The predecessor of the modern Loadicator and other computerized calculators was the Ralston Stability and Trim Indicator. I can still see the captain and first officer hunched over this mysterious fully analog instrument and moving the small weights over the ship’s plan which was engraved inside the box. All very impressive we thought.
The instrument consisted of an aluminium base plate upon which was engraved an outline diagram of the ship and its compartments. The plate was set in a heavy brass frame and could be balanced on suspension points in a fore-and-aft, or athwartshps direction. A mechanical calculating device is fitted to the upper part of the frame and this includes various scales for calculating the ship’s stability and trim. The instrument is housed in a mahogany case which contains two drawers for storing weights.