

internal diameter was purchased

and welded to each end of the

blade shaft. The complementary

flange for connection to the chassis

and small pulley was fabricated by

using a flange blank. A hole was

drilled in its center and a smaller

diameter billet of 20mm diameter was welded into it so that the pulley and chassis

mounting Plummer block could be fitted onto it.

4.3 FITTING OF DRIVER PULLEYS – One of the more thought

Figure 20: Shaft-end Flange

Figure 21: Pulley press-fitted with MS sleeve

Figure 22: Fine Internal Threads on sleeve

21

requiring phases of the fabrication was that of fitting the bigger 8 inch driving pulley to

the hub of the wheel so that they could rotate together to drive the belt around the

smaller pulley and rotate the shaft. For that, it was thought to make use of the threading

which was provided on one side of the wheel hub.

It is a fine thread that is provided there and its complementary fine thread had to be

made in the inside of the bigger pulley. This proved to be a problem though as the pulley

is of cast iron material and was not suitable for machining such a fine thread in it. This

problem was overcome by boring a larger hole in the pulley and press fitting an MS

sleeve into the hole and machining the fine threading into the sleeve instead. This let

the pulley be freely screwed on and off of the hub of the wheel. To ensure that the

pulley doesn’t unscrew itself during operation, a lateral hole was drilled into the pulley

and a bolt was placed in it to restrict motion between the pulley and the Mild Steel

sleeve with the threading. Zip tags were also tied between the wheel spokes and the

pulley spokes to restrict relative motion between the pulley and the wheel.

4.4 PLUMMER BLOCK MOUNTS – The center distance between both pulleys

was determined during the design of the

transmission system to be 9xds. This

distance was appropriately located and

marked on the chassis where the Plummer

block holding the smaller pulley was to be

mounted. A pair of MS plates of

dimensions 50x100x6mm were welded to

the c-bends at the appropriate locations and

Figure 23: fine threads on wheel hub Figure 24: Pulley fastened onto the wheel hub

Figure 25: Plummer block mounts

22

bolt holes were drilled in them for fixing the Plummer block to them. After the Plummer

block was fixed to the chassis, the connecting flange with the 20mm billet could be

assembled to the blade shaft and put in place. The location of the smaller pulley on that

billet (lateral position) was then determined visually so that both pulleys be in the same

plane. A small hole was drilled in the side of the pulley similar to what was done on the

bigger pulley and a bolt was screwed into it against the billet to keep the pulley’s lateral

position fixed on the billet.

4.5 ASSEMBLY OF FRAME – A typical push cart contains 4 c-bends. They are

assembled in two sets, one on each side. Two bends hold two wheels, one at each end

of the set. Holes are provided on the c-bends where the hub screws of the wheels can

sit. Based on the positioning of the bigger pulley screwed onto the wheel hub of the

rear wheels, the appropriate spacing between the pair of c-bends was determined.

Adequately sized spacers were fabricated from small MS billets and placed on the hub

screws to maintain equal spacing between the pair of c-bends at the front and back. All

the four c-bends needed to be fixed rigidly in their respective lateral positions. A

support structure of lateral and longitudinal constraints was made using wooden beams

which were all bolted together to fix the c-bends in place from the top. A simple

plywood sheet was bolted on top of the wooden support structure to act as a top covering

for the entire machine. Two handles, one on each side of the machine, were made using

MS pipes and welded to the c-bends to Sheet metal pieces were cut to appropriate sizes

and attached underneath the wooden frame and between the two pairs of c-bends to

form a tunnel shape in the direction of the machine’s motion above the blade shaft. This

helps keep the turning operation confined to the space underneath the tunnel and also

provides a shape for good air flow through the material as it is being turned.

23

CHAPTER 5

ANALYSIS AND TESTING

5.1 ANALYSIS

There are two major components which are subjected to significant stresses:

1) Blade shaft

2) Flange shaft

5.1.1 Blade shaft - The blades are welded to the shaft. This means that there will be

enormous cantilever effects especially on the tips of the blades at the bent portion.

