مجید رجبی وندچالی

Nowadays, with progress in different sciences and entering logging software and decision-make systems, decision has been deviated from trial and error in agriculture mechanization and aimed to predict prospective and targeted accordingly. Therefore in this research, the Analytic Hierarchy Process (AHP) with the help of EXPERT CHOICE11 software was employed to select the most appropriate hole-digger for usage in gardens. Three different types of hole-diggers including manual hole-digger, hydraulic hole-digger and three point hitch hole-digger were evaluated in this study. The criteria of selection consisted of the device's price, maneuverability in confined space, ergonomics, ease of utilization and work progression. The importance of device's price, maneuverability in confined space, ergonomics, work progression and finally ease of utilization were equal to 0.366, 0.277, 0.168, 0.121 and 0.068, respectively. The manual hole-digger, which is the cheapest type of diggers, is selected and introduced with 0.403 final value among the three types of hole-diggers as the most appropriate choice option. Inconsistency ratio was calculated equal to 0.05 that is acceptable amount in saaty’s opinion.

Nowadays, the best method for fertilizing trees is spot treatment via hole-digger. Conventional mechanical hole-diggers have several drawbacks such as auger’s non-continuous and limited speeds due to using a mechanical gearbox, and risks of getting stuck inside the hole and motor reaction force to the operator. On the other hand, a three-point hitch hole-digger has problems such as the lack of maneuverability in confined spaces and high prices. Meanwhile, preparation of these hole-diggers by most farmers and gardeners has no economic justification. Thus, in this research it has been aimed to handle the mentioned problems and to optimize the working quality of hole-diggers via designing and manufacturing a new hydraulic hole-digger.
To start design the machine, displacement volume and power requirement of the hydro-motor and consequently displacement volume requirement of a hydro-pump were calculated using the appropriate formulas (70.83 cm3, 2.3 kW & 7.5 cm3, respectively). According to available hydro-motors and hydro-pumps in the market and using obtained values of displacement volume, an orbital hydro-motor, BMR-80 model with the maximum torque of 220 N.m and an external gear pump REXPORT-2APF8 with displacement volume of 8 cm3 and flow rate of 12 L.min-1 were chosen. In the following, hydro-pump’s parameters were used to select the internal combustion engine. The engine power requirement was 2.875 kW (3.85 hp); thus according to the available engines in the market, a single cylinder gasoline engine, WX168F-1 model that made in Kato company of China with 6.5 hp power and maximum speed of 3600 rpm was chosen. To transmit the power from the engine to the hydro-pump, a coupling DK-42 model was used. Also, two pressure gauges, LB-250 model with maximum pressure of 250 bars were used in the entrance and the exit of the hydro-motor. An hydraulic oil tank with total volume of 24 liters was made from a sheet metal with thickness of 3 mm. The helical auger used in this research, was made in china by LIONS Company with cone tip, total diameter of 200 mm and pitch of 180 mm. The fabricated digger has a working depth and diameter of 30 cm & 20 cm, respectively; rotational speed between 100-160 rpm and maximum power equal to 6.5 hp. In order to evaluate the stress distribution in the auger set, the static analysis based on maximum dynamic torque exerting on auger’s axle and maximum dynamic force exerting on auger’s blades, was used in SOLIDWORKS 2013 software. The maximum force 214.07 kgf (2100 N) proportional to the maximum exerting torque (210 N.m) from soil to the edge of the auger’s blade were considered in the modelling. Farm experiments were carried out in two citrus gardens with silty-clay and sandy-loam texture based on factorial test in Completely Randomized Design with three replications. Soil moisture content as high and low humidity levels (24.85% and 16.12% in sandy-loam and 25.95% and 16.48% in silty-clay) as the first factor and soil depth as the second factor varied in three levels of low, medium, and high (10, 20 and 30 cm), respectively. The measured parameters consisted of specific fuel consumption, machine efficiency, auger torque, auger power and used energy. To determine the auger’s torque, the oil pressure measurement method with two manometers was used in the entrance and the exit of the hydro-motor. After measuring the time and power needed to dig pits, for determining the used energy, the area under the power-time graph was calculated in Excel software. Also, to determine the fuel consumption during the experiments, the filled fuel tank method was used. Data analysis including analysis of variance (Anova), mean comparisons and interaction between the parameters were performed using the SPSS 22 software.
The numerical stress analysis results of the auger showed that the maximum von - Mises stress is occurred in the position of the blade-auger axis connections, with a magnitude of 86 MPa. The obtained experimental results in this study indicated that influence of soil depth and moisture content on the measured parameters were significant. in both soil textures and the influence of soil moisture on machine efficiency was non-significant in the silty-clay texture. With increasing soil depth, measured parameters excluding machine efficiency were increased in both soil textures. In high depth and also in low moisture, regarding to the increasing soil bulk density and shear strength, more torque was needed for the rotating auger in the soil that this has led to an increasing in specific fuel consumption of the device. Regarding the results obtained in this study, minimum specific fuel consumption value of the device (0.0014 liter pit-1) was obtained at the low working depth (10 cm) and the high soil moisture (25.95%) in the silty-clay soil. The hole-digger working capacity at 30 cm working depth and soil moisture content as high and low humidity levels in silty- clay obtained equal to90 and 88 pits per hour and in sandy-loam obtained equal to 101 and 95 pits per hour, respectively. Also, the maximum device’s power (2.548 kW) occurred in deep soil (30 cm) and low soil moisture in silty-clay texture.
Stress analysis and field qualitative observations results indicated that the fabricated device has sufficient resistance and strength against maximum torque from tested soils. Field evaluation of the fabricated machine showed that pit digging operations in soil is not appropriate in low moisture content because of the high fuel consumption and environmental pollution issues.

