Grant Experimental Model Calculating Machine

George B. Grant’s so-called grasshopper calculating machines sold in only modest numbers. However, he remained intrigued by the prospect of improving calculation, and continued to design prototype machines. This is the experimental model for a reversing machine designed to subtract and divide as well as to add and multiply.

As in Grant's earlier invention, this connection pawl non-printing manually operated machine has an open iron frame with steel and brass parts and paper labels. Five pins at the front of the machine slide to set numbers. Next to two pins is a thin strip of paper with the digits from 0 to 9 printed on it, the digits increasing toward the back of the machine. Moving back a pin not only drives back one toothed rack but has the reverse affect on a rack adjacent to it, bringing it forward. There also is a second rack with a single tooth at the far right.

Behind the racks is a movable carriage with one group of 11 gears and another group of six gears on it. A paper strip with digits on it is next to each gear. The spiral shaft above the carriage is for carrying. The carriage is not fixed in the frame and does not engage the racks as presently arranged. It appears that the larger set of racks is intended to drive the 11 gears to form results, while the smaller set of gears is driven by the single rack and serves as a revolution counter.

A crank on the right zeros the result shaft.

The model was given to the Smithsonian by Grant’s half-brother, Edwin A. Bayley.

Reference:

Accession file.

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