Chapter 1 Ff

1

CHAPTER 1.

INTRODUCTION

1.1 Tea Cultivation In India.

India is the largest producer and the largest consumer of tea in the world(31% of

global production). Total area under tea cultivation in India is 5.12 Lakh Ha. Tea

constitutes an important part of Indian life. The tea bush known as Camellia Sinensis

grows in loose, deep, acid soil, at high altitude, with summer and autumn rain, in a

little heat and little wind. In these climatic conditions most of the plants die but the tea

bush flourishes fantastically. Today tea is grown in more than 25 countries around the

world. It is cultivated as a plantation crop, grows well in acidic soil, and a warm

climate with at least 50 inches of rain per annum.

The North eastern states of India accounts for 2.8 lakh ha (55 %) of area under

tea cultivation with 455 million kg. annual production. Tea is cultivated in an area of

1.14 lakh hectares in South India with an annual production of more than 2,000 lakh

kgs. About 12.5 lakh people are employed under tea estates and factories. A tea bush

has life span of about 100 years. It loses its economical productivity after 40 or 50

years of age. Around 2,21,000 ha area which fall into vulnerable category of low

yielding areas in India is to be targeted for replantation and rejuvenation immediately.

(Anon, 2007).

In 2009 Indian Tea Association (ITA) reported that due to improving finances,

most Indian tea companies, big and small, were going in for massive replantation to

upgrade the quality of their tea (Ghosal, 2009). Replacement of the old tea plants with

new improved varieties will be necessary if economic production levels and

productivity is to be maintained, particularly in the small holder sub sector so as not to

expose the farmers to economic vulnerability.

1.2 Why old tea bushes have less economical productivity?

1. Low yields.

2. Increasing number of empty spots due to death of weak bushes.

3. Branches become thin and diseased.

4. Increasing rate of diseases of the top and of the roots.

5. Increase in the proportion of unproductive (brown and woody) tissues on tea plants.

6. Buds and crown buds are small and scarce.

7. Many shoots at the base of the bush, or sprouting up from the ground.

2

1.3 Existing Uprooting Practices

1. Manual Digging

2. Uprooting with help of elephants.

3. Uprooting by bulldozer.

4. Uprooting by tractor.

5. Rack type Uprooting Machine.

1. Manual digging

This is tedious and time consuming.(Wilson and Clifford, 1992). The manual

system of' uprooting old seedling tea bushes relies entirely on the use of hand-labour

or all the required operations like digging of stumps using hoes or any other

implement that enhances the number of stumps lifted per man-day. Within the Manual

Uprooting System there are, in turn, two alternative methods based on the type of

labour used in the operation.( G.M. Limwado, 1995)

1. Contract Labour Method involves the use of households to which a known number

of bushes is allocated at an agreed charge per bush. Under this method each

household uproots between 50 and 60 bushes per day.

2. Regular Labour Method which involves the use of the existing labour force, usually

tea pluckers, in the uprooting operations during the slack period. Under this method

each worker is able to uproot between 20 and 30 bushes per man-day.

2. Uprooting with help of elephants

Elephants should be trained for this type of practice. This method doesn’t

require any type of tool.

3. Uprooting by bulldozer

Because of heavy weight of bulldozer it causes more soil compaction. Also it

is very much costlier. Bulldozer uprooting caused highest soil compaction giving

mechanical impedance to penetration, heavy destruction of soil structure and

significantly reducing water infiltration rate compared to winching and hand

uprooting (Obaga and Othieno, 1986).

4. Uprooting by tractor

An clamping system with frame is attached to tractor 3-point linkage and with

help of hydraulic system bushes are uprooted. With the mechanical uprooting system

between 250 and 300 bushes are uprooted per tractor hour, depending on tractor size,

age and size of the seedling tea bushes, type and moisture content of the soil in the

field being uprooted. (G.M. Limwado, 1995).

3

1.4 Objectives

1. Design of a manually operated tea bush uprooting machine.

2. Fabrication of a prototype manually operated tea bush uprooting machine

3. Testing of the above prototype for the rated load in laboratory condition.

4. Trial of the above prototype for uprooting young tree plants.

4

CHAPTER 2

REVIEW OF LITERATURE

2.1 Tea reviews

Ananda coomaraswamy, et al. (2000) reported that the tea plants are grown at spacing

of 1.2 m x 0.6 m. the canopy diameter of tea plant is around 1 m to 1.2 m and tea plants from

a continuous, smooth canopy at 0.8 – 1 m height as they are planted at a close spacing.

Excavation studies shown that clonal tea has a maximum rooting depth of around 0.9m – 1 m,

but more than 90 % of the roots are located within top 0.6 m of the soil profile. The lateral

spread of the tea root system is over an area of 1.2 m in diameter.

