Odometer

The noun derives from ancient Greek ὁδόμετρον, hodómetron, from ὁδός, hodós ("path" or "gateway") and μέτρον, métron ("measure").

[dubious – discuss] Possibly the first evidence for the use of an odometer can be found in the works of the ancient Roman Pliny (NH 6.

Both authors list the distances of routes traveled by Alexander the Great (r. 336-323 BC) as by his bematists Diognetus and Baeton.

From the nine surviving bematists' measurements in Pliny's Naturalis Historia eight show a deviation of less than 5% from the actual distance, three of them being within 1%.

However, in 1981 engineer Andre Sleeswyk built his own replica, replacing the square-toothed gear designs of Leonardo with the triangular, pointed teeth found in the Antikythera mechanism.

By the 3rd century (during the Three Kingdoms Period), the Chinese had termed the device as the 'jì lĭ gŭ chē' (記里鼓車), or 'li-recording drum carriage' (Note: the modern measurement of li = 500 m (1,640 ft)).

[5] Chinese texts of the 3rd century tell of the mechanical carriage's functions, and as one li is traversed, a mechanical-driven wooden figure strikes a drum, and when ten li is traversed, another wooden figure would strike a gong or a bell with its mechanical-operated arm.

[5] Despite its association with Zhang Heng or even the later Ma Jun (c. 200–265), there is evidence to suggest that the invention of the odometer was a gradual process in Han dynasty China that centered around the huang men court people (i.e. eunuchs, palace officials, attendants and familiars, actors, acrobats, etc.)

[6] The historian Joseph Needham asserts that it is no surprise this social group would have been responsible for such a device, since there is already other evidence of their craftsmanship with mechanical toys to delight the emperor and the court.

There is speculation that some time in the 1st century BC (during the Western Han dynasty), the beating of drums and gongs were mechanically-driven by working automatically off the rotation of the road-wheels.

[6] This might have actually been the design of one Luoxia Hong (c. 110 BC), yet by 125 AD the mechanical odometer carriage in China was already known (depicted in a mural of the Xiaotangshan Tomb).

[7] The passage in the Jin Shu expanded upon this, explaining that it took a similar form to the mechanical device of the south-pointing chariot invented by Ma Jun (200–265, see also differential gear).

However, unlike written sources of earlier periods, it provided a much more thoroughly detailed description of the device that harkens back to its ancient form (Wade-Giles spelling): The odometer.

[The mile-measuring carriage] is painted red, with pictures of flowers and birds on the four sides, and constructed in two storeys, handsomely adorned with carvings.

In the 5th year of the Thien-Sheng reign-period (1027 AD) the Chief Chamberlain Lu Tao-lung presented specifications for the construction of odometers as follows:[6] What follows is a long dissertation made by the Chief Chamberlain Lu Daolong on the ranging measurements and sizes of wheels and gears, along with a concluding description at the end of how the device ultimately functions: The vehicle should have a single pole and two wheels.

[8] When the middle horizontal wheel has made 1 revolution, the carriage will have gone 1 li and the wooden figure in the lower story will strike the drum.

Benjamin Franklin, U.S. statesman and the first Postmaster General, built a prototype odometer in 1775 that he attached to his carriage to help measure the mileage of postal routes.

[11] In 1847, William Clayton and Orson Pratt, pioneers of the Church of Jesus Christ of Latter-day Saints, first implemented the Roadometer they had invented earlier (a version of the modern odometer), which they attached to a wagon used by American settlers heading west.

By 1925, Stewart-Warner odometers and trip meters were standard equipment on the vast majority of automobiles and motorcycles manufactured in the United States.

The trip meter may be used to record the distance traveled on each tank of fuel, making it very easy to accurately track the energy efficiency of the vehicle; another common use is resetting it to zero at each instruction in a sequence of driving directions, to be sure when one has arrived at the next turn.

A form of fraud is to tamper with the reading on an odometer and presenting the incorrect number of miles/kilometres traveled to a prospective buyer; this is often referred to as "clocking" in the UK and "busting miles" in the US.

With mechanical odometers, the speedometer can be removed from the car dashboard and the digits wound back, or the drive cable can be disconnected and connected to another odometer/speedometer pair while on the road.

Many jurisdictions have chosen to enact laws which penalize people who are found to commit odometer fraud.

Companies such as Carfax then use these data to help potential car buyers detect whether odometer rollback has occurred.