I've been attempting to measure a half-marathon course with a Protege 8.0
over the past month. The roads I'm riding have suffered quite a bit from
a combination of near-record winter precipitation and delayed maintenance,
so there are lots of potholes, loose pieces of asphalt and other hazards.
Much of the the last 9 miles of the course is over streets with little
curbing and ample opportunities for the unintended acrobatic maneuvers
that follow inattention to a safe, shortest path.
The Protege 8.0, set up with 2 magnets and a circumference of 5000, seemed
problematic. According to my 2 most recent rides, 3/15 and 3/16/08, it seems
that I was off by 0.5, 1.0, or 1.5 full revolutions when measuring the same
mile. Here's the data (I omitted the first fractional segment):
Counts for calib #1: 772.650 revs
Counts for calib #2: 772.500 revs
MM Ride #1 Ride #2
-- ------- -------
12 772.650 772.325
11 772.650 772.300
10 772.650 771.000
9 772.650 771.900
8 772.650 772.075
7 772.650 771.025
6 772.650 772.400
5 772.650 772.300
4 772.650 772.175
3 772.650 772.550
2 772.650 771.925
1 772.650 772.275
Other details: Odometer was reset to 0 after putting 0 point on target line
and rolling forward about 1/4 rev so that upper magnet was in front of sensor.
The rim is marked into 40 equally spaced segments, so each mark is .025 revs.
Conclusion: I hope the new JR counter will fit on my front wheel.
Who did you consult before making your measurements?
If you repeat a ride over the same mile course your rim reading should be within 0.1 rev of that in the first ride wether you have a Protege on board or not . Clearly this is not the case with your results, and you therefore have at least one problem unrelated to operation of the Protege.
I suspect that you may have labelled the rim backwards, so that numbers go down as the wheel rotates forward. For instance you thought your original miles were marked at 772.65, but they may actually have been at 772.35. If your second ride had been tighter by 0.4 this would have given you an apparant reading of 771.00 and an apparant difference of 1.65 as in the case of mile 10.
It's possible that you may have sometimes lost a count by letting the meter go to sleep and moved off without awakening it.
I am not clear as to why you do not estimate actual rim readings, but just go to the nearest division. Also, to quote down to one thousandth of a revolution is incorrect.
I am puzzled as to why you went with the two-magnet rather than the simpler one-magnet method. I suggest you try the latter.
Thanks for your comments. I appreciate all the work you and the Committee do to make my measuring easier.
I first marked my rim per your web site's directions; they were very helpful in getting it set up. I decided to use 40 marks per rim because it would give me differences of about 2 inches. Only one side of the wheel is marked; this way, it's obvious if the wheel is mounted backwards. As the bike rolls forward, the numbers increase (I have the '0' spoke set to the one just before the valve for the tube.).
Per an earlier post of yours, I tried a Bell computer originally when measuring, so had to use 2 magnets because of its limitations in setting the circumference. When the Bell died earlier this year (corroded contact), I installed the Protege (purchased late summer of 2007), carefully following the directions for sensor positioning relative to the magnets, but kept the same circumference of 5000mm.
Now, as to your analysis:
>>If you repeat a ride over the same mile course your rim reading should be within 0.1 rev of that in the first ride whether you have a Protege on board or not. Clearly this is not the case with your results, and you therefore have at least one problem unrelated to operation of the Protege.
==>For the smaller variances, the course is rather challenging in sections, with many slow, tight turns near curbs, traffic stops and restarts, sudden pedestrian appearances (necessitating more stops and restarts), lengthy rough brick surfaces in places, etc. By my arithmetic, .08% works out to about 0.6 revs per mile, so variances of 0.2 revs seem to be well within the usual tolerances.
>>It's possible that you may have sometimes lost a count by letting the meter go to sleep and moved off without awakening it.
==>For each mile segment, I restarted the computer at 0.00, as indicated in Other Details.
>>I am not clear as to why you do not estimate actual rim readings, but just go to the nearest division. Also, to quote down to one thousandth of a revolution is incorrect.
==>Each rim marking is 0.025 (half a nickel), so 0.65 = 26 marks, and 0.35 = 14 marks. I'm just converting the marks to decimal, and so use 3 places to report it. If you prefer, I can post it using fractions. I don't estimate the rim readings because I don't think the extra work gets me a more accurate course. The stripe of paint I used for each mile is about 1/3 of the distance between 2 rim segments, so I am not confident that I'm accurate to within, say, 1/5 of a rim segment during a remeasure.
