OTIS KING Model K, 1920
Inventor
OTIS Carter Formby King
Invention date
Around 1920
Manufacturing date:
1922 to 1972 (n° Y 7059)
Manufacturing location
London, UK
Manufacturer
Carbic, Ltd.
Dimensions
L 21
Reference Number
213
History and Functionality
Otis Carter Formby KING (1876 – ?) was an English engineer. He invented a slide rule with a helical cylindrical scale and filed a patent in his name. It was manufactured by CARBIC, Ltd. in London from 1922 to 1972. Production reached 150,000 devices. It has two logarithmic scales wound around the cylinder.
This is the equivalent of a straight slide rule of 1.72 meter long. The K model can perform multiplications, divisions, proportions and percentages. The L model incorporates the features of the K model and can do powers and roots.
To multiply two numbers, one must match the index at the bottom of the cursor (black sleeve) with the multiplicand taken on the lower scale, and align the origin of the upper scale on the upper index of the cursor and then slide the cursor on the multiplier on the upper scale. The result is indicated by the index at the bottom of the cursor on the lower scale.
This instrument is easily handled and transported. However, its selling price was high compared to straight slide rules.
About The Inventor
Otis Carter Formby King (1876–1944) was both a grocer and an electrical engineer who lived in London.
He invented and produced the Otis King’s Patent Calculator, a cylindrical slide rule with helical scales, primarily aimed at business applications initially.
This invention was manufactured and sold by Carbic in London from about 1922 to about 1972.
Despite its intended precision, the Otis King calculator had some inaccuracies in tic-mark placement, affecting its scale readings
