ELECTRONIC CYLCOCOMPUTERS AS REVOLUTION COUNTERS IN THE RRTC METHOD FOR COURSE MEASUREMENT
NEVILLE F WOOD
5309 CHAMISAL PL, RALEIGH NC 27613
Revised 20 August 04
ABSTRACT
I describe a simple modification of electronic cyclocomputers that allows them to be used as precise revolution counters for bicycle wheels in the RRTC method for the measurement of running courses. A circumference of 2.5 meters is entered into the computer memory, and three additional magnets are attached to the spokes. For each revolution of the wheel, the computer senses that a wheel of 2.5 meters in circumference has turned four times and therefore increments the trip distance by one (10 meters). Thus the trip distance display can be taken as showing the number of whole revolutions, and precise synchronization with a graduated wheel rim allows measurement to within 0.01 rev.
I also describe variations on the above method with only one or two magnets . In these variations each increment of the meter display is equivalent to four and two revolutions, respectively, and any remaining revolutions are counted by watching the wheel turn. Some cyclocomputers with such a sluggish response that they do not work with the four-magnet method may well work with one or two of the variations.
As far as I know the three Protégé cyclocomputers made by Bike Planet are unique in they allow a circumference entry of 9.999 meters. Thus, with a slight variation in operating technique, they can be used to record precisely individual revolutions using only one magnet.
An electronic counter offers many advantages over the Jones, a non-zeroing mechanical counter, recommended in the current RRTC method:
1. Clarity of readings -- All have much bigger displays and the Cateye OS is over three times bigger. Also, they can easily be read while riding -- something impossible with the standard Jones. Safety and the ability to do night measurements are improved, and error rate reduced.
2. Instant zeroing capability -- Far fewer readings and calculations are necessary, so that efficiency is improved and error rate reduced.
3. Permanent installation -- Many measurers will want to remove the Jones after use because of noise, drag, and wear. Electronic counters can stay in place and be instantly converted to normal bicycle computers.
4. Availability -- The Jones is available from only one supplier that may have to cease production if component parts become unavailable. Sources and models for electronic counters are almost unlimited and are likely to remain so. Measurers that travel to distant locations for measurements and develope problems with their counters can probably replace them from the local bicycle shop.
5. Cheapness -- The Jones costs $80-120 whereas suitable cyclocomputers have been on sale recently for as little as $11. Many measurers will already have a suitable cyclocomputer and will not have to buy another for use as an electronic counter.
6. No wrap-around -- With electronic counters the meter display never returns to zero before the end of the measurement, whereas this is always a possibility with the Jones.
CONTENTS
I. Introduction
II. Typical Set-up
III. Basic Measurement
IV. Unique Operation of the Outstanding Protégés
VI. Techniques for Special Situations
VII. Single-Magnet Method
VIII. Two-Magnet Method
IX. Validation
X. Advantages
XII. Sensor Response
XIII. RRTC Acceptability
XIV. Examples of Actual Course Certifications