5,174 reputation
11731
bio website
location
age
visits member for 3 years, 2 months
seen 5 hours ago

Jul
10
awarded  Informed
Jul
9
comment Analysis of Stages high-speed data
Welcome to bicycles.stackexchange, Andy.
Jul
8
revised Analysis of Stages high-speed data
deleted 22 characters in body
Jul
8
revised Analysis of Stages high-speed data
Describe why exact crank angle is unneeded, and describe algorithm to find peaks.
Jul
7
revised Analysis of Stages high-speed data
added 321 characters in body
Jul
7
comment Analysis of Stages high-speed data
@Oscar The negative parts do reflect counter-acting torque but it appears dbr may have been coasting at the time rather than pedaling. I included the calculation just to show the anomaly. If I were were doing this in "production mode" I would almost certainly record that as zero power, and tine-tune the analytical algorithm to produce average power over a second rather than over a crank revolution.
Jul
7
revised Analysis of Stages high-speed data
added 131 characters in body
Jul
7
answered Analysis of Stages high-speed data
Jul
7
comment What is the effect of changing length of crank arms?
It's been studied quite a bit but usually from the perspective of muscle shortening speed so searching for "crank length" won't always find the right studies. But perhaps this little empirical experiment is closer to what you had in mind: bikeblather.blogspot.fr/2014/07/…
Jul
6
comment Analysis of Stages high-speed data
He may not have pedal angle but he does have a timestamp and thus elapsed time between peaks of the force or torque curve. Since the Stages only measures forces on the left crank, you could integrate over the cycle and do what Stages does: double it to get total power. If you were obsessive, you could do what has been proposed elsewhere: use the difference in trough-to-peak time to peak-to-trough time as an estimate of L/R balance to get a refined estimate of total power.
Jul
5
comment Analysis of Stages high-speed data
Here's my concern and hesitation: I'm puzzled because the patterns of those torque or force values aren't what I expected to see. Here is a plot of torque measured from special force-sensing pedals from the classic Kautz study on pedaling dynamics. anonymous.coward.free.fr/rbr/kautz.png In particular, single-sided torque (such as I would expect from the Stages) isn't as even as what I'm seeing in your data.
Jul
5
comment Analysis of Stages high-speed data
@dbr, here's a plot of the kgf and timestamp from your "full" data file: anonymous.coward.free.fr/wattage/stages/dbr2.png (and here's a plot of the first 128 kgf samples: anonymous.coward.free.fr/wattage/stages/dbr1.png)
Jul
5
comment Analysis of Stages high-speed data
Can you say a bit more about the full data set? Could it be that you did about 20 seconds worth of pedal strokes at roughly 60rpm, then coasted down, then did another 15 seconds or so at a slower cadence? Or am I completely off?
Jul
2
comment What is the effect of changing length of crank arms?
The Martin et al. study looked only at max power but the results have been the same for submaximal power: over a wide range of crank lengths, submaximal power does not appear to be affected. That means you can choose crank length on other criteria, including personal preference, clearance or cornering issues, fitting or range of motion issues, or even because a crank is on sale, without worrying that it will decrease sustainable power. It also means that changing crank length won't increase sustainable power. Which is to say, it's been studied a lot.
Jun
28
comment Is it worth it to get a bike computer with cadence?
What was it about the Cateye Micro that it gave excellent cadence, and how do all current cadence measurements fall short of that? For what purposes does one need Cateye-level cadence accuracy that one cannot achieve with other levels of accuracy?
Jun
27
comment Allen Coggan power profile table for Cyclo cross riders?
Closer to an all-rounder but there's a slight difference depending on the type of cyclocross you race on. Generally speaking, European cyclocross runs are a little longer, North American cyclocross runs are a shorter and steeper. Also, it appears Coggan is de-emphasizing power profiles and is switching to FRC profiles.
Jun
16
revised Is it worth separating your vo2 max wattage's on the flat and hill climbs in order to provide clearer goals during training?
added 223 characters in body
Jun
16
comment Is it worth separating your vo2 max wattage's on the flat and hill climbs in order to provide clearer goals during training?
I'm guessing you're referring to Coggan's Power Profiling Chart. Coggan has always disliked that particular use of his chart and has been de-emphasizing the Power Profile in favor of his (newer) fucntional reserve capacity.
Jun
15
answered Is it worth separating your vo2 max wattage's on the flat and hill climbs in order to provide clearer goals during training?
Jun
14
comment Giant Revolt 2 vs Giant Anyroad 2 drag/roll resistance
Blam, he can't know why until he knows whether the issue is truly rolling resistance or aero resistance. Measurement will tell him that.