Patent GB-349989-A (GB)
Abstract: 349,989. Anti-aircraft gunnery. HENDERSON, SIR J. B., 38, Blackheath Park, and PERHAM, A. L., 23, Girdler's Road, both in London. Dec. 31, 1929, No. 39908. [Class 92 (ii).] Sights and methods of sighting.-A predictor mechanism, for use with the apparatus for sighting and controlling anti-aircraft and other guns described in Specification 331,895, [Class 92 (ii), Ordnance &c.], determines the direction of the target or the required direction of the gun's axis with respect to two horizontal co-ordinate axes whose azimuth does not necessarily vary with azimuthal movements of the said direction. The required directions are determined in each case by the line of intersection of two planes angularly movable about the co-ordinate axes OX and OY and called the X and Y planes respectively. 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 the predictor which adds the vector represented by the product of speed of target and time of flight of projectile suitably corrected for wind and speed of platform, and thereby determines the co-ordinates of the future position of the target. The determined direction of the gun to hit the target, which may be referred to axes OX<1>, OY<1> movable in azimuth with respect to the axes OX, OY, is passed on to the gun through ideal and dummy guns as described in the prior Specification. The predictor shown in the Figure has pointers 5, 6 moved by repeat motors 1, 2 in accordance with the Y and X angles transmitted from the sighting pedestal of the prior Specification and followed by pointers 5<1>. 6<1> moved by vertical slots in slides 7, 8 which slots engage over crank pins 9, 10 the radius of which is adjusted for height set up on a dial 19 by the repeater motor 16. The movements of slides 7, 8 therefore give the x and y co-ordinates of the present target position. The target speed and heading are set on a crank pin 30, and the x and y components of this speed are obtained by slides 32, 33 and multiplied by the time of flight through levers 38, 39, the resulting components being added through slides 52, 53 to the motion of the slides 7, 8 by differential rack gears 521, 53<1> to operate bars 54, 55 and position a pin 56 in accordance with future horizontal range. The time of flight is conveyed to the levers 38, 39 by a bar 43 operated by a hand-wheel 44 which sets an index 47 to the appropriate height curve on a " time of flight " drum 48 which is rotated in accordance with future range by a cord 57 connected to the pin 56. Corrections for true wind and speed of platform are introduced by the crank pins 66, 68, set to the appropriate phase and radius which combine through levers 75, 77 to give the components of relative wind on sliders 76, 78. These components are through a bar 82 and levers 84, 85 multiplied by the factor Hg cosec #/v obtained from drum 62 as described in the prior Specification, and through bars 89, 92 and differential rack gear 89<1>, 92<1> the corrections are added to the movements of the bars 54, 55 to move slides 96, 97 in accordance with the co-ordinates of future gun axis position. The motion of these slides is conveyed to slotted disc mechanism 121, 122 as described in the prior Specification and transformed by using the Hg curves on drum 61 into the appropriate X and Y angles on pointers 137, 138 which are followed by pointers 137<1>, 138<1> moved by motors 148, 149 which convey the setting to the ideal gun. As in the prior Specification, the discs 121, 122 may be free to rotate to give an azimuthal displacement to to axes OX, OY to a position OX' OY<1> more suitable for the gun. Such displacement is conveyed by rod 134 to a training dial 135. This dial is fitted with differential gear so as to aggregate the displacements due to (1) training of OY relatively to the gun platform conveyed by motor 179, and (2) angle YOY<1> conveyed by rod 134, the aggregate being conveyed to a commutator arm 163 which controls the motor 180 that restores the arm to zero. Transmitter 181 conveys the training angle to the dummy gun. Targets at low angles of elevation are followed by training and by elevating the X plane only, the Y plane being kept vertical. Horizontal range is then used in place of target height and a switch 108 is operated to bring into use the range dial 105 in place of the height dial 19. Rate of change of horizontal range is conveyed to pointer 104 by motor 181<1> and variable speed gear 182 controlled by linkage 186, 188, operated by the bar 33 and slide 78. Spotting corrections are applied by hand-wheel 191 through differential gear 183. The pointer 104 is followed by pointer 104<1> operated from the slide 8 which is moved by the motor 101, the pointer carrying contacts to stop the motor when the pointers coincide. The sighting pedestal shown at the right-hand bottom corner of the Figure and described in the prior Specification has its canopy trained by hand gear 156 the transmitter 154 conveying the setting for direction and heading of target shown by scale 210 to the disc 31. When used on board ship, a gyro-compass 159 applies the correction for yaw or change of course, a transmitter 155 conveying the displacements to disc 67 and to motor 179. In a modification, Fig. 10 (not shown) the drum charts 61, 62, 48 are replaced by rotary snail cams and a modified means is employed for converting the components of range into the X<1> and Y<1> angles furnished by the discs 121, 122.