Sh. Sedighi; D. Kalantari; J. Rédl
Abstract
IntroductionThe most important adverse effects of noise on humans have reduced work efficiency and physiological damaging effects such as increased heart rate, high blood pressure, permanent and temporary hearing loss, impaired vision, disrupting the body's balance system, causing nervous disorders and ...
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IntroductionThe most important adverse effects of noise on humans have reduced work efficiency and physiological damaging effects such as increased heart rate, high blood pressure, permanent and temporary hearing loss, impaired vision, disrupting the body's balance system, causing nervous disorders and even nervous disorders. Much of the occupational disturbance is due to acoustic vibrations in agricultural mechanization, which is affecting a large number of farmers. In this regard, most of the noise and vibration come from two-stroke or four-stroke engines that are used in lawn mowers, sprayers, pits and more. These high-vibration equipment causes a great deal of damage to their operators. Portable lawn mowers are popular for working in urban and rural areas due to their low cost, low maintenance cost, high maneuverability and affordability. Therefore, the possibility of optimizing the muffler of a small combustion engine for a lawn mower was investigated and studied in the present stud.Materials and MethodsTo optimize the existing muffler, geometry of the factory muffler was first redesigned in solidworks 2014 software. Then the optimized muffler, along with the factory muffler exported into ANSYS CFX software and simulated in terms of velocity and pressure distributions. To evaluate the built muffler and compare its performance with the factory standard muffler, the mufflers were then mounted on a DOMA’s lawnmower model WPGD501 with a 42 cm3 engine volume and tested outdoors in a radius of 5 m. All sound recording tests were performed in steady state at a distance of 1m with a 45° angle and position along the exhaust outlet to reconstruct the user's ear position. A digital thermometer TEM-8820 and a PSA-V01 digital barometer were used to measure the sound pressure and an environment temperature.Results and DiscussionThe results showed that at 3000 rpm, the sound pressure level of the modified muffler decreased by 6.4% compared to the modified muffler. The same decrease in sound pressure level was achieved at 5000 rpm, equal to 4.5%. The results of this study showed that with increasing engine speed, pressure changes in the muffler had an upward trend. These changes in the modified muffler increased by 0.02 kPa at 3000 rpm and by 0.07 kPa at 5000 rpm. According to the outputs of the FFT diagrams, the intensity and amplitude of the output frequencies from the modified muffler significantly decreased almost at most frequencies. Therefore, effective pressure difference (ΔPrms) was used for the further investigations. The results of this study showed that the pressure changes in the muffler had an upward trend with increasing the engine speed. These changes in the modified muffler increased by 0.02 kPa at 3000 rpm and by 0.07 kPa at 5000 rpm.ConclusionAccording to the results of the present study, by optimizing the internal muffler geometry of the lawn-mowers by installing internal blades and neutralizing the sound intensity inside the muffler, it is possible to reduce the sound pressure level by 4% to about 7% over the original muffler. It is a very simple and inexpensive method for the manufacturers of such engines.
M. A. Rostami; A. Javadi; M. Heidari Soltanabadi; A. Mehdinia; M. Shaker
Abstract
Introduction: Different models of tractors have been imported from foreign countries or assembled in Iran for many years. Consistency of foreign manufactured products with native specifications and the improvement of locally manufactured tractors are important problems that must be considered. Moreover, ...
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Introduction: Different models of tractors have been imported from foreign countries or assembled in Iran for many years. Consistency of foreign manufactured products with native specifications and the improvement of locally manufactured tractors are important problems that must be considered. Moreover, tractor dimensions, sitting space and some other important factors such as the ability of Iranian users to operate them must be taken into consideration. In this study, we surveyed the proper proportion of tractors dimension, location of control tools and driver’s work space, with Iranian users’ anthropometric data of drivers from five provinces. Human factors are of paramount importance in developing farm machinery given that these machines will often be operated by persons with minimum skills. Therefore, farm machinery should be made simple to operate and as free from hazards as possible.
Materials and methods: Firstly, the anthropometric data for 250 users 20-60 years old was calculated. The drivers were selected randomly. Then the specifications of 4 tractors including: Ferguson 285, Ferguson 399, Valtra and New Holland were compared with the anthropometric data of user in 5th and 95th percentile value and their adaptation was studied. Anthropometric Data of subjects consisted of: standing height, full hand length, popliteal length, seat pan width, seat pan depth, elbow height, seat back support height, hand pan width, hand grip and full-leg length. Getting on the tractor is the first contact of an operator with a tractor. In assessing the suitability of the provision made for getting on the tractor, an experiment was arranged in which operators tried to get on 3 tractors. The mode of getting on the tractors, the agony on the operator’s face, the muscular reactions and individual opinion on the difficulties or comfort while undertaking the task were observed and recorded. The specifications of tractors compared with Anthropometric Data were measured, whiles the tractors were positioned on a level ground for measurements after the tires had been ganged. These specifications were tractor height, steering wheel height, footrest height, foot set height; tractor seat geometry as seat pan width, seat pan depth and seat pan support height; steering geometry as distance of steering wheel from seat reference point, steering wheel radius, steering wheel thickness, steering wheel inclination to the horizontal and seat reach adjustment; levers and pedals distance from seat reference point as gear lever, parking brake lever, hydraulic control lever, clutch pedal, accelerator pedal, brake pedal, front panel, workspace width and workspace length.
Results and Discussion: The experiment that was conducted with operators attempting to get on the tractors indicated that tractor steps heights were higher than the desirable limit. Therefore, based on the ideas of the researcher and tractors drivers, getting on all tractors is difficult. With an increase in the number of steps or a decrease in their heights, the desirable condition can be created. Seat depth of new Holland and Valtra tractors were great for drivers in the 5th percentile value. A variable thickness pad can solve this problem. Results of studies indicated that Seat depth of Massey Ferguson 285 and 399 was shorter than driver’s leg length of 95th percentile value. To solve the problem an increase of 10 centimeters to pad height of these tractors was suggested. Seat pad of tractors were short for drivers in the 95th percentile value. Distance of steering wheel from seat reference point (SRP) in Massey Ferguson 285 and Valtra was further than drivers hand length in the 5th percentile value. Therefore, the drivers hand is short for driver’s good operation. Surveys indicated that drivers had problems for gear lever access in Massey Ferguson 399. Therefore, for good access on gear lever we must increase seat stroke range by 5-10 centimeters. The record available from Meteorological Organization indicated that air temperature and rain throughout the year in the study area is between 20 to 40degrees Celsius and 100to 300mm change. Valtra and New Holland tractors having a driver cabs with heating and cooling equipment have the ideal space for the performance of their driver. Massey Ferguson 285 tractor does not have any driver cab and Roll Over Protection Structure (ROPS).
Conclusions: This research was conducted in five provinces of Iran to assess ergonomics of some commonly and new used tractors in Iran containing Ferguson 285, Ferguson 399, Valtra and New Holland. As there was no data base with required details, data was collected directly by personal contact with tractor users. A questionnaire was filled out for each person and anthropometric data was calculated in all provinces for 250 users 20-60 year old that were selected at random. Then relevant specifications of 4 tractors were measured and compared with the relevant anthropometric data of users in the 5th and 95th percentile value and their adaptation was studied. The results indicated that tractor steps, Seat depth, distance of steering wheel and distance of some levers and pedals from seat reference point should be amended.
