Vibration characteristics of a power tiller

The vibration characteristics of a power tiller (two-wheel tractor) were studied. Tests were conducted at 1000, 1200, 1400, 1600, 1800, 2000, and 2200 rpm engine speeds in a stationary condition, and at 1000, 1200, 1400, 1600, and 1800 rpm engine speeds during transportation and tillage. Tests during tillage operation were conducted in the Bangkok clay soil. For the measurement of vibration, three semiconductor strain-gauge-type accelerometers, capable of sensing vibration signals in three mutually perpendicular directions, i.e. horizontal, lateral and vertical modes at the same time, were used. Vibration characteristics of the power tiller were found to be quite complex. In general, it was observed that, in any working condition, due to an increase in engine speed of the power tiller, the acceleration and frequency of vibration increased. At the same operating speed and test condition, the intensity of the vibration was the highest in the vertical mode and the lowest in the lateral mode. The maximum vibration intensities were observed during second plowing and the lowest vibration intensities were when stationary on an off-road surface. The vibration intensities, when compared to the ISO standard 2631, were found to exceed the standard during field operations.     

Effects of tyre inflation pressure and forward speed on vibration of an unsuspended tractor

Relationships among intensity of vibrations, tractor speed, soil moisture content and tyre inflation pressure are important for the design of tractor suspension systems. This study was designed to evaluate the effect of tyre inflation pressure and forward speed on tractor vibration in the paddy fields of Southern China by using a two-wheel-drive unsuspended tractor with different combinations of forward speed, tyre inflation pressure and soil moisture content. During experiments, the vertical vibration accelerations in front and rear axles and triaxial vibration accelerations of the tractor body were measured using three accelerometers. Fourier analysis was applied to determine root mean square acceleration values in the low frequency range from 0.1 to 10 Hz. The results of the study indicate that tractor vibration is strongly affected by changing forward speed and tyre inflation pressure, and especially by changing forward speed and rear tyre inflation pressure. The research also shows the variation in the pattern of vibration intensity especially at the tractor’s front axle when field soil moisture content is changed.     

Effects of tire inflation pressure and tractor velocity on dynamic wheel load and rear axle vibrations

The objective of this study was to evaluate the effects of agricultural tire characteristics on variations of wheel load and vibrations transmitted from the ground to the tractor rear axle. The experiments were conducted on an asphalt road and a sandy loam field using a two-wheel-drive self-propelled farm tractor at different combinations of tractor forward speeds of approximately 0.6, 1.6 and 2.6 m/s, and tire inflation pressures of 330 and 80 kPa. During experiments, the vertical wheel load of the left and right rear wheels, and the roll, bounce and pitch accelerations of the rear axle center were measured using strain-gage-based transducers and a triaxial accelerometer. The wavelet and Fourier analyses were applied to measured data in order to investigate the effects of self-excitations due to non-uniformity and lugs of tires on the wheel-load fluctuation and rear axle vibrations. Values for the root-mean-square (RMS) wheel loads and accelerations were not strictly proportional and inversely proportional to the forward speed and tire pressure respectively. The time histories and frequency compositions of synthesized data have shown that tire non-uniformity and tire lugs significantly excited the wheel load and accelerations at their natural frequencies and harmonics. These effects were strongly affected by the forward speed, tire pressure and ground deformation.     

Effect of rotation direction of a rotary tiller on draft and power requirements in a Bangkok clay soil

Experiments were conducted in a Bangkok clay soil to evaluate the performance of a rotary tiller equipped with reverse or conventional blades. The conventional rotary tiller was equipped with C-type blades whereas the reverse-rotary tiller had new types of blades. Tests were conducted on wet land as well as in dry land. Tests were conducted at tractor forward speeds of 1.0, 1.5 and 2.0 km/h. A power-take-off (PTO) power consumed was calculated from the PTO torque and speed. The results indicated that the PTO power consumption was less for the reverse-rotary tiller compared to the conventional tiller for all passes and forward speeds. For both rotary tillers, power consumption decreased as the number of passes increased, whereas power consumption increased when the forward speed was increased. At all forward speeds, the power consumption was the highest during the first pass and lowest during the third pass. The maximum difference of PTO power requirement was after the first pass at 1.0 km/h forward speed. The reverse-rotary tiller consumed about 34% less PTO power under this condition.     