It's the large variances that concern me. Clearly, the magnets are not always detected as they pass the sensor, and either one could be missed (sometimes more than once) during a particular mile segment. How is a measurer to know if one is missed or not without using a mechanical counter to double-check it? How is a certifier supposed to know how a magnet and sensor are mounted on the measurer's bicycle, and that they are working correctly?
After my rides, I do not have confidence in the accuracy of the magnet / sensor combo for measuring courses to certification standards. However, I love it for laying out courses more quickly.
Thanks again for taking the time to respond to my post, and for all that you do.
I don't see why you feel the Protoge is the problem. From your description of the course, I would expect different counts each mile. It sounds like it is next to impossible to ride the exact route from each direction (assuming you did ride each direction). Even if you rode the same direction, I wouldn't expect exact readings, unless it was a straight course. And, I doubt that the 9 miles was straight - you are in Illinois, not Nevada.
You only had two separate miles that were off by more than a revolution, which, given the pavement you describe, isn't bad.
I use an electronic counter, and find it quite accurate. My only qualm with electronic counters is that if you stop with the magnet too close to the sensor, you will get spurious incrementing. But, once I discovered that, I don't have that issue.
I think your readings are well within reason, all things considered. And, I don't think a JO/JR/ReigelSuperDuperCourseClicker would give you any more accuracy in this situation.
Another possible factor is that Cal #1 was off by a small amount, giving you a very-slightly-longer mile than you should have had. It doesn't take much change in calibration to vary the mile by .15 revolution.
Thanks for the note. I didn't post all of the columns from my spreadsheet, but at least 2 of the mile segments are off by more than 10 feet each! This is well outside the usual .08% tolerance.
I'm used to a variance on the order of 8-16 inches. I once measured a winding 2 mile course in a local park where the variance with the remeasure for the entire course was 1 count on a Jones counter (approx 0.05 rev).
I, too, am careful when stopping to ensure that a magnet is not close to the sensor. This is pretty easy to do with 2 magnets on the wheel - I just make sure one the magnet I see in front is near a horizontal position.
The RiegelSuperDuperCourseClicker (wow! wish I'd thought of that!) will give me an independent way to double-check the magnet/sensor combo, and it uses a mechanical technology. If the counter gets more than 40 counts per revolution, I should expect similar accuracy with it.
Your note about Cal #1 being off by a small amount seems reasonable, since I was using a 1000' course for all of this, but I haven't done the arithmetic yet to see how much variance to expect from it.
I would imagine the new counter is similar to the old - 23.333 clicks per revolution.
I, too, have gotten within a click over a 5k course, so I know it is certainly possible. It just looked like maybe you had lots of potholes to dodge, which would have varied your path.
I have had a Jones die on me. Visually, nothing seemed amiss. But, on the Cal course, I had anywhere from 800 to 1200 extra clicks. The gears inside had broken, so my counts were nowhere near accurate. Glad it was a Cal ride, and not a course! But, Jones counters can go bad, too.
I don't know how super-duper it is, but the counter I'm anxiously waiting for will have 23.6363 counts per revolution, or about 3.58in, 91mm, per count. The irrational number comes from the gear ratio of 11:26 that was used in the original JO, and helps distribute wear in the gears. If I'm not mistaken, the same two gear teeth will only come in contact with each other after the wheel rolls about 850'.
Tom, Tom, Tom. I'm sure you know that irrational numbers do not arise from that type of ratio.
You are Right! I am not smarter than a fifth-grader. Repeating decimals are real, rational, and WIKI says they result from a vulgar fraction. Hmmm. Nothing new under the sun, except what we forget.
Alan, my experiences with electronic measurement are much the same as yours. I installed my Bell with two magnets and even when calibrating would have my rides be off by a full revolution. I haven't yet tried with a Protege, but will admit to be a little intimidated by the procedure necessary to make it work with one magnet.
I think I could make the procedure work in a pinch, but am much more comfortable with my old mechanical counter. Plus the reality that the Jones counter works in almost any conditions while at least the Bell does not work well when temperatures are cold. I don't much enjoy measuring in cold weather, but race directors schedule races in April, and municipalities are slow to approve courses, so the bottom line is that we bundle up and measure in March in Chicago.
Duane, if you think a race in Illinois has to have curves, you have obviously not spent much time in much of central Illinois. Try driving US 136 west from Rantoul some time...
And one of the reasons I like working with the metric system is that I pretty much find all fractions to be vulgar.
Originally I rode hundreds of miles while operating a Jones simultaneously with a Protege and results were always exactly the same from both meters. I have never seen the occasional loss of a count with the Protege.
