6. REVOLUTIONS OR COUNTS?

The gearing of the Jones-Riegel counter is such that it gives 260/11 = 23.64 counts per revolution of the front wheel. However, we don't have to remember this number because each time we calibrate the bike and measure the course we shall record and use Jones counter COUNTS rather than front wheel REVOLUTIONS which we called rev.counts on the last two pages.

Although we started this introduction by talking about wheel revolutions and fractions (ie rev. counts), from now on (and the rest of your measurement career!) you can forget about wheel revolutions and think entirely in terms of counts recorded on the counter.

However, we will make just one use the gearing number now to calculate that for a typical bike wheel with a circumference of about 2 m, One Jones-Riegel COUNT will be 200/23.64 = 8 cm approx. Amazingly, this is how accurately we can read the distance travelled by the front wheel. In fact if we record the reading at both ends of a ride to the nearest 0.5 of a digit, we can resolve a distance of just 4 cm. However before you get to carried away with achieving that precision we will have a more detailed look at calibration.

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