The Jones Counter is a device fitted to the front wheel of a bicycle which counts the revolutions of the wheel. It was invented in 1971 by Alan Jones in order to measure the length of road running race courses.[1] It has gears that drive a mechanical digital counter. Depending on the gear ratio used, one count typically corresponds to about 1/20th of a wheel revolution. This provides a resolution of about 10 cm in course length, although overall accuracy, depending on calibration and other factors, is lower, but normally better than 1 part in 1000.
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This was the original production version, manufactured by Alan Jones's son Clain from 1973-1982. The gearing produces 20 counts per revolution of the bicycle wheel.
Production was taken over by New York Road Runners Club from 1983 to approximately 1990.
Paul Oerth took up production around 1990 and continued to around 2006. These models have a different gear ratio (260/11 counts per wheel revolution). In 2006 supply of the gears dried up, and an alternative plastic-encapsulated set of gears was introduced. This was short lived and the Oerth model went out of production
The JOL counter is a variation of the Jones-Oerth model. Created by Laurent Lacroix in 2000,[2][3] its distinguishing feature is a 27" rotary cable that allows the user to mount the Veeder-Root Counter on the handlebars.
Development of a new model started in 2007.[4] The first production units became available in April 2008, and were used for the measurement of the London Marathon which took place on 13 April 2008.
The gearing (260/11 counts per wheel revolution) is identical to the Jones-Oerth model.
To measure road race courses the counter is fitted to a bicycle between the left fork leg and the front wheel.[5] The tab or tabs on the large ring gear engage with the spokes, thus providing drive to the Veeder-Root counter.
In use the bicycle must first be calibrated by riding between marks on a straight section of road whose separation has been accurately measured by steel tape. A calibration can then be calculated in terms of counts per kilometer. Next the bicycle is ridden over the race course to determine its length. Finally the bicycle is recalibrated by riding again over the calibration distance. This is done to check for changes in bicycle wheel diameter due to temperature changes, air leakage and other causes.