Studies on the Earth-Drilling Machine for Orchard (I)

Abstract

The authors have conducted some experiments connecting upon the faculty of earth drilling machine.
Some results from our earth drilling tests by means of a new experimental device, equipped with a torque pick up, are expressed.
(1) Total drilling torque to dig the hole into the earth may be considered to be expressed as follows:
T=T_f+(T_a+T_m+T_s)×1/η×i≤T_e
where T: total earth drilling torque, kg-m
T_f: driving torque of flexible shaft itself, kg-m
T_a: driving torque of auger itself on no load, kg-m
T_m: torque influenced by moving conditions of auger such as penetrating and peripheral speed under the ground, kg-m
T_s: torque influenced by soil conditions such as the hardness, moisture content, roots and gravel, and others under the ground, kg-m
η: mechanical efficiency of machine
i: reduction ratio
T_e: required mean torque of engine, kg-m
(2) Torque requirements of flexible shaft increased with the degree of bending were measured. (Fig1-4).
The torque diagrams of flexible shaft repeat complicated periodic cycle according to the bending, radius of curvature and rpm etc.
The inverse torque (minus torque) occured at the bending of 90°, 120° (Fig 5)
(3) The torque of earth drill increases as the weight fixed upon handle does. (Fig7-(1)).
The drilling speed of earth drill is influenced by the weight x
y=0.0121x+1.36075
where y: drilling speed into the earth, (cm/sec)
x: total weight mounted on an auger, kg.
(4) The comparison of the reacting torque between the different size of auger may be considered to be expressed by following relation:
T_L=K×(R_L/R_S)²×T_S
where T_L: reacting torque of the larger auger (radius of the auger is R_L)
T_S: reacting torque of the smaller auger (radius of the auger is R_S)
K: constant, (K=0.97, using total mean torque in this experiment)
The reacting torque appears sensible according to the existence of obstacle in the earth, and often occurs beyond the theoretical value.