Chattopadhyay, et al (2004) reported that tea contains a number of chemical

constituents possessing medicinal and pharmacological properties and it is expected that tea

root might also be a store house of many chemicals of medicinal and pharmacological

interest. TRE (tea root extract) was found to possess anti-inflammatory, analgesic and

antipyretic activities. The tea plants are uprooted 30-100 years after plantation, the roots are

used either for making ornamental and furniture or as a fire wood.

Rishiraj Datta (2011) have done research on a spatio – temporal analysis of tea

productivity and quality in north east india. Economic life of the tea bush is 40 – 50

years.Older plantations show a decreased yield.

2.2 Uprooting reviews

John Albert Garret, (1899) invented a transplanting tree clamp for transplanting any

size of plant without any injury. When the clamp is contracted the circular opening and

radiating arms are reduced diametrically and narrowed respectively, and when clamp is

expanded said opening is made larger and its arms are correspondingly widened.

5

Alvin E. Herz, Nutley, N.J.(1974) developed a method of tree extraction and engaging

clamp to tree stump. The clamp is used designed for extracting trees by vertical lifting force.

Tree stump holding members of clamp are shown in fig.

Fig.1 Clamp.

Sexsmith (2002) invented a mini shrub spader for unearthing and transporting trees

and shrubs. The mini shrub spader has a basketed U-blade which allows it to unearth, shape

the root ball and transport a tree or shrub utilizing the same device. The mini shrub spader is

preferably mounted to the rear of a small tractor. It is constructed of a steel frame which

houses the hydraulic systems. The frame is H-shaped having a basketed U-blade pivotally

secured to the front of the frame. The U-blade is actuated through two hydraulic cylinders

mounted on the top of the frame. The rear of the frame has a three-point hitch to allow the

mini shrub spader to be secured to a small tractor or similar towing device.

Fig. 2 Mini shrub spader.

6

K.A. Campbell, et al (2004) uprooted paper birch trees in summer using tripod and a

winch device to measure the maximum vertical force required for uprooting. He concluded

that uprooting resistance is operationally relevant not only for slope stabilization but also for

windfirmness, and tree productivity (diameter). In his study he stated pruning treatment did

not impact uprooting resistance. His study also found strong relationship between GLD

(Ground Line Diameter) and uprooting resistance.

Horváth- Szováti and Czupy (2005) determined the relation of vertical lifting power

to the diameter of the stump stumps of Norway spruce in sandy soil on the plains by 20%

water capacity.

F = 6.542 × (DSH0.6369

+ e0.041189 × DSH

-1)

Where F is the required vertical uprooting force in kN and DSH is the stump diameter in cm.

Sonal Valvi (2008) concluded that tea bush which required maximum uprooting force

of 640 kg, was having stem diameter of 6 cm and tea bush which required lowest maximum

force of 245 kg was having smallest stem diameter of 3 cm. The age of tea bushes he

experimented was 10 – 12 year.

Ola Lindroos, et al (2010) found the maximum forces required to vertically uproot

stumps of Norway spruce (Picea abies) and birch (Betula spp.). According to him stump sizes

ranges from 15 – 35 cm required uprooting force 15-150 kN.

A.S. Akinwonmi, et al (2012) designed a simple, efficient, cheap and affordable

cassava uprooting device for local cassava growing farmers. He concluded that average force

required for uprooting cassava plant was 1000 N. He used mild steel for cassava harvester

because it is cheap and easily available.

Fig.3 Cassava Uprooting Device

7

Timothy C. Dearman, (1989) invented a plant uprooting apparatus having a pair of

jaws movable relative to one another between open and closed position in response to

movement by a person of an actuating grip and linkage. The movement in one direction of

the grip is limited so that the force that must be exerted by a person to maintain the jaws in

their closed position is minimal.

Fig.4 Apparatus for uprooting plants.

2.3 Human strength

Bao and silverstein (2005) conducted experiments on one hundreds and twenty

subjects to estimate the hand grip strength and the hand force and test for muscle activities of

hand and fore arm. He collected normative data of pinch and power grip strength with a

digital dynamometer and studied about ability of hand grip force using hand dynamometer.

Estimates of normative power grip strength were 294.0 and 470.0 N for women and men,

respectively. Estimates of normative pinch group strength are 89.2 and 125.1 N for women

and men respectively. Power grip force ranges between 78.1 N to 103. 1 N while performing

three different test activities like screw driving, ratcheting and lifting/carrying

P.S. Tiwari et al (P.S. Tiwari et al) concluded that the mean values for isometric push

and pull strengths in a standing posture with both hands (in the horizontal plane) are 254.1 ±

53.0 N and 234.5 ± 43.2 N, respectively, for male subjects and 183.4 ± 35.3 N and

185.4±30.4 N, respectively, for female subjects.

