Wind readings inconsistent

Wind readings inconsistent

Postby brookside » Wed May 04, 2016 9:33 am

Did a ride yesterday, basically out and back with only a two mile section different but on parallel roads (roughly miles 10.3 to 12.3 on way out and 20.3 to 22.3 on way home) It was a south to north to south ride, wind was reported out of east at about 4mph. The first 10 miles north Isaac shows a helping wind average of .5 mph, and that makes sense, the last 10 miles it shows a helping wind of 2.5 mph average. The ride back started with other riders and I drafted for about 2.5 miles, so Isaac shows a high trailing wind. But after I left those riders Isaac continues to show a steady trailing wind when it should look like the outbound leg since the wind was at about 90 degrees to direction of travel. I've attached the file, can you see anything that indicates a problem with the Newton?
Thanks,
Attachments
iBike_05_03_2016_1647_33_Miles.ibr
(608.57 KiB) Downloaded 37 times
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Re: Wind readings inconsistent

Postby Velocomp » Wed May 04, 2016 11:44 am

I don't see anything wrong with your file.

On the outbound portion it looks like winds are calm. You do some drafting and then ride home, in what appears to be a slight tail wind (2 mph).

Your ride was nearly 2 hours long and it's entirely possible winds changed a little bit during that time.
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Re: Wind readings inconsistent

Postby brookside » Mon May 16, 2016 2:27 pm

Attached is another file re: questionable wind readings. The middle lap, ending at mile 6.5, represents 6 circuits of an almost 1 mile, roughly oval course, oriented North-South. The wind was from the wnw. It just seems impossible that I'd get an average negative of wind of 2.5 mph for a trip like this. In fact there was a strong headwind from about mile 1.1 to 1.3 (first lap) but this file shows a very small HW for a little of that distance then a significant TW for the remainder. The file also shows drafting at spots, there was absolutely no drafting, this was a time trial and overtaken riders were passed at a good distance. I had done a wind cal a few days before and it looked to have completed correctly.

Some of the slopes are also wrong, this was essentially a flat course with a very modest rise at about 1.1 miles that looks OK but the corresponding descent .2 mi. later was nowhere close to the 6% shown.

Thanks,
Attachments
iBike_05_15_2016_1003_9_Miles.ibr
(85.98 KiB) Downloaded 40 times
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Re: Wind readings inconsistent

Postby Velocomp » Mon May 16, 2016 3:30 pm

I can see you were doing laps.

Here is what I did:

1) I highlighted the loops, from mile 1.0 to mile 5.9

2) I extracted this part of the ride with the File/Combine-Split/Keep Selection Only... command. This, section is, effectively an out-and-back-ride

3) I used the Analyze/Check Calibration feature on the selected portion. This results in a significant adjustment of the profile, which is stored in Isaac.

4) I reopened the original ride file, then used the Tools/Switch Profile After the Ride... to correct the overall ride file

The slope readings are nothing to be concerned about. When you see slope variations on flat terrain this is because of bike accelerations.

Corrected ride file and profile are attached.
Attachments
Screen Shot 2016-05-16 at 3.13.43 PM.png
Screen Shot 2016-05-16 at 3.13.43 PM.png (268.11 KiB) Viewed 1001 times
Screen Shot 2016-05-16 at 3.15.21 PM.png
Screen Shot 2016-05-16 at 3.15.21 PM.png (127.11 KiB) Viewed 1001 times
iBike_05_15_2016_1003_9_Miles_corr.ibr
(109.68 KiB) Downloaded 30 times
TT_Bike.ibp
(546 Bytes) Downloaded 27 times
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Re: Wind readings inconsistent

Postby brookside » Tue May 17, 2016 1:17 pm

Thanks for that. Makes a lot more sense. I used your procedure and did the same but also tweaked the Crr as I saw I was using a stock number (.004) and the tires/tubes I used have a measured Crr of .003 which brings the average power down just a couple watts.

Question: how did the Newton get so out of wack? Bad Cal ride? Bad Wind Cal?

Thanks for your help,
Ken
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Re: Wind readings inconsistent

Postby Velocomp » Tue May 17, 2016 2:51 pm

I looked at your older ride file and wind was a bit low there, too.

You have an older model Newton and we have made improvements since then that improve stability.
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Re: Wind readings inconsistent

Postby brookside » Mon Jun 06, 2016 10:02 pm

Is there anything I can do to this unit to improve the wind readings? I went for a ride today and the wind it read was completely off. In the ride file attached I basically went north for 10 miles, did 3 2.5 minute efforts back and forth on the same west to east road, #1 and #3 were in the same direction, all done another drafting a rider which the Newton didn't pick up. But it shows that for legs 2&3 I have a tailwind (draft?) but leg 1 it shows a head wind. On the way home from miles 22.5 to 30 I was headed due south, the opposite of the outbound leg but on a different road. The outbound, north leg, shows a headwind of about 2.5 mph, the inbound south leg shows a headwind of 2.1 mph. Just can't be. I did a wind CAL in my garage, hand over front of Newton, just before leaving.

The power readings on the 3 efforts are completely off. I can tell by my heart rate. According to the Newton these were VO2M efforts, no way my HR maxes at only 145, and just for a moment on the 3rd one. The rider I was drafting had a hub based power meter and he was averaging 235 watts on each effort (TT bike, full aero kit, deep rim front, covered rear, very low position). I was drafting him in the drops and the Newton said I was 60 to 100 watts higher.
Attachments
iBike_06_06_2016_1412_33_Miles.ibr
(404.94 KiB) Downloaded 16 times
brookside
 
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Re: Wind readings inconsistent

Postby Velocomp » Tue Jun 07, 2016 7:08 am

You need to a true out-and-back cal ride. I used Analyze/Check Calibration to try to improve things, but since there was drafting involved, this is not necessarily correct.
Attachments
Brookside_06_06_2016_1412_33_Miles.ibr
(592.52 KiB) Downloaded 18 times
John Hamann
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Re: Wind readings inconsistent

Postby brookside » Tue Jun 07, 2016 1:57 pm

I've been thinking I need new Cal Rides for all my Profiles. I'll do them and let you know if it helps.
Thanks,
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