GB114341A - An Aircraft Attack Instrument for Directin the Fire of Anti-aircraft Guns. - Google Patents

Abstract

114,341. Harris, F. March 29, 1917. Differential speed indicators; time-distance recorders; speed indicators operating by sighting acrial objects.-Consists of an instrument wherein the movements of an aerial target are reproduced to a known scale bv an indicator moving on an horizontal table which is adjustable in height to represent the height of the target. In the apparatus shown, the height, angle of site, and speed of an aerial target are determined from observations taken at two stations. The triangle having the target as apex is reproduced in miniature in the object plane by two rays of light produced by electric lanterns controlled respectively by the home sighting-device 10 and by a protractor device 33, 34, which is set in accordance with directions signalled from the distant station. The home sight 10, the two lanterns 12, 13 and the protractor 34 are all mounted in the same plane on an horizontal frame or shaft which is rotated by the sight to bring all the devices into the object plane. The rays are directed downwards on to an horizontal indicator 46 which is adjusted over an horizontal table 39, which itself is adjusted in height, until the rays fall beyond their points of intersection on two spots on the indicator spaced apart a distance equal to the distance between the pivots of the lanterns. The indicator 46 may be fitted with a pencil 46w, Fig. 11, to trace a graph on a map placed on the table. The pencil is moved up and down at regular speed by clockwork mechanism so that it marks a series of dashes, thus recording the speed of the target. A wheel 46m rolling on the table is provided with a clicking device whereby the speed of the target can be determined by counting the clicks in a given period of time. Reference has been directed by the Comptroller to Specification 13213/15, [Class 97 (i), Optical systems &c.].