Talk:Speedometer
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[edit] Any help?
Would it help if I add a picture of a speedometer showing 172km/h? Petros The Greek 18:23, 29 October 2005 (UTC)
- That's all you can do? Nova SS 03:40, 25 March 2006 (UTC)
[edit] Factually incorrect statements
It is probably factually incorrect that tire inflation causes much of a difference in speedometer readings. I have removed that statement. Tires are a woven collection of rubber (that does not expand like a balloon) and a mesh of metal (which does not permit balloon-like inflation under normal circumstances). The rolling circumference of a tire is generally fixed and does not change with inflation.
Also, it is questionable that speedometers are intentionally calibrated to read too high. As of 1997, federal standards allowed a 5% speedometer error either way. Any contention that they are indeed calibrated high needs to be backed up with a citation. Otherwise, such a statement has the appearance of a communally-reinforced misconception.
This statement may be substantially true, but needs a lot more work and citation before it is put back:
- A GPS system may also be used as a speedometer. This is usually more accurate than car speedometers as GPS systems are not calibrated to display a higher reading. Another advantage of using a GPS as speedometer is that it is easy to install and only depends on a somewhat clear view of the sky and a power supply. However it takes up to a minute before it has "tracked" all the satellites and only updates the reading every second or two. Bad signal will lead to it being inaccurate.
Nova SS 23:12, 15 March 2006 (UTC)
[edit] Inventor of the speedometer
As far as I can tell Josip Belušić did not invent THE speedometer, that has been credited to Charles Babbage who died in 1871, if you look on Josip's page you will see it has "the first electric speedometer." which I believe is correct, I am trying to track down a patent No. or similar for Babbage to confirm though.
FzerozeroT 23:05, 9 June 2006 (UTC)
[edit] how does a speedometer work
- "A speedometer is an eddy current device...ie, a permanent magnet rotating close to a conductive disk or cup causes electrical current to flow in small rotating eddies. These currents, being "shorted out" by the continuous conductive disk, cause a drag torque. The torque produced is a function of several things, but primarily the velocity of the magnet and the flux produced by the magnet. The torque winds up a spring on the needle until the spring torque is the same as the eddy current torque." -- http://www.pelicanparts.com/techarticles/Mult_gauge_repair/mult_gauge_repair.htm
I wish the article had a diagram of how (mechanical) speedometers work. The "pelicanparts" description (one magnet, one conductive cup) seems inconsistent with the "The speedometer itself is two rotating, barrel-shaped magnets." description currently in the article.
Are these 2 partial descriptions of the same thing thing, or are there really 2 different kinds of (mechanical) speedometers, working under different physical principles? --70.177.117.132 22:32, 3 September 2006 (UTC)
