From the Stark Patent Drawings
The Chapin machine, like that of Hill, was made without thought as to what would happen when a key was depressed with a quick stroke, as there was no provision for control of the numeral wheels against overthrow. As stated, the machine was designed to add two columns of digits at a time, and with an attempt to provide means to shift the accumulator mechanism, or the numeral wheels and carry-transfer devices, so that columns of items having four places could be added by such a shift. Such a machine, of course, offered less than could be found in the Hill machine, and that was nothing at all so far as a possible operative machine is concerned.
The Stark Machine
The [reproduction of the patent drawings] of the Stark machine illustrated on the opposite page show a series of numeral wheels, each provided with three sets of figures running from 1 to 9 and 0.
Description of Stark machine
Pivotally mounted upon the axis of the numeral wheels at each end are sector gears E¹ and arms E⁴, in which are pivoted a square shaft E, extended from one arm to the other across the face of the numeral wheels. The shaft E, is claimed to be held in its normal position by a spring so that a pawl, E², shiftably mounted on the shaft, designed to ratchet or actuate the numeral wheels forward, may engage with any one of the numeral wheel ratchets.
A bail marked D, is pivoted to standards A¹, of the frame of the machine, and is provided with the two radial racks D³ which mesh with the sector gears E¹. It may be conceived that the act of depressing the bail D, will cause the actuating pawl E², to operate whichever numeral wheel it engages the ratchet of.
The bail D, is held in its normal position by a spring D², and is provided with nine keys or finger-pieces d, eight of which co-act with the stepped plate G, to regulate the additive degree of rotation given to the numeral wheels, while the ninth has a fixed relation with the bail and the bail itself is stopped.
The keys d, marked from 1 to 8, are pivoted to the bail in such a manner that their normal relation to the bail will allow them to pass by the steps on the stepped plate G, when the bail is depressed by the fixed No. 9 key. When, however, any one of the keys numbered from 1 to 8 is depressed, the lower end of the shank of the key will tilt rearward, and, as the bail is depressed, offers a stop against the respective step of the plate G, arranged in its path, thus stopping further action of the actuating pawl E², but offering nothing to prevent the continuation of the force of momentum set up in the numeral wheels by the key action.
There was small use in stopping the action of the pawl E², if the ratchet and numeral wheel, impelled by the pawl, could continue onward under its momentum.