On Wednesday, July 4, 2018 at 12:15:54 AM UTC-7, wrote:
On Tuesday, July 3, 2018 at 11:15:12 PM UTC+2, sms wrote:
On 7/3/2018 11:58 AM, wrote:
On Tuesday, July 3, 2018 at 7:14:03 PM UTC+2, jbeattie wrote:
On Monday, July 2, 2018 at 10:41:15 AM UTC-7, Frank Krygowski wrote:
http://www.businessinsider.com/canno...ance-2018-6#-3

This has been the talk of the house. https://www.youtube.com/watch?v=ppgthzi9_0Y 100 watt savings descending? Really? I suppose if you have an incredible spin and are drag racing straight descents, although 100 watts still seems like a stretch. 2 kilo weight penalty going up.

My son's peak power output descending on the way to work this morning was 1,100 watts. That was on a 16% descent with no pedaling. Got to love strain gauges. The road is so broken up that when you have the crank arms horizontal and you hit a bump while posting, the power spikes.

-- Jay Beattie.

Power is force times speed. If his crank arms are stationary while hitting a bum he doesn't suppose to measure a power spike. Besides that the force on the left en right crank are in opposite directions. I don't know what power meter he uses but if it is the garmin Vector 3 pedals the power spikes are caused by a ****ty designed battery holder.

Some crank-arm power meters just have one strain gauge, and it's
accurate enough to just double the amount. Peaks are meaningless anyway..
The firmware should be filtering out obviously bogus data.

I know that's why I asked. Power meters have an accuracy in the 1-2% range. A left right balance of 52-48% is not unusual. At a typical total power value of 250 Watt doubling one side measurement gives you a total of 2*(250/100)*52 = 260 Watt; 10 Watts error. That is 4%. If you want accurate values I don't understand the one sided option.

You can buy Stages two-sided, if you're into accuracy, which may be an issue if you're switching between bikes or really concerned about accurate calorie burn numbers-- or are in some sort of competition with other riders (who may or may not be posting accurate power data). Otherwise, I think consistency is more important than accuracy. Spikes can be filtered with data ceilings, etc., but the spike my son had -- which was actually 1,732 watts is within the one second power output of Chris Hoy. It was recorded by having the right crank forward on a bumpy descent and not by massive quads, but the meter is just recording numbers accurately. It's not going to filter that out. Maybe he is Chris Hoy! You can download the data and apply filters later.


-- Jay Beattie.