The resolution of the Jones Meter is more than adequate for measuring race courses, but much less so for calibration courses particularly if they are short. Users of the Jones would be better to use the rim-reading method instead for wheel calibration with the following advantages:
1.More accurate determination of the calibration factor.
2.Easier readings.
3.Instant comparison between individual rides over the calibration course.
4.Fewer calculations.
For a 36-spoke wheel the spokes should be numbered 0 to 35. (Even though this takes only a few seconds, inexplicably several old timers like Rick Recker continue to count spokes.) In electronic counting it is debatable whether to mark the rim in decimals instead, but there is no debate in this application.
At start, the tire should be pumped up to the same pressure each time, so that a known number of whole revolutions will be obtained on the course. There are several ways of determining this number initially including just measuring the distance covered by one revolution over the ground.
A calibration run is made by placing the zero spoke over the start and taking a reading at the finish in tenths of spoke intervals. In postcalibation the number of whole revolutions should be checked in case there has been a large air leak.
For instance for a calibration course of 300 m requiring 143 rev, the following formula gives the calibration factor with the SCPF for a Jones with gearing of 23.6363:
Jones counts/ km = 11,277.9 + 0.0548 (s1+s2+s3+s4)
where s1-4 are tenths of spoke intervals on a 36-spoke wheel.
Substituting readings of 180, 182, 183, and 181 in the above formula gives a calibration factor of 11,317.7 cts/km.
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