Revolving Circular Charts

Revolving Circular Charts

Revolving circular charts, also known as rotating circular charts or circular slide rules, are mechanical devices used for calculation and measurement. They consist of two or more circular disks that rotate around a common axis, with markings and scales engraved on their surfaces. The disks are typically made of metal or plastic and are mounted on a central spindle or pivot. The user rotates the disks to align the desired scales or markings, and then reads the result from the intersection of the aligned scales. Revolving circular charts were widely used in the early to mid-20th century for a variety of applications, including navigation, engineering, and mathematics. They were particularly useful for calculations involving trigonometry, logarithms, and other complex mathematical functions. They were also used for converting units of measurement, such as distance, speed, and time. One of the most famous examples of a revolving circular chart is the E6B flight computer, which was used by pilots to perform a variety of calculations related to aviation. The E6B consists of two circular disks, one with scales for airspeed, altitude, and temperature, and the other with scales for fuel consumption, time, and distance. By rotating the disks and aligning the desired scales, pilots could calculate their ground speed, fuel consumption, and other important flight parameters. Although revolving circular charts have largely been replaced by electronic calculators and computers, they remain popular among collectors and enthusiasts. They are also still used in some specialized applications, such as navigation and surveying.

mechanical devices, calculation, measurement, trigonometry, logarithms

— Joseph Nelson

CITATION : "Joseph Nelson. 'Revolving Circular Charts.' Design+Encyclopedia. https://design-encyclopedia.com/define/revolving-circular-charts?E=399491 (Accessed on October 14, 2026)"