In this study a favorable relationship between Lawn mower, environment and the operator’s comfort is examined. An anthropometric survey was conducted to determine the anthropometric data in order to reduce stresses of the lawn mower operators in Rivers State, Nigeria. To achieve this, measurements of randomly selected 10 mower operators within ages of 21 to 45 including students both males and females were taken and the parameters were analyzed. The results of the 5th and 9th percentile were discussed. The average age of operator was 38 years, body weight was 67 kg, functional leg height was 846 mm, Arm reach length was 558 mm and Chest expansion was 380 mm. The average comfort rating from 10 points scales for 5th and 95th percentile were 8.3 and 9.1 respectively for comfortable operations. These values when strictly adhered to by the designer will ensure comfort ability and reduce physical stress of lawn mower operators

1. http://www.iaeme.com/IJARET/index.asp 43 editor@iaeme.com
International Journal of Advanced Research in Engineering and Technology
(IJARET)
Volume 6, Issue 7, Jul 2015, pp. 43-51, Article ID: IJARET_06_07_007
Available online at
http://www.iaeme.com/IJARET/issues.asp?JTypeIJARET&VType=6&IType=7
ISSN Print: 0976-6480 and ISSN Online: 0976-6499
© IAEME Publication
___________________________________________________________________________
ERGONOMIC EVALUATION OF LAWN
MOWER OPERATION FOR COMFORT IN
RIVERS STATE, NIGERIA
S. O. Nkakini
Department of Agricultural/Environmental Engineering, Faculty of Engineering,
P. M. B. 5080, Rivers State University of science and Technology Port-Harcourt,
Nigeria
Ndor. M. Vurasi
Department of Mechanical Engineering,
Rivers State University of Science and Technology, Port Harcourt, Nigeria
ABSTRACT
In this study a favorable relationship between Lawn mower, environment and
the operator’s comfort is examined. An anthropometric survey was conducted to
determine the anthropometric data in order to reduce stresses of the lawn mower
operators in Rivers State, Nigeria. To achieve this, measurements of randomly
selected 10 mower operators within ages of 21 to 45 including students both males
and females were taken and the parameters were analyzed. The results of the 5th
and 9th percentile were discussed. The average age of operator was 38 years,
body weight was 67 kg, functional leg height was 846 mm, Arm reach length was
558 mm and Chest expansion was 380 mm. The average comfort rating from 10
points scales for 5th and 95th percentile were 8.3 and 9.1 respectively for
comfortable operations. These values when strictly adhered to by the designer will
ensure comfort ability and reduce physical stress of lawn mower operators.
Key words: Ergonomic Data, Anthropometric Data, Operator’s Comfort,
Operators, Chest Expansion and Lawn Mower.
Cite this Article: Nkakini, S. O. and Vurasi, N. M.. Ergonomic Evaluation of
Lawn Mower Operation for Comfort in Rivers State, Nigeria. International
Journal of Advanced Research in Engineering and Technology, 6(7), 2015, pp.
43-51.
http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=6&IType=7
_____________________________________________________________________
1. INTRODUCTION
In human factor or biomechanics engineering otherwise known as ergonomics, stress
free operation and comfort of the lawn mower operators in relation to his environment
IJARET

