Cyclocomputer Measurement

Hi Pete,

I have a Protege 9.0 from Planet Bike. I used both a JO and this cylcocomputer to measure a course. I numbered each spoke as a percent of a total rev. and set the computer at 99.99 and used 1 magnet. This gave me 1 count per rev. I recorded the reading as number of revs on the computer followed by the fraction from the wheel (148.37). I did some approximating between spokes but always recorded a 2 digit number.

My only problem was the fact that when you reset the computer, the first rev turns on the device and the next rev gives you a count of 1. The problem was that I wasn't sure if the next count would turn it on or count as 1. To be sure I put on a count or 2 so I knew where I was.

With this straight in my mine the device worked perfectly. I love it.

The course was a loop with an out and back. I rode the first 2 miles to a point on the out and back that would be common to the finish leg, the finish leg and then the out and back to give the correct distance.

Here is the results

Start to common first 2.1218766 JO
Start to common first 2.1219713 NFW

Start to common second 2.1225214 JO
Start to common second 2.1225683 NFW

Common to finish first 0.5526218 JO
Common to finish first 0.5526609 NFW

Common to finish second 0.5527293 JO
Common to finish second 0.5527371 NFW

Common to turn first 0.2161572 JO
Common to turn first 0.2161360 NFW

Common to turn second 0.2161035 JO
Common to turn second 0.2160598 NFW

The difference in the complete 5k course by the 2 methods is 3 inches. The largest difference in any measurement is 6 inches.

I like this system with only one magnet. You are less likely to get a false count and it gives you a 7 to 8 foot window so if you only overshoot a little, there is no problem.

I have another course to measure shortly and I plan to use the NFW as the primary and see how mixed up I get after used a Jones counter for 19 years.

Bill Grass

Bill, I've got the same unit and had the same concern. The trick is to roll the wheel backward before you begin each measurement after resetting.

I've yet to use it on a full-scale measurement, but your experience seems to highly recommend it. I have an out and back 5k to do Wednesday and will try it then.

Magnetic Dead Zone

When I use the Wood method of electronic measurement I have four magnets on the front wheel. I am very careful to stop at a point where the magnet is far from the sensor, as I fear that if I stop with the magnet adjacent, small rocking back and forth will add spurious counts.

To assist me in this I painted four yellow stripes on my front wheel. They are located such that when a stripe is adjacent to the ground, the magnets are well-separated from the sensor. This helps.

One of the reasons I went w/ the Protegé is that the single magnet method can be used, which virtually eliminates that problem.

I measured a 5k course today and was happy with the way it went. It took a bit of mental stretching to get used to looking for 823.26 revolutions/mile rather than 16,024 Jones counts.

Another thing I noticed is that after years of measuring with a J/O, I have a pretty good feel for how far a certain number of counts are in the real world, i.e. if there are 590 counts to the next split I know it's going to be beyond the next intersection, etc. I couldn't do this with the cyclocomputer, but I think it's just a matter of experience.

email from Neville Wood to Pete Riegel

Pete:
I should like to congratulate you as the first measurer to dare to embrace the new method of using electronic counters in course measurement .

However, I am disappointed that you continue to harbor fears that they may skip impulses and give wrong measurements without your knowing it. I should like to reassure you that, if you use any of the many models I recommend, that there is not the slightest danger of this happening.

With the four-magnet method you would almost certainly detect it if it occurred through the destruction of the synchronization of the meter with the rim calibration. Also, I rode hundreds of miles and measured several courses with the simultaneous use of the Jones, the Sigma Sport 600, and the Protégé 8 and always got precisely the same results from all three. I concluded from this agreement that it likely that all three were measuring revolutions accurately.

Since then I have given up using the Jones, but have evaluated many other cyclcomputers against the first two mentioned above. In this way I have identified some that very occasionally miss an impulse and some (mostly cordless) that never register any impulses at a walking pace or less.

The only stressful thing might be the fear of generating a spurious impulse at an emergency stop, but it is easy to check for this if it occurs. You should probably purchase one of the Protégé models which record individual revolutions using only one magnet and are usual on sale for less than $20. With these it needs only a quick glance at where the wheel touches the ground to avoid stopping at the zero point on the rim. I have now identified another model, dBase 4L, which also uses only a single magnet and is almost as convenient to use as the Protégés.

If you are only interested in using my method for calibration, then you do not even need a cyclocomputer. Read the Jones once to get the number of whole revolutions and for all partial revolutions you can read the calibrated rim. With the old gearing it is easy to calibrate the rim in counts.

I am afraid your advice about never rolling back is not good. I describe in detail the way to do this in my on-line report(http://home.earthlink.net/~caverhall/newrevcounter/abstractcontents.htm), but I will give one example of where it is accurate and useful.

