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Old 07-16-2009, 10:01 PM
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Nashville Kat Nashville Kat is offline
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Join Date: Apr 2009
Location: Jacksonville, Florida
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Default Re: Why I don't trust mechanical speedometers.

if the circumference is pi X wheel diameter, then that's 26" X 3.14= 81.64 inches, or 6.8 (approx) feet per wheel revolution

6.8 X 200 wheel revolutions is 13,600 feet, per minute

since there are 5, 280 feet in a mile, that equals just over 2.5 miles in a minute

which of course is over 30 miles an hour- so no, it appears that the revs scale at least does not match the speed scale

the accuracy of the speed scale could be determined on a pre-measured course at a constant rate of speed, 60 mph for one minute,

so say, 20 mph which would take 3 minutes to cover a mile.
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