Whole-body vibration: Evaluation of emission and exposure levels arising from agricultural tractors

A study was conducted to quantify whole-body vibration (WBV) emission and estimated exposure levels found upon a range of modern, state-of-the-art agricultural tractors, when operated in controlled conditions (traversing ISO ride vibration test tracks and performing selected agricultural operations) and whilst performing identical tasks during ‘on-farm’ use. The potential consequences of operator WBV exposure limitations, as prescribed by the European Physical Agents (Vibration) Directive:2002 (PA(V)D), upon tractor usage patterns were considered. Tractor WBV emission levels were found to be very dependent upon the nature of field operation performed, but largely independent of vehicle suspension system capability (due to the dominance of horizontal vibration). However, this trend was reversed during on-road transport. Few examples (9%) of tractor field operations approached or exceeded the PA(V)D Exposure Limit Value (ELV) during 8 h operation, but this figure increased (to 27%) during longer working days. However virtually all (95%) ‘on-farm’ vehicles exceeded the Exposure Action Value (EAV) during an 8-h day. The PA(V)D is not likely to restrict the operation of large, state-of-the-art tractors during an 8-h day, but will become a limitation if the working day lengthens significantly. Further ‘on-farm’ WBV data collection is required to enable creation of a robust, generic WBV emission database for agricultural tractor operations, to enable estimation of likely WBV exposure by employers.     

Analysis of the PTO load of a 75 kW agricultural tractor during rotary tillage and baler operation in Korean upland fields

In this paper, the PTO severeness of an agricultural tractor during rotary tillage and baler operation was analyzed. The S–N curves of the PTO driving gears were obtained through fatigue life test. To obtain the S–N curves of the PTO driving gears, the breakage time and rotational speed of the gears were measured through observation of the bending stress with changing torque. The torque acting on the PTO was measured and analyzed during rotary tillage and baler operation. Rotary tillage and baler operation were conducted at two ground speeds and two PTO rotational speeds at upland field sites with similar soil conditions, respectively. The load data were inverted to a load spectrum using rain-flow counting and SWT equations. Modified Miner’s rule was used to calculate the partial damage sum. The severeness was defined as the relative ratio of the damage sum. The results showed that the damage of the PTO increased when the ground speed or the PTO rotational speed increased. The effect of the PTO rotational speed on the severeness of the PTO was more significant than that of the ground speed. The severeness of the PTO of rotary tillage was greater than that of baler operation.     

Performance of an oscillating subsoiler in breaking a hardpan

A single shank tractor mounted oscillating subsoiler was developed to break hardpan, common in sugarcane (Saccharum officinarum) farms especially after harvest when heavy trucks transport the cut canes from the field to the sugar factory. Field experiments were conducted to determine the optimum combination of performance parameters of the subsoiler. Field tests were conducted at frequencies of oscillation of 3.7, 5.67, 7.85, 9.48 and 11.45 Hz; amplitudes of 18, 21, 23.5, 34 and 36.5 mm; and forward speeds of 1.85, 2.20 and 3.42 km h⁻¹ at moisture contents close to the lower plastic limit of the clay soil. A reduction in draft but an increase in total power requirement was found for oscillating compared to non-oscillating subsoiler. The draft and power ratios were significantly affected by the forward speed, frequency and amplitude. Their combined interaction, expressed in terms of the velocity ratio (the ratio of peak tool velocity to forward speed), however, had the strongest influence. At the same velocity ratio, the draft reduction and power increase were less at higher amplitude of oscillation. For the field conditions tested, the optimum operation for least energy expenditure was obtained at an amplitude of 36.5 mm, frequency of 9.48 Hz and speed of 2.20 km h⁻¹ with a draft ratio of 0.33 and power ratio of only 1.24. It could be concluded that the oscillating subsoiler reduces draft for breaking hardpan, reduces soil compaction and promotes the use of lighter tractors by utilizing tractor power-take-off (p.t.o.) power to achieve higher efficiency of power transmission. ©     

