Vol. 8(44), pp. 5530-5537,14 November, 2013
DOI: 10.5897/AJAR2013.7290
ISSN 1991-637X ©2013 Academic Journals
http://www.academicjournals.org/AJAR
African Journal of Agricultural
Research
Full Length Research Paper
Development of ergo refined coconut tree climbing
device
A. P. Mohankumar*, D. Anantha Krishnan and K. Kathirvel
1
Department of Farm Machinery, Agricultural Engineering College and Research Institute, Tamil Nadu Agricultural
University, Coimbatore- 03, Tamil Nadu, India.
Accepted 24 September, 2013
Climbing coconut trees is an important activity in rural agricultural wage workers. Generally, skilled
workers are employed to collect the coconuts from the tree. Agricultural workers employed for
coconut tree climbing suffer musculoskeletal disorders than any other type of injury or illness. The
developed tree climbing device (T 1) was evaluated based on ergonomical parameters and ergo
refinements were carried out. The inclination of upper frame of climbing device is increased (T 1) with
respect to the horizontal, while moving towards the top of the tree. As a result, the centre of gravity of
the user moves towards outside of the body making him feel insecure and unstable. The upper frame
of coconut tree climbing device was suitably modified to avoid downward inclination such that ergo
refined device (T2) improves the safety and ease of operation. The ergo refined coconut tree climbing
device (T 2) enhanced the comfort and safety of male subjects with 7.8, 12.2, 10.7 and 20.5% reduction
in heart rate, energy expenditure, overall discomfort rating and body part discomfort score,
respectively and 2.6 and 4.1% increase in overall safety and ease of operation rating respectively when
compared to T1. The ergo refined coconut tree climbing device resulted in 20.6% savings in cost and
11.8% savings in time of climbing and harvesting coconut when compared with T 1 model.
Key words: Coconut tree, climbing device, ergo-refinements.
....
INTRODUCTION
Coconut (Cocos nucifera L.) palm is an important cash
crop in India. India is the third largest producer of coconut
in the world. Coconut is grown in an area of about 18.7
million ha with a productivity of 5718 nuts per hectare in
India (National Horticulture Board, 2011). Generally,
skilled workers climb to harvest the coconuts from the
tree without any safety device. The coconut trees are
very tall and injuries associated with coconut tree
climbing, particularly falling from coconut trees is
common in coconut plantations in India. The workers
employed for climbing coconut tree suffer musculoskeletal
disorders than any other type of injury or illness. With
sufficient attention to the larger goals of whatever work is
underway, investments in ergonomics can often pay for
themselves many times over. George et al. (2012)
reported that a total of 35.5% (78 cases out of 220
climbers) fell down from coconut trees while doing their
job. A 7.9% (19/240) of the tree climbers in the study
area withdrew from their traditional profession and
remained unemployed. Among them, only 5.3% (1/19)
stopped climbing trees due to health problems and 94.7%
(18/19) withdrew because of casualties that happened
*Corresponding author. E-mail: mohankumarfmp@gmail.com. Tel: +91 78458 65365.
Mohankumar et al.
5531
device parameter (anthropometric data of climber).
Crop parameter
Fifty tall coconut varieties were selected at random in a 23 year old
coconut farm located at Negamam village (10.7333°N 77.1°E),
Pollachi Taluk, Coimbatore district. The girth of these fifty trees was
measured at three levels of height detailed as follows:
i) Height of coconut tree at 1 m above ground level (H 1);
ii) Height of coconut tree at 1 m below the bottom most frond level
(H2);
iii) Height of coconut tree at middle portion (H 3).
Since the cross section of the trunk is circular, the cross sectional
diameter of the coconut trees were calculated.
Figure 1. Gripping mechanism of tree climbing device.
Climbing device parameters
Gripping aid
during their occupation. Joseph (2006) developed a
coconut-climbing device having two frames (left and
right). Each frame was having flexible adjustable
encircling iron rope mounted around a tree and tree
gripping rubber pad. The two main frames were fitted on
the tree side by side enabling the operator to lift the
frames conveniently using the sliding member.
Laborde (2006) developed a climbing tree stand
apparatus with upper and lower platforms that were
independently movable up the tree from under
alternatively sitting and standing on one or the other of
the platforms. Mohanty et al. (2008) investigated that the
comparative study on the ergonomics of farm women in
pedal threshing with single and double operators suggest
modifications for further reduction of human drudgery.
