2. Content
➢ Introduction
➢ Types of Tractor Vibration
➢ Effect of Vibration
➢ Subject Response to WB Vibration
➢ Vibration Evaluation
➢ Prediction of Tractor Ride Vibration
➢ Improving Operator Comfort
➢ References
3. Introduction
➢ Vibration occurs in all moving bodies and tractors are no exception
➢ The frequency range of 2-6 Hz has been observed to be the most harmful for the
human operator
➢ Suspended seats fitted to most
➢ Tractors reduce the vertical component of vibration, but the levels are still
undesirably high
➢ Introducing wheel suspension makes the system complicated and costly
➢ Cab suspension is another method of reducing ride vibration which is almost as
expensive as wheel suspension
➢ The objective of this review is to collect information regarding tractor vibration and
research work done to date to reduce it at the operator's level
4. Types of Tractor Vibration
➢ Vibrations primarily are of two types: sinusoidal
and random
➢ Sinusoidal vibration is regular in nature and
predictable
➢ Random vibration is irregular and unpredictable.
➢ The mechanical vibrations that affect the human
body can be grouped into two directional
vibrations, i.e. rectilinear and rotational
➢ The rotational mode of vibration does not usually
cause much discomfort but over rough terrain
region more disturbing than rectilinear vibrations.
Directions of basicentric coordinate system for
mechanical vibrations influencing the human body
5. Effect of Vibration
➢ Physiological effect
○ The transmission of excessively large forces to the body.
○ Pressure exerted over a long period of time can cut off blood supply to the tissue and
cause mechanical damage
○ Buttock problem while sitting for extended time periods
➢ Health effect of whole body vibrations
➢ Performance effects of vibration
6. Subject Response to WB Vibration
Equal sensation contours produced in the
laboratory by different investigators.
7. Vibration Evaluation
➢ Four physical factors of primary
importance in determining the human
response to vibration - namely
intensity, frequency, direction and the
duration of the vibration
➢ In the practical evaluation of any
vibration, physical description can be
given in terms of above 4 factors
○ Fatigue-decreased proficiency
○ Exposure limit
○ Reduced comfort boundary Vertical (az) acceleration limits as a function of
frequency and exposure time: fatigue-decreased
proficiency boundary
8. Prediction of Tractor Ride Vibration
Transverse (ax, ay) acceleration limits as a function
of frequency and exposure time: fatigue decreased
proficiency boundary
➢ Several studies have simulated the ride
vibration characteristics of unsuspended
tractors.
➢ very few cases simulations have been tested
against measured results
➢ Dale has described a linear frequency
domain simulation based on a rigid body
tractor with a pivoted front axle and linear
tyre characteristics
➢ Crolla etal. showed that root mean square
(rms) accelerations in excess of 40% are not
unusual, and that, for some tractors
9. Improving Operator Comfort
➢ Suspended seat with Fixed OOS
➢ Suspended Seat with Suspended OOS
➢ Suspended Seat with Fixed Cab
➢ Suspended Seat with Suspended Cab
Mechanical model of seat with the operator as a single
degree damped spring mass system
Two degrees of freedom model of a
suspension seat + Cab
10. References
➢ https://www.researchgate.net/publication/222329289_Tractor_ride_vibr
ation-A_review by NIRANJAN PRASAD*, V. K. TEWARI* and RAJVIR YADAV*
➢ https://png.toolxox.com/kidp?p=iwRxhh_old-tractor-clipart-antique-
tractor-clipart-black-and/ - Page 1
➢ https://www.researchgate.net/figure/Resonance-frequencies-of-human-
body-organs_tbl1_274471590 - Page 6
➢ https://www.deere.com/en/tractors/utility-tractors/5-family-utility-
tractors/ - Page 9