Introduction Tillage is a main operation for seedbed preparation and is one of the major items of energy and cost expenditure in crop production. In the conventional rotary tillers, using the L-shape blades has numerous problems such as severe vibrational problems, weeds wrapping around the blades, and lower performance due to the limited power of such small tillers. Therefore in order to overcome the addressed problems, design, fabrication and evaluation of a new rototiller adapted for small farms and gardens were considered in this research.
Materials and Methods To start the design, the power requirement was estimated using a semi-theoretical model for the given working depth, working width, forward and rotational speed of the machine. Then a suitable engine was chosen based on the estimated power. The estimated power was 3.4 kW (4.5 hp); therefore, according to the available engines in the market for single cylinder gasoline engines, a Kato engine with 5.5 hp power and maximum speed of 3600 rpm was chosen. By reducing the rotational speed of the engine in three stages, rotational speed of the rotor was obtained in the range of 140-260 rpm. To transmit the power from the engine to the rotary axis, first, a pulley and belt mechanism (two V-shaped belt, type B) and then two chain mechanisms (roller chains 40 and 60) were used. Rotary axis with the diameter of 2.5 cm was made from steel E295. The fabricated rototiller has a working width of 60 cm, working depth of 7 cm, rotational speed between 140-260 rpm, forward speed equal to the operator’s translational speed, and maximum power equal to 5.5 hp.
The maximum force exerted on each of the blades was calculated equal to 84.10 kgf (824.73 N) using the theoretical approach proposed by Bernacki (1972). In the next step, numerical simulation of blades, flanges and rotating shaft for stress and strain analysis was performed using the Ansys software.
Farm experiments were carried out as split plots in citrus gardens based on randomized complete block design with three replications. The soil moisture content as the main plot varied in two levels (13.5-21.9 and 21.9-30.3 percent based on dry weight) and the rotational speed of blades as subplots varied in three levels (140-170, 170-200 and 200-230 rpm).
The measured parameters consisted of clod mean weight diameter, soil relent percentage, soil bulk density and specific fuel consumption. To determine the diameter of aggregates, a set of standard sieves with the diameter ranging from 0.5 to 8 mm were used. Then a laboratory shaker was used to sift the samples. Each sample was shaken for 30 sec. To determine the fuel consumption during the experiments, the filled fuel tank method was used. Data analyses including analysis of variance (Anova), mean comparisons and interaction between the parameters were performed using the SPSS 16 software.
Results and Discussion The numerical stress analysis of the flange showed that the maximum van - Mises stress occurred in the position of the blade-flange connections, with a magnitude of 52.98 MPa for the given working conditions, including soil engineering properties, working depth and other important parameters. The experimental results obtained in this study indicated that influence of soil moisture and rotational speed of blades on the clod mean weight diameter, soil relent percentage and specific fuel consumption were significant (P<0.01). The clod mean weight diameter was measured equal to 8 mm at high rotational speed (200-230 rpm) and high soil moisture content (21.9%-30.3%) and equal to 15 mm at low rotational speed (140-170 rpm) and low soil moisture content (13.5%- 21.9%). The maximum soil relent percentage was obtained equal to 97% at high rotational speed (200-230 rpm) and high soil moisture content (21.9%-30.3%).
Regarding the results obtained in this study, the specific fuel consumption increased first in a light slop, then in a steep rise with increasing the blades rotational speed. The reason can be the higher relent percent of the soil at higher rotational speeds and higher moisture contents, albeit at the examined range of 21.9-30.3. The specific fuel consumption was maximum at higher soil moisture content, i.e., 30 %. The results indicated that the blades rotational speed and soil moisture content had no significant effect on the field efficiency of the examined rototiller. Reduction of the rotational speed of the rototiller from high-to-moderate speeds yields decreasing the fuel consumption of 17 liter/ha, which could be significant in a wide scale soil tillage operations. As a general result, reduction of the rotational speed has some considerable advantages such as reducing the power requirements, reducing the blade wearing and maintaining the soil structure.
Conclusion The stress analysis of the fabricated machine together with the experimental and field measurements indicated that the new proposed and fabricated blades were a suitable choice for construction of small rototillers. The fabricated machine with the new blades showed some additional advantages including less specific energy consumption, less weeds wrapping around the blades, and less vibrational problems

