This is the U.S. Patent Office model for a printing pinwheel calculating machine patented by Frank S. Baldwin of St. Louis, Mo., in 1875. The machine has a brass base, two open brass pieces on each side that form a frame, and a brass, steel, and wooden mechanism. A cylindrical drum mounted horizontally on the frame is 11.5 cm. (4-1/2”) in diameter and 5 cm. (2”) in height.
Both ends of this drum are perforated with six round holes. The drum slides along the shaft into a series of position and may be fixed in place by a small lever. Along the surface of the drum are three slots in which levers slide. The levers may be set at any digit from 0 to 9. Moving a lever from 0 to a given number moves a steel arc that pushes the corresponding number of pins above the surface of the cylinder opposite the lever. Rotating the large cylinder rotates a series of intermediate wheels in proportion to the number of raised pins.
These wheels are linked to a set of seven cogwheels, each having ten teeth. On the outer edge of each tooth is a number in type, the numbers ranging from 0 to 9. These cogwheels are linked to a second set of three larger cogwheels that also have digits in type. These wheels may be intended to indicate the multiplier. The front of the two sets of type-wheels has a brass cover that contains a manually operated printing mechanism. The machine has no paper or ribbon
The machine is marked on the large cylinder next to the slots for the three levers: F.P. Baldwin (/) St. Louis, Mo.
Baldwin applied for his patent September 8, 1873. A few examples were manufactured and sold by the Reliance Machine Works of Philadelphia.
Compare to a production model of the machine, MA.310229.
U.S. Patent 159244, February 2, 1875.
“Baldwin’s Arithmometer,” Philadelphia, Reliance Machine Works, about 1875.
P. A. Kidwell, “The Adding Machine Fraternity at St. Louis: Creating a Center of Invention, 1880–1920,” IEEE Annals of the History of Computing, 22 #2 (April–June 2000), pp. 4–21.
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