Probably it is not very wise to blame poor results on the Protege when your course is so bad that your ability to duplicate your path is in doubt. You should make tests on a regular street where final rim readings should be within 0.1 rev for a course of about a mile (which of course does not have to be calibrated).
One way to test that a Protege is operating correctly is to use it with another simultaneously. Of course you can use a Jones simultaneously.(Why are you not doing this already?)
Thought - Alan may have Protoge problems due to two magnets, and the Protoge was designed to use one magnet per revolution? The VR counter I have is considered a "low-speed" counter. Two magnets would likely result in missed counts at higher (maybe over 15 mph) speeds.
If Alan is riding over 20 mph (my number, pulled out of the air), maybe the Protoge is designed for an impulse once a revolution, up to 35 or 40 mph, so maybe, there are more pulses than it can handle?
Just a thought.
So much new stuff in this thread!
1) I imagine another vulgar ratio would be the total number of dollars in a structured transaction with 'Kristen' divided by the number of sperm in a certain blue dress stain.
2) Did you know there are more transcendental numbers than rational numbers? I'm not sure if that will contribute to your peace of mind, however. If you like puzzles: Every year has at least one Friday the 13th. Can you prove it? (I had to do this on a number theory exam in college.)
3) The speed may be related to the issues I'm having with the Protege. The course does have some downhills that I go quite a bit faster on (likely in excess of 20mph near the bottom). However, it was 52 degrees and sunny for the remeasure, and a cloudy 46 for the original measurement, so temperature may play a significant role in lowering the computer misbehavior threshold (CMT).
4) The reason I don't use a Jones counter at present is that there is not a model I can purchase that fits on my bicycle wheel. The JO counter is too wide to fit. Count yourself lucky if you have one that fits.
5) My individual rides of the mile segments are pretty uniform but, again, I get pedestrians (and cars!) doing unexpected things in front of me that necessitate stopping and restarting. Since my bike has toe clips and the shoes I used are not well designed for clips (but they work great for keeping my feet warm!), I got a little more wobble than I would like when I started up again after many of these stops. I can guarantee you that I was not off by anywhere close to 120+ inches between 2 rides over the same mile segment.
Of course, it's only been about 22 years since I received the first certificate for a course I measured, so I may not be as sharp as I was back then.
It would be informative to see raw data for all your calibration rides to see how well you are able to duplicate final rim readings under ideal conditions.
A certifier reviewing a submission can get a good idea of correct operation of an electronic counter from calibration data. Also, if the two rides of the course differed by much less than 1 rev/5 km, correct operation would be likely. Previous demonstration that a measurer had got identical results with a Jones should also be reassuring. Note a certain amount of trust in the measurer is necessary even if a Jones is used.
Duane is correct in pointing out that counters have a limit to the number of counts/sec they can handle. As Pete has recently pointed out, it is perfectly possible to exceed the rating for the Jones counter on a bicycle. (This may be very conservative.) The Protégé has one of the best ratings I have seen for an electronic counter because I have not exceeded it with the four-magnet method during normal certification, the two-magnet method at 35 mph, and the single-magnet method at 45 mph. Moreover when counters exceed their rating many counts are lost not just one. Therefore you cannot postulate a lost count by going too fast on a downhill.
The temperature of 46 deg is unlikely to have been a problem unless maybe you have a very poor battery. Cyclocomputers are rated down to 32 deg, but I do not know how consevative this is because I have not tested below this temperature.This message has been edited. Last edited by: Neville,
Hi folks. I'm new to this forum, but have been measuring race course in upstate New York for many years using the traditional Jones or, more recently, Jones-Oerth counter. It finally gave up the ghost this past weekend. I have never been impressed with these things--the construction has always seemed to be rather flimsy. Also, I had a rather bad experience with the cable in Jones-Oerth counter sticking, which caused the counter to periodically skip, ultimately leading to short measurement. That problem was remedied with a new cable graciously provided by Laurent Lacroix --the manufacturer.
In any case, I am very interested in getting away from use of the mechanical design, and using something electronic. The RRTC minutes state:
"limited approval was granted last year to use certain commercially available electronic cyclocomputers which, with some trickery, can be adapted to serve as revolution counters in the calibrated bicycle method."
Can you tell me: what is the device in question, and is it accurate?
Welcome. There are lots of differing viewpoints in this forum, which allow for thorough examination of the issues. Then, you can make a choice that you are comfortable with.
For electronic counters, there are a few threads regarding various counters. One thread is http://measure.infopop.cc/eve/forums/a/tpc/f/89510622/m/7741023332. You can find others in the Electronic Counters topic. Review as many as you can, then go forward.