2. S. O. Nkakini and Ndor. M. Vurasi
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are determined and evaluated. A lawn mower is a mechanical device that uses
revolving blade or blades to share a lawn at an even length. Lawn mower which
employs a blade that rotates about a vertical axis are known as rotary mower, while
those employing blades assembly and rotate about a horizontal axis are known as
cylindrical or reel mowers.
In the Niger Delta region, there is incessant rainfall leading to fast growing tall
grasses which tends to keep our environments bushy, dirty and unhygienic [1]. This
adversely affects farmers and inhabitants of the envirous and is exposed to the danger
of reptiles and mosquitoes breeding in our environment.
The lawn mower mostly used in cutting grasses and aesthetics of our residential
environments, has its ergonomics consideration focused on health, safety and comfort
of the operators which leads to effectiveness and efficiency in mowing operations.
Considering the ergonomic point of view of a mower, it is imperative to initially study
the functionability, stress and risk free implement. This becomes a proper procedure
to evaluating the discomfort, injuries and other inconveniences that might be caused
to the operators leading to extreme danger to the operators.
Lawns clearing operation is done in gardens and the surroundings to ensure
environmental sustainability and cleanliness. Manual lawn clearing operation involves
the use of axes, machetes, brush hooks, power saws, sickle, which seems boring,
cumbersome, stressful and most times inflate injuries to the operator. This manual
grass cutting method is expensive, more time and energy expended.
The first designed lawn mower was the mechanical type, based on cutting tools
used for uniform trimming of carpets [2]. It was a reel-type mower that had series of
blades arranged in cylindrical form. He further reported that various kinds of mowers
such as engine powered, gasoline and steam-powered lawn mower operated with
petrol and paraffin as fuel were earlier manufactured by designers. Most rotary push
mowers are powered by internal combustion engines, of two or four-stroke cycle
engines with petrol or other liquid fuels. Their powers range from 2–7 hp (1.5–6.75
KW). Their engines are usually carbureted and required a manual pull crank to start,
though some models had electric starters. An engine powered lawn mower, was
designed and fabricated by Okoro [3] a research student, but did not consider
ergonomically factors for operators comfort. Study had shown that some mowers
produce the some amounts of pollutants which were four times the amount from a car
per hour. A significant noise pollution causing hearing loss if used without ear
protection was generated from mowers.
Hansson [4] stated that man-machine relationship must be studied using
anthropometric and ergonomic principles to improve efficiency of machine, reduce
risks and enhance operator’s comfort as cited by Nkakini [5]. McCormick [6]
discovered that poorly designed operating arm and leg of machines contributes to
muscle fatigue and discomfort in operation. Yiljep [7] revealed that in Nigeria, most
of the simple agricultural machines and equipment are produced by artisans and do
not consider anthropometric data in their design and fabrication.
It is imperative to know that poor posture and tool design can increase the
discomfort of both the healthy and less fit individuals [8]. It is essential that working
equipment be designed ergonomically and be user friendly, if the health, safety, well
being and improvement in the quality of work life and higher productivity be ensured
[9]. Several researchers, like Mishra et al. [10] had stated that the ergonomically
improved sickle resulted in higher field capacity than simple sickle because of less
required pushing force and reduction in drudgery by using serrated sickle. The

3. Ergonomic Evaluation of Lawn Mower Operation for Comfort in Rivers State, Nigeria
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prevention or control of vibration in machine is an important ergonomic consideration
against ill-health of mower operator. He further stated that fluctuating stresses by
vibration also caused fatigue failure [11].
The use of manual cutlasses and other locally manufactured implements is not
only inefficient but very tedious, strenuous, time consuming and low output which
causes delay in handling large area of land [12]. Furthermore, the users of these
implements are often exposed to arm pains, muscular disorder and blisters on their
palms being caused during the operational exercise. Many are prone to backache as a
result of bending for a long time.
In an attempt to proffer solution to these problems ergonomic design
consideration becomes necessary. Thus, the ergonomic evaluation of Lawn Mowers
was carried out, taken cognizance of anthropometry of the human body. However,
Mganilwa et al [13] as cited by Nkakini et al [14] stated that anthropometry is
basically the listing of data and information due to variation in human body sizes,
weights, strength and shapes. Weights and statures were taken because they form a set
of useful basic body descriptions allowing the data set to be compared to others [15].
To proffer solutions to remedy the problems associated with the operators of the
Lawn mower, ergonomics considerations of the operators were considered.
Subsequently, in an article by Carlos [2] it was stated that the use of ergonomics
techniques avoid misleading in the machine operations, facilitates its maintenance and
improves the safety and security of its operator. Lawn maintenances remain the most
important constrains to keeping a clean and fresh looking gardens and environments.
In view of the literatures reviewed, it is clear that much has not been done to
ascertain ergonomic or comfort considerations of the lawn mowers operator especially
the locally fabricated mowers.
Thus, the objective of this research is to evaluate human factors, comfort, safety
and efficiency of the lawn mower operator.
2. MATERIALS AND METHODS
Site selection: The experimental test was conducted at the field between Faculty of
Engineering car park and ICT, Rivers State University of Science and Technology,
Port Harcourt.
Description of Lawn Mower : The engine powered Lawn Mower used for this
research consists of the following functional parts: The Frame, Mower pan, Engine,
Rotary blade, Drive wheels ,Chassis, Axle, Cutting depth adjuster, Handle bar
Frame: The Frame is a supportive component to the pan which has a lifting screw for
adjustment and other parts are fastened to it. It is made of cast aluminum sheet or
plate. It is designed to withstand different working conditions of vibration, stress and
other hazard during operation.
The Mower pan: The Pan of the mower serves as the housing to the rotary blades. It
protects sand, grass and other impediments from having contact with the operator
during operation.
The Engine: The engine supplies power required to drive the machine. It is of small
horse power rating due to the small nature of the machine.
Rotary blade: The main function of the blade is to cut the grasses. However, the size
and cutting efficiency of the mower depends on the blade quality.
Drive wheel: The mower consists of 4-wheels arranged in order of two rear and two
front wheels of various sizes which makes mobility easy during operation. It protects