Twisting moment arises throughout the shaft. The entire shaft rotates through the heap

and undergoes continuous but gradual loading. So the setup is as follows:

i) Motion constraint: displacement is constrained on of the surfaces of the

bent portion of each blade since the bent profile is responsible for scooping

the sand and undergoes stress in lifting the sand throughout the heap. So,

displacement in X,Y and Z directions are constrained on the bent portion

of the blade.

ii) Loading: The shaft is rotated by the torque provided from the wheels and

this torque is applied on the flanges of the shaft. So, the transmitted torque,

33.15 Nm is applied as twisting moment on both the flanges.

The setup is then meshed and solved.

Figure 26: Deformation analysis of shaft in ANSYS

24

It can be observed that the maximum deformation of 0.00456 mm occurs near

the flanges.

Figure 27: Equivalent stress analysis of shaft in ANSYS

It is observed that the maximum stress of 6.0877 MPa occurs near the flanges.

5.1.2 Flange shaft - The same amount of torque is transferred to the blade shaft

through the flange shaft from the wheels. Here, the stress lies on the bolt holes

because they are the points of stress raisers as they are discontinuities in the disc.

i) The constraint is applied on the bolt holes.

ii) The torque of 33.15 Nm is applied on the free end of the shaft.

Figure 28: Simulated result; plot of factor of safety for flange shaft

25

5.2 TESTING AND OBSERVATIONS – Testing of the machine gave way to

many necessary changes and even some very important design modifications. As was

discussed earlier, it was approved by the officials to use dry sand as an analogous

material for actual compost in both the design and testing of the machine. An ideal

testing heap was decided to be made in a suitable outdoor ambience with sample

dimensions of height 1.5ft, width 3ft and length about 4ft.

5.2.1 First Test - The first model of the

machine had a cross belt drive with an

A53 size belt. The transmission ratio

was 1:4 since the pulleys were of 2inch

and 8inch diameters. The actual heap

size varied slightly in dimension than

the ideal heap defined earlier due to

minor human difficulties in forming the

heap perfectly. The heap was actually a

bit wider and more voluminous than the predefined ideal heap and the testing was

conducted by pushing the machine through it at different speeds. It was observed that

Figure 29: simulated result; plot of factor of safety for the shaft portion of the flange shaft

Figure 30: First test setup

26

the shaft rotation was inhibited immediately upon contact of the blades with the heap

regardless of the speed of pushing. There was basically zero penetration and upon

further forced rotation of the driving wheels, either wheel skidding or belt slipping was

observed. The inferences made from the testing was that the resistance provided by the

heap of dry sand was much greater than the theoretically calculated resistance and that

the torque was not being sufficiently transferred to the shaft for such a resistance. The

direction of the blade shaft rotation being opposite to the direction of motion of the

shaft was also observed to be an important reason for the unexpectedly high resistance

being faced by the machine.

5.2.2 Second Test – Based on the inferences from the first test, possible design

parameters which could be modified were listed out and whatever changes could be

made immediately and without incurring any extra expense were first done before the

second testing.

Since the direction of the shaft rotation being opposite to shaft motion against the heap

seemed to be a main problem in the previous setup, the shaft rotation was reversed by

making the

cross belt

drive into a

straight belt

drive with the

same A53

size belt. The

size and

shape of the

heap were

Figure 31: Schematic of straight belt drive

Figure 32: Straight belt drive testing

27

also reduced to match that of the ideal test heap better and testing was conducted by

pushing the machine through the heap at various speeds again. A great deal of slack

was observed in the belt drive but nevertheless the shaft was able to rotate freely

through the heap even at low speed without any hindrance. There was no belt slippage

and the mixing ability of the shaft was just ok but not great. The major inference from

this test was that the belt needed to be of a smaller size so as to avoid so much slack

and have a good tight tension. The reversal of the direction of rotation of the shaft by

using a straight belt drive seemed to be very effective in easing the motion of the blades

through the heap. The torque transferring ability of the transmission system no longer

seemed to be a problem if the slack could be adjusted.

