Patent GB-331895-A (GB)
Abstract: 331,895. Henderson, Sir J. B., and Perham, A. L. Feb. 13, 1929. Gunnery calculators.-R,elates to mechanism for sighting and controlling guns and particularly anti-aircraft guns which can be set by elevating, training, and cross-tilting gears to deal with targets from the horizon up to, and through, the zenith. According to the invention, a direction in space, such as the line of sight to the target, or the required direction of the gun's axis, is determined with respect to two co-ordinate axes which are maintained horizontal irrespective of the tilt of the supporting pedestal, sight, or gun and whose azimuth does not necessarily vary with azimuthal movements of the target, sight, or gun. The required direction in space is determined by the line of intersection of two planes angularly movable about the co-ordinate axes. The present position of the target having been found by the angular co-ordinates thus obtained, these are applied in the form of a vector to a predictor which adds the vector represented by the product of speed of target and time of flight of projectile suitably corrected for wind, and thereby determines the co-ordinates of the future position of the target. These are applied to an ideal gunforming part of the control device and passed on to a dummy gun pivoted on the same system as the actual gun. The systems of co-ordinate axes corresponding to the line of sight and the axis of the ideal gun are mounted on platforms which are automatically maintained level for all training positions of the gun platform. The present and future positions P, F, of the target are taken to be in the horizontal plane of the target shown in Fig. 2, and the height, speed, and course of the target are assumed constant during the time of flight of the shell. OX, OY are the axes of reference, and PA, PB the components of range obtained by the sighting device. Fig. 6 is a diagram showing how the components or range are applied by adjustable slides 4, 5 to a pin 8 on a pantograph, the pin 11 on which is set in a slotted disc 10 to a radius corresponding to "target speed X time of flight," the pin 14 receiving the vector addition of OP, PF, and the future position OF being conveyed to the ideal gun through a disc 12 carrying a diametral slide 13 with a radial slot for the pin 14. The disc 12 may in certain circumstances be free to rotate so as to give an azimuthal displacement of the axes OX, OY to a position more suitable for the ideal gun. The predictor, shown in Fig. 19, has pointers 92, 93 moved from the sighting device, and followed by pointers 102, 103 moved by hand-wheels 108, 109 to set a pin 114 for the components of present range. The movements imparted to the pointers 102, 103 are corrected for height of target " set up on a dial 94. The pin 114 corresponds to the pin 8 of Fig. 6, the pins 114, 116, 117 of the pantograph being shown symbolically on a link 115. The disc 131 corresponds to the disc 10, Fig. 6, and the throw of the pin 116 is adjusted bv a rack bar 130 moved in accordance with the product of the speed of the target, set by a pantograph gear 127, and the time of flight set up from a drum 118 by a bar 121 and bell crank 122. The movement of the pin 117 gives the future horizontal range OF and a second pantograph 117, 135, 136, the pin 136 of which receives the wind correction through a rack 150 similar to the rack 130, has its intermediate pin 135 connected by a pantograph link 156 to slotted-disc mechanisms 152, 153 which correspond to the disc 12 of Fig. 6. These resolve the movement of the pin 135 into components of future range set up by pointers 177, 178. The movements imparted to the pointers are corrected for quadrant elevation by introducing a height factor Hg=R tan #, where R is the future horizontal range, and the angle of quadrant elevation. The factor Hg is given by setting a pointer 182 to curves on a drum 132 which, together with the drum 118, is rotated proportional to R by a cord 134 connected to the pin 117. The wind correction, that is the vector displacement of the pantograph pin 136 for the initial deflection of the path of the shell as it leaves the gun with velocity V, is given by the formula Hg cosec # w/v where w is the wind velocity. This is applied to the rack 150 by a bar 140 which gives Hg cosec # obtained from w the drum 132, the factor - being introduced by v a pantograph gear 145. The pointers 177, 178 are followed by pointers 186, 187 rotated by gears 188, 189, the movements of which are conveyed to motors for setting the ideal gun, which setting is then applied to a dummy gun pivoted in the same manner as the actual gun.