Force relationships and power requirements of sugar beet shares

Abstract

The forces and torque were measured direct under field conditions, using strain gauge instruments on two plots of medium soil and one of heavy soil, with a total of 11 models and versions of lifting tool. The forces acting on individual models of lifting tool in the vertical plane parallel to the direction of travel were studied in detail and their nature assessed. For rotary lifting tools, high vertical forces are characteristic, whereas with lifting shares, they are relatively small. Of the latter, the prong-type share has the highest draught, slightly higher than with a share having a negative cutting angle; however, the differences are not very great. The draught of non-driven lifting wheels was higher on all plots than that of the lifting shares examined. The lifting tools are compared not only from the point of view of draught but also total power requirement. It has been established that although by driving the rotary lifting tools their draught is reduced, the total power requirement is in each case higher than with non-driven lifting wheels and more than double that of conventional production models of shares with a negative cutting angle. From the point of view of power it is therefore disadvantageous to use rotary lifting tools and particularly driven ones, and their use can be justified only by possible functional merits. A study has also been made of the effects of forward speed and working depth of the most important lifting tools, as well as, in the case of rotary lifting tools, the effect of peripheral speed of driven wheels and of wheel setting. Over the forward speed range of 1·0–2·0 m/s the draught increases with shares having a negative cutting angle and with non-driven wheels, following a curve very close to a straight line; in the case of rotary tools having one driven wheel it remains almost constant and the drive input to the wheel does not change either. Draught and drive power increase very rapidly with working depth for all types examined. The peripheral speed of the driven lifting wheel does not affect the draught but only the driving power, so that if it is reduced to the minimum at which the wheel will function properly, a reduction in power input to the tools can be achieved. From the point of view of power requirement, the optimum angle of convergence of the lifting wheels in the horizontal plane α=25–30° while the angle in the vertical plane β should be as small as possible compatible with proper functioning. However, larger angles do not lead to a substantial deterioration in the relationships. The maximum values of forces and torques acting on the lifting tools, which are also indicated, enable the harvester components, particularly the framework, drawbar, shafts, and transmission, to be correctly dimensioned.