There is a new mechanical Jones that will be available shortly, and appears to be sturdier than old versions. It has its own topic, so you can read all about it there.
I use an electronic counter. It is a Veeder-Root. The model escapes me (as I am at work and can't look at it), but it was about $120, I believe. I chose it because if I overshoot a point, I can ride my bike back to any point on the correct course while the counter counts-down, then turn around and continue measuring (have to flip a switch, but no big deal). I saw in one of Neville's posts that there is a cheaper VR available that will do the same thing. http://measure.infopop.cc/eve/forums/a/tpc/f/89510622/m/3831057932 Don't know what the differences are, but I like mine - illuminated, reversible. The Protoge is not reversible, and is not illuminated. I also like the larger numbers on my VR.
Bottom line is, there are electronic options available, and there will be a new model of the Jones available shortly.
The new counters are ready for delivery. Go to the following --> http:/www.jonescounter.com
I have mine and it's great. Easy to read and in my view the best one ever produced.
I have found the original Jones surprisingly rugged. Whether the new version is as rugged remains to be seen, but it should last longer because of the new feature that allows the counter to be easily disconnected when not being used in a measurement. (The original version can probably be retrofitted with this feature.)
Electronic counters are just as accurate as the Jones, and the rim-reading feature used with them allows calibration to be done more accurately. I much prefer them because of their vastly superior readability, instant zeroing, and smaller number of digits required. Thus fewer readings and calculations are required, and error rate reduced.
The slightly derogatory word “trickery” is used with the Protégé counters (as little as $10 for the # 5 model), and was coined by someone who favors the Jones and would like their use discouraged. It simply means that they have to be programmed for a use not intended by the maker. Programming is no more difficult than that of any other cyclcomputer or TV recorder, but, surprisingly, it has proved a challenge for many measurers. Fortunately, I have found several suitable commercial counters ($40-100) that require no programming and can be used as is with “always-on” display. They are a little easier to use than the Proteges, but the downside is that some cannot be used over 25 mph. (This should not be a problem unless you are Lance Armstrong or go down a very steep hill without brakes. The Jones has a similar specification but it might be very conservative.)
See my post on spurious counts today because it describes the use of two counters that I think will help you.
I read your article about the spurious impulses, but I don't think it applied to my measurements.
The 2 rides I wrote about in the original post for the half-marathon measurement were my 3rd and 4th rides of a couple variations of the course in March.
The segments that generated what I believe to be missed impulses were also the ones that involved the longest downhill sections of the course and the fewest number of stops. Only one of them involved a single stop, and the others were ridden continuously from the start to just before the mark, then rolled forward through the mark (just like the previous rides).
Because I used 2 magnets, it's easy to tell where the rear magnet is by just looking at the position of the forward magnet.
When I get a new counter (and presuming it will fit my wheel), I will compare those 2 methods during a free weekend and post the results (likely not before May 10th, however - race scoring season has started for me).
Although I have never seen a missed impulse, I see that you are still holding to that theory. I suggest using two Proteges because not only would allow a check for spurious impulses, but would also check for missed impulses. Of course comparing with a Jones would do the same thing.
Incidently, with the two-magnet method, a gain or loss of an odd number of impulses shows up by the fact that the meter starts to increment at a rim reading of 0.5 instead of 0.0.This message has been edited. Last edited by: Neville,
As Nevelle has suggested, I have set up two Protege counters on my wheel. This practice is something I highly recommend. The cost is negligible, especially when calcilated against the opportunity costs associated with measuring a specific course.
The double readout gives me a great sense of confidence as the measurement is proceeding, and makes it unlilely that a count will be missed.
Actually, if the magnet and sensor are carefully placed, I think it more likely that a spurious count will be added, rather than having one missed.
As one is moving along a course, it is not uncommon to have to stop for one reason or another, and if the wheel comes to a stop with the magnet too close to the sensor, it may trigger an extra pulse.
Using the new JR counter, and with a little extra assistance from Jay Wight to fix some missing street names on my course map, the half-marathon course (Lincoln Memorial Half Marathon) is now certified.
I rode the course a couple of times one weekend, but got rained on before finishing, so rode the course twice for a complete remeasurement the next weekend. The earlier ride also got me a little more practiced at 'careful riding'.
Bottom line: with the new JR counter, the 2 measurements of the entire half-marathon course (complete with brick streets, etc.) used for the certificate application were within 24.4 inches of each other. It was great not having to worry about missed magnetic impulses.
Thanks to all who participated in the redesign, manufacture, etc. of the JR counter. You've got a very happy customer here in Springfield, Illinois.
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