5.2.3 Third Test – It was decided that the transmission system be kept as a straight drive

belt system itself and by revising the calculations of the transmission system design for

a straight belt drive, instead of cross belt drive as it was earlier, a belt of size A52 was

decided to be used.

The belt length for straight drives is given by,

[4]

Upon substituting the values of dL, dS and C, the belt length was determined to be

52.106 in.

The test heap was also made very carefully to match the size and shape of the ideal test

heap and testing was conducted by pushing the machine through the heap at various

speeds. The motion of the blades and shaft through the heap was very smooth and a fair

level of mixing of the heap was observed although still not perfect. A more ideal mixing

scenario would have been possible with the cross belt drive setup but the torque in that

case was observed to be insufficient so it was ruled out as a possibility after the second

test itself. It was also observed however that the general shape of the heap was greatly

distorted after pushing the machine through the heap. This was seen to be attributed to

the size of the shaft pushing through the heap. It was designed by keeping in mind the

design of commercial windrow turners but happened to be too large for the particular

sort of testing setup with much lower shaft rotation speed and torque compared to the

28

commercial machines. With higher speeds, the contact of the shaft with the heap is

greatly reduced and the contact with the blades is much more so better mixing and less

distortion are observed in commercial machines. In our machine though, since the rpm

is significantly lower, the shaft is in contact with the heap more than the blades and

hence the distortion seems to be arising. A totally different kind of shaft design would

have to be proposed for such lower speed operation and that could be achieved with

more dedicated research in the area. But otherwise, the testing proved to be successful

as there was a fair mixing of the contents of the heap.

Figure 33: test setup 3

29

CHAPTER 6

CONCLUSIONS

The prototype of a small scale fully mechanical windrow turner was designed and

successfully fabricated. Upon its testing, inferences were drawn based on which scope

for further optimization of the design were identified.

1) It was observed that the torque transmission had minor deviations from the actual

theoretical deduction. The rotating direction of the shaft proved to develop too much

resistance while rotating through the heap due to which the rotation direction had to be

reversed. Further research can be carried out on improving the transmission system

which can deliver torque more properly to overcome the resistance that arose in the first

orientation.

2) The current shaft and blade profile were developed from commercially existing large

scale machines. It was observed that for such low speed mechanically operated

machines, the central cylindrical portion of the shaft was distorting the shape of the

heap. Further research on the shaft and blade profiles of such small scale mechanical

models of windrow turners could prove useful for better designs.

30

REFERENCES

(1) http://www.rfcafe.com

(2) MENART SP Turners catalog.

http://www.menart.eu

(3) Density of common building materials – RF cafe

http://hypertextbook.com

(4) V. B. Bhandari, 2012, Design Of Machine Elements Third Edition, Belt

Drives pp 499-540

31

Personal Information

Name Gautam Merwan Balagopala

Reg. No. 10BME1045

Date of Birth 02/11/1991

Age 22 years

Education B.Tech Mechanical

College VIT University, Chennai

Contact details

Address S/o Meher Isaa Balagopala

8/S1, Vesta Selva,

5th Street, Sarathy Nagar,

Velachery, Chennai

Pin: 600042

Contact no. +91-9884064451

E-mail ID [email protected]

32


Name S. Surotham

Reg. No. 10BME1086


Age 22 years



Contact details

Address S/o C S Suresh

New No:10 , Old No: 15

Kesava Perumal Sannidhi Street

Mylapore, Chennai

Pin: 600004

Contact no. +91-9551077475


33


Name Thulasiram Reddy Padala

Regn No. 10BME1106


Age 21 years



Contact details

Address S/o Venkata Reddy Padala

Do.no.129, rukmini Nagar,

1st Street, Maduravoyal,

Chennai

Pin: 600095

Contact no. +91-8939081388


34


Name Varun Moorthy

Regn No. 10BME1110


Age 22 years



Contact details

Address S/o C V Sundaramoorthy

48/10 Syndicate Bank Officers Qts,

Nandini Layout

Bangalore

Pin: 560096

Contact no. +91-9626949100


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