Search Results

A machine was built to study non-rolling tire stiffness and damping coefficient of agricultural tractor tires in the vertical direction. Measurements of static deflection and contact area on a rigid surface can be performed. During dynamic experiments, a sinusoidal deflection function is imposed to the test tire to determine dynamic stiffness and damping coefficient. The experimental setup and methodology are described in this paper. A complete sample test and its analysis are also presented. This paper was approved for publication by the Director of the Louisiana Agricultural Experiment Station as publication number 93-07-7238. Trade names are used solely to provide specific information. Mention of a trade name does not constitute a warranty of the product by the Louisiana Agricultural Experiment Station of the LSU Agricultural Center nor an endorsement to the exclusion of other products not mentioned. The authors are François P. Brassart, Graduate Research Assistant, and Malcolm E.

Sweet potato harvesting requires the destruction of a massive amount of above ground vine material before digging can begin. The efficiency of harvesting is greatly increased if the potatoes are detached from their root stems before they are dug. The development of a machine in a university mechanization research program which successfully accomplished these two tasks is reported, including field testing on commercial farms and laboratory test results. Further, the development of drawings and bills of material resulting in a “know-how” contract between the university and the manufacturer, and the subsequent cooperation between these two, are described.

A vibrating digger blade with one input to move the blade horizontally and one input to move the rear of the blade vertically was tested to determine a mode of vibration that would produce the most effect on the soil at acceptable torque and power inputs. A kinematic and dynamic simulation program which accounted for the frictional and inertial effects of the moving parts of the machine and a block of soil on the blade was written and used to help decide which independent parameters and their levels to use in a field test program. The optimum combination of elements yielded by the study for use in a commercial digger design was an eccentricity of 9.52 mm for horizontal movement, an eccentricity of 12.7 mm for vertical movement, and an operating velocity ratio of 1.0.1

The evolution of an experimental prototype vibrating digger blade for harvesting root crops is described. The prototype had two independent oscillatory inputs, one to vibrate the whole blade horizontally and another to vibrate the rear edge vertically. It was to be used in later field experiments to determine the effect of changing directions of vibration on the dependent variables of draft, torque, and soil break-up. Torque measurements were made in the laboratory for eccentricities of 0.0, 9.53, and 12.70 mm and frequencies of 6.96, 9.28, 10.44, 13.92, 15.66, and 20.89 Hz, the range of these variables which would subsequently be used in field tests. The outputs of two computer simulation programs, one written by Rodriguez and a commercial software mechanisms analysis program, compared favorably with the measured laboratory results. 1

Vertical stiffness and damping coefficient values were measured, in non-rolling conditions, on eleven agricultural drive tires, with sizes ranging from 14.9-30 to 18.4-38, and both types of carcass construction, bias and radial, were tested. Tire stiffness was measured both in static and dynamic conditions. The mechanical model representing the tires was made of a parallel spring-and-damper system, simplified to a single spring in static conditions. Tire stiffness was linearly related to inflation pressure in all cases, but dynamic stiffness was higher than static stiffness. The use of different tire models for static and dynamic conditions is recommended during simulation and tire behavior prediction.

The performance of three similar types of vibrating potato digger blades was estimated by observing the potato separation and material flow on the bottom plate. Each machine was tested with different drive amplitudes, frequencies, and travel speeds. Blade performances were observed in three categories: (1) success by acceptable digging and soil/potato separation, (2) partial success by good material flow but poor soil/potato separation, and (3) failure by bulldozing or stalling. Three parameters, λ, the ratio of the vibrating blade speed to travel speed, ρ, the ratio of blade acceleration to travel speed, and K, the ratio of blade acceleration to gravitational acceleration, were compared to see which best predicted the interface between acceptable and marginal digging and separation. K was the most consistent predictor and a value of K ≥ 2.0 is suggested as an absolute minimum design criterion of a vibrating digger.1