Load Characteristics and Horsepower Requirements of Rice Hull Soft-Expanded Instrument

by PTO Drive of Farm Tractor

Abstract

This experiment was made to clarify the load characteristics and to know the horsepower requirements on the rice hull soft-expanded instrument driven by the power take-off (pto) of a farm tractor. The results obtained were as follows.
(1) The soft-expanded rice hull was visually satisfactory in quality at the capacity which was more discharged on 1-8 of the other notch numbers, except 170kg/h of the smallest discharge capacity when a variable speed motor attached for varying the capacity rotated on 0 mark in the notch number. In the case of too small capacity to flow evenly, it has sometimes been clogged at the part which was pressed hard on a compression shaft. The material which was concentrically distributed between 1mm and 3mm in screen size before processing changed to which was uniformly distributed in the wide range between 0.5mm and 4mm by sifting through several screens. And comparing the both distributions of weight percentage of rice hull soft-expand-ed in the case that the clearance of a discharge port was regulated 7mm and 4mm, the case of 4mm was a little finer than another.
(2) When loading on the pto shaft with increasing the feeding rate of material, in the case of 7mm the rotational speed of a pto shaft slowed down only by about 4rpm in steady rotation and a torque rose only by about 3kg·m in an average peak value at the discharging rate between 170kg/h and 300kg/h, the speed reduced hastier and the torque rose up to 27kg·m at 350kg/h, and further the speed slowed down fast with large fluctuations and the torque reached to 35kg·m at 500kg/h. And in the case of 4mm the speed slowed down with a constant rate and the average peak value of torques was about 10kg·m larger than that in the case of 7mm, the differences between the average peak values and the average bottom values of each torques were about 8kg·m on an average.
(3) The rotational speed had a tendency to slow down rectilinearly with increasing torque. Now if comparing this correlative graph with a curve of the torque which have previously measured with a dynamometer on the same tractor used for this experiment, it was known for the pto torque curve to lie between the average peak values and the average bottom values of torques within the range of partial load. Consequently, it was seemed proper to apply an average torque in calculating the horsepower required for driving this instrument, but the small torque of about 1.5kg·m had already acted on the pto shaft even without feeding, so it should be rather better to use the average peak value. And the rotational speed to each torques should be assumed to be all at 540rpm, because it is necessary to keep its rotational speed constantly while operating under various load conditions.
(4) The relations of the horsepower requirement to the discharging rate were that in the case of 7mm the horsepowers required 12ps to 15ps between 170kg/h and 300kg/h, 20ps against 350kg/h, 30ps against 500kg/h in the discharging rate, and that in the case of 4mm these required 18ps against the smallest rate of 150kg/h, 31ps against the largest rate of 390kg/h.
Consequently, it was desired to require for this instrument about 30ps in the highest horsepower of pto shaft against the largest discharging rate, but if we were expected to keep continuously operating within the range of partial load in torque curve of a tractor, it should be to require 36ps in consideration of the load factor of 1.2 obtained in this experiment.