Reviving an old thread here, as I am again attempting coast-downs with the Honda Insight.
This time around, instead of using a GPS to record speed reduction while coasting, an old camera with video mode is being used to record the speed from the digital speedometer.
So far the camera has been used to record the Crr component of coast down testing, from speeds up to 35 mph, all the way down to 2 mph.
So far the results are not as consistent as I would expect, but are presented just as recorded.
Shown below is a graph that shows the 13 coast down runs thus far, and the thicker red line shows the average of this data.
All the runs are done on the same section of road on the way to work and back. The road is reasonably flat over this section according to Google Earth (within several feet). The road typically has almost no traffic in either direction during my use of the road.
It can clearly be seen that the Crr curve does not go to zero at zero velocity, but instead stops at something close to a deceleration of 1.0 meter/second-squared. This was something that I did not expect based on most information that I have seen.
The Crr graph for bicycle coast down testing is from:
The Recumbent Bicycle and Human Powered Vehicle Information Center
It shows that Crr stays to a non-minimum value at zero velocity.
Jim.