Thiyagarajan et al. (2013) conducted ergonomics study
on different sugarcane harvesting knives and
improvement carried out among one knife which having
minimum physiological cost. There is no device available
with safety features and ergonomically designed.
Keeping the aforementioned facts in view, the simple
device was fabricated with safe and easy to use device
for climbing coconut palms, which could even be
operated by an unskilled person.
Proper selection of material for gripping aids of the tree climbing
device is a crucial factor as it influences the weight of the device,
the flexibility and resistance to wear and tear. The gripping
mechanism of tree climbing device is shown in Figure 1. Let, A Point of contact of gripping aid with trunk, α - the inclination of
frame with respect to horizontal, W - the load due to weight of
climber on the frame, S - horizontal distance between A and point
of action of CG (W) of climber, R - reaction force exerted by tree, E
- vertical distance between the centres of gripping aids, μ coefficient of friction of surface of trunk. Taking the moment about
A,
W×S=R×E
(1)
For stability of frame without slipping, the frictional force
experienced by the gripping aids should be more than the vertical
component of weight of climber (W):
2R×µ>W
(2)
Anthropometric criteria for the design of tree climbing device
Anthropometry is the measurement of physical features of body
including linear dimension, clearance, reach, posture, weight and
volume. The following anthropometric parameters relevant to the
development of tree climbing devices of Tamil Nadu agricultural
workers were taken from the anthropometric data bank of
agricultural workers of Tamil Nadu (All India Coordinated Research
project on Human Engineering and Safety in Agriculture, 2000) and
the values are furnished in Table 1.
MATERIALS AND METHODS
The developed tree climbing device must ensure the following
requirements. It should withstand enough loads exerted by climber.
It should accommodate all kinds of climber. It should provide
effective gripping over a wide range of tree diameters. It should
conform to the shape of the tree trunk as much as possible for
effective gripping. It should distribute the gripping forces uniformly
over the tree surface to prevent damage to the tree surface and to
prevent wear and tear of the gripping aids. It should grip the tree
securely without any possibility of accidental failure. The climbing
device was working as first class lever type principle. The important
parameters that are associated with the design of tree climbing
devices are crop parameter (tree trunk diameter) and climbing
Construction of climbing device
The device (T1) is constructed of two sections which include upper
and lower frames. These frames are independently movable and
positionable along the coconut tree trunk. The upper frame member
is a tubular frame work consisting of a rigid base section and an
adjustable tree gripping section. The rigid base section carries a
seating arrangement for accommodating the user, front support rail,
cross rear rail and side rails. The user can sit comfortably facing the
tree and receive support from the cross rear rail and the side rails.
The seat is a flexible sagging type made of rexin fabric attached
through loops between the rear and front cross rails of the frame.
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Afr. J. Agric. Res.
Table 1. Anthropometric criteria for the design of tree climbing device.
S/N
i
ii
iii
iv
v
vi
vii
viii
ix
x
Xi
Dimensions
Age (years)
Weight (kg)
Trochanteric height
Knee height sitting
Buttock to knee length (cm)
Hip breadth sitting (cm)
Functional leg length (cm)
Grip diameter (inside) (cm)
Heel breadth (cm)
Foot breadth (cm)
Lateral malleolus height (cm)
Mean
35.92
56.14
84.60
47.41
53.97
29.97
101.39
5.02
5.51
8.79
6.81
The tree gripping section consists of gripping aids to engage it on
three points on the circumference of the tree. The gripping aid is a
rubber bush inserted into a tubular square bar. The gripping section
has three members which form a triangular throat that
encompasses the upright coconut tree trunk, thereby permitting the
upper frame member to be fixed to the tree. One of the removable
gripping members is attached to the extendable arm and the other
two are attached in “V’ shape to the front support bar of the seating
frame. The spacing between the gripping members is adjustable
with the help of extendable arm to suit the girth of the coconut tree.
The lower frame member is also a tubular frame work consisting of
a rigid base section and a tree gripping section similar to upper
frame member except that the rigid base section is located adjacent
to the tree trunk to support the weight of the user when the upper
frame is repositioned on coconut tree. The rigid base section
carries a pair of parallel tubular bar with rubber bushes for the user
to insert his feet and lift the unit. Cushioning material is also
provided around the rubber bushes for sophisticated purpose of
user feet. The upper and lower frame members are connected with
canvass belt to prevent them from slipping down the tree trunk.