K.N. Dewangan et al (2010) concluded that the mean right handgrip strength was

300.3 N, right hand push strength was 118.0 N, right hand pull strength was 148.9 N, right

leg strength was 363.2 and right foot strength was 271.4 N.

8

CHAPTER 3.

THEORETICAL CONSIDERATIONS

This chapter deals with the theoretical considerations in designing and selecting the

various components of prototype tea bush uprooting machine.

3.1 Design of tripod.

A tripod is a portable three-legged frame, used as a platform for supporting the weight

and maintaining the stability of some other object. Tripod is designed according to the

buckling analysis of its legs. Following procedure is considered for design of tripod.

3.1.1 Design considerations.

1. The legs of tripod considered as fixed-fixed ended columns.

2. Tripod should be able to withstand a load of 2000 Kg.

3. Tripod should be light in weight so that two men can easily transfer it from one bush

to another.

3.1.2 Terminology for column design

Column: A long slender bar subject to axial compression is called column.

Short Columns: A short column is usually defined as one whose slenderness ratio is less

than about 100.

Long columns: Those columns whose slenderness ratio is more than 100 for ductile material

and more than 80 for CI are called long columns.

Failure of column:

Failure of column occurs by buckling. In compression failure of short compression member

occurs by yielding of material, buckling, & hence failure of column may occur even though

the maximum stress in the bar is less than the yield point of the material.

Critical load (Pcr):

The critical load of a slender bar subject to axial compression is that value of the axial

force that is just sufficient to keep the bar in slightly deflected configuration.

Slenderness ratio:

The ratio of the length of the column to the minimum radius of gyration of the cross

sectional area is termed as the slenderness ratio.

9

Radius of gyration (k):

The radius of gyration of a body is defined as the radius at which the entire mass of

the body could be concentrated such as the resulting model will have the same moment of

inertia as original body.

√

…..Eq (3.1)

Moment of inertia (I):

Area moment of inertia is also known as second moment of inertia. It is a property of

shape that is used to predict deflection and stress in beams

Area moment of inertia of a hollow cross section:

Fig.1 Cross section of pipe.

do = Cylinder outside diameter.

di = Cylinder inside diameter.

…………..Eq.(3.2)

10

3.1.3 Determination of size of tripod according to size of plant.

Fig.5 Dimensions of tripod according to the size of plant.

Tripod is small in size and cannot be used for bigger tea plants. Height of tripod must

be 1 meter high above tea plant canopy. But available tripod is not suitable for old tea bushes

because of small height. There will be difficulty in operation.

3.1.4 Free body diagram of tripod leg

F2 = 𝐹1

cos𝛼

F1 = load acting at the centre of tripod.

F2 = load coming on the tripod leg due to ground support.

11

Required uprooting force for old tea plant is 19.6 kN. So this much force will act at the centre

of tripod during uprooting. This force will equally transmit through three legs of tripod.

Actual load coming on each leg of tripod can be calculated as;

F2 =

cos

F2 = 7.046 kN

3.1.5 Buckling load for a column with fixed ends.

In this case the ends of the column are subjected to fixing moments, MF, in addition

to axial load (fig.4 (c)). In this case the ends of the column are subjected to fixing moments,

MF, in addition to axial load.

Fig. Buckling of fixed ended columns.

……Eq(3.3)

……Eq(3.4)

Rearranging

…..Eq(3.5)

General solution of above,

⁄ ……Eq(3.6)

………. Eq(3.7)

V

P P

P P

12

When z = 0, v = 0 so that A = -MF/Pcr. Further v = 0 at z = L

…….Eq(3.8)

[

] ………Eq(3.9)

Note that again, v is indeterminate since MF cannot be found. Also since dv/dz = 0 at

z = L.

We have,

……Eq(3.10)

And kL = nπ. When n = 0, 2, 4,………

For a non-trivial solution, i.e. n ≠ 0, and taking the smallest value of buckling load

(n = 2), we have.

……Eq(3.11)

This is Euler’s formula for fixed ended columns.

3.1.6 Columns with other end constraints:

Effective length (Le):

Effective length of any column is defined as the length of pinned-pinned

column that would buckle at the same critical load as the actual column.

Table 3.1 Values of effective length for different end conditions.

