That row of numbers, usually in an LCD display or in analog form, generally on the speedometer dial, in our vehicles is something we take for granted. Our humble odometers and trip meters provide instant information and have a surprising history.
Many car makers brag about the longevity of their vehicles. The evidence they use, is provided by odometer readings. The same meter is also used by second-hand vehicle sellers to prove “cherry” vehicles have been driven few miles. Service technicians and mechanics consult odometers to determine when regular maintenance will be performed.
Besides the odometer function in my car, I use both trip meters regularly. At the beginning of a long car trip, I reset both of them to zero. I check one, then reset it at each phase of the trip. The other trip meter I use to keep track of cumulative, total mileage of the journey.
My trusty Encyclopedia Britannica says the ancient Roman author, architect and engineer Marcus Vitruvius gets the credit for inventing the first crude form of the odometer in approximately 15 BCE. His invention is just a footnote in the long list of his many major achievements. His machine resembled a wheelbarrow. It used a large wheel of a specific circumference. As the machine was pushed across the surface, it automatically dropped a pebble into a jar after each revolution. To determine the distance travelled, all one needed to do was to multiply the wheel’s circumference by the number of pebbles in the jar.
Several years later, Chinese astronomer, mathematician, seismologist, hydraulogist, geographer, engineer, calendrical scientist, ethnographer, metaphysician, and poet Zhang Heng, invented his own prototypical odometer. His carriage used a mechanically powered wooden character’s arm that struck a drum after travelling one Li. After ten Li were covered another character’s arm struck a gong.
Jumping ahead to the 17th century, French inventor, mathematician, philosopher, theologian, and physicist Blaise Pascal constructed his own version of the odometer, the pascaline. The pascaline used a series of gears and wheels. Each gear consisted of ten teeth. When the first gear completed one revolution, it advanced the next gear by one tooth. When the second gear completed one revolution, it advanced the next gear by one tooth, then on to the next gear, and so forth. This is the same principle that is used in modern mechanical odometers.
Among the many things American statesman, writer and inventor Benjamin Franklin developed, was his own simple odometer. During Franklin’s tenure as Postmaster General, he invented a device that was attached to his carriage to measure mail delivery routes.
The device that most closely resembles the modern odometer came about by three Mormon pioneers as they crossed the Great Plains from Missouri to Utah. William Clayton and Orson Pratt designed the “roadometer” and carpenter Appleton Harmon constructed it. Clayton determined that when his particular wagon wheel had completed 360 rotations, one mile had passed. Along with Pratt, the pair affixed a set of cog wheels, made by Harmon, to that wagon wheel. Their invention operated in the fashion of Pascal’s device. The “roadometer” kept track of the miles travelled on their long journey. The device was first used on May 12, 1847.
Since the nineteenth century, the odometer has undergone perfections and refinements. Now we have mechanical and electronic odometers for land vehicles and boats along with the “Hobbs Meter” that measures hours in aircraft.