Handles provided on the side rails of the upper frame enable the
user to lift the unit during ascending or descending the tree. After
reaching the coconut tree top, the unit can be fitted to one of the
front with the help of hook so that the user can get into the crown of
tree for harvesting coconuts. The spacing of the gripping members
is set initially to engage both the upper and lower frames with the
outermost ends such that the inclination of the seat and foot rest
being horizontal or parallel to the ground. To ascend the coconut
tree, the user places his feet on the lower frame member. The user
then rests his weight on the seating section of the upper frame
while using his feet and legs to pull the lower frame upward. The
user then stands by resting his feet on the lower frame and using
his hands raises the upper frame to waist high position. The user
then sits and again raises the lower frame with his feet and legs.
The view of the climbing device (T1) is shown in Figure 2. The
various physical parameter of developed tree climbing device (T 1) is
furnished in Table 2. The operational view of developed tree
climbing devices (T1) is shown in Figure 3.
Centre of gravity (CG)
Mass of all bodies is equally distributed through their CGs. Location
of the whole body centre of gravity is the resultant of the location of
the segmental centers of gravity in the space. Determination of
whole body centre of gravity of a coconut tree climber subject helps
to understand the stability of the whole body while adapting the
particular posture during climbing with a tree climbing device. The
SD
10.55
9.69
5.15
3.16
2.64
3.147
7.14
0.75
2.38
0.73
0.377
5th percentile value
18.56
40.21
75.60
42.21
49.62
24.79
89.65
3.79
1.60
7.59
5.54
95th percentile value
53.28
72.08
92.55
52.61
58.32
35.13
113.13
6.25
9.43
9.99
8.07
centre of gravity of a coconut tree climber subject was measured by
segmental method (Hamil and Knutzen, 1995). The inclination of
tree climbing device was calculated with various diameter of tree
with various adjustable distances.
Inclination of tree climbing device
The inclination of tree climbing device was calculated using the
following Equation 4. θ - Inclination of tree climbing device with
respect to horizontal (°); X - diameter of the tree trunk (cm); Y distance between the two gripping aids in throat area (cm):
θ = tan-1 (Y/X)
(3)
Ergonomic evaluation
The developed coconut tree climbing devices was evaluated with
twelve male coconut plantation workers. The subjects were
screened for normal health through medical investigations. The
age, weight and height of the selected male subjects were 32 ± 2.6
years, 58.8 ± 4.5 kg and 165.5 ±.6.8 cm respectively. The selected
twelve male subjects were calibrated in the laboratory by indirect
assessment of oxygen uptake. Ergonomic evaluation of the
selected coconut tree climbing practices was conducted for
assessing the suitability of the user with respect to comfort, safety
and ease of operation. The evaluation was carried out with the
twelve selected subjects in terms of heart rate (HR), oxygen
consumption rate (OCR), energy cost of operation (ECR),
acceptable work load (AWL), limit of continuous performance
(LCP), over all discomfort rating (ODR), over all safety rating
(OSR), over all ease of operation rating (OER) and body part
discomfort score (BPDS). The heart rate data was recorded using
computerized heart rate monitor (Polar S 810i).
From the down loaded data mean values of heart rate, oxygen
consumption rate and the energy expenditure rate for all the
subjects were computed. The energy cost of operation was graded
as per the young Indian male workers given in ICMR report (Sen,
1969). The acceptable workload (AWL) for Indian workers was the
work consuming 35% of VO2 max (Saha et al., 1979). To ascertain
whether all the selected coconut tree climbing practices were within
the acceptable workload (AWL), the oxygen consumption rate in
terms of VO2 max was computed. To have a meaningful
comparison of physiological responses, work pulse (H) values
(increase over resting values) were calculated. The mean values of
work pulse for coconut tree climbing operation were compared with
Mohankumar et al.
(a)
(b)
Figure 2. View of upper and lower frame of the climbing device (T 1). a)
Upper frame, b) Lower frame.
Table 2. Specification of developed coconut tree climbing device (T1).