Assessment of the influence of the eccentricity of tires on the whole-body vibration of tractor drivers during transport on asphalt roads

Agricultural vehicle operators are exposed to high levels of whole body vibrations (WBVs) which are related, above all, to surface irregularities, forward speed and vehicle setting. European Parliament Directive 2002/44/EEC sets the minimum requirements for the protection of workers from risks to their health and safety due to exposure to mechanical vibrations, and it is therefore of utmost to investigate any source of vibration during agricultural works and any machine-related transmission element. Tractor tires play a key role in damping vibrations; their response varies according to the tractor mass and tire inflation pressure and, during transport, they have to be taken into account at different forward speeds. The eccentricity of the tire is one of the factors thus influences the amplitude of the solicitations acting on the tire. This study was aimed at evaluating the influence of the “tire eccentricity” parameter on driver comfort and at introducing a test method for its assessment for validation purposes.     

Damping characteristics of seat cushion materials for tractor ride comfort

The cushioning material in a tractor seat plays a dominant role in supporting operator posture, isolating vibration and improving ride quality. Vibration attenuation in a tractor seat is achieved by selecting proper suspension and damping mechanism. This paper describes damping characterisation of tractor seat cushion materials to improve operator’s comfort. Nine commercially available seat cushion materials of different densities, thickness and compositions were selected for the study. A sinusoidal displacement exciter was designed to measure damping characteristics of the seat cushion materials in the frequency range of 1–8 Hz with displacement amplitudes of 10, 15 and 20 mm peak-to-peak. It was observed that the equivalent viscous damping coefficient (C_eq) of cushion materials decreased with the increase in frequency and peak-to-peak amplitude of vibration and decrease was very sharp in the lower frequency range up to 3 Hz. The average percentage reduction in C_eq increased with increase in peak-to-peak amplitude of vibration from 10 to 20 mm for the selected seat cushion materials. The average percentage reduction in C_eq was the highest for thinner high density polyurethane (PU) foam (thickness of 44 mm, density of 19.09 kg/m³) at different frequencies of vibration. It may be concluded that the high density PU based cushion material is good for dampening vibrations transmitted in tractor under dynamic condition.     

A decision support system for selection of tractor-implement system used on Indian farms

The selection of tractor and its matching implements has now become very difficult in India because of availability of variety of tractor models ranging from 10 to 45 kW. To overcome the problem of matching of tractor-implement system, an expert system modelling approach leading to decision support system (DSS) was adopted to make the step wise decision. The application of DSS was demonstrated in the paper to select either an implement to match the tractor or to select a tractor to match the implement under different soil and operating conditions. The DSS leading to computer software developed in Visual Basic™ programming provided the intuitive user interfaces by linking databases such as specifications of tractors and implements, tractor performance data, soil and operating conditions, to support the decision on selection of tractor-implement system. The programme calculates working width of implement based on input data for the most critical field operation and helps in selection of a suitable implement having width nearer to the calculated value among the commercially available implements. The software calculates the required drawbar power of the tractor based on draft and working speed of the selected implement. Finally, the PTO power requirement of a tractor is calculated by the software. Based on calculated PTO power, the software suggests available makes and models of tractor/machinery from the compiled data bank. The developed DSS was tested with a case study to demonstrate the flexibility of the software. The DSS can be used effectively in selection of a tractor or an implement of particular size from various makes and models of commercially available tractors and implements.     

