The Brownrigg Keyboard was a fairly clumsy but flexible manual means of plotting range cuts on the range plot of a Dreyer Fire Control Table invented by Commander Henry J. S. Brownrigg. It represented each observation by pricking a hole in the paper from the bottom up.
Impetus and Design
The Original Dreyer Table and the early revisions of the Mark III Dreyer Table had automatic plotters for range. This design, however, did not readily lend itself to permitting more than the single rangefinder connected to the plotter to lend its input to the fire control problem. The practice taken in those events was to disengage the automatic plotter and to use coloured pencil marks applied by hand at the proper position[Citation needed]. An effort was made to scale up the original plotter with an automatic pneumatic plotter designed by Lieutenant Patrick Macnamara which apparently proved problematic,[Inference] leading to a search for a simple expedient. The Brownrigg keyboard was chosen on 6 July 1914, and 9 more keyboards were ordered on 7 August 1914.
The keyboard recorded range cuts by punching small holes in the range plot paper at the proper position. It was rather cumbersome in design. It locked into detents spaced at 1000 yard (5 inch) intervals on a bar across the range plot (a large spacebar-like key functioned to free it to move between detents). 40 smaller keys each represented a different offset at 50 yard intervals from this central position, ranging from 1000 yards below the central position to 950 above it. When any one of these was struck, a separate needle would pierce the plot at the corresponding position.
Nine Brownrigg keyboards were ordered on 7 August 1914, probably going to the Mark IV and IV* tables. The Brownrigg keyboards were probably on most or all Dreyer tables through the Battle of Jutland, although it is possible that some Mark III tables used the pencil-in-hand method. During 1917,[Citation needed] it was replaced by the Range Typewriter, which was more elegant to use and could represent the data from up to 9 individual rangefinders with identifying marks to assist in judging the quality of the separate sources.
- Captain F.C. Dreyer's Fire Control Apparatus, Mark IV. Fig. V.
- Brooks. Dreadnought Gunnery and the Battle of Jutland. p. 171.
- Brooks. pp. 171-2 and endnote 158.
- Brooks, John (2005). Dreadnought Gunnery and the Battle of Jutland: The Question of Fire Control. Oxon: Routledge. ISBN 0714657026. (on Amazon.com and Amazon.co.uk).
- Elliott Brothers, London (1916). Captain F. C. Dreyer's Fire Control Apparatus, Mark IV. Copy 19 "as fitted in H.M.S. Royal Oak" at H.M.S. Excellent Library, Portsmouth, United Kingdom.