Suppose the measurer plans to stop at 1200.34 rev with rezeroing afterwards. He overshoots to a meter reading of 1202 . All he has to do is roll back twice through the rim zero point and on to a rim reading of 0.34.

I hope the above information might persuade you to relax more when using electronic counters.
Nev

NEVILLE WOOD 919-846-6374 (Day & night, use as FAX by arrangement)
5309 CHAMISAL PL 530-884-4472 (FAX)
RALEIGH NC 27613-6108 nfwood@hotmail.com

Pete's reply to Neville's note:

Dear Neville,
I already knew about how to handle overshoots. When it's only a revolution or two, no problem. Otherwise it becomes an occasion to record a count, calculate, and measure backwards to the desired point. With the Jones counter I can roll backwards 20 or 30 meters without having to think.

I like not having to think any more than I have to during a measurement. I know I can check to see whether a count has been missed, and have done so. But it is something I don't have to do when using the Jones counter. Also, if I find I have lost a count, what then do I do? Roll back to the last reliably-recorded place? Maybe. But I'd have to think about it. I am not at all worried about losing a count and not knowing it. It is the continual checking that I find an added and unwelcome burden.

I did have an occasion where I lost a count. I measured a course that included an 80 foot climb up a flight of stairs going to the top of a dam. Rolling the bike up the stairs produced a length of about 75 meters. Rolling down the stairs got me about 72 meters, and at the bottom I noticed that I'd lost a count somewhere. I had tried to be careful when wheeling the bike, but there was some bumping up and down. I used the 72 meters as official.

I have also found that when I later write up the results of the measurement I find it nicer to have an unbroken string of data. Just personal preference.

Now that I have tried the electronic way, and am satisfied that I can use it, I have concluded that I will think of it as a nice fallback position. The Jones counter allows me to think less, and save my mental resources for the task at hand.

I think you have done a valuable service in presenting your work to the measurement community.

Best regards, Pete

Pete,

Thanks for the measured and courteous reply to Neville and the rest of the community.

I have been shipping the correspondence to the teenager brothers whom I have trained. While they have computers on their bikes, they prefer the Jones method. They are comfortable with it.

I like your comment about not wanting to think during a measurement. Very true. There's enough to do out there without the burden of analyzing what happened when I overshot the last split.

Alan

Pete:
I agree it is very desirable to reduce the amount of thinking during measurement. Tasks that are very simple done in the comfort of the home can become difficult and prone to error when attempted on the road. My idea of introducing the electronic counter as a replacement for the Jones is to make tasks easier by improving the clarity of meter reading, and reducing readings and calculations needed.
One of the great advantages of the clarity of reading is to dramatically reduce the incidents of overshooting. At normal cycling speeds the meter reading can be continuously monitored as a small number without the necessity of stopping from time to read the meter as with the Jones. If I am very careless I do still very occasionally overshoot with the electronic counter, but it is always less than a revolution. To correct, I simply roll the wheel back to the desired rim reading! If I desire to retain meter reading and a magnet has to pass by the sensor (less likely with the single magnet technique), I temporarily disconnect the meter by sliding it back on its mount. ( Cateyes have an off switch.) I do not find this sort of correction requires a lot of concentrated thinking!
I know you have been using the BC600 meter and this meter does not lose impulses. Therefore, when you talk about “lost counts” I think you really mean “gained spurious impulses”. You should not be reluctant to use the meter for uninterrupted rides, because these are the very times when gained spurious impulses are impossible!
You say you lost a count during a measurement up stairs climbing 80 feet. Actually, I believe you gained three impulses, and I am not surprised since there must have been a strong tendency for the bike to roll back. Going down there should have been no such tendency, and I am sure you made the right choice in choosing the down measurement as the valid one. There should be no problem with electronic counters if stairs are measured in a downward direction. I tried out my Protégé with a single magnet measuring up and down my ten-foot high deck stairs and found no spurious impulses.
You say you prefer an unbroken string of data, and there is no reason why you should have to sacrifice this preference with electronic counters. You do not have to rezero after each split, but can easily prepare a table of goal values for splits at various values of total distance. This is easier to do than for the Jones and unlike the Jones is valid for repeated measurements. Also, in addition to showing trip distance, all electronic meters have odometers and some have two.
With the special single-magnet Protégé method you would not have the “unwelcome burden” of checking for spurious impulses. About all you would have to be alert for is the case where you have a very sudden emergency stop at the zero point on the rim. I know you would find the Protégé a delight to use.

I have to agree with Neville that the Protegé is great - I measured a course yesterday as the light was fading and it was nice to have larger digits a foot from my face rather than smaller ones by the wheel hub.

That said, I have yet to use the re-zeroing method, and wouldn't anticipate doing so under normal measuring - I measure too many split points on a metric course - it would seem to equire more, rather than less, calculations to figure out the interval between, say, 3km and 2 miles. I may try it on an Imperial course where mile splits are the only ones I locate.

