Grant Experimental Model Calculating Machine

This lever-set non-printing connection pawl calculating machine is the last experimental model of George B. Grant, designed to incorporate subtraction and division as well as addition and multiplication. It has a wooden base and a brass frame. Five pins slide to set numbers. Positions next to the pins are labeled from 0 to 9. Moving back a pin drives back a toothed rack.

Behind the racks is a movable carriage with 11 gears on it. The carriage can be set at six different positions. When the racks are pushed back (there is no cam to drive the racks), the gears are engaged, and rotate in proportion to the number set. The gears move in the opposite direction when the racks are moved forward. Carry teeth are arranged in a spiral shaft above the carriage. A lever at the front of the machine may be rotated in a way that may affect the action of the carry shaft. A crank on the right zeros the result shaft.

This model represents Grant’s enduring interest in the improvement of calculating devices. It did not lead directly to any commercial product.

Currently not on view