Sl. No. End condition Effective length

a. Pinned-Pinned L

b. Fixed-Pinned 2L

c. Fixed-Fixed L/2

d. Fixed-Pinned 0.7L

13

3.1.7 Rankin’s-Gordon Formula:

Prediction of buckling load, by Eulers formula is only reasonable for very long

and slender struts that have very small geometrical imperfection.

Most of the struts suffer plastic knockdown and the experimentally obtained

buckling load are much less than the Euler’s prediction.

For struts in this category, a suitable formula is Rankines-Gordaon formula,

which is semi-empirical formula and takes in to account the crushing strength of the

material, it’s youngs modulus and its slenderness ratio (L/k).

L = length of strut.

K = least radius of gyration of the struts cross-section.

PC = ………Eq(3.12)

Where

A = cross sectional area.

= crushing stress.

The

……..Eq(3.13)

Where PR = Rankine – Gordon buckling load

Pcr = Eulers buckling load

Pcr =

for pin – ended strut

…..Eq(3.14)

......Eq(3.15)

…..Eq(3.16)

…..Eq(3.17)

14

……..Eq(3.18)

(

)(

)

...........Eq(3.20)

Let

…….Eq(3.21)

Thus

(

) …………Eq(3.22)

Where a is constant in Rankin – Gordon formula, which is dependent on boundary

condition and material properties.

Table 3.2 Value of

and for different material

Material

Mild steel 17500 300

Wrought iron 8000 250

Cast iron 18000 560

Timber 1000 35

3.1.8 Limitations of Euler’s formula.

Predictions of buckling loads by the Euler’s formula are only reasonable for

very long and slender struts that have very small geometrical imperfections.

Euler’s formula is valid only for the columns whose slenderness ratio is greater

than 100.

General equation for crippling load

(

) ………Eq(3.23)

15

Crippling stress:-

(

) ……….Eq(3.24)

Crippling stress will be high if slenderness ratio is small. (

) is slenderness ratio.

Crippling stress can not be more than crushing stress of column material.

For mild steel column:

Crushing stress for mild steel is 330 N/m2

Young’s modulus is 0.21 × 106 N/m

2

Now equating crippling stress to crushing stress,

( )

( )

(

)

(

) ………….Eq(3.25)

Hence if slenderness ratio is less than 80 Euler’s formula is not valid for mild steel

Table 3.3 Properties of mild steel.

1 Ultimate stress (σu) 410 Mpa

2 Yield point stress (σy) 248 Mpa

3 Crushing stress (σc) 320 Mpa

4 Allowable stress (σA) 60 Mpa

5 Rankin’s constant (a) 1/7500

6 Density (ρ) 7850 kg/m2

7 Young’s modulus (E) 210 Gpa

16

3.1.9 Calculation of crippling load for pipe size 3/4.

Length of leg pipe = 3.23 m. (shown in fig .2)

External Diameter (do) = 0.026 m

Internal Diameter (di) = 0.02 m

Cross sectional area of pipe =

(

).

=

= 2.17 × 10-4

m2.

Volume of pipe =

(

) .

=

= 7 × 10-4

m3.

Area moment of inertia

= 1.45 x 10-8

m4

Radius of gyration (k) = √

= √

= 0.0082.

Euler’s Load for fixed end condition

=

= 11510 N.

= 1174 kg.

Rankine’s Crippling load

( )

17

=

(1 1

)

= 11274 N.

= 1150 kg.

Mass of pipe =

=

= 4.82 kg.

3.1.10 Calculation of crippling load for pipe size 1.

Length of leg pipe = 3.23 m. (shown in fig.2)




(

).

=

= 3.89 × 10-4

m2.

Volume of pipe =

(

) .

=

= 12.5 × 10-4

m3.


= 4.75 x 10-8

m4.


18

= √

= 0.011.


=

= 37747 N.

= 3851 kg.


( )

=

(1 1

11)

= 32382 N.

= 3304 kg.

Mass of pipe =

=

= 9.8 kg.

3.1.11 Calculation of crippling load for pipe size 1 ¼.

Length of pipe = 3.23 m. (shown in fig 2)




(

).

=

= 4.23 × 10-4

m2.

Volume of pipe =

(

) .

=

19

= 13.6 × 10-4

m3.


= 7.9 x 10-8

m4.


= √

= 0.0136.


=

= 62747 N.

= 6402 kg.


( )

=

(1 1

1 )

= 47315 N.

= 4828 kg.

Mass of pipe =

=

= 10.7 kg.

20

3.1.12 Calculation of crippling load for pipe size 1 ½.





(

).

=

= 5.53 × 10-4

m2.

Volume of pipe =

(

) .

=

= 17.8 × 10-4

m3.


= 1.34 x 10-7

m4.


= √

= 0.0156.


