AeroPod, PowerPod and Newton

In the past I have noted on the forum that the power readings on rides occasionally drops to zero. I thought it was something with my speed/cadence module, but it isn't.

I have noticed recently that the power drops to zero on rough surfaces, not chip and seal, but broken, patched surfaces (that's the way the city does things here in Vancouver). In the attached file, you will see at 1 hr 10 min to 1'11" that the power drops considerably (displayed zero) and Isaac thought that I was standing. In fact, I was pedaling the same a minute prior, 40.0 km/h, 316W, +.49 grade, 4.3 km/h tailwind seated. After the road was a bit smoother, the power came back up, albeit slowly. A speed of 39.7 km/h, grade of -.72 and a 6 km/h tailwind should be more than 180W. Without tailwind, wattage should be around 250. It seems that the accelerometer in the Newton doesn't like big changes in background motion. The power recorded is still too low.

I have noticed this on other rides as well.

I have the Newton mounted to a Tate Labs Bar Fly Universal mount. My questions are; is there something up with the Newton? Is it the Bar Fly? Or is it an combination or another cause?

The mount is your problem. It is not stiff, so on rough roads the Newton vibrates and it gets confused.

Thought that might be then cause.

Thanks for confirming.

Velocomp wrote:The mount is your problem. It is not stiff, so on rough roads the Newton vibrates and it gets confused.

Now I'm confused.

I thought you were right about the mount being the source of the issue of power drop-outs, but now I'm not so sure.

Since the last post, I remounted the Newton onto a Dual Mount. I did a wind cal, a cal ride and a coast-down cal. Still, on chip-seal surfaces when speeds a over except for when I am climbing.

I also noticed that after the coast-down ride, Newton/Isaac set the CdA to .235 from .339.

Suggestions?

Unless you are riding a TT bike your CdA is way too low. Coast Downs are tricky things to do and I don't think yours was done correctly.

Low CdA would result in artificially low watts, particularly on flats or downhills.

You are using the same bike as in your prior ride, so I returned your CdA to the previous value of 0.369. File is attached.

I do not see any obvious places where there is any problem with watts readings.

I did reset the CdA to .339, but will use your number, .369. (77kg total weight, 68 kg, 175 cm tall, Continental 4000S tires, 7 bar rear, 6.5 bar front)

Am I understanding you correctly John, the Newton is recording the watts correctly, just not displaying correctly?

I had a note from Tom Gore to set the power smoothing from dynamic to 5 second. This did eliminate the zeros, but I think in some cases the readings were still low over rough surfaces. Also, I like the dynamic feature.

I just did another Cal Ride on the chip-seal road surface, and the result was better.

One of the features of Dynamic Power Smoothing is that it can show second-to-second variations, if those variations exceed a certain threshold. When wattage is more even, the filtering reverts to a longer time period.

In fact, under some circumstances DPS is as close as you can get to raw, unfiltered data displayed on your bike computer. While it is theoretically possible for one-second-long "0W" to display, those numbers obviously are meaningless, and they contribute nothing to the overall results of your riding. They are like the single pixels that some times light up in a large video display.

Based on the data you have posted I really think your Newton is working just great.

Enjoy the ride!