Origin of modern calculating machines

by J. A. V. Turck

The Barbour Multiplier

The accumulator mechanism of the Barbour machine, including the numeral wheels and their devices for transferring the tens, is mounted in a sliding carriage at the top of the machine ([see Fig. 1]), which may be operated by the hand-knob.

Description of Barbour Multiplier

Extending through the bottom of the carriage are a series of pinions, one for each ordinal numeral wheel, and connected thereto by a ratchet and pawl action. The pinions are each so arranged as to be operative with a gear rack beneath the carriage when the carriage is slid back and forth.

Thus the wheels received action from one direction of the motion of the carriage and remain idle during the movement in the other direction. The degree of motion so received would, of course, depend upon the number of teeth in the racks below encountered by the pinions.

The gear racks employed by Barbour were numerous, one being provided for each multiple of the nine digits, arranged in groups constituting nine sets mounted on the drums marked B ([see Fig. 4]). Each of these sets contain nine mutilated gear racks, the arrangement of the teeth of which serve as the multiples of the digit they represent.

The teeth of the racks representing the multiples of the digits were arranged in groups of units and tens. For instance: 4 × 6 = 24, the rack representing the multiple of 4 × 6 would have two gear teeth in the tens place and four gear teeth in the units place, and likewise for the eighty other combinations.

Adding the multiples of the digits by overlapping the orders was accomplished by a very simple means, the arrangement of the racks being such that as the carriage was moved from left to right the numeral wheel pinions would move over the units rack teeth of a multiplying rack of one order and the tens rack teeth of a multiplying rack in the next lower order.

By close examination the reader will note [from the drawings] that the lower one of the sets of multiplying gear racks shown on the drum B, to the left in [Fig. 4], is the series of one times the nine digits, the next set or series of racks above are the multiplying racks for the multiples of two, the lowest rack in that series having but two teeth, the next higher rack four teeth, the next rack six and the next eight.

So far no multiple of two has amounted to more than a units ordinal place, therefore these racks operate on a lower-order numeral wheel, and are all placed to the right of the center on the drum B, but the next rack above for adding the multiple of two times five requires that one shall be added to a higher order, and is therefore placed on the left side of the center of the drum.

Thus it will be noted that by reading the number of teeth on the right of each rack as units and those on the left as tens, that running anti-clockwise around the drum, each series of multiplying racks show multiples of the digits from one to four, it being obvious that the racks for adding the multiples of the higher digits are on the opposite side of the drums.

From the layout of the racks it is also obvious that the starting or normal position of the carriage would be with the numeral wheel pinions of each order in the center of each drum, so that as the carriage is moved to the right the units wheel will receive movement from the units teeth of the rack on the units drum, while the tens wheel will receive movement from the units teeth of the tens drum and the tens teeth of the units drum, and so on with the higher wheels, as each numeral wheel pinion except the units passes from the center of one drum to the center of the next lower and engages such teeth as may be presented.

Each of the drums B are independently mounted on the pivot shaft C, and are provided with the hand-operating setting-racks I and E, co-acting with the gears R and D, to help in bringing the proper racks into engageable positions with the pinions of the accumulator numeral or total wheels.

The hand-knob G, [Fig. 4], and the gears f, fast to a common shaft, furnish a means for operating the whole series of drums when the right multiple series of racks of each drum have been brought into position.

As an example of the operation of the Barbour calculator, let us assume that 7894 is to be multiplied by 348. The first drum to the right would be moved by its setting-racks until the series of multiplying racks for adding the multiples of four are presented, the next higher drum to the left would be set until the series of multiplying racks for adding the multiples of nine were presented, the next higher drum would be set for the multiples of eight, and the next higher drum, or the fourth to the left, would be set for the multiples of seven. Then the hand-knob G, first turned to register zero, may be shoved to the right, engaging the pinions f with the gears D, and by turning the knob to register (8), the first figure in the multiplier, the racks are then set ready to move the numeral wheels to register as follows: The drum to the right or the units drum has presented the multiplying rack for adding the multiple of 8 × 4, thus it will present three teeth for the tens wheel and two teeth for the units wheel. The tens drum presenting the rack for adding the multiple of 8 × 9 will present seven teeth for the hundreds wheel and two for the tens wheel. The hundreds drum presenting the rack for adding the multiple of 8 × 8 will present six teeth for the thousands wheel and four for the hundreds wheel.

From Drawings of Bollee Patent No. 556,720

The rack of the thousands drum representing the multiple of 8 × 7 will present five teeth for the tens of thousands wheel and six for the thousands wheel. Thus by sliding the carriage to the right one space, the numeral wheel pinions will engage first the units teeth on one drum, then the tens teeth on the next lower drum and cause the wheels to register 63152. The operator, by turning the knob G to register (4), the next figure of the multiplier, turns the drum so that a series of multiplying racks representing multiples of 4 times each figure in the multiplicand are presented, so that by sliding the carriage another space to the right, the multiple of 4 × 7894 will be added to the numeral wheels. The operator then turns the knob to register three and moves the carriage one more space to the right, adding the multiple of 3 × 7894 to the wheels in the next higher ordinal series, resulting in the answer of 2747112.

There are, of course, many questionable features about the construction shown in the machine of the Barbour patent, but as a feature of historic interest it is worthy of consideration, like many other attempts in the early Art.