Powerpod issue wind

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Merlingraphy
Posts: 8
Joined: Thu Sep 27, 2018 11:36 am

Powerpod issue wind

Post by Merlingraphy »

Hello,

I'm having the idea that my powerpod is having wrong readings with headwind/tailwind. Especially if I start with a headwind and ride back with a tailwind, I get the idea the readings are too high. I also have the idea the wattage is a bit too high in general. Could anyone check this for me? I've attached my latest ride (with lots of wind).
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iBike_02_07_2019_1301_24_Miles.ibr
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kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Re: Powerpod issue wind

Post by kq6up »

It looks ok to me. Average winds equal average wheel. That is a good sign as long as you returned to the place you started and the wind did not change during the ride. I have no way to confirm any other parameter however. Nothing looks out of the ordinary if you are riding a road bike, and weigh 165lbs.

Regards,
Chris Maness
Merlingraphy
Posts: 8
Joined: Thu Sep 27, 2018 11:36 am

Re: Powerpod issue wind

Post by Merlingraphy »

Thank you! I guess I got a bit more power then expected, haha.
kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Re: Powerpod issue wind

Post by kq6up »

If you have an indoor trainer, you can put it in trainer mode and do an FTP test (make sure you can stay cool enough to do the 20min test indoors). Then do an outdoor FTP test on a different day (rested) outdoors going up a slight hill for 20min. If they are comparable, you are good. The power pod uses totally different maths to calculate power on the trainer -- it is a cheap and dirty comparison if you have no DFPM to compare your results with.

Regards,
Chris Maness
Merlingraphy
Posts: 8
Joined: Thu Sep 27, 2018 11:36 am

Re: Powerpod issue wind

Post by Merlingraphy »

Unfortunately I don't have an indoor trainer. I did a proper test about a year ago at a sports centre and my FTP was 285 watts back then with a HR of 176. I suppose it should be a bit higher now, I had a good year and just came out of the CX season.
kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Re: Powerpod issue wind

Post by kq6up »

I did a power curve for your ride. if you rode pretty hard (it looks like you did), then you FTP is about what you tested at previously (or higher if you held back on this ride). I would say, your power data looks pretty good. This is by no means scientific -- you would have to do what I suggested to make a better measurement. Check craigslist/offerup for a bicycle trainer. Make sure the model you purchase is in Isaac as a trainer profile (I believe most are in there). The power pod can give very accurate results if the inputs are correct -- even within a couple of percent. That takes some careful measurements to get it that close (or dumb luck).

Regards,
Chris Maness
Merlingraphy
Posts: 8
Joined: Thu Sep 27, 2018 11:36 am

Re: Powerpod issue wind

Post by Merlingraphy »

Thank you! I did some hard efforts but nothing really crazy. I am planning on doing a ftp test tomorrow, see where that goes. As I don’t have any serious climbs I’ll be doing it in headwind/crosswinds (Netherlands eh). Hope the crosswinds wont effect the reading too much.
kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Re: Powerpod issue wind

Post by kq6up »

The PowerPod does not deal with crosswinds too well. Especially at 3 and 9 o'clock positions (as far as I can tell). If it is windy, do your FTP test on a steeper hill if you can still get your ideal cadence with your lowest gear. I imagine overheating won't be an issue in the Netherlands :D If your Crr is correct for your tires and your weight is spot on, PowerPod is VERY good at power measurement up steep hills. It will be accurate to the Watt (aero power is only a very small percentage when you are doing a climb on a steep grade).

Regards,
Chris Maness
Merlingraphy
Posts: 8
Joined: Thu Sep 27, 2018 11:36 am

Re: Powerpod issue wind

Post by Merlingraphy »

Thanks! I'm gonna try either way because the longest hill here is around 8 minutes.. The Netherlands is pretty flat and I live a a hilly area haha.
Merlingraphy
Posts: 8
Joined: Thu Sep 27, 2018 11:36 am

Re: Powerpod issue wind

Post by Merlingraphy »

So I've done a 20-minute test, but the wind came a bit more form the side then expected. The wattage-data doesn't look really goed in my opinion since it's fluctuating a lot and I had the feeling my power was pretty constant, but the outcome looks pretty good and in line with my performance and what i expected. Hope you can shed some more light on it, I added the file.
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iBike_02_08_2019_1059_25_Miles.ibr
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Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Powerpod issue wind

Post by Velocomp »

Welcome to the world of power measurement! Power is a much more sensitive measurement than HR, bike speed, or any other factor.

In fact, your power was NOT constant during the test: even though your route was pretty level, you actually fluctuated in bike speed during the ride. Wind conditions changed, too, near the end (drafting?). Both are enough to affect significantly your moment to moment power.

So, while your HR was constant, your power actually moved around some.

But your result is fine!
Attachments
Screen Shot 2019-02-09 at 3.57.47 PM.png
Screen Shot 2019-02-09 at 3.57.47 PM.png (172.12 KiB) Viewed 6025 times
John Hamann
Merlingraphy
Posts: 8
Joined: Thu Sep 27, 2018 11:36 am

Re: Powerpod issue wind

Post by Merlingraphy »

Thanks for your answer! Like I said there were pretty heavy winds, mostly crosswinds, about bft 4/5. The 'drafting' part is just riding into a small village and having shelter from the wind. I am riding with the powerpod for a while now, but had it fixed during the summer and just starting training with it again. Like I said, I felt my power was pretty consistent throughout, not like it was fluctuating between 180 en 500 watts.
Since the road wasn't completely straight but meandering a bit, could it be that the different angle of the wind had an effect on what the powerpod shows? This is my Strava activity, you can see where I did the test in analysis. the wind was SSW.

https://www.strava.com/activities/2131986328
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Powerpod issue wind

Post by Velocomp »

Your HR also "meanders" in pretty much the same way...but not as much, because it is not as responsive.

I really think you are OK. It is extremely easy to get short (and significant) changes in power. This can be accelerations, wind gusts, gear changes, elevation/slope changes, and more.

At mile 8 you had a cadence spike. It looks like you changed gears. This caused a 600W spike. I would ignore that
John Hamann
Merlingraphy
Posts: 8
Joined: Thu Sep 27, 2018 11:36 am

Re: Powerpod issue wind

Post by Merlingraphy »

I guess you are right :) Thanks!
kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Re: Powerpod issue wind

Post by kq6up »

Golden Cheetah gave you a CP(1hr) of 312W, that is pretty much equal to FTP. That is a pretty beastly FTP. If that is what you expected, you are good to go. That would put you as a Cat 2 racer per your FTP/Kg.

Regards,
Chris Maness
kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Re: Powerpod issue wind

Post by kq6up »

p.s. Change the smoothing to 30s in the profile or on your garmin, and you won't see the gnarly spikes.

Regards,
Chris Maness
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