5. THE JONES COUNTER (Go to Lessons Menu)
How do we measure the revolutions of the front wheel?
When in 1961 John Jewell of the RRC developed the calibrated bicycle method for measuring road races he used a revolution counter to count the whole rotations of the front wheel of his bicycle and counted the number of spokes for fractions of a revolution. In 1970 Alan Jones designed a geared counter which would count fractions of a revolution. Today we use a version of this, the Jones-Oerth counter.
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The Jones-Oerth Counter mounts between the left front fork and the wheel. The picture shows the view looking over the front handle bars and down on the counter. The reading shown is between 65,215 and 65,216. We would record this as 65,125.5 when calibrating the bike a a short calibration course. When measuring a 10k we would record to the nearest whole number of counts. in this case either 65,215 or 65,216. When the counter reaches 99,999 it "rolls over" to 00,000, so in the calculations we have to remember to add 100,000 every time it has rolled over. We will include examples of this in the exercises which follow. You have to be alert to spot when this has happened. When you are bicycling along you will not be watching the counter closely enough to notice it actually happening.
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