Speedometer
A speedometer is a type of gauge that shows the speed a vehicle is moving. It usually shows the speed in miles per hour (mph) for countries that use the statute mile for distances or kilometres per hour (km/h) for countries that use the metric system. Originally, a speedometer was an option that car owners could buy to put on their car. Beginning about 1910 it was built into all cars.[1]
History
[change | change source]The electric speedometer was invented by the Croatian Josip Belušić[2] in 1888, and was originally called a velocimeter. Charles Babbage is credited with creating an early type of a speedometer. These were usually fitted to locomotives.[3][4]
A speedometer was patented by a German, Otto Schulze on October 7, 1902,[5] it uses a rotating flexible cable usually driven by gearing linked to the output of the vehicle's transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel.
Speedometer accuracy
[change | change source]Most speedometers have tolerances of some ±10%, mainly due to variations in tire diameter.[6] Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size. Vehicle manufacturers usually calibrate speedometers to show the vehicle is going faster.[6]
Underinflation
[change | change source]When a tire has less air pressure than it should, it is underinflated. Underinflation causes excessive heat and reduces the diameter of the tires.[7] This causes it to rotate faster than the speedometer shows it is. Tires underinflated by only 10 psi can mean a car or truck reading 70 mph on the speedometer is actually traveling at 72 mph.[7]
References
[change | change source]- ↑ William Harris. "How Speedometers Work". HowStuffWorks/InfoSpace LLC. Retrieved 10 September 2015.
- ↑ Sobey, Ed (2009). A Field Guide to Automotive Technology. Chicago Review Press. p. 78. ISBN 978-1-55652-812-5. Retrieved 30 January 2015.
- ↑ "Charles Babbage and the Difference Engine - NewMyths.com". google.com. Retrieved 30 January 2015.
- ↑ "Udini → Flow". proquest.com. Retrieved 30 January 2015.
- ↑ "Speedometer". Siemens. 26 April 2005. Archived from the original on 28 February 2009. Retrieved 30 January 2015.
- 1 2 "Ask the experts: Speedometers and speed cameras". Fairfax Media. 13 August 2012. Archived from the original on 11 February 2016. Retrieved 10 September 2015.
- 1 2 Frank Markus (April 2002). "Speedometer Scandal!". Car and Driver/Hearst Communications, Inc. Retrieved 10 September 2015.
