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OJHAS Vol. 9, Issue 2:
(2010 Apr-Jun) |
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| Study of vibration and its
effect on health of the motorcycle rider |
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Shivakumara BS, Asst. Prof., in I & P Engineering, PES College of Engineering, Mandya - 571401, India,
Sridhar V, Professor, P.E.S College of
Engineering Mandya-571401, India. |
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Address For Correspondence |
Asst. Prof., in I & P Engineering,
PES College of Engineering,
Mandya - 571401, India.
E-mail:
shivakumarabs@gmail.com |
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Shivakumara BS, Sridhar V. Study of vibration and its
effect on health of the motorcycle rider. Online J Health Allied Scs.
2010;9(2):9 |
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Submitted: Apr 12, 2010;
Suggested revision:
Jul 13, 2010; Resubmitted: July 20, 2010; Accepted: July 25, 2010; Published: Jul 30, 2010 |
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| Abstract: |
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The motorcycle riders are subjected
to extreme vibrations due to the vibrations of its engine, improper structural
design of the motorcycle and the bad road conditions. The literature review
reveals that the vibrations are most hazardous to the health if it exceeds the
limit. The experiments were conducted to measure the magnitude of the
vibrations acting on the rider during motorcycle riding under various road
conditions. Experimental values of accelerations and frequencies which are
beyond permissible limits according to the literature confirm
that vibration certainly affects health of the motorcycle rider.
Key Words: Health, Motorcycle
rider, Vibration
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The majority population
in India is depends on motorcycles for their transportation due to economic
reasons. The vibration is common in most of the machine tools and it is more in
the motorcycle because of its dynamic nature. Vibration energy waves transferred into the body
of the rider are transmitted through the body tissues, organs and systems of
the individual causing various effects on the structures within the body before
it is dampened and dissipated.
On the other
hand, the health problems are also increasing and the rate of patient
population is growing at 14% per year.(1) In this context, it is essential to
identify whether there is any relation between the health problems of the
people and vibration of the motorcycles they are riding.
Hence,
the objectives of this paper are to study the:
- Vibration and its effect on health.
- Effect of vibration on driver/rider
- Measurement of magnitudes of vibration in
motorcycles while riding
Vibration
and its effect on health:
Vibration is defined as the oscillation of a
body about a reference position and can be described in terms of amplitude and
frequency. The factors such as ergonomic design, damping and attenuation,
resonance and many more have a great influence on the exposure characteristics
and intensity levels of vibration exposure experienced by machine
operators. The human body can tolerate
certain levels of vibrational energy but starts to deteriorate & cause
long-term damage and disruption of the natural processes of the body.(2)
The frequency of vibration and its affects on the human body are depicted in the Table 1.[3,4]
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Table 1: Frequency of vibration and its affects on the human body |
| Frequency of vibration |
Types of effect |
| Below 1 Hz |
Motion
sickness |
| 3.5 to 6 Hz |
Alerting
effect |
| 4 to 10 Hz |
Chest
and abdomen pain |
| Around 5 Hz |
Degrades
manual actions |
| 7 to 20 Hz |
Communication
Problems |
| 8 to 10 Hz |
Back
ache |
| 10 to 20 Hz |
Intestine
and Bladder pain |
| 10 to 30 Hz |
Degrades
manual and visual controls |
| 10 to 90 Hz
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Degrades
visual actions |
According
to the Health guidance zones specified by ISO 2631-1, 1997 the impact of the
vibration on the health of a worker depends on weighted rms acceleration and
exposure duration/ day.(5)
Three important
factors which decide effects on the health in respect of exposure to vibration are
(6):
- Threshold value or
the amount of vibration exposure that results in no adverse health effects
- Dose-response
relationship i.e., the relationship between severity of the ill-health effects and the amount of exposure
- The latent period
i.e. the time gap between first exposure and appearance of symptoms
Vibration can be classified based on the target on which it effects
as hand arm vibration and whole body vibration.
Hand arm vibration and its effects
Hand arm
vibration (HAV) is vibration transmitted from hand-held equipment such as
jackhammers and steering wheel/ handle bar into the hands and arms of workers.
It leads to vibration induced white finger (VWF). If detected early, this
disease is curable. If not, it can cause permanent disability in the use of the
hands.(4)
Whole body vibration and its effects
Whole body
vibration (WBV) occurs when workers sit or stand on vibrating seats or foot
pedals. Prolonged exposure
to high levels of WBV causes motion sickness, fatigue and headaches. WBV is one
of the strongest risk factors for low back disorders.(7) Vibrations with Less
than 0.315m/s2
are found to be comfortable between 0.315m/s2 and 2.5m/s2 are found to be
uncomfortable greater than 2.5m/s2 are found to be extremely uncomfortable.(5)
Effect of vibrations on health during driving/riding
The drivers of
automobiles are subjected to different magnitude of the vibrations while
driving. The magnitude of the vibration also depends on the type of the
automobile, engine size, body weight, age of the automobile, type of seating,
type of suspension and road surface factors etc.(7) These vibrations are
transmitted to the buttocks and back along the vertical axis via the base and
back of the seat. On the other hand, the pedals and steering handle transmit
additional vibrations to the feet and hands of the rider. During motor cycle
riding, due to its unbalancing nature, it creates enormous vibration and affects
the bioelectric phenomena.
