Carries Stripped to the Bone: Episodes in the History of Coaxial Modular Digital Counters

Mechanical counters have been ubiquitous, and they had become so commonplace that little thought now is given to them. We could find such counters in many cars, where they served as odometer displays. They could and still can be found on other vehicles, such as bikes, on various machines, and so forth. The most common construction for such counters is made of rotating disks, which are all similar and located on the same axis. Such counters also were components of cash registers and of various calculating machines. Although they look simple in appearance, and perhaps standardized, they have a history of their own. Many such counters have been built for a variety of purposes until the current counters became widespread and before their replacement by electronic displays.

Alas, although much has been written on the history of calculating machines, very little attention has been paid to these components and their evolution.

In this article, we analyze three of the earliest known models of counters, which can be viewed as ancestors of the modern mechanical.

A Brief History of Counters

Analog Counters

The first counters were odometers (properly hodometers). This word is from the Greek hodometron (way measurer, from hodós, path, and métron, measure) and refers to a device for measuring a distance. Usually, what actually is measured is the number of steps of a person (we then speak of pedometers) or the number of revolutions of a wheel.

Odometers usually were made of various gears, especially wormgears, to slow down the motion and their display was by hands on dials. Such a display inherently was analogical. Actual pedometers are more specialized, and count the number of times a small weight has moved due to walking. Therefore, they can count steps and be used to estimate distances. In this article, we will focus on devices for measuring rotations and will not go into the details of pedometers.

The earliest (distance) odometers seem to go back at least to Vitruvius (1st century BC). Leonardo da Vinci (1452–1519) designed an odometer, probably inspired by Vitruvius. In the 16th century, some of the odometers were used for surveying and measuring distances in a territory. Beckmann^1,pp.2–19 mentions the odometers made by John Fernel around 1550, by Paul Pfinzing at the end of the 16th century, and others, although some of these odometers were not counting anything. Fernel's "odometer" seems to have merely struck a bell after each turn of a wheel, and one then had to count the number of such strikes.

Improvements in odometers were mainly about ensuring that they were automatic, that they counted properly, and that they could count large numbers of revolutions. Some constructions made use of differential gears; that is, they used two wheels moving at slightly different speeds, and the position of one wheel would be used on a dial placed on the other. This was the case, for instance, of Vaussin-Chardanne's "célérimètre" patented in 1835.^2,3

Most of these counters would never stop, but after a certain number of turns, they would repeat themselves.

Some of the odometers were not reversible. That was the case of the odometer invented by Meynier in 1724. Since it did not work backwards, an excedent of distance would have to be subtracted from the distance given by such a counter, if at some point the carriage went backwards and again forwards (the same distance being then counted twice). Outhier's improvement of Meynier's odometer in 1742 overcame this problem.^4–6

Other odometers were very much operating like chronometers, sometimes triggered by impulsions.⁷

During the 19th century, counters found new uses, for instance with the development of gas meters. The most widespread solution in the 1840s was the Samuel Clegg (1781–1861) counter, as improved by Crosley. A detailed description is given in a treatise by Clegg.^8,pp.319,320 Another interesting construction is the one patented by Thomas Edge in 1842.⁹

Analog odometers are, of course, related to flowmeters, used to measure the speed of water...