The motion of grain and straw on the movable plane is subjected to influence by the coefficient of friction, thereforce, in the investigation on the motion, knowing of the exact coefficient of friction is positivily necessary. This paper deals with results of the experimental study on the coefficient of friction of grain and straw using circular oscillatory motion and twining to the pulley. The main results are as follow ;
1) In the static and kinetic coefficient of friction using circular oscillatory motion.
(1) In general, the coefficient of friction is given by the following equation (3).
μ = (xω＾2)/g
μ : static and kinetic coefficient of friction of grain
x : radius of circle of grain balancing to the centrifugal force (cm)
ω : angular velocity (radian/sec)
g : acceleration of gravity (cm/<sec>^2)
(2) Regarding with the frequency, the coefficient of friction is kept in constant within about 80 rpm, but decreases gradually over than about 80rpm.
2) In the kinetic coefficient of friction using the angle of contact on the pulley. In this case the centrifugal force applying to the straw is neglected.
(1) The kinetic coefficient of friction is given by the following equation (9).
μ = 1/φ log ((W_1/W_2))
μ : kinetic coefficient of friction of straw
φ : angle of contact (redian)
W1 , W2 : pulling force applied to the tight side and to the slack side, respectively(kg)
(2) Increasing of relative velocity between straw and pulley, the kinetic coefficient of friction decreases in gradually, but the tendency differs from the nature of contacting material and pulley.
(3) After driving, the kinetic coefficient of friction decreases gradually regarding with the contacting material having the high water content, but after about three minutes, it becomes to the constant value.
3) From upper results these methods can be easily able to measure the kinetic coefficient of friction.