From: mcconnel@rodan.acs.syr.edu (Terry R. McConnell)
Subject: Re: Mileage meters
Keywords: mileage bicycles
Organization: Syracuse University, Syracuse, NY
Distribution: usa
Date: Mon, 23 Nov 92 20:33:12 EST

In article <857@jgaltstl.UUCP> terry@jgaltstl.UUCP (terry linhardt) writes:
>Does anyone know where you can get the 'gadget' which is attached
>to a bicycle and then used to measure distances? I know they are
>often used by race officials to lay out a certified course.
>What are they correctly called?
>-- 
>  Terry Linhardt                ...!wupost!jgaltstl!terry 
>                                terry%jgaltstl.uucp@wupost.wustl.edu  

TAC Rule 133 states that all certified race courses must be measured
according to standards set down by the Road Running Technical Committee
(RRTC) and must include an addition of 0.1% of the stated distance. (i.e.,
courses are to be measured intentionally long.) The RRTC has prepared a
booklet entitled "Course Measurement Procedures" which is obtainable
by sending $4.00 postpaid to

		TAC/USA 
		Book Order Department
		P.O. Box 120
		Indianapolis, IN 46206

The method described in this publication requires the use of a "Jones"
counting device in connection with a 1000 foot calibration course measured
by steel tape (procedure also described in the book ) or by a more accurate
surveying technique. The counting device is attached to the wheel of a 
bicycle and assigns an arbitrary (but fixed on the time scale of the 
measurement) number of counts to each revolution of the wheel. The original
device was invented by a man named Alan Jones and manufactured by his son,
Clain. For many years it was sold through the NYRRC for about $40. Eventually
the manufacture of the device was discontinued when a key gear part became
unavailable. A new version is now made by a man named Paul Oerth. It can
be obtained for $45 postpaid from

		Paul Oerth
		2455 Union Street
		Apt 412
		San Francisco, CA 94123

The price may have changed by now. 

The method of use of the Jones counter is simple, practical, and elegant. 
One rides the 1000ft calibration course and notes the number of counts
elapsed. This establishes the number of counts required for 5K, 10K, or
whatever, after a bit of simple arithmetic. One then rides the desired
course and marks the point where the computed number of counts runs out.
(The official method requires some repetition and elaboration, but this
is the basic idea. ) 

You don't need to know the radius of your bicycle tire, and you don't
even need to ride particulary straight, so long as you tend to wobble
to the same extent on the race course as you do on the calibration
course. The sum of many random "wobbles" tends to have a remarkably
predictable long term effect. Moreover, the effect of the wobbles on the
measurement of the race course enters with the opposite sign from that
on the calibration, and the two tend to cancel.

Experience has shown that this method has an accuracy of about .05%.
When I measure a 10K course with another person, our two measurements
seldom differ by more than a bike length or so. It's amazing.
-- 
************************************************************************
Terry McConnell       Mathematics/215 Carnegie/Syracuse, N.Y. 13244-1150
mcconnel@rodan.acs.syr.edu                NeXTmail: tmc@barnyard.syr.edu
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