An automobile’s most prominent yet unexplored part is the odometer. It is placed behind the steering wheel on the dashboard. It displays the distance the car has run. Odometer readings are beneficial to car owners when selling the vehicle. It helps evaluate the mileage or plans for car service.
Odometers can be mechanical, electrical, or a combination of the two. They are also known as mileometer or milometers in countries with imperial units or US customary units. Odometer is the most widely used name, especially in the UK and the Commonwealth countries.
An odometer is a device used to measure the displacement of an object. It measures the distance travelled between the start point and the endpoint. Odometer is derived from two Greek words that mean path and measure.
Who invented the odometer?
Vitruvius, a Roman architect and engineer, is credited for the invention of the odometer in the 15th century. He used a standard chariot wheel, mounted on a frame with a 400-teeth cogwheel, and turned it 400 times in a Roman mile. The cogwheel employed a gear that slipped a stone into the box for every mile. Thus, it helped learn the miles covered by counting the pebbles.
In the 16th century, Blaise Pascal invented a calculating machine called Pascaline. It was a prototype of an odometer—the Pascaline comprised gears and wheels, where each gear had ten teeth. Every time a tooth completed a revolution, the second gear was engaged. This principle is used in the mechanical odometer.
English military engineer Thomas Savery invented an odometer for ships. In 1775, Ben Franklin, a statesman and a writer, created a simple odometer that measured the mileage of the routes. He attached it to his carriage.
In 1847, the Mormon Pioneers invented an odometer while crossing the plains from Missouri to Utah. Also known as a roadometer, they attached it to the wagon’s wheel, and when the wagon started the journey, it counted the wheel revolutions. Orson Pratt and William Clayton designed the odometer, and Appleton Milo Harmon, the carpenter, built it.
In 1854, Nova Scotia’s Samuel McKeen designed another early version of the odometer. The device measured driven mileage. He attached the device to the carriage side and measured the miles with wheels turning.
Types of odometer
There are two types of odometers.
Mechanical odometers start with the transmission. The transmission system contains a small gear that measures the odometer advancing. This small gear is connected to the speedometer drive cable. The other end of this cable is connected to the instrument cluster.
The internal transmission gear turns when the engine is turned on, and the car starts moving. This internal transmission gear motion is conveyed to another set of gears linked to changeable digits by the connected drive cable. Thus, the counting begins from the right side of the group of numbers.
The process continues till the distance travelled by automobile compels the left side digits to roll over. This counting process repeats until all the adjacent numbers touch their apex values. Then, all the digits are set back to zero, and it starts again.
Mechanical odometers are not always precise and a hundred per cent accurate.
After the mechanical odometers came the electronic ones. They are also known as digital odometers. They depend on the automobile’s electronics for establishing accurate mileage.
Electronic odometers, like mechanical ones, employ a special gear for changing the count seen on the dashboard. In addition, a magnetic sensor replaces the drive cable to track the gear turns in the transmission. The wires conduct the obtained signal to the car’s onboard computer that interprets and converts the data into mileage count.
The advantage of electronic odometers over mechanical ones is that they provide better accuracy. In addition, no one can manipulate electronic odometers easily, hence giving an accurate count of the vehicle’s mileage.
Odometers come with an additional trip meter called a trip odometer. It helps the car owners determine the mileage for any particular distance without interfering with the primary odometer reading.
The primary purpose of an odometer is to measure the distance travelled by the vehicle. In addition, odometer readings help determine various maintenance milestones such as tyre rotations, oil changes etc. Dealers use odometer readings to estimate the vehicle’s valuation in the used car market. Resetting odometer values require changing the entire transmission system of a car. Hence, odometer readings are very difficult to reset. Also, tampering with the reading is considered a fraud and punishable by law.