Patent GB-274526-A (GB)
Abstract: 274,526. Henderson, Sir J. B., and Perham, A. L. Feb. 16,1926. Gunnery calculators. - Anti-aircraft fire-control apparatus, for determining the angle at which a gun should be aimed to hit a moving aerial target is designed so that the air is taken as the datum of reference the angles of elevation and bearing appropriate to a virtual future position of the target due to its air speed, assuming there is no wind and neglecting the speed of the gun, being first calculated, and corrections to compensate for the deflections due to the gun speed relatively to the air being then superimposed on these predicted angles. Preferably the apparatus comprises three adjustable vector or crank mechanisms representing respectively the course and speed of the target relatively to the air, the course and speed of the target relatively to the gun, and the direction and speed of the wind relatively to the gun. These vector mechanisms are linked together and are also linked to pointers which indicate the vertical and lateral angular velocities of the line of sight so that the apparatus may be operated at will on the basis either of the course and speed or of the angular velocities. It is assumed that the height, course and speed of the target remain constant during the time involved in prediction, and that the height is known by actual measurement. The average horizontal component of the velocity of the shell (A.V.h) is adopted as the independent variable. The apparatus shown in Fig. 1 comprises predicting mechanism, a sight having transmitters 200, 201 for transmitting the angles of sight and bearing to the predictor, a gun having elevation and training receivers 190, 191, and a gyro compass 207 which controls the bearing indicator through differential gearing. The predicting mechanism is designed to solve continuously the following four equationsin which t is the time of flight of the projectile, E.S.t and E.S.a the enemy speeds towards and across respectively, e the vertical angular velocity of the line of sight and b the angular velocity of the line of sight in azimuth, S1 the present angle of sight, S2 the future angle of sight, H the height of the target, and Z the azimuthal deflection of the line of sight in the time t. In applying the wind and gun speed corrections the following equations are usedin which # is the quadrant elevation, V the initial velocity of the shell, W, the component of relative wind up the range, and w2 the relative wind component across the range. The enemy air speed crank 3, enemy apparent speed crank 2, and relative wind crank 1, 1<b> are linked together as shown in Fig. 2, by a pantographic linkage and are geared by a chain 4<a> to the target bearing dial 4 so as to rotate in unison therewith, the wheel 1<b> of the wind crank being shown of half the diameter of the others as it drives its crank through a two to one gear. Equations (3) and (4) are solved by mechanism controlled by the enemy air speed crank 3, this mechanism causing a shaft 87 carrying a quadrant elevation drum 88 to be rotated through an angle proportional to S2, and also causing deflection of a bearing indicator 64. The mechanism for solving equation (4) comprises a cross-head 14, sliders 11, 55, and 61 and lever 58 acting on an arm 64 which by a pointer 94 indicates Z on the target bearing dial 4. The future bearing is transmitted to the gun by a transmitter 101<a>. The slider 55 is set in accordance with A.V.h by means of a handle 56a and with reference to a drum 59 rotating with the shaft 87 and carrying curves involving A.V.h and H. The right-hand side of equation (3) is solved by the floating lever 70 which is influenced by the sliders 10, 55. lever 51 and link 53 and also by a slider 65 influenced by a stud on the bearing arm 64, the final result being that a bar 73 attached to the end of the floating lever 70 receives a movement proportional to The left-hand side of equation (3) is solved by mechanism, shown separately in Fig. 8, for coupling two shafts together so that the cotangents of their angles of rotation are always in a definite ratio, this ratio being capable of adjustment. this mechanism comprises a worm wheel 74, Fig. 1, turned through S1 by the spindle 46. The shatt 74<a> of the worm wheel carries a frame 75 having guides 76 on which a slotted cross piece 77 slides. The cross piece has a transverse groove 78 engaged by a pin 79 on the bar 73 and is the equivalent of the centre disc of an Oldham coupling. On the other side of the cross piece is a central pin 82 engaging a slot in an arm 81 on a shaft 80 which operates the drum shaft 87 through differentia gear 83, 84 also operated by the worm wheel 74 in such a manner that the shaft 87 is rotated through 4S2. The quadrant elevation is obtained by moving a pointer 89, by means of a hand-wheel 91, on to the appropriate curve on the drum 88, and this quadrant elevation is transmitted to the gun by a transmitter 90<a>. The fuse time is obtained by moving a pointer 211 by means of a hand-wheel 214 with reference to a drum 87 and is transmitted by a transmitter 215. Equations (1) and (2) are solved by mechanism comprising sliding cross heads 6, 7 operated by the enemy apparent speed crank 2 a sliding height bar 29 set by a hand-wheel 32 and various sliders and levers shown at the bottom of Fig. 1. The angle of sight is set on the dial 47 by means of a hand-wheel 48 and sin 2S, is derived from this and applied to a slide 38 by a crank and pin mechanism 39, 40, the crank being rotated through 2S1. A slide 42 is moved a distance proportional to tan S1 by a pinion 43 rotated by cam gearing 44, 45. If the enemy apparent speed and course is known it is set on the crank 2 and the angular velocities of the line of sight are indicated by the pointers 21, 22. If the course and speed is not known the handles 7<b>, 9<b> are operated to set the pointers in accordance with the observed angular velocities and the crank is set thereby. To apply the wind and gun speed corrections, the quadrant elevation drum 88 and the shaft 101 which sets the bearing dial 4 are moved axially by mechanism operated b the relative wind crank 1 and designed to solve equations (5) and (6)