Table 2
depicts ISO standards with respect to the vibration exposure and its effects on
health of the driver/rider.(8)
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Table 2: ISO standards for vibration exposure and its effects on health
of the driver/rider
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Exposure duration in hours
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International
Standard |
| ISO 2631-1, 1997 Average
rms acceleration limits in m/s2 |
| Likely health risk |
Caution zone |
Comfort level |
| 8 |
0.8 |
0.5 |
0.315 |
| 12 |
0.7 |
0.4 |
0.315 |
Physical
factors that influence the effects of vibration on rider during riding are
acceleration and frequency, duration of exposure, automobile maintenance and
protective practices. Biodynamic factors like grip force, position of the
hand/arm relative to the body, texture and type of material of the handle causes
the effect. Individual factors like operators control, automobile speed, and
skill of driving and individual susceptibility to vibration also leads to the
effects.(6)
Hand arm vibration and its effects
Steering wheel vibration levels as high as 1 m/s2 have
been reported in one study. HAV at this level may present a slight risk of
injury considering the long exposure durations of driving. It was also observed
that the rates of finger numbness, finger stiffness, shoulder pain and shoulder
stiffness were significantly higher among traffic motorcyclists as compared with
the control group. The subjects with a lifetime vibration dose of more than 20.1
m2h3/s4 (natural log scale) showed higher prevalence rates for symptoms in the
fingers and shoulders.(9)
Whole body vibration and its effects
Typical whole-body vibration exposure levels of heavy vehicle
drivers are in the range 0.4 - 2.0 m/s2. Vibration is highest in the frequency
range 2 - 4 Hz. For a seated person vibration in the range of 4 to 8 Hz cause
the entire upper torso to resonate and should be reduced and avoided.(7) Health
effects that associated with WBV and especially the driving environment are
piles, high blood pressure, kidney disorders and impotence.
The HAV and WBV accelerations were measured by conducting
experiments using different motorcycles on different roads.
The
acceleration measuring experimental set up is depicted in Fig.1 and consists of:
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One
accelerometer mounted on handle of the motorcycle to measure HAV
acceleration
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Another
accelerometer mounted on seat base of the motorcycle to measure WBV
acceleration
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Instrumentation amplifier with power supply
A lap top
computer to store data of 10000 points scanned per minute. The data stored
in lap top computer were then analyzed using vibration analysis software.The
actual accelerations and frequencies were noted, analyzed and summarized.
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Fig. 1:
Experimental set up to measure HAV and WBV accelerations |
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The 4 types of
motorcycles (Table 3) and 7 types of roads (Table 4) at Mandya city (India) were
selected for experiments.
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Table 3
Motorcycle Specifications
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Specifications |
Type 1 |
Type 2 |
Type 3 |
Type 4 |
| Stroke of engine (petrol) |
Four |
Two |
Two |
Two |
| Capacity in cc |
99 |
125 |
150 |
150 |
| Wheel width in mm |
100 |
90 |
95 |
95 |
| Wheel diameter in mm |
640 |
370 |
480 |
480 |
| Weight in kg |
101 |
85 |
120 |
110 |
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Table 4
Specifications of Road
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Road No |
Average International Roughness Index* in mm/m |
| 1 |
1 |
| 2 |
2 |
| 3 |
3 |
| 4 |
5 |
| 5 |
7 |
| 6 |
10 |
| 7 |
12 |
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*International Roughness Index is the index used to
specify roughness of the road surface. |
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Experimental observations |
The HAV accelerations on different roads are tabulated in Table 5, the graphical illustrations of average HAV
acceleration on different roads are shown in Fig.2 and maximum, minimum and Rms (Root mean square) HAV accelerations on different roads are shown in Fig.3.
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Table 5: HAV acceleration (m/s2)
on different roads |
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Road 1 |
Road 2 |
Road 3 |
Road 4 |
Road 5 |
Road 6 |
Road 7 |
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Ave |
0.003 |
0.006 |
0.007 |
0.009 |
0.011 |
0.013 |
0.014 |
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Maximum |
6 |
12 |
30 |
38 |
52 |
54 |
56 |
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Minimum |
-3 |
-6 |
-12 |
-15 |
-18 |
-21 |
-22 |
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Rms |
1.4 |
1.6 |
1.8 |
2 |
2.2 |
2.4 |
2.6 |
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Fig. 2: Graphical illustration of average HAV
acceleration (m/s2) on different roads |
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Fig. 3: Graphical illustration of maximum, mnimum and Rms
HAV acceleration (m/s2) on different roads |
WBV accelerations on different roads are tabulated in Table 6. The graphical illustrations of average WBV acceleration on
different roads are shown in Fig.4 and maximum, minimum and Rms WBV accelerations on different roads are shown in Fig.5.