=

= 107044 N.

= 10922 kg.

21


( )

=

(1 1

1 )

= 72917 N.

= 7440 kg.

Mass of pipe =

=

= 14 kg.

3.1.13 Calculation of crippling load for pipe size 2.





(

).

=

= 7.03 × 10-4

m2.

Volume of pipe =

(

) .

=

= 22.7 × 10-4

m3.


= 2.77 x 10-7

m4.


22

= √

= 0.019.


=

= 219992 N.

= 22448 kg.


( )

=

(1 1

1 )

= 119552 N.

= 12199 kg.

Mass of pipe =

=

= 17.8 kg.

23

Table 3.4 By using above Formulae and calculations crippling load is calculated for selected mild steel pipe columns.

Sl.

No.

External

dia. (m)

Internal

dia. (m)

Length.

(L)

(m)

Area.

(A)

(m2)

Volume.

(V)

(m3)

M.I.

(m4)

Radius

of

gyration

. (m)

Effective

length.

(Le)

(m)

Eulers load.

(N)

Eulers load

(kg)

By

considering Le

Rankine’s

constant

(a)

Rankine’s

load (N)

Rankine’s

load (kg)

Mass.

(kg)

(M=V

/A)

1 0.026 0.02 3.23 0.000217 0.0007 1.45 x 10-8 0.0082 3.23 2891 295 0.000133 3197 326 4.82

1.615 11510 1174 11274 1150

2.261 5901 602 6226 635

6.46 722 73 827 84

2 0.033 0.026 3.23 0.000389 0.00125 4.75 x 10-8 0.011 3.23 9436 962 0.000133 10055 1026 9.8

1.615 37747 3851 32382 3304

2.261 19258 1965 18931 1931

6.46 2359 240 2675 272

3 0.042 0.035 3.23 0.000423 0.001367 7.90 x 10-8 0.0136 3.23 15686 1600 0.000133 16030 1635 10.7

1.615 62747 6402 47315 4828

2.261 32014 3266 29126 2972

6.46 3921 400 4398 448

4 0.048 0.04 3.23 0.000553 0.001785 1.34 x 10-7 0.0156 3.23 26761 2730 0.000133 26390 2692 14

1.615 107044 10922 72917 7440

2.261 54614 5572 46617 4756

6.46 6690 682 7429 758

5 0.06 0.052 3.23 0.000703 0.002272 2.77 x 10-7 0.019 3.23 54998 5612 0.000133 49679 5069 17.8

1.615 219992 22448 119552 12199

2.261 112240 11453 82445 8412

6.46 13749 1402 14883 1518

24

3.1.14 Allowable stress calculation for compression members.

(

) ………..Eq(3.26)

K= effective length factor for compression member.

L = Length of column.

k = Radius of gyration.

√

……..Eq(3.27)

E = Young’s modulus.

Fy = Yield stress.

Allowable stress.

When, (

)

[ (

)

]

(

)

(

)

………Eq(3.28)

When, (

)

(

) ………………Eq(3.29)

25

Table 3.5 Effective length factor for various end support condition of column.

Sl. No. Support condition of

column

Effective length factor (K)

1 Pinned- Pinned 1

2 Fixed- Fixed 0.5

3 Fixed- pinned 0.7

4 Fixed free 2

Table 3.6 Calculation of allowable stress.

Sl.

No.

Pipe

dimensions

Length

of

column,

L

(m)

Effective

length

factor.

(K)

Table

3.5

Radius

of

gyration

(r)

Eq. 3.1

(

)

Slenderness

ratio.

Slenderness

ratio

Cc

Eq.3.27

Allowable

stress

Fa (Mpa)

Eq. 3.28,

3.29

do di

1 0.026 0.02 3.23 1 0.0082 393 129

7

0.5 196 28

0.7 275 14

2 787 2

2 0.033 0.026 3.23 1 0.011 292 129 13

0.5 146 51

0.7 204 26

2 584 3

3 0.042 0.035 3.23 1 0.0136 236. 129

19

0.5 118 75

0.7 165 39

2 472 5

4 0.048 0.04 3.23 1 0.0156 206 129

25

0.5 103 89

0.7 144 52

2 413 6

5 0.06 0.052 3.23 1 0.019 162 129 41

0.5 81 106

0.7 113 79

2 325 10

………Eq(3.30)

26

Table 3.7 Factor of safety for columns by using Yield strength.

Table 3.8 Calculation of safe load for columns with fixed-fixed end condition.

Sl. No. Pipe size Euler’s

load

Pcr

(kg)

(table

3.4,

column

10)

Rankin’s

load Wcr

(kg)

([table

no.4,

column

14)

Actual

load

(kg)

Calculated

above.

