A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2019 Dec 30, 15:01 -0800
"Unfortunately, I find it incomprehensible. It seems to be one of those "explanations" which make sense if you already have a clue, which I clearly don't. For instance, you time a mile at 65 seconds, so at the end of the mile the second hand is stopped at the 5 second mark. Speed is about 55 mph, but I don't see how to read that from the tachymeter."
I was confused by the explanation at first as well. But I think the solution would be to look on the tachymeter scale for the total number of seconds elapsed, and then read the number opposite (the seconds scale in reality) as the speed. The number 65 on a [non-rotating] tachymeter scale is roughly opposite the '11' or 55 seconds on a watch face.