Polar Power Output Calibration

Hi,

I have installed the polar power output on my bike.
My bike is a TREK 5200 and the ratio is 39/53 and 12-25.
I test on the trainer with a fix 25km/h speed and
60sec per gear.

First test, no spacing, just install the chain tension on the bike.
gear = [12 13 14 15 17 19 21 23 25]
power_39 = [141 138 148 155 209 235 187 164 163]
power_53 = [181 143 147 155 167 116 251 142 150]

Second test with new installation at 5mm spacing for the chain tension
gear = [12 13 14 15 17 19 21 23 25]
power_39_new = [135 136 142 147 195 246 248 194 181];

Do you have suggestion? (Installation, chain, etc.)
I have more than 100W of difference for the gear!
I'm not very happy with these product!

Thank you

Hi. I have tried all sorts of things to see if I could get the Polar Power option to work right. I weighed my chain, measured it, used different height spacers for the chain tension pickup- all to no avail. The product simply does not work. I tried talking to Polar and all they kept telling me was what was already in the installation instructions- they get a "0 "as far as consumer satisfaction is concerned. I want my money back. It is one of the worst cycling products I have ever purchased. It is a shame that they sell something like this that will/has begun to ruin their reputation especially when their 720i HRM is so good. I do not think you will find a solution to your problem. I am very good at fixing mechanical/electrical gadgets and fabricating parts to improve functionality. Nothing has worked with this product. I believe the product design is faulty and probably only works with certain bikes and under the strictest of conditions in the lab. I even sent the unit back to Polar thinking that the unit that I got was defective. When it came back nothing had changed and no one there has offered any help whatsoever.

Art

There is *currently* only one study examing the Polar S710, comparing it to an SRM crank. The study found that it wasn't overly accurate, see http://www.thieme-connect.com/cgi-bi...5/s-2003-39083

I'm working on the next paper!

Ric

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http://www.cyclecoach.com

The polar is notoriously bad at power readings on a trainer. Test it on the road up a steep incline and I think you'll be happier.

I theorize that the polar's erroneous readings on trainers is due to vibrations from the rollers interfering with the measurement of the chain's vibrations.

Good luck.

Interesting! I hope you're not using an SRM as the "gold standard" for your tests though! Are there some studies verifying SRM's accuracy?

Are you doing any of your testing on a trainer? If you are, I'd highly recommend finding a NVH or Noise Vibration and Harshness engineer to help you in your design of experiment. The polar definitely has issues with this and there is no sense in re-inventing the wheel. An NVH guy will have the equipment to zoom right into the issues. Or you can contact me for some ideas, I worked on a couple products for the auto industry that worked very similarly to the polar unit.

-Andy B.

yes, there's a few studies verifying SRMs accuracy, especially the Pro and Science crank. I'm well aware that there are some not very well calibrated SRMs about.

I'll certainly your thoughts in mind about the noise reduction.

Thanks
Ric

__________________
http://www.cyclecoach.com

The Polar Unit does not perform well on a trainer. The fluctuations of rolling resistance from a trainer unit are quite different than the dynamics affecting chain tension and vibration on a road ride. You will find the Polar unit much more accurate if you can establish a "climbing load" on your trainer. I ride a computrainer, and my polar unit does not always correlate with thepower readings of the trainer. They correlate much more closely when under load.

You cannot do the power calibration on the turbo trainer this does not work with the Polar Power Meter (PPM). All readings are void when the bike is installed on the turbo - it just so happens that the readings look like real power ratings, take it from me they are not! I have had several discusions with the designer of the PPM over this.

If you want to calibrate your PPM then find a section of flat and quiet (few cars) road and mark both a start and an end point at least 800m to 1Km away. Then ride at constant speed you can maintain in each of your gears recording the power settings. Go back to the start for each new gear and ride each gear in the same direction and use your lapcounter to mark the start and end points. This will help identify the test run when you down load the session to your computer. This should give you readings within 5-15 watts for each gear as long as you keep your speed constant. (This is best done on a day with no or little wind as possible).

You will find that the wattage will creep out at extreme chain angles and height variations between the chain and the sensor
(e.g. large chainring to large rear cog - but you shouldn't be using this combo anyway).

R.

I have been using the Polar 720i since Aug. 2002. I have the power option on 2 bikes. When using the 720 on the road I usually have no problem with power readings, unless I whack the pickup unit on the chainstay, which happens occaisionally, but can usually be fixed right away.

However, I too have noted that power reading on the trainer can be problematic. I used to have a magnetic trainer, so I attributed it to that. This Winter I am using a fluid trainer, but still occaisionally have problems. Although since getting the fluid trainer, I have only had 2 problem sessions in 2 months of riding.

Good luck.

Marc

I have just posted the result of a very positive road test on the equipment forum:

http://www.cyclingforums.com/t89259.html
http://www.cyclingforums.com/t89259.html

I have my bike on a computrainer, and have ridden the polar setup side-by-side with the computrainer...bottomn line...the polar power system does not work well outside of the "real road" environment. However, if you have it set up right, it is VERY good in terms of accuracy in the real world.