4. S. O. Nkakini and Ndor. M. Vurasi
http://www.iaeme.com/IJARET/index.asp 46 editor@iaeme.com
sand, grass and other impediments from having contact with the operator during
operation.
Axle: The axle consists of front and rear axles that support the wheel for movement.
Cutting depth adjuster: The Cutting depth adjuster made adjustment either by
increasing or decreasing the depth of cut of the machine. It operates with the principle
of screw jack and it is made up of pipe and screw device.
Handle bar: This is made up of pipe and serves as component where the operator
places his hands and directs the machine to his desired direction. Its inclination is in
accordance to operators’ position during operation.
Test procedures: An anthropometric and ergonomic data were obtained from 10
randomly selected people males and females in the Department of
Agric/Environmental Engineering and campus lawn mower operators. The ages were
selected at random ranging from 21 – 45 years. The type of grasses grown and the
average height of grasses population were noted. Times of operation were recorded
before and after the exercise. An area of 50 m × 25 m was mapped on this field. Lawn
mowing operation was carried out by each of the participating operators involved in
the procedure [16]. The instruments used to carry out the field test are: Engine
powered Lawn Mower, Measuring tapes, Bathroom scale. Plate 1, shows the engine
powered Lawn Mower used for the field experiment.
Plate 1 Field operation of the Lawn Mower
Figure 1 shows the body dimensions of selected Anthropometric variables. The
anthropometric measurements of operators include: 1)Standing height (mm), 2) Chest
expansion (mm), 3) Arm reach (mm), 4)Functional leg height (mm), 5) Body weight
(kg), and Age (yr),

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At the end of the operation, each of the operators gave information concerning
comfort rating within the range 0 to 10 i.e. uncomfortable to very comfortable rating.
Based on their comfort ratings the comfort scale –10point scale was obtained from the
answers given by the operators
Figure 1 Body dimensions of selected Anthropometric variables.
Figure 2 shows the components of the Lawn mower which are as follows: (1)
handle bar (2) drive wheel (3) engine (4) rotary blade (5) mower pan (6) depth
adjuster
5
4
6
2
3
1
Figure 2 Experimental Lawn Mower
Statistical Analysis: The data were statistically analyzed using arithmetic mean and
percentile calculations.
Arithmetic Mean 11
1
1
1
1 xf
n
f
f
n
i
n
i
X
∑
∑
∑ ==
−
=×=
where;

6. S. O. Nkakini and Ndor. M. Vurasi
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X
−
= Mean Notation
n = Total Frequency
1x = The class mid-point
1f = Frequency of the ith class
Percentile












−+= 11
1
11
100
PF
fP
N
LP
where
1L = The LCB of the ith percentile class
F1 P1 = Cumulative frequency immediately before the ith percentile class
N = Total frequency
1fP = Frequency in the ith percentile class
2. RESULTS AND DISCUSSION
To evaluate the lawn mower through ergonomic point of view, 10 respondents in the
age group of 21- 45 years were selected at random and average age of the respondents
engaged in the mowing operations was 31 years, standing height 1510 mm, body
weight 169 kg, chest expansion 375 mm, arm reach length 607 mm and functional leg
height 849 mm, respectively(Table 1). Table 1, depicts the anthropometric data for the
operators, in respect to their ages and various anthropometric parameters.
Table 1 Shows anthropometric parameters for the operators
Number
of persons
(n)
Age
(yr)
Standing
height
(mm)
Body
weight
(kg)
Chest
expansion
(mm)
Arm
reach
length
(mm)
Functional leg
height (mm)
1 34 1650 550 300 620 900
2 41 1520 630 420 600 870
3 30 1300 60 350 550 760
4 21 1340 50 270 550 750
5 45 1600 70 440 600 900
6 27 1500 55 380 640 850
7 24 1350 65 420 500 700
8 29 1450 68 320 650 830
9 28 1800 69 450 740 1050
10 32 1590 75 400 620 880
Mean 31 1510 169 375 607 849
Table 2 shows the average percentile for all the operators’ ages and their
dimensional elements. The average percentile of operators’ ages was 38 years,
measured standing height 1614 mm, body weight 67 kg, functional leg height 846
mm, arm length 558 mm and chest expansion 380 mm.