Jim:
You could measure a course once with the rezeroing method at mile splits and then again rezeroing at kilometer splits. This would give you two measurements for certification of the overall course.You would have only one measurement for each split, but I do not think this matters very much since certification of these points is not normally required.

In all my years measuring, I never thought of doing one "metric" ride and the other "imperial." Good idea.

One metric ride and one imperial ride is fine only if you know how long the course is before you start. It's generally wasted effort to lay down splits on an unmeasured course, as when it doesn't come out right you will likely have to adjust everything, repainting and redocumenting all the splits.

The first ride serves to tell you what you need to do to get the course to come out to the proper length. Only when this is done is it a good idea to lay out splits. Whether a third ride, confirming all split positions, is to be done is an individual choice, as the overall course will have been measured twice.

Pete:
I am not sure what you mean by the following:"The first ride serves to tell you what you need to do to get the course to come out to the proper length"
I assume before making imperial and metric rides, the measurer would plan the course in detail. (I like to do my planning using "Streets" because I can place all points along the course with an accuracy of about 1 in 1000.)Of course if the rides do not agree within 0.08% a third ride would be required and it might be desirable to redo some of the splits as you indicate.

To Neville:

I also use maps to rough out courses before I ride. This does not always work well enough to be sure the course will work out. If my first ride of a 10 km course comes out to 9500 meters, and I have already laid down the splits, I have wasted my time. I need to find 500 more meters, and establish the start and finish where the race director wants them. Combining these measurements yields my "first ride." Only then is it possible to lay down splits. When I have done so, I have my "second ride."

In general I don't do a third ride to check the splits.

An exception would be on a pure out-back course on which I can lay out all the splits going out, and check them coming back, thus getting two measurements of the course.

Checking the Protégé Cyclocomputer

According to Neville Wood’s investigations, and the experience of some measurers, the Protégé cyclocomputer permits setting the wheel circumference at 9.999 meters, thus permitting it to operate with a single magnet.

If the bike is stopped with the magnet near the sensor, and a mild back-and-forth movement is made, an extra impulse can be inadvertently recorded. When four magnets are used, a check can be made to see whether this has occurred.

How does one check for extra impulses when the Protégé is used?

How can one determine the characteristics of a cyclocomputer without buying it? Usually the general characteristics are described in the sales material, but I have not seen information on whether the thing can be calibrated to 9999 mm/revolution or to 2500. Neville Wood has provided this information for many counters, but the only way I can figure to do it is visit a bike shop and ask to open a package and read the detailed instructions.

Pete:
Unfortunately reading the detailed instructions or talking to the vendors is no assurance that you can learn the meter characteristics.
For instance the instructions for the Cateye OS1.1 indicate you can enter a cirumference of 9.999 meters, but actually you can only go to 3.999. Protege instructions make no mention of going to 9.999 and Planet Bike who sell it had no idea this is possible.

This seems like a hell of a way to run a railroad. Cyclocomputer measurement shows great promise, yet the only way to obtain the information we need about a certain unit is to buy it. Couple this with the inevitable model changes, and the future unavailability of presently-available models, and we have an information problem.

Sooner or later Neville must get tired of buying and testing these devices, and then where will we be?

This problem cries out for a solution. Any good ideas?

Although I'm a great proponent of electronic cyclometers for measurement, I am duty bound to report a problem I encountered the other day.

After unloading my bike from the car, I reinstalled the front wheel, gave it a few spins and - Nothing. No counts recorded on the Protegé. After fiddling around a bit, I was able to cock the wheel slightly off kilter in the fork so that the magnet came close enough to the sensor that counts were recorded. I deduced the problem was due to the removal of the J/O counter from the opposite side of the hub, thus allowing the wheel to shift slightly away from the sensor.

To be sure, this bike has a wide clearance fork, and I had to mount the sensor in a shim to get it close enough to read the magnet. Looks like I may have to increase the shim's thickness to prevent this from happening again.

My only worry is that if the tolerance is that close, what's to keep the sensor from getting moved enough by hitting a bump or something to get knocked out of whack and stop receiving impulses? By the time you noticed, the measurement would be screwed.

Jim:
My tests indicate that the Protege sensor operates up to a clearance of 8mm from a Sigma magnet so that adjustment is not very critical. Perhaps you do not have the optimum vertical alignment.
I mount sensors on the top of the inside of the forks and so it is practically impossible for them to be knocked out of position.
The problem you envisage for lost impulses through bumping does not seem to occur in actual practice. Over the last two years, over thousands of miles, and over the ceritification of about 25 courses, I have never observed it. I suppose anything is possible, but if it did occur it would be instantly detected by the measurer because the meter reading would stop incrementing.

See my post for "Is this counter malfunctioning?" under "General Measurement" for an example of the advantage of the non-skipping Protege over the Jones.