One of the most important problems arising with operation of the conventional rototillers is severe vibration of the machine handle which is transmitted to the user’s hands, arms and shoulders. Long period exposure of the hand-transmitted vibration may cause various diseases such as white finger syndrome. Therefore in this study, vibrations of a new type of rototiller with ridged blades were investigated at the position of handle/hand interface in different working conditions. Finally, the maximum allowable exposure time to the rototiller users in continuous tillage operation was obtained according to ISO 5349-1.
Experiments were carried out in one of the farms with silty clay soil texture, located in Sari city, Mazandaran province, Iran. Vibration measurements were performed according to ISO 5349-1 and ISO 5349-2 standards in two different modes, including in situ mode and tillage mode. Vibrational parameters were obtained in three blade rotational speeds, i.e., low speed (140-170 rpm), medium speed (170-200), and high speed (200-230). Blade rotational speed varied by changing engine speed using the throttle control lever. In each experiment, different vibrational values were individually recorded in three directions (x, y, and z). Experimental design and data analysis were performed in a Randomized Complete Block Design with three replications using the SPSS16 software.
Based on the obtained results in this study, the RMS of acceleration increased by increasing in rotational speed for all of the conducted experiments. The reason is that number of cutting per unit of time and consequently the frequency of changing in the dynamic forces exerting on the blades dramatically increases with increasing the rotational speed of the blades. Noteworthy is that in most cases the variation of acceleration in the tillage mode showed similar trend with vibrational values in the idling mode. This represents a significant contribution of the combustion engine in vibration of the examined rototiller. Meanwhile, contribution of the engine in the total measured vibration was more than 50% at different rotational speeds and different directions. The minimum engine contribution was measured equal to 56.39% in z-direction at 155 rpm, whereas the maximum engine contribution was observed equal to 79.5%, in x-direction and rotational speed of 215 rpm. These results indicate the importance of selecting a proper combustion engine for reducing the rototiller vibration. It should be noted that the contribution of the engine in total vibration reached its minimum value at the speed related to the maximum generated torque, i.e., 185 rpm of the rotor speed.
This result indicates that using the combustion engine in its optimum speed reduces the entire device vibration in the vertical direction. By increasing the rotational speed of the blades in the y-direction, engine contribution in device vibration showed different trends in compare to the other directions. The most value was equal to 74.25% which was obtained at the rotation speed of 185 rpm. By increasing blade rotational speed from 155 rpm to 215 rpm, the engine contribution in device vibration in the z direction and the total acceleration steadily increased.
With growing mechanization and entering various types of machines to the farm, importance of considerations to human health is also increased, especially in working with rotational machines. Therefore, the current study was undertaken with the specific attention to the rototillers operational vibration at the handle/hand interface. Results of the conducted experiments showed that vibration of the examined rototiller depends more on the operation of the mounted combustion engine, rather than the soil working blades. Therefore, it is suggested to select a higher quality engine with less vibration or isolate the engine from chassis by a damper (such as a compressed rubber) to reduce the vibration transmitted to the operator’s hands and arms.

Nowadays, the world is facing to increasing loss of fossil resources, energy crisis and environmental problems. On the other hand, diesel engines due to wide application in various sectors such as transport, agriculture, industry, etc., are the main sources of emissions and fuel consumption. Accurate measurement of fuel consumption and engine pollution is time-consuming and costly. Hence, the main objective of this study was to develop proper linear regression models of some important performance parameters of ITM285 tractor engine based on engine torque and engine speed. Experiments were carried out in 11 levels of primary engine speed (1063, 1204, 1346, 1488, 1629, 1771, 1818, 1913 and 2054 rpm) by 10 N.m steps of torque from zero (no load) to full load. The measured parameters include fuel consumption mass flow, exhaust temperature, instantaneous engine speed, maximum and mean exhaust opacities. Four different linear regression models were used to estimate the parameters. The results of regression models performance evaluation showed that quadratic model had the highest efficiency and the lowest RMSE for all parameters. The maximum and minimum effects of engine torque were on exhaust temperature and instantaneous engine speed, respectively; while, this result was completely reverse for primary engine speed. The results of regression models evaluation showed a high adaptation between the output of each model and the desired output. Also, the fuel mass flow and exhaust temperature were highly correlated to the maximum and mean exhaust opacity with correlation coefficients of 0.96 and 0.99, respectively.