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Table 6: WBV acceleration (m/s2) of on different roads
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Road 1 |
Road 2 |
Road 3 |
Road 4 |
Road 5 |
Road 6 |
Road 7 |
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Average |
-0.018 |
-0.019 |
-0.02 |
-0.021 |
-0.022 |
-0.023 |
-0.026 |
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Maximum |
9 |
16 |
30 |
32 |
38 |
40 |
48 |
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Minimum |
-6 |
-13 |
-34 |
-37 |
-37 |
-40 |
-42 |
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Rms |
3.4 |
3.7 |
3.8 |
4 |
4.5 |
4.7 |
5 |
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Fig.4 Graphical illustration of average WBV
acceleration (m/s2) on different roads
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Fig.5 Graphical illustration of maximum, minimum and Rms WBV acceleration (m/s2) on different roads |
The frequency of
both HAV and WBV varies from 1 Hz to 500 Hz while riding. From Fast Fourier
Transform (FFT) analysis it was observed that the maximum HAV acceleration and
maximum WBV acceleration all occurs within the frequency of 30 Hz. Between the
frequency of 250 Hz and 400 Hz, minimum values of HAV acceleration and WBV
acceleration were observed.
Vibration plays a dominant role in creating ill health. The
vibrational energy waves transferred to the body of the exposed operator is
transmitted through the body tissues, organs and systems of the individual
causing various effects on the structures within the body before it is dampened
and dissipated. Different magnitude of frequencies effects human body in
different types. Even to some extent the human body withstands the vibration and
beyond that the health will be affected depending upon the type of vibration,
intensity and duration of the exposure in the lifetime.
The effect of vibration on driver/rider depends upon so many
physical, biodynamic and individual factors. HAV leads to finger numbness &
stiffness and also shoulder pain & stiffness. Further, it leads to
Vibration-induced white finger. WBV is one of the strongest risk factors for low
back disorders. The vibration with acceleration more than 2.5m/s2 is found to be
extremely uncomfortable. But, Long-term vibration exposure (Average acceleration
x Exposure duration) is better indicator of the effects on the health of the
driver/rider.
In the experiments conducted using different motorcycles on
different roads, it was observed that the Rms values of HAV acceleration and WBV
acceleration of all roads 1 to 7 is well above likely health risk level of 0.8
m/s2 (Table 2) considering 8 hours exposure duration. Practically both HAV and
WBV act together while riding. Hence, the effect of sum of Rms values of HAV and
WBV accelerations is to be considered while riding which varies from 4.8 (=1.4
HAV + 3.4 WBV) m/s2to 7.6(=2.6 HAV + 5.0 WBV) m/s2 on roads 1 to 7. These high
magnitudes are dangerous even considering short duration of exposure.
Considering HAV acceleration alone, its value above 1m/s2 is
a slight risk of injury considering the long exposure durations involved in
driving/riding. The observed Rms values of HAV of all roads 1 to 7 (Table 5) is
well above the risk level of 1 m/s2. Similarly, considering the Rms values of
WBV acceleration alone, its value above 2.5m/s2 are found to be extremely
uncomfortable. The observed Rms values of WBV (Table 6) are well above this
uncomfortable level of 2.5 m/s2.
According to literature, frequency up to 90 hz (Table 1) affects human body
in different types. Since, the frequency of both HAV and WBV varies from 1 to
500 hz while riding definitely it will affect the rider depending on duration of
exposure. The low frequency and high acceleration combination creates early
fatigue. FFT analysis showed the occurrence of this in both HAV and WBV cases.
Vibration is a physical disturbance that occurs in machines
and automobiles. The nature of vibration that is present in a vehicle depends
upon the dynamic characteristics of the automobile and road surface characters.
Its effect on the human body depends mainly on the frequency, magnitude,
direction, area of contact and duration of exposure.
Exposure to HAV and WBV will result in transmission of
vibratory energy to the entire body and leads to localized effects. It affects
comfort, normal functioning of the body and health. Exposure to certain
frequencies of vibration may have profound effects on specific systems of the
body depending upon the natural frequencies of it and acceleration of the
vibration at that frequency. The acceleration depending upon its magnitude
and duration of exposure leads to unhealthiness of the human being. The HAV and
WBV accelerations measured on different roads on different motorcycles shows it
is dangerous even considering short duration of riding.
The vibrational effects are more hazardous on motorcyclist.
As for as possible, measures is to be taken to avoid prolonged exposure to
vibration. Also, it is very important to keep the Rms value of HAV acceleration
well below 1m/s2, WBV acceleration within 0.315 m/s2 and total acceleration
within 0.8m/s² as safety standard levels of the vibration. If possible it is
necessary also to avoid vibrational frequency below 90 hz.
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Chent JC et al. Predictors of whole-body vibration levels among
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