S/N
i
ii
iii
iv
v
vi
vii
viii
ix
x
xi
xii
xiii
xiv
xv
xvi
xvii
xviii
Particulars
Size of the upper frame ( cm)
Size of the lower frame (cm)
Size of the rigid base section in upper frame (L × B) (cm)
Size of tree gripping section (L × B) (cm)
Number of cross rail in upper frame
Number of cross rail in lower frame
Diameter of locking knob gripping section (cm)
Diameter of rubber gripping bush (cm)
Length of rubber gripping bush in inclined rail of tree gripping section (cm)
Length of rubber gripping bush in cross rail of tree gripping section (cm)
Gripping diameter of tree trunk in extendable arm (cm)
Number of bushes in upper frame
Number of bushes in lower frame
Length of safety strap (cm)
Width of the belt (cm)
Weight of the upper frame (kg)
Weight of the lower frame (kg)
Width of canvas belt (cm)
Values
106 × 51
62 × 51
54 × 51
47 × 51
5
4
6
5
15
20
25 - 35 adjustable in 5 steps
3
7
110
5
6.7
6.1
5
5533
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Afr. J. Agric. Res.
y = -0.3053x + 37.015
2
R = 0.9881
35
30
25
20
15
10
5
0
(cm)
Diameter of tree (cm)
Figure 3. The operational view of developed tree climbing devices (T 1).
0
5
10
15
20
25
30
35
40
45
50
Angle of tree climbing device (°)
Figure 4. Effect of tree diameter on the inclination of tree climbing device with 32.5
cm adjustable distance.
the acceptable work pulse values of 40 beats min-1 as limit of
continuous performance. For the assessment of overall discomfort
rating (ODR) and localized discomfort (BPDS), a 10 - point
psychophysical rating scale was used which is an adoption of
Corlett and Bishop (1976) technique. The work time was fixed as 60
min of operation. At the end of each trial with the selected coconut
tree climbing practice, the subject was asked to indicate their ODR
and BPDS level on the 10-point rating scale.
RESULTS AND DISCUSSION
The diameter of coconut tree is important morphological
character that influences the performance of tree climbing
device. Adjustable distance of removable gripping aids of
coconut tree climbing device was fixed based on the
diameter of the tree. From the collected data it was
observed that, the minimum and maximum adjustable
distance was 22.5 and 32.5 cm, respectively. Hence, the
tree triangular throat of tree climbing device
accommodated to tree trunk.
Centre of gravity of operator’s body posture
The centre of gravity of tree climber was located with
different inclination of tree climbing device in lab
condition. The inclination of tree climbing device was
calculated with various diameter of tree. The inclination of
tree climbing device is influenced by the diameter of tree
at various adjustable distances. From that analysis it was
inferred that the minimum and maximum inclination of
tree climbing device at maximum adjustable distance of
32.5 cm is 16 and 47°, respectively with the horizontal.
The inclination of tree climbing device is shown in Figure 4.
Centre of gravity
The centre of gravity of the operator while climbing
coconut tree using the tree climbing device of different
inclinations of the upper frame was calculated. The
Mohankumar et al.
5535
Table 3. The anthropometric criteria of ergo refined coconut tree climbing device.
S/N
Anthropometric dimensions
i
ii
iii
iv
v
vi
vii
Buttock to knee length (cm)
Hip breadth sitting (cm)
Functional leg length (cm)
Grip diameter (inside) (cm)
Heel breadth (cm)
Foot breadth (cm)
Lateral malleolus height (cm)
Corresponding work space dimensions in
coconut tree climbing device
Seat centre to tree
Sitting frame breadth
Length of the connecting belt
Width of handle
Length of foot rest (rear) in lower frame
Length of foot rest (front) in lower frame
Gap between two foot rest of lower frame
Percentile
value chosen
58.32 (95th)
35.13 (95th)
89.65 (5th)
3.79 (5th)
9.43 (95th)
9.99 (95th)
8.07 (95th)
Ergo refined
unit dimension
41.5
43
110
1
10
10
9
Figure 5. The ergo refined tree climbing device (T2).
centre of gravity of tree climber shifted outside of the
body at more than 40° inclination of tree climbing device.
Hence, the safe inclination of tree climbing device is less
than 40° with horizontal. While operator moves towards
top of the tree, with increase in height of tree, the
diameter of coconut tree trunk decreases. The inclination
of upper frame of coconut tree climbing device is
increased with respective horizontal. As a result the
centre of gravity of the user shifts outside of the body
(Grimshaw and Burden, 2007) and the user feels
insecure and unstable. The upper frame of coconut tree
climbing device was suitably modified to avoid downward
inclination.
