Rangekeeper

[1] These warship-based computing devices needed to be sophisticated because the problem of calculating gun angles in a naval engagement is very complex.

[3] Even during the American Civil War, the famous engagement between the USS Monitor and the CSS Virginia was often conducted at less than 100 yards (90 m) range.

[3][5] Between the American Civil War and 1905, numerous small improvements were made in fire control, such as telescopic sights and optical rangefinders.

While the British were thought by some to have the finest fire control system in the world at that time, during the Battle of Jutland only 3% of their shots actually struck their targets.

The one British ship in the battle that had a mechanical fire control system turned in the best shooting results.

Pointer following could be accurate, but the crews tended to make inadvertent errors when they became fatigued during extended battles.

[11] [12] During their long service life, rangekeepers were updated often as technology advanced, and by World War II they were a critical part of an integrated fire control system.

The incorporation of radar into the fire control system early in World War II provided ships with the ability to conduct effective gunfire operations at long range in poor weather and at night.

The battleship USS North Carolina during a 1945 test was able to maintain an accurate firing solution[15] on a target during a series of high-speed turns.

The effectiveness of this combination was demonstrated in November 1942 at the Third Battle of Savo Island when the USS Washington engaged the Japanese battlecruiser Kirishima at a range of 8,400 yards (7.7 km) at night.

[17] The Japanese during World War II did not develop radar or automated fire control to the level of the US Navy and were at a significant disadvantage.

1/1A's mechanism support plates, some were up to 1 inch (25 mm) thick, were made of aluminum alloy, but nevertheless, the computer is very heavy.

On at least one refloated museum ship, the destroyer USS Cassin Young (now in Boston), the computer and Stable Element more than likely still are below decks, because they are so difficult to remove.

Individual mechanisms were mounted onto thick aluminum-alloy plates, and along with interconnecting shafts, were progressively installed into the housing.

[21] [full citation needed] Practical rangekeepers had to assume that targets were moving in a straight-line path at a constant speed, to keep complexity within acceptable limits.

A sonar rangekeeper was built to track a target circling at a constant radius of turn, but that function was disabled.

Shrewd design meant that the data carried by these shafts required no manual zeroing or alignment; only their movement mattered.

1/1A included many miter-gear differentials, a group of four 3-D cams, some disk-ball-roller integrators, and servo motors with their associated mechanism; all of these had bulky shapes.

Space was at a premium, but for precision calculations, more width permitted a greater total range of movement to compensate for slight inaccuracies, stemming from looseness in sliding parts.

However, it had no mechanical multipliers or resolvers ("component solvers"); these functions were performed electronically, with multiplication carried out using precision potentiometers.

These were stabilized primarily by rotary magnetic drag (eddy-current) slip clutches, similar to classical rotating-magnet speedometers, but with a much higher torque.

This spring offset the null position of the contacts by an amount proportional to motor speed, thus providing velocity feedback.

A more elaborate scheme, which placed a rather large flywheel and differential between the motor and the magnetic drag, eliminated velocity error for critical data, such as gun orders.

1A computer integrator discs required a particularly elaborate system to provide constant and precise drive speeds.

[10] Rangekeepers were only one member of a class of electromechanical computers used for fire control during World War II.