7. Ergonomic Evaluation of Lawn Mower Operation for Comfort in Rivers State, Nigeria
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Table 2 Anthropometric data showing 5th, 50th and 95th Percentile for lawn mower
operators.
Table 3 shows the difference between 5th and 95th percentile of the dimensional
element as age 2 years, body weight 20 kg, functional leg height 20 mm, arm length
120 mm, chest expansion 100 mm and that of standing height 60 mm.
Table 3 Shows differences between 5th and 95th Percentile
Dimensional Elements
5th
Percentile
95th
Percentile
Difference Between 5th
and 9th Percentile
Age (yr) 35 33 2
Body Weight(kg) 55.5 75.5 20
Functional Leg Height (mm) 900.5 880.5 20
Arm Reach Length (mm) 620.5 500.5 120
Chest Expansion (mm) 300.5 400.5 100
Standing Height (mm) 1650.5 1590.5 60
Comfort rating: At the end of each operation, operators were asked on their
respective feeling (otherwise known as comfort rating) within the range of 0 to 10
point scale (uncomfortable to very comfortable), of their individual reactions to
handle bar, drive wheel and depth adjuster. Based on this comfort rating, the comfort
scale -10 point scale was obtained from the answers given by the operators.
Table 4, describes basically the average 5th and 95th percentile to be 8.3 and 9.1
respectively on 10 points scale operation. It is also shown on the table average
difference between 95th
and 5th
percentiles as 0.8. Operators’ anthropometric
parameters were obtained and analyzed for average 5th, 50th and 95th percentile
distribution.
Table 4 Comfort Rating values for Lawn operation control at 10 points scale
Dimensional elements
Value of 5th
Percentile
Value of
50th
Percentile
Value of
95th
Percentile
Diff. between 95th
and 5th Percentile
Handle bar 8.5 9.0 9.5 1.0
Drive wheel 8.5 9.0 9.5 1.0
Depth adjuster 8.0 8.0 8.5 0.5
Average 8.3 8.6 9.1 0.8
The ergonomic parameters for the lawn mower are indicated in Table 5, and all
the functional values are in millimeters (mm) and the weight in (kg). The study of
Dimensional Elements
Value of
5th
Percentile
Value of 50th
Percentile
Value of
95th
Percentile
Average
Percentile
Age (Yr) 34.5 46 32.5 38
Standing Height (mm) 1650.5 1601 1590.5 1614
Body Weight (Kg) 55.5 71 75.5 67
Functional Leg Height (mm) 900.5 756 880.5 846
Arm Reach Length (mm) 620.5 552 500.5 558
Chest Expansion (mm) 300.5 441 400.5 380

8. S. O. Nkakini and Ndor. M. Vurasi
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ergonomics in the design and manufacture of the lawn mower has fostered the
required knowledge in man-lawn mower relationship (MLR). Also the ergonomic
data for the functional parts of experimental lawn mower were obtained and found
suitable for design of lawn mower for operator’s comfort.
Table 5 Ergonomic data for lawn mower functional parts
Dimensional Element Ergonomic specification
Length of Handle bar (mm) 7500
Length of Mower pan (mm) 6000
Width of Mower pan (mm) 4500
Weight of the Mower (kg) 60
The results shown indicate that ergonomic should be part of the design and
development process of the mower in order to ensure safety, comfort and optimize
performance efficiency.
4. CONCLUSION
This study reveals that the data obtained be used for design of a lawn mower. This is
to reduce physical and mental stresses and improve comfort in operation. The results
obtained indicated that average percentile operators’ age 38 years, body weight 67 kg,
functional leg height 846 mm, arm reach length 558 mm, chest expansion 380 mm
and standing height 1614 mm. In conducting the experiment, it was observed that the
engine was over loaded as a result of tall grasses being common in the south-south
deltaic terrain of the country where there is incessant rainfall. An investigation in this
study proved that lawn mower operators experienced discomfort on their shoulders,
necks, backs (spinal cord) and in their kneels, during operation. To ensure efficiency,
the mower should be designed based on these values obtained.
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