Ergo refined tree climbing device
To achieve better efficiency of performance with more
human comfort, it is necessary to modify the operator’s
work place in the coconut tree climber device keeping
anthropometric suitability. To suit the convenience of the
tree climber, the values of pertinent anthropometric
criteria of ergo refined coconut tree climbing device
dimensions of agricultural workers of Tamil Nadu
considered are furnished in Table 3. The tree holding
section with triangular gripping aids was replaced with
telescopic ‘I’ section and ‘U’ shaped gripping member.
The ‘U’ shaped member with single gripping aid encircles
the girth of coconut tree aiding in gripping the tree trunk
rigidly. Initially the upper frame is fitted in an inclined
position towards the trunk of the tree. As the user
ascends the tree with decrease in diameter, the upper
frame becomes exactly horizontal and parallel to the
ground. This prevents shifting of center gravity of user to
unsafe position and ensures stability. Back rest was also
provided for user safety purpose. The ergo refined tree
climbing device (T2) is shown in Figure 5. The centre of
gravity of T1 and T2 trees climbing device is shown in
Figure 6.
Evaluation of ergonomic parameters
Ergonomic evaluation was carried out on both T1 and T2
model. The trials were conducted between 7.00 AM to
5.00 PM with twelve plantation workers. The temperature
5536
Afr. J. Agric. Res.
Figure 6. The whole body CG of T1 and T2 model located by segmental method.
Table 4. Ergonomic parameters of T1 and T2 models.
S/N
i
ii
iii
iv
v
vi
vii
viii
Parameters
Heart rate (beats min-1)
Energy expenditure (kJ min-1)
-1
Work pulse (∆H) (beats min )
Grading of energy cost
ODR
Over all safety rating (OSR)
Ease of operation rating (OER)
BPDS
T2 model
138.1
28.6
51.8
Heavy
5.6
6.9
5.9
41
T1 model
127.3
25.1
43.8
Heavy
5.0
6.4
3.8
34
Table 5. Cost economic of coconut tree climbing and harvesting.
S/N
i
ii
iii
iv
v
vi
vii
Parameters
Harvesting capacity (number of coconuts hr-1)
-1
Cost of harvesting (Rs. nut )
Savings in cost of harvesting coconut with ergo refined unit (%)
Total number of trees per ha
-1
Total time required for climbing and harvesting coconut per ha hr
Time required for climbing and harvesting coconut in one tree (min)
Savings in time of harvesting coconut with ergo refined unit (%)
and relative humidity varied from 28 to 32°C and 56 to
65% respectively during the period of evaluation. The
comparison of T1 and T2 models values are furnished in
Table 4. Among the two models of coconut tree climbers,
T2 model recorded the lower value of physiological cost
and reduced discomfort and higher values of safety and
ease of operation when compared to T1. The energy
expenditure in terms of VO2 max for T1 and T2 models are
shown in Figure 6.
Coconut tree climbing device
T2
T1
56
44
0.75
0.95
20.6
178
178
13.35
15.13
4.5
5.1
11.8
Costs and benefits analysis
Ergonomics-costs and benefits
The effectiveness of harvesting coconut using ergo
refined coconut tree climbing device in terms of savings
in cost and time is compared with initial coconut tree
climbing device. The values are furnished in Table 5. The
ergo refined (T2) device resulted in 20.6% saving in cost
Mohankumar et al.
and 11.8% saving in time of climbing and harvesting
coconut when compared with T1 model.
Conclusion
Among the developed two models of coconut tree
climbing devices, T2 model recorded the lower value of
physiological cost and reduced discomfort and higher
values of safety and ease of operation when compared to
T1 model. The ergo refined coconut tree climbing device
(T2) enhanced the comfort and safety of male subjects
with 8.5, 14.2, 14.2, 14.2, 18.3, 11.4 and 21.3% reduction
in heart rate, oxygen consumption, energy expenditure,
acceptable work load, limit of continuous performance,
overall discomfort rating and body part discomfort score
respectively and 2.6 and 4.1% increase in overall safety
and ease of operation rating respectively when compared
to T1 model.
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Medical Emergencies, Body Mass Index and Occupational Marks: A
Quantitative and Survey Study. J. Clin. Diagn. Res. 6(1):57-60.
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