The determination of plough draught—Part II the measurement and prediction of plough draught for two mouldboard shapes in three soil series

The draught of a 3-furrow reversible plough fitted with two types of bodies was measured at five separate test sites. Each site was ploughed on four different days to provide a range of soil moisture contents. The plough was operated at three different speeds in sequence for each type of body. The horizontal and vertical forces transmitted to the tractor were measured on a three-point linkage dynamometer. Tachogenerators monitored tractor wheel speed and fifth wheel ground speed. Cone index and soil specific weight were recorded at 30 mm intervals throughout the top-soil profile. Cone index at median plough depth was found to be a satisfactory measure of soil strength for the prediction of plough draught. Characterising specific plough draught by soil cone index, specific weight, moisture content, plough mouldboard tail angle and ploughing speed provided predicted values in closer agreement with measured draught compared with earlier equations. The sensitivity of cone index to soil moisture content supports the use of the cone penetrometer as a practical monitor of soil conditions in the field and as a management tool for judging the opportune times for agricultural tillage operations.     

Modelling the traction of a prototype track based on soil–rubber friction and adhesion

An experimental track layer tractor, based on an Allis Chalmers 8070 tractor (141 kW) was tested on bitumen covered concrete and on cultivated sandy loam at 7.8%; 13% and 21% soil water content. The two articulated beam-type tracks (500 mm wide × 2000 mm soil contact length) were constructed out of 500 mm long and 70 mm wide rubber covered steel track elements, carried by five steel cables (36 mm diameter). The tracks resisted inward deflection but allowed outward articulation between two smooth rear driving and two smooth front pneumatic truck tires (1060 mm diameter) per track. The contact pressure and the tangential force on an instrumented track element, as well as the total torque input to one track, were simultaneously recorded during the drawbar pull/slip tests.

Different possible pressure distribution profiles under the tracks were considered and compared to the recorded data. Two possible traction models are proposed, one constant pressure model for minimal inward track deflection, and a deformable track model with inward deflection and a higher contact pressure at both the front free-wheeling and rear driving tires. For both models, the traction force was generated mainly by rubber/soil friction and adhesion and limited soil shear. A close agreement between the measured and predicted contact pressures and traction force for individual track elements, based on the deformable track model, was observed. The recorded and calculated coefficient of traction based on the summation of the force for the series of track elements were comparable, but were considerably lower than the predicted values, probably due to internal track friction rather than soil sinkage. The tractive efficiency for both a hard or soft surface was also unacceptably low, probably caused by internal track friction.     

车轮多边形激励下高速列车制动界面摩擦学行为分析

高速列车车轮多边形磨耗是一种沿车轮周向的不均匀磨耗,是列车服役过程中常见的车轮失效现象,其产生的剧烈轮轨激励严重威胁车辆系统服役可靠性. 制动系统作为保障高速列车服役安全的核心部件,其界面摩擦学行为直接受到轮轨激励的影响. 为探究车轮多边形激励下的制动界面摩擦学行为,建立了刚柔耦合车辆动力学模型和制动系统热机耦合有限元模型,并分别通过线路试验和台架试验验证了模型的正确性. 然后,提出一种考虑车轮多边形激励的制动界面摩擦学行为分析方法,能够真实地反映服役过程中制动界面摩擦学行为. 基于此,研究了不同车辆运行速度下车轮多边形激励对制动系统动态接触、温度以及振动特性的影响规律. 结果表明:车轮多边形磨耗导致系统接触面积、摩擦热、接触应力和振动等摩擦学行为更为复杂且剧烈. 此外,系统接触面积标准差和振动加速度均方根值随速度的增加而增大. 因此,车轮多边形磨耗对制动界面摩擦学行为具有不可忽略的影响. 该研究成果可为制动系统界面摩擦学行为研究及结构优化设计提供有效方法与工程指导.      

