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Old 12-27-2009, 01:47 PM   #16 (permalink)
3-Wheeler
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Quote:
Originally Posted by MetroMPG View Post
...Until we hear back, have you seen this? Measure the drag coefficient of your car
Hi Metro,

Yes, that is the link from the "instructables".

If you dig around that site, there is another link to what looks like a Wikipedia styled page.

There is a spreadsheet attached that shows some calculations on how to do coast downs.

The Crr shown is a fixed value regardless of temperature or velocity. I think both of these factors do affect the Crr. On the web there are several sites regarding bicycle coast downs that discuss the effect of temperature and velocity regarding it's affect on Crr.

As I get more data, factors that affect Crr will incorporated into a spreadsheet which is already started with the three coast down tests that have been done so far. It shows that velocity does indeed affect the Crr, and changes as the car slows down during the test on a flat road.

Jim.
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