. Deep borehole surveys and problems. Boring. PENDULUM METHODS 169. Fig. 105. equalizes the elasticity constant proper to each of the two perpendicular axes, making it the same in all directions.^ An ingenious mechanism gives the necessary impulse to the pendulum at each station. For convenience in reading, the ellipse caused by the pendulum under this impulse should be as nearly a circle as possible. This mechanism consists of a crank on point P (Fig. 106) capable of being dis- placed along its vertical axis. It is brought to its initial angular position by a coiled spring and to its vertical
. Deep borehole surveys and problems. Boring. PENDULUM METHODS 169. Fig. 105. equalizes the elasticity constant proper to each of the two perpendicular axes, making it the same in all directions.^ An ingenious mechanism gives the necessary impulse to the pendulum at each station. For convenience in reading, the ellipse caused by the pendulum under this impulse should be as nearly a circle as possible. This mechanism consists of a crank on point P (Fig. 106) capable of being dis- placed along its vertical axis. It is brought to its initial angular position by a coiled spring and to its vertical position by a plate spring. By the action of a surface-operated electric motor placed above the pendulum top, a half turn is given to the coil spring and simultane- ously, by means of a ramp, the crank is displaced on its vertical axis. P strikes against a copper dome on the pendulum and the crank is liberated from the action of the motor, and under the influence of the spring it describes an arc aM and rises back to its former position. Point a, struck by P, describes a tangential trajectory to the arc. At the moment of release a is going along the tangent M and the pendu- lum has to describe the ellipse of major axis NN'. If the impulse is suited the path NN' will equal a circle MM'. Actually in the grating or grid the thin bars (reglets) or coordinate lines are fine V grooves cut in the spherical silver grating plate (Fig. 107). The pendulum point (Figs. 104 and 108) breaks circuit with the grating surface at these coordinate lines, the break being recorded by the electromagnet controlled pen in the surface receiver. This receiver (Fig. 109) is a ^Loc. cit., pp. 72 et seq. The counterforce of the cross springs in the suspension is analyzed here with the aid of Fig. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the o
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