Kerrison Predictor
It was used to automate the aiming of the British Army's Bofors 40 mm guns and provide accurate lead calculations through simple inputs on three main handwheels.
Such devices had been used on ships for gunnery control for some time, and versions such as the Vickers Predictor were available for larger anti-aircraft guns intended to be used against high-altitude bombers.
Kerrison's analog computer was the first to be fast enough to be used in the demanding high-speed low-altitude role, which involved very short engagement times and high angular rates.
Machine guns had been the preferred weapon against these targets, aimed by eye and swung by hand, but these no longer had the performance needed to deal with the larger and faster aircraft of the 1930s.
However, existing gunnery control systems were inadequate for the purpose; the range was too far to "guess" the lead, but at the same time close enough that the angle could change faster than the gunners could turn the traversal handles.
The "output" of the device drove hydraulic servo-motors attached to the traversal and elevation gears of the otherwise unmodified Bofors gun, allowing it to follow the predictor's indications automatically without manual intervention.
The Kerrison predictor did not calculate fuse settings, as the shells fired by the 40 mm Bofors gun, with which it was designed to work, were contact-fused.
[5] In September 1940, General George C. Marshall asked the British for the loan of four Bofors 40 mm guns with Kerrison Predictors for testing.
During testing the Kerrison Predictor provided accurate fire control to a range in excess of 1,500 m (4,900 ft), and the Bofors gun was reliable.
To ease production problems, the Army reluctantly standardized on the 40 mm in February 1941; the U.S. was building the Bofors for the British under the Lend-Lease Program.
The Predictor's plans were passed to Sperry Corporation, who were just commencing production of their own complex high-altitude system, the M7 Computing Sight, and had no excess capacity to produce the new design as well.
[8] To produce the devices rapidly enough, Singer implemented massive changes in the company, including building new factories and the switching of a foundry from steel to aluminium.
The timing proved excellent; late that summer, the Germans started attacking London with the V-1 flying bomb, which flew at high speeds at low altitudes.
John Whitney purchased one (and later a Sperry M7) and connected the electrical outputs to servos controlling the positioning of small lit targets and light bulbs.
