Patent GB-842009-A (GB)
Abstract: 842,009. Calculating-apparatus. XAMAX A.G. Aug. 14, 1956 [Sept. 14, 1955], No. 24804/56. Class 106 (1). In a gunnery calculator having intersecting index arms which automatically pick off the appropriate trajectory and flight time curves from charted families of these curves in accordance with set height and position data, these arms are also adjusted in accordance with certain other settable factors related to air density and muzzle velocity. A table 23, Figs. 1 and 15, has a part circular cut-out 24 and an azimuth turntable 27 is rotatable about the centre 54 of the cut-out. A zero marker 142 for a reference bearing is plugged into holes 143 in the table and azimuth values of the turntable position are read on a scale 145 against the marker. A chart 60 of trajectory curves 146 and flight-time curves 147 is secured to the turntable, a transparent index arm 81 for horizontal trajectory distance overlying the chart and being carried by a distance slide 68 traversible along rails 69 and 70 of the turntable by rack and pinion mechanism 74. A second index arm 82 for trajectory height is carried by a slide 76 on an arm 75 extending outwardly from the slide 68. Map co-ordinate positions are represented by scales 30 and 31 which are marked off so that the gun position corresponds approximately to the centre point 54. The scale 30 is fixed to the table 23, whilst the scale 31 is carried by a slide 35 adjustable along the scale 30, position table 40 being adjustable along the scale 31. In using the apparatus, as so far described, the table 40 and slide 35 are adjusted to the exact gun position co-ordinates and a needle disposed at the centre 54 operated to puncture the table 40. The table 40 and slide 35 are next adjusted to the target co-ordinates and the turntable 27 and slide 68 then adjusted to bring a reference marker 111 on the slide over the puncture point in the table. Finally, the slide 76 is adjusted to the difference in height of gun and target. The required values of gun elevation and flight time can now be read-off from the trajectory curve 146 and flight time curve 147 picked-off on the chart 60 by the crossed-over index arms 81 and 82. In order to correct for azimuth deviation due to spin of the projectile, the reference marker 111 (see also Fig. 10) is moved relative to the slide 68, its carrier arm 108 being pivoted at 109 and urged by a spring 127 against the follower 117 of a cam 112 adapted to be driven, through gearing 115 and 116, from the rack and pinion mechanism 74 which traverses the slide 68 in the target direction. The cam 112 is a multiple one with the sections distributed axially, the section appropriate to the size of charge used being engaged by traversing the follower 117 axially on its support 122 by turning a handle 129. The invention provides mechanism for adjusting the index arms 81 and 82 relative to the distance slide 68 in order to allow for variation in muzzle velocity, due to other factors than size of charge, and for variation in air density. The arm 81 is supported on the slide 68 by the engagement of rollers with a bar 206, Fig. 1, secured in the slide. A further roller 208 on the arm 81 travels along a straight bar 150 as the slide moves, and the two ends of this bar are adjustable by means of knobs 156 and 157, and scales A and E. The arm 75 carrying the index arm 82 is guided between rollers 192 in the distance slide 68 and has a further roller 196 adapted to travel along a pair of pivotally connected straight edges 151 and 152. These straight edges are mounted upon a correction slide 170 which is adjustable along the rails 69 and 70, and relative to the distance slide 68, by means of a handle 177, a scale 189 and index 188 showing the adjusted position. The free ends and centre joint of the straight edges are adjusted by handles 174, 175 and 176, scales B, C and D showing the adjusted positions.