3.1.4

Factor of

safety

[table

no.7,

column

6]

Load

considering

safety

factor

di do

1 0.026 0.02 1180 1146 719 9 6471

2 0.033 0.026 3851 3304 719 4.8 3451

3 0.042 0.035 6402 4828 719 3.3 2372

4 0.048 0.04 10922 7440 719 2.7 1941

5 0.06 0.052 22448 12199 719 2.3 1653

Sl.

No.

Pipe size Column condition Yield

strength

(Mpa)

Given in

table 3.3

Allowable

stress

(Mpa)

Given in table

3.6, column 8.

Factor of

safety.

(Given in

Eq.3.30)

do di

1 0.026 0.02 Pinned- Pinned 248 7 35

Fixed- Fixed 28 9

Fixed- pinned 14 17

Fixed free 2 124

2 0.033 0.026 Pinned- Pinned 248 13 19

Fixed- Fixed 51 4.8

Fixed- pinned 26 9.5

Fixed free 3 82

3 0.042 0.035 Pinned- Pinned 248 19 13

Fixed- Fixed 75 3.3


Fixed free 5 49

4 0.048 0.04 Pinned- Pinned 248 25 9.9

Fixed- Fixed 89 2.7


Fixed free 6 41

5 0.06 0.052 Pinned- Pinned 248 41 6

Fixed- Fixed 106 2.3


Fixed free 10 24

27

3.1.15 Selection of pipe:

From above calculation, we know that pipe no. 1 and 2 have Euler’s load value is

nearer to value of the load considering factor of safety.

But pipe no. 2 have Rankine’s crippling load value less than the value of load

considering factor of safety.

The pipes are made of mild steel and for mild steel there are limitations for using

Eulers design criteria as shown in Eq(3.25), so we can select pipe on the basis of Rankine’s

crippling load.

According to Rankines crippling load, Pipe of size 1 ¼ is suitable for tripod design.

28

CHAPTER 5

RESULTS AND DISCUSSION

5.1 Testing of a tripod and chain available in laboratory for strength.

Testing of tripod and chain was done simultaneously for strength. Before the test we

have selected a hard plane ground to avoid sinking of legs in soil. Tripod was kept on that

hard plane ground. For applying force on tripod we have used a hydraulic lift system, chain

and a metal rod deeply inserted in soil. Arrangement was done in such a way that, the metal

rod was to be uprooted from the soil and to uproot it there is large requirement of force and

this much amount of force is supported by tripod legs. In arrangement the hydraulic lift

system was attached in such a way that, one end was fixed to the centre of tripod and another

end was connected to the metal rod. Dynamometer was used to measure the force. Chain was

used to connect the end of hydraulic system to metal rod, so from that strength of chain can

be measured. After the arrangement we stared lifting the metal rod with the help of hydraulic

lift system. As the lifting occurs load gradually increases on the tripod and chain and the

observations were taken.

Plate.1 Testing of tripod.

29

Plate.2 Dynamometer reading

Table 5.1 Testing of tripod and chain available in laboratory

Conclusion

1. We cannot use chain for load more than 1800 kg load.

2. Slipping of chain occurred many times during operation so it takes more time to set chain

again and again.

3. Tripod can withstand for load more than 1800 kg, but is heavy in weight and difficult to

transport.

Sl. No. Breaking load (Kg) Remark

Tripod >1800 withstand

chain 1800 Broken.

30

5.2. Trials of a tripod, chain and clamp on small Akashpani trees available in the field

laboratory.

The set of trials were taken on Akashpani trees available in field. They were irrigated

one day before uprooting, because tea bushes are generally uprooted in rainy season and in

rainy season the moisture content of soil is high. Due to high moisture content of soil they

can be easily uprooted from earth.

After irrigation the actual uprooting of small trees was done with the help of a tripod

and chain pulley block. During uprooting following parameters were measured.

1. Uprooting force.

2. Time required for uprooting.

3. Girth of plant to be uprooted.

4. Time required for fixing chain/clamp.

5. Time required for transferring tripod.

6. Time required for tightening the chain.

7. Time required for removing clamp/chain.

8. Vertical displacement of chain.

9. Moisture content of soil.

31

Table 5.2 Trials of a tripod, chain and clamps available in laboratory for uprooting akashpani plants. (Date 9/3/2013)

No. of

Plant

Time taken for the followings Circumference

of the plant in

(cm)

Pull in

(kg)

Vertical

displacement

of the chain in

(cm)

Total

Time

(min)

Remarks

set the

dynamometer

in (sec)

set the clamp or

chain (sec)

tightening the

chain in (sec)

uproot the

plant in (sec)

remove the

clamp from

the plant in

(sec)

transferred the

tripod in (sec)

1 35 78 13 - 23 - 19 900 - 2.48 Unable to uproot

plant because of

chain slippage.

