Wind data might be off???

Wind data might be off???

Postby GeorgeHotopan » Thu May 21, 2015 4:40 pm

Hi everyone:

On the ride I did today (it's almost an out-and-back but not 100%) I have noticed that the wind data might be off. What I mean is that before the middle of the ride, the wind speed is bellow wheel speed, and right after the middle, where I circled a roundabout and turned the other way around the wind was still below wheel speed. Should I be concerned? Normally in such a situation from my understanding the wind should be symmetrical, at least around the middle portion of the ride.

Can anyone share his thoughts on the matter? Attached you can find the ride file. The only fiddling I did to the file was to enter known elevation in analyze route, everything else was left unchecked. Ah and when asked if I did drafting I answered no, as there was no draft throughout the ride, even though Isaac was suggesting I did draft.

Best regards,

George.

PS: John or Fernando, I could really use your opinion on the matter :)
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Re: Wind data might be off???

Postby racerfern » Thu May 21, 2015 7:17 pm

Agreed, the wind seems low. However...
1) How much vehicular traffic did you have to deal with? A roundabout means you were on roads with cars. It's amazing how much the wind is pushed along with you by cars.
2) Check your wind port. About once a year I GENTLY clean it with a Q-Tip. Give it a rap against your hand with the unit facing down, maybe a bug is stuck. It could be anything. Also, placing the unit perpendicular to your mouth, blow across it. If there is something in there, you might jostle it out as opposed to pushing it further in. Note the chances of any of this are very small.
3) You might want to do a cal ride ideally in nearly calm conditions without car traffic so the unit picks up the slightest difference in wind scaling. If I ever need to do one, it's on a lonely river trail away from as much as possible.

All that said, check your last couple of rides, is this a route you do on a regular basis?
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Re: Wind data might be off???

Postby GeorgeHotopan » Fri May 22, 2015 1:59 am

Thanks Fernando:

1. There was some traffic but quite scarse...

2. I checked the wind port and everything seems ok, no signs of cluttering, double and triple checked using a flashlight. What I did was to mildly blow air into the wind port using a fan and looking at Wind speed in the unit in Hill-Wind Menu the speed was constantly zero even though I was blowing wind at the unit (note that the unit was not Ant+ connected to speed/cadence sensor as the bike is in the basement and I performed the procedure in my appartment).The slope, on the other hand it changes as the unit is tilted in my hand, but the wind speed stays at 0. Shouldn't it mark some wind value when I blow air at it using a fan? I have tried at least 3 times, with wind blowing straight into the port as well as from the sides and the wind speed is at 0.

Is there the possibility that the unit must first pick up speed/cadence sensor data and a trip initiated in order for it to display wind values?

3. I will make another calibration one of these days (probably today) and let you know.

Many thanks!

PS: could you please comment on point 2 which worries me a little
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Re: Wind data might be off???

Postby GeorgeHotopan » Fri May 22, 2015 4:06 am

Hi again:

Reading a bit through the "whys-and-hows of wind offset", I will probably check wind offset inside the garrage and if the numbers are sufficiently close to zero I will leave it as it is and do a new cal ride.

By what margin should the wind sensor be off in order to requiere a new wind cal? What value?
I would prefer to leave wind cal as it came from factory, unless absolutely necessary.

Regards,

George.
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Re: Wind data might be off???

Postby racerfern » Fri May 22, 2015 8:00 am

George, you're a 100% right. I haven't done a wind offset check in about 6 months so I completely forgot about it.

I think a number less than 2 is fine. Perhaps the day of your ride was an exception weather wise, so try to do the wind offset in "normal" conditions as far as temp and humidity for your area.

FWIW I checked mine this morning and it was at 1.x so I won't even bother with it.

Also note that your ride file is an excellent candidate for analysis by Isaac. Checking out/back in your case makes perfect sense. Note that is something I normally do not resort to unless there is an obvious problem with the ride data.
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Re: Wind data might be off???

Postby GeorgeHotopan » Fri May 22, 2015 8:38 am

Thanks Fernando!

I did check Out-and-back initially, but when I did that the power numbers jumped and I saw an average increase in power of about 30W for the whole ride. Instead of 133W it was showing around 166W, which is a value higher than what Newton displayed as soon as I finished the ride (around 135W) and before doing trip reset. So, beacause of that in the end I left out-and-back unchecked and only entered same start and ened elevation(10 m).

Can you comment on that please?
Thanks,

George.

PS: I looked an hour ago in wind cal to see wind offset and it was showing values of around -2.2, so I did a wind cal in ideal conditions (inside). Now it seems to be around -+0.x
I will try and repeat today the same course and maybe also do a cal ride along the course ride.
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Re: Wind data might be off???

Postby racerfern » Fri May 22, 2015 10:43 am

Did it feel like a 133w AVG or 166w? You can certainly tell the difference between those two numbers.

You did the same thing I always do. I do not check out/back because that forces the wind to about zero. Entering the start/end elevation only makes a minor adjustment for any changes in barometric pressure. However, if the wind was off because of the -2.2 offset then you could check out/back or adjust the wind speed up via Isaac.

Go out and do the exact same ride with your new wind offset and you'll have your answer right away as long as it's the same overall time more or less.
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Re: Wind data might be off???

Postby GeorgeHotopan » Fri May 22, 2015 1:29 pm

Dear Fernando:

I did almost the same route (an out-and-back) with about 10 km less than previous. I also did a cal ride and then appended todays ride files to create only one. Cal Ride was successful (checking calibration from analyse menu no changes whatsoever). And the whole ride after the files were merged seems much better than yesterday. Attached is a print screen: you can see a tail wind on the first part and a head wind on the way back which is exactly how it felt and what I could observe ( as here people use to hang flags outside their homes so the clues were there).

Regarding your question about 130W vs 160W? That's exactly why I initiated this thread as it seemed to me that I was pushing more than the 130W recorded. I do this kind of ride pretty often, and in the past I was consistently over 150-160W. And if you take a look at the data in the image you can see I am at 161W, within what I usually get without pushing the limits.

Many thanks Fernando for your time and your valuable feedback. In the end, after the wind cal+ new cal ride things seem to be at normal again.

Still, I wonder what could have been the cause of it??? , as for example I do not tweak the profile once a cal ride is performed so from my side there should not be any error added later on.

Best regards,

George.
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Re: Wind data might be off???

Postby racerfern » Sat May 23, 2015 5:13 pm

Glad it all worked out! I honestly don't have any idea why the wind was off on this ride. But it makes sense that based on your previous statement
I did check Out-and-back initially, but when I did that the power numbers jumped and I saw an average increase in power of about 30W for the whole ride. Instead of 133W it was showing around 166W,
the wind was the culprit. Remember, checking out/back forces Isaac to try and zero the wind or at least reasonably close. In this case that yielded a better result. Not something I do unless there's a problem with the ride and in this case there was a problem.

Yup, no tweaking is best. Just get on and ride. Have fun!
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