高速铁路碎石道砟振动的离散元模拟

道砟振动对其磨损、破碎和道床累积变形有显著影响,为揭示高速车辆移动荷载作用下道砟动态响应特性,建立有砟道床离散元模型,开展车辆-轨道耦合动力学计算得到离散元模型输入荷载,模拟分析高速车辆以不同速度通过时有砟道床的振动响应,并与车辆-轨道耦合动力学计算结果进行对比分析。结果表明,轨枕、道砟和道床块振动位移波形相似,位移幅值沿道床深度方向减小,道床块振动位移与轨枕底面以下0.3m处道砟的振动位移相当;轨枕、道床块振动速度与加速度随行车速度提高而增大;受道砟颗粒间复杂相互作用的影响,道砟振动加速度会出现突变。道床离散元模型能合理反映道砟颗粒的振动响应特性,道床块模型体现了道床层在有砟轨道结构中的动力传递与减振特性,两种道床模型的计算结果具有一定的相似性。     

Soil compaction management: Reduce soil compaction using a chain-track tractor

Modern agricultural production requires research for new design and layout plans of the track-chained mover, providing a reduction in soil compaction. One of many ways to improve the efficiency of machine-tractor aggregate (MTA) use is to improve the geometry of the support part of the chain-track tractor. Flat geometry of the support part of a chain-track tractor with a semi-rigid suspension creates maximum pressure on soil with the first and last track rollers, which causes increased soil compaction. Research objective is to ensure the uniform pressure on soil from the tractor with a semi-rigid suspension by justifying the geometry of the supporting part of the track-chained mover.Based on experimental and theoretical studies a model of pressure distribution along the length of the support part was developed. Thus, the geometry of the support part of a track-chained tractor with a semi-rigid suspension was substantiated. Pressure decrease on soil and compaction reduction are achieved by changing the geometry of the support part and rational location of the tractor mass center. To achieve the elliptical geometry of the support part of a track-chained tractor with a semi-rigid suspension lower track rollers were placed at different heights.To test the formulas and to study the influence of the support part geometry, of the hitch height and the force on the hook of a track-chained tractor on soil compaction, experiments were conducted. As a model for experiment, the tractor actively used in agriculture was modernized; chain-track tractor T-170M1.03-55 with flat and elliptical caterpillar bypasses. The pressure was measured directly by pressure sensors that were placed into the ground. Soil density in the track left by a track-chained tractor mainly depends on mover pressure and the number of impacts per pass. Track-chained mover makes two impacts on soil with the flat support part. If the support part geometry is changed, the number of impacts on soil is reduced to one. To create typical working conditions for T-170M1.03-55 track-chained tractor the third and fourth support rollers should be lowered by 9.5 ± 1.5 mm, the second and fifth-by 4.5 ± 0.5 mm relatively, which leads to a decrease in the maximum pressure on soil and reduces its compaction in the track left by the mover by 15–25%.     

Speed advice for power efficient drawbar work

Tractor manufacturers already offer engine - transmission control systems in which the operator decides whether low fuel consumption or high output is the priority and let a control system provide engine and transmission management. Less sophisticated tractors, as well as older equipment, still rely on the operator awareness upon what driving parameters most enhance efficiency. The objective of this study is to analyse the effect of driving parameters, namely forward speed and engine speed on the overall power efficiency. The overall power efficiency of a tractor performing drawbar work is the ratio between the output power at the drawbar and the energy equivalent of the fuel consumed per unity of time. Experimental data obtained from tractor field tests in real farm conditions, within the range of 0.2-0.4 for the vehicle traction ratio (ratio of the drawbar pull to the total weight of the tractor), show that increments of 10-20% on the overall power efficiency can be obtained by throttling down from 2200 min⁻¹ to 1750 min⁻¹ (idle speed). The reduction in ground speed and therefore in the work rate, may be overcome by shifting up the transmission ratio.     

Comparison of the tractive performance of a tractor driving wheel during its first and second passes in the same track

The tractive performance of a conventional 13.6–38 tractor driving wheel tyre was measured in 19 different fields using the NIAE Single Wheel Tester. In each field the performance was measured on the undisturbed ground and again in the rut formed by a previous run with the same tyre. The second run simulated the operation of the rear wheels on a four-wheel drive tractor.The performance during the second pass was generally better than during the first pass. On average, the coefficient of traction increased by 7%, rolling resistance reduced by 11% and maximum tractive efficiency increased by 5%. The improvement increased as ground conditions deteriorated but was never large enough to fully explain the differences in performance between two and four-wheel drive tractors previously measured. It is suggested, therefore, that these differences may be primarily due to the greater ease with which power, weight, implement size and working speed can be matched with four-wheel drive tractors.     

