Showing 3 results for Draft
Mohammad Loghavi, S. Reza Ashrafizadeh,
Volume 1, Issue 2 (10-1997)
Abstract
The effects of three levels of soil moisture content (8-10, 10-12 and 12-14% d.b.) and three levels of plowing depth (15, 20 and 25 cm) on draft, specific draft and drawbar power requirement of a 7-shank chisel plow in a clay loam soil were investigated. The experimental design was a randomized complete block design with a 3×4 factorial. The effect of plowing depth on all of the parameters mentioned was highly significant. Implement draft and drawbar power requirement both increased with plowing depth, whereas a decreasing trend of specific draft with depth was observed. Soil moisture content had no significant effect on draft and specific draft of chisel plow in the range of moisture contents studied, though both parameters were minimized at 10-12% m.c. At this moisture level, the drawbar power requirement showed a significant reduction comparing with the other two moisture levels. This indicated that the soil was close to its optimum friability at this moisture content. Soil penetrometer readings, taken before and after plowing, indicated the existence of a hardpan from about 8 to 20 cm below the surface which was broken by chisel tines, but another hard layer formed under the plowing depth by the chisel points. Comparison of the results from the present study with those from the previously published works on chisel plow draft at similar plowing depths showed that the values obtained for draft and specific draft were acceptably close to those previous investigators. Also, a comparison with the findings of Loghavi and Moradi on moldboard plow draft under similar conditions confirmed the reports of previous investigators to the effect that a chisel plow requires approximately one-half of the draft of a moldboard plow with the same working width and depth.
Mohammad Loghavi, Saeed Behnam,
Volume 2, Issue 4 (1-1999)
Abstract
The effects of three levels of soil moisture content (10 - 12, 13 - 15 and 16 - 18% d.b.) and three levels of plowing depth (15, 20 and 25 cm) on draft, specific draft, and drawbar power requirements of a 3 - bottom disk plow and on soil pulverization and inversion in a clay loam soil were investigated. The experimental design was a randomized complete block design with a 3 × 3 factorial. Except in soil inversion, the effect of soil moisture on all of the performance parameters mentioned, was highly significant. Mean values of draft, specific draft and drawbar power requirements and clod mean weight diameter were minimized at 13 - 15% and 16 - 18% soil moisture contents, respectively. The effect of plowing depth was highly significant only on draft and drawbar power requirement of disk plow, in such a way that the mean values of these two parameters were significantly increased with plowing depth, while specific draft showed only a mild decreasing trend. In order to provide a quantitative index to express the degree of soil pulverization by tillage implements, a tractor-pulled rotary sieve was designed and fabricated. With this apparatus, in-field determination of soil clod mean weight diameter (MWD) following plowing was possible. The results showed that the effect of soil moisture content on MWD was highly significant, such that, plowing at 10-12% moisture content produced the largest clods, whereas the effect of plowing depth on MWD was not significant. The decreasing trend of MWD with soil moisture content persisted to the highest moisture level studied (16 - 18%), in which the average clod MWD (33.8 mm) was about 72% smaller than those formed at 10-12% moisture content. The effects of plowing depth and soil m. c. on soil inversion by disk plow were not significant and the overall soil inversion was about 54% which was in agreement with those reported by other researchers.
D. Lotfi, A. Hemmat, M. R. Akhavan Sarraf,
Volume 11, Issue 1 (4-2007)
Abstract
For measuring draft force and drawbar power requirements for mounted implements, precise instruments such as three-point hitch dynamometers and tractor speed measurement devices are needed. In this research, a frame-type three-point hitch dynamometer was built and evaluated. Forces applied to dynamometer are measured by three separate load cells located on a frame which can be attached to tractor’s three-point hitch. Each dynamometer’s load cell measures load using a strain gauge bridge circuit. Each load cell was calibrated by applying a known load and measuring bridge circuit’s output voltage. Dynamometer was calibrated by the application of known forces and measuring the output voltage of the strain gauge bridges. The calibration showed a high degree of linearity between the applied forces and the bridge outputs (R2 = 0.996). The hysteresis effect between loading and unloading as well as the effect of the position of the applied forces from the longitudinal axis of the dynamometer was small. For measuring actual tractor speed, a fifth wheel equipped with an encoder shaft was designed and built. The calibration on tarmac and soil surfaces showed a highly linear relation between measured forward speed and output of encoder’s rotation (R2 =0.994). The errors in speed measurements at low speed in field and at high speed (up to 12.5 km/h) on tarmac surface were approximately 3 and 8%, respectively. The data acquisition system, not only could display the instantaneous force and speed, it could also show force-time and force-distance curves on the system’s monitor.