Recently, employment of rotary tillers has been expanded in gardens and small farms, especially in the northern of Iran. However using the L-shaped blades in the conventional rotary tillers have some problems such as severe vibration problems, weeds stucking around the blades, forming the plow pan and lower performance due to the less powers of such small rototillers. Therefore in order to overcome the above mentioned problems, a rototiller with new ridged blades was designed, fabricated and tested in this research.
Experiments were carried out in one of the citrus orchards in Mazandaran, Sari. The experimental design was split plots based on randomized complete block design with three replications. The soil moisture as main plot varied in two levels of 13.5-21.9 and 21.9-30.3 percent based on dry weight and the rotational speed of blades as subplots varied in three levels of 140-170, 170-200 and 200-230 rpm. The measured parameters consist of soil particle mean weight diameter, soil bulk density, soil crumbling percentage, specific fuel consumption and machine efficiency. The diameter of soil particles was measured using a set of standard sieves with diameter ranging from 0.5 to 8 mm. Then a laboratory shaker was used to sift the samples. Each sample was shaken in 30 sec. The fuel consumption during the experiments was determined by the filled fuel tank method. Analysis of variance (ANOVA) and mean comparisons and interaction between the parameters were performed using the SPSS 16 software.
The results indicated that the soil particle mean weight diameter reduced by increasing blades rotational speed in both examined soil moisture contents. Results indicated that the soil crumbling percent increases with increasing the rotational speed. The main reason for this effect could be due to the more energy transferring to the soil at higher rotational speeds, which result in further crumbling of the soil slices. Regarding the results obtained in this study, the specific fuel consumption increased at first in a light slope, then in a steep rise with increasing the blades rotational speed. The reason can be the higher crumbling percent of the soil at higher rotational speeds and higher soil moisture contents (at the range of 21.9-30.3%), providing the more specific energy consumptions. The specific fuel consumption was the maximum at higher soil moisture content of 30 %. The results indicated that the blades rotational speed and soil moisture content had no significant effect on the field efficiency of the examined rototiller. The field efficiency varied in the range of 92 to 97% in all of the experiments, i.e., rotational speed between 140 to 230 rpm and moisture content ranging from 13.5 to 30.3%. The reason for that was due to the roughly similar turning times, minor adjustments, changing operators and some other parameters influencing the field efficiency. Reduction of the rotational speed of the rototiller from high-to-moderate speeds leads to decrease the fuel consumption to 17 liter ha-1, which could be significant in wide scale of soil tillage operations. As a general result, reduction of the rotational speed had some considerable advantages such as reducing power requirements, reducing blade wearing and maintaining soil structure.
Influence of soil moisture and rotational speed of blades on the soil particle mean weight diameter, soil crumbling percentage and specific fuel consumption were significant (P

About 60% of the mechanical energy consumed in mechanized agriculture is used for tillage operations and seedbed preparation. On the other hand, unsuitable tillage system resulted in soil degradation, affecting soil physical properties and destroying soil structure. The objective of this research was to compare the effects of three types of secondary tillage machines on soil physical properties and their field performances. An experiment was conducted in a wheat farm in Jouybar area of Mazandaran as split plots based on randomized complete block design with three replications. The main independent variable (plot) was soil moisture with three levels (23.6-25, 22.2-23.6 and 20.8-22.2 percent based on dry weight) and the subplot was three types of machine (two-disk perpendicular passing harrow, Power harrow and Rotary tiller). The measured parameters included: clod mean weight diameter, soil bulk density, specific fuel consumption, machine efficiency and machine capacity. The effects of treatments and their interactions on the specific fuel consumption, machine efficiency and machine capacity and also the effects of treatments on bulk density were significant (P<0/01). The bulk density decreased 15.3%, the specific fuel consumption increased 11.8%, whereas the machine efficiency and machine capacity increased and decreased with the decrease in soil moisture, respectively. The maximum value of the bulk density and machine efficiency were obtained by the use of rotary tiller and the maximum value of the specific fuel consumption and machine capacity were obtained by the use of power harrow. A criterion was defined for selecting machine type and moisture content for optimum condition. The results suggested power harrow working at soil moisture condition of 24.3% (based on dry weight).