2 - 37 - - - 145 23 460 - 3 Unable to uproot

plant due to

chain slippage.

3 - 93 9 26 18 269 18.5 375

680

400

-

30

45

6.91 Plant

successfully

uprooted.

4 - 86 14 55 22 130 19.5 880

1350

1380

1500

-

-

-

43

5.11 Plant uprooted

successfully.

5 - 48 11 30 59 88 9 400

700

280

-

20

27

3.93 Plant uprooted

successfully.

Uprooting was

done by using

clamp.

32

6 - 49 21 230 73 210 31 1200

1700

1800

1900

-

-

30

47

9.3 Successfully

uprooted.

(Dynamometer

broken.)

Table 5.3 Trials of a tripod, chain and clamps available in laboratory for uprooting Akashpani plants. (Date 18/3/2013)

No.

of

Plant

Time taken for the followings Plant to

Plant

Distance

(m)

Circum

ference

of the

plant in

(cm)

Pull in

(kg)

Vertical

displace

ment of

the

chain in

(cm)

Total

Time

(min)

Moisture

content of soil

(%)

Remarks

set the

dynamomet

er in (sec)

set the

clamp or

chain

(sec)

tightenin

g the

chain in

(sec)

uproot the

plant in

(sec)

remove

the chain

from the

plant in

(sec)

transferre

d the

tripod in

(sec)

Tripod

Setting

time in

(sec.)

Dry

basis

Wet

basis

1 11 131 6 155 43 - - - 27.5 500

600

700

500

400

5

10

20

50

60

5.7 26.1 20.7 Successfully

Uprooted

2 - 128 11.59 112 - 22.44 25 1.36 37.3 700

800

- 4.97 - - Bolt Broken,

chain slipped,

Unable to

33

1100

1200

1500

uproot

2 - 92 21 58 68 - - - 37.3 1200

1300

1400

1480

- 3.9 - - Unable to

Uproot.

3 - 111 22 Chain

slipped

after 36

sec

- 15.82 34 1.75 28 700

850

900

1080

- 3.64 - - Chain slipped

after 36 sec.

Unable to

uproot

3 - 95 18.29 Chain

slipped

after 21

sec

87 - - - 28 600

700

800

900

- 3.68 - - Chain slipped

after 21 sec

Unable to

uproot.

34

4 - 148 9 49 51 24 29 3.43 31 700

800

1000

700

600

30.5

5.16 40 29 Successfully

uprooted

5 - 103 9 - - 25 35 3 22.5 900

1180

1300

1500

1800

2000

2.86 Unable to

Uproot

Chain broken

after 2000 kg

force.

6 - 94 18 223 106 22 27 80 25.5 900

1100

1300

1600

1780

1800

2000

43 8.16 20 16.7 Successfully

uprooted

35

7 - 159 15 85 97 56 45 4.2 27.5 700

900

1200

1500

1800

>2000

1500

800

300

38 7.61 15 13 Successfully

uprooted

36

Plate 3. Irrigating the plants before uprooting.

Plate 4. slipping of chain. Plate 5. Dynamometer reading.

37

Plate 6. uprooting the plant with the help of tripod and pulley block

Plate 7. Clamp Plate 8. Dynamometer reading

38

REFERENCES

Alvin E. Herz, Nutley, N.J.1974. Tree And Stump Extraction US patent No. 3,958,613., L. B.

Foster Company, Pittsburgh, USA.

Anandacoomarswamy, A., De costa W. A. J. M. Shyamalie, H. W. and Campbell, G S. 2000.

Factors controlling Transpiration of mature field grown tea and its relationship with yield,

Agricultureal and Forest Meterology ISSN 0168 – 1923, vol: 103, Elsevier Publications,

Amsterdam.

Bao, S. and Silverstein, B 2005. Estimation of Hand Forces in Ergonomic Job Evaluations.

Ergonomics ISSN 0014-0139, vol: 48(3), Taylor and Francis Ltd, USA.

Basu Majumder A., Bera B. and Rajan, A. 2010. Tea Statistics: Global Scenario. Inc. J. Tea

Sci. 8 (1): 121-124

Chattopadhyaya, P., Bersa, S. E., Gomes, A., Das, M, Sur, P Mitra, S. 2004. Anti Inflamatory

activity of tea root extract. Life sciences ISSN 0024-3205, vol 74.