The lateral stability of tractor and trailer combinations

A model has been developed to predict the lateral stability characteristics of tractor and unbalanced trailer combinations. For present combinations, stability deteriorates with speed culminating in instability at forward speeds in the region of 18 m/s. The effect of tractor and trailer size and other parameter variations on this speed dependent instability are examined.The effect of braking with and without axle locking are analysed. The stability of the combination is sensitive to the braking distribuion between the axles, which affect the hitch forces developed. Locking the tractor rear or trailer axle results in instabilities, commonly termed jack-knifing and trailer swing respectively. Jack-knifing is the more hazardous instability, whereas trailer swing although potentially dangerous has a divergence approximately an order of magnitude less.The potential of the model for predicting lateral dynamic behaviour of design concepts for future high speed farm transport which would operate at higher speeds than the current maximum of 9 m/s for tractor and trailer combinations is discussed. The scope for generalizing the model to examine other aspects of lateral behaviour, such as steering response is restricted by the limited amount of data available on the side force generated by tyres in agricultural conditions.     

Dynamics of a powered disk in clay soil

Experiments were conducted with a single powered disk in a laboratory soil bin containing Bangkok clay soil with an average moisture content of 18% (db) and 1100 kPa cone index. The disk was 510 cm in diameter and 560 mm in radius of concavity. During the tests the disk angle was varied from 20° to 35°, ground speed from 1 to 3 km/h and rotational speed from 60 to 140 rpm. The working depth was kept constant at 12 cm. The vertical, horizontal and lateral reactions of the soil were measured by force transducers. The forward and rotational speeds were recorded. It was observed that disk angle, rotational speed and ground speed had significant effects on soil reactive forces and power requirement. With a small disk angle, low ground speed, and high rotational speed, the soil longitudinal reactive force was a pushing force and became a resistive one at larger disk angles and ground speeds. The soil transverse reactive force increased with an increase of rotational and ground speed but decreased with the increase of disk angle, whereas the vertical relative force increased only with the increase of ground speed but decreased with the increase of rotational speed and disk angle. It was found that the powered disk required the least power at a disk angle of 30° and rotational speed between 80 and 100 rpm. Increase in ground speed from 1 to 3 km/h increased the total power requirement by 31.8%. Upon driving the disk forward, the draft reduced considerably compared to that of the free-rolling disk. By driving the disk in the reverse direction, the draft reduced slightly. At a disk angle of 30°, rotational speed of 100 rpm, and ground speed of 3 km/h, the total power requirement of the forward-driven disk was 65% higher than that of the free-rolling disk. The predicted engine power of the forward-driven disk, however, was only 21% higher than that of the free-rolling one owing to the more efficient power transmission through the PTO, as opposed to the drawbar. The effects of reverse driving and free rolling of the disk were also studied.     

Development and implementation of an IOT based instrumentation system for computing performance of a tractor-implement system

A high precision and compact IOT based digital instrumentation setup to measure, display and record various tractor and implement system performance parameters was developed and installed on a 28.3 kW Tractor. The setup was capable of continuous monitoring and wirelessly transmitting tractor-implement performance parameters on a cloud platform such as engine speed, radiator fan speed, fuel consumption, draft, forward speed, lift arm angle, wheel slip, wheel slip, PTO speed, geo-location/position of the tractor, choking of seeds in the implement and vibrations experienced by the implement. For precision measurements, commercial transducers used in the system were calibrated and assessed under both static and dynamic conditions. The average calibration constant for fuel consumption, forward speed, lift arm angle and load cell were 0.00009804 L/pulse, 0.01610306 km/h/pulse, 0.056 mA/degree and 0.2575 mV/kN respectively. The system based on DataTaker DT 85 Data logger connected to a micro-computer through transducers capable of transferring data wirelessly was installed on John Deere 5038 tractor and was tested with a Spatially Modified No-Till Drill in agricultural field with varied implement depth.