No power while putting force on pedals

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blp
Posts: 164
Joined: Mon Mar 26, 2012 12:06 am
Location: Vancouver, BC, Canada
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No power while putting force on pedals

Post by blp »

Hi

After following Johns suggestion of getting a new cadence sensor, I am still having an issue with power.

Unlike the last issue which was spiking (hence the new sensor) I am getting zero power reading on descents while putting force on the pedals. (File attached, about 41 minutes in.)

I have recently done a calibration and this is the result.

I currently have Garmin Vector 2 attached to the bike and it recognized the pedal force, about 100W.

Can you look to see if the calibration is correct. You guys see things I don't.

Thanks
Attachments
activity_2558254071.tcx
Garmin file
(2.84 MiB) Downloaded 364 times
iBike_03_12_2018_1649_3_km_CalRide.ibr
(89.97 KiB) Downloaded 356 times
iBike_03_15_2018_1448_33_km_HiDef.ibr
Look at around 41 minutes
(1.04 MiB) Downloaded 368 times
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: No power while putting force on pedals

Post by Velocomp »

Four comments:

1) Your new cadence sensor seems to be working just fine

2) In general your Vector is reading lower than PP. I did checking with bikecalculator.com, using your settings (181 bike/rider weight). Bike calculator agrees with the PowerPod readings. So, it's possible your Vector was not properly calibrated.

3) When I adjusted your bike/rider weight to 171 pounds, the two devices were nearly identical, and furthermore, downhill watts at the 50 minute mark increased a bit. Most certainly, you can check your total weight; if it is close to 181, then perhaps your Vector was a bit unruly

4) You're correct that the Vector shows some higher downhill pedaling watts than PP. In my view this is not meaningful. At minute 50 you had about 1 minute of downhill pedaling; Vector showed 30.8W, PP, 12.8W. But this accounts for only 1 calorie of your total effort. At the 1:03 mark, you had another short downhill pedal; Vector was 46W, PowerPod, 12W. But again, this was only 4 calories worth of work! You burned 758 total calories on this ride, so these differences are extremely minor and would have zero effect on any training scores.

It looks like your PP is working just fine. I can't tell if your Vector is slightly off, or if your PP settings are a bit high. In any event, I would not worry about the downhill watts.
John Hamann
blp
Posts: 164
Joined: Mon Mar 26, 2012 12:06 am
Location: Vancouver, BC, Canada
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Re: No power while putting force on pedals

Post by blp »

Thanks John. FYI, it's a Newton 6, but your answers still apply.

Yes, the new cadence sensor does make a difference, no more rouge spikes at 230 RPM. Thanks for that advice.

I weighed myself and the bike together just prior to the ride to accurately set the weight in Settings in the N6, 82 Kg, that's approx 181#, so that is correct. (Less red wine in my immediate future I think.)

I agree with you about the energy expensed downhill, not really anything to quibble about, just something I noticed while riding that I though might be odd.
I used Gribble to compare power (adding wind scaling at .11% gradient to each 1 km head wind) and got very close results for the Newton.

I haver to say I am not 100% confident with the Vector because i seem to have difficulty with torque calibration, values seem to wander and don't settle down, but that's a Garmin issue not for here.

Thanks again John.
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