Dr. T. H. G. Megson, 2000, STRUCTURAL AND STRESS ANALYSIS, Second edition, A

division of Reed Educational and Professional Publishing Ltd,page no. 608-612.

Dr. Kim D. Coder,2008, Tree Stump Removal From Landscapes, Warnell School of Forestry

& Natural Resources, University of Georgia.

E Yamaguchi, 1990, Structural Engineering Handbook, Boca Raton: CRC Press LLC.

G.M. Limwado. 1995 Economic assessment of alternate alternative system of old tea bush

uprooting, TRF.

H. D. Hess, 1992, Machine Design, Hoists, Derricks, Cranes, Philadelphia And London J. B.

Lippincott Company

John Case, 1999, Strength of Materials and Structures, Fourth edition, John Wiley & Sons

Inc., 605 Third Avenue,New York,NY 10158-0012.page no. 424-430

K.N. Dewangan, G. Gogoi, C. Owary, D.U. Gorate 2010 Isometric muscle strength of male

agricultural workers of India and the design of tractor controls, International Journal of

Industrial Ergonomics 40 (2010) 484 – 491.

39

Lindroos, O., Henningsson, M., Athanassiadis, D.& Nordfjell, T. 2010. Forces required to

vertically uproot tree stumps. Silva Fennica 44(4): 681–694

Mohotti, A. J., Damayanthi,M.M.N., Anandacoomaraswamy, A. & Mohotti, K. M.. Plant

Physiology Division, Tea Research Institute of Sri Lanka, Talawakele, Sri Lanka, 2008.

Comparative dynamics of tea (Camellia sinensis L.) roots under organic and conventional

management systems with special reference to water use.

P.S. Tiwari, L.P. Gite, J. Majumder, S.C. Pharade, V.V. Singh 2009. Push/pull strength of

agricultural workers in central India, International Journal of Industrial Ergonomics 40

(2010) 1–7.

Robert L. Norton, 2006, MACHINE DESIGN An Integrated Approach, Third Edition.

Pearson Education, Inc.Upper Saddle River, NJ 07458 page no. 189-198.

Tea plantation development scheme for the XI period 1-4-2007 to 31-3-2012 TEA

BOARD(Ministry of Commerce and Industries- Govt. of India)14 B.T.M. SARANI

KOLKATA-700 001.

Valvi Sonal Dattatraya, 2008, design and development of manually operated bush stalk

pulling machine. IIT kharagpur.

Wilson, K.C. Clifford, M.N 1992 Tea cultivation and consumption, Chapman and hall

Publication, 2-6 boundary row, London, UK.

William A. Nash, 1998, Schaum's Outline of Theory and Problems of STRENGTH OF

MATERIALS, Fourth Edition, McGRAW-HILL, New York, USA.356-357

40

APPENDIX-A

A.1 Chain Hoist

It helps to lift heavy load. It has two chain one is pulled by hand and another lifts the

load. It concentrates the force by transforming a small effort exerted over a long distance in

to a huge force exerted over a short distance. When hand chain is pulled it rotates the cog and

cog turns the drive shaft and gear on drive shaft. The hand chain is fit in to the seven

specially designed slots in the cog. As hand chain is pulled it turns the cog. The cog first

screw tight to the friction plate which is attached to the ratchet wheel. So as the cog plate and

ratchet wheel turns together it catch clicks on to the teeth of ratchet wheel preventing the cog

from slipping backward under the weight of load.

So in chain hoist force from hand chain get concentrated more and more. As cog turns

it also turns the drive shaft. At the other end of shaft there is a small gear with five teeth. As

that gear turn with drive shaft the force applied to cog by hand chains already started to

increase so far it’s been multiplied by 7:5 ratio which means one force on seven chain link

goes to 5 teeth on the gear.

Small gear is now turning with more force which puts stress on the teeth of gear to

decrease the stress there. That gear turns the two identical gear wheels at the same time. In

this way the stress of the small gear force is distributed across the two teeth. So the small gear

turns the 18 teeth each of the identical gear wheels. These gears have an four teeth axle on

other side. Essentially another small gears which will in turn multiply the force by ratio 18:4.

Those small gear turns the another larger gear having 19 teeth. Those teeth concentrate their

force on few links of lift chain fit in to the lug sprocket.

41

Force multiplication in chain hoist

1. No. of teeth on gear 1 (T1) = 5.




5. Hand chain wheel no. of sprocket = 7

6. Load chain wheel no of socket = 4

Force multiplied:

= (T2/T1) x (T6/ T4) x (hand chain links pulled /load chain links to be lifted)

= (18/5) x (19/4) x (7/4)

= 29.94.

Force multiplies 30 times in chain hoist.

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