Wednesday, 27 December 2017

Specialized (S-Works) Quarq Power Meter Calibration


Static weight calibration of a Quarq S-Works Spider ANT+ power meter.

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Monday, 18 December 2017

Power Meter vs Smart Trainer Power - Hello Cadence. Goodbye Accuracy? (ERG Mode)

Here's a brief run-down of a day of testing trying to get to the bottom of why I'm seeing some major differences in power numbers (well beyond the maximum combined margin of error) when putting my Garmin Vector 3 Power Meter pedals up against the Tacx Neo Smart Trainer in steady state ERG mode.

Background: 

After receiving my Vector 3 pedals (retail/production) last week, I installed them as per the manual, went 45km ride outside on them (sprints, etc to bed them in, then performed my standard Lama Lab Test on them with the Tacx Neo Smart Trainer (control/baseline for power and ERG). The full ~16 minute video is over on YouTube

Aside from the no-show for Bluetooth power meter support (at this stage) the other glaring issue was the +20W discrepancy between the Tacx Neo and the Vector 3 at 200-220W during a sustained ERG effort. This discrepancy is greater than the combined accuracy error margins (Neo -+1%, Vector -+1%, and a generous drivetrain loss estimation of -+5%). What was strange is this difference wasn't seen when 'just riding along' or in a continual ramp test I performed in SIM mode. So it wasn't going to be a simple calibration/zero-offset fix.


Today's Tests:

Cadence. What was the impact of changing the pedalling cadence on the ERG mode power readings, using the same gear? I typically pedal at 90-95rpm for my ERG mode tests and haven't seen any major power reporting issues in those zones... until now. 

Test 1 - Tacx Neo | Garmin Vector 3


Observations: 
- Switching from 150W ERG to 200W ERG at the 12:30 minute mark
- The higher the cadence, the more the Neo and Vector 3 disagree on power. 
- Cadence under 80rpm shows acceptable accuracy ranges. 
- Cadence greater than 100rpm results in power reporting up to +20W from the Vector 3. 




Test 2 - Tacx Neo | PowerTap P1


Observations: 
- ~+10-12W differences in power reported at higher cadence ~110 (Vector 3 was ~+20W). 
- Lower cadences ~60rpm appear optimal for having the Neo and P1 agree on power. 



Test 3 - Discarded (Forgot to perform a sensor calibration on the Elite Drivo)


Test 4 - Elite Drivo | Garmin Vector 3


Observations: 
- ~+10W differences in power reported at 90rpm+ 
- Lower cadences ~60rpm appear optimal for having the Drivo and Vector 3 agree on power. 



Test 5 - Elite Drivo | PowerTap P1


Observations: 
- NICE!.... Only start to see disagreement at 130rpm+.



Conclusions....

ERG is a strange beast. It's never a constant application of resistance from the Smart Trainer. It'll oscillate slightly above and slightly below the set target watts as the very inefficient human motor stomps away on the pedals. This means the power measurement becomes a complex task.

At this point, I'll conclude: 

- The power reporting of the current Vector 3 pedals (Firmware 2.30.0) appears to be influenced greatly by cadence when in steady state ERG mode on an indoor trainer. Lower cadences appear to match smart trainers with power accuracy ranges of -+1%.

- The PowerTap P1 pedals appear to also suffer from high rpm power reporting differences, but at much higher RPM than the Vector 3 and with a smaller margin of error.

Thoughts....

Could this be related to sample rate at which these power meters calculate power? 

Side thought..... The PowerTap P1 are compatible with oval chain-rings, which means they're doing some high sample-rate and averaging due to the changing velocity of the pedal stroke. Is this why they have the edge over the Vector 3 (no support for oval rings) for these higher RPM ERG tests?

My focus here is on understanding what's happening with the Vector 3 pedals, I also have a suspicion the Tacx Neo itself starts to struggle with power reporting at higher RPM ERG efforts. I did have a Quarq power meter on for a number of these tests..... but I've omitted that for now as I focus purely on the pedals vs the world. 

As always... more data needed. Stay tuned.


Next day updates...

Because this is 100% doing my head in.

Static weight tests/verification on the Vector 3:

20.000kg certified weight + 21g hook/mount. 172.5mm cranks. Calculated Nm: 33.845 

Readings from the Edge 520:

R: 33.41, 33.50, 33.47. 33.46 avg. 98.86% of calculated Nm.
L: 33.66, 33.59, 33.72. 33.65 avg. 99.42% of calculated Nm.


Test 9 - Vector 3 | Tacx Neo. 

Post static weight tests on Vector3

39/15 gearing. No gear changing. 
Head units: Garmin 520, Garmin 820. 1 second recording. Latest firmware on both.

- 3 minutes 200W ERG test. Cadence change every minute. (90/60/120)
- Cycling Dynamics turned off at 5min.
- 3 minutes 200W ERG tests / cadence change every minute. (90/60/120)
- Cadence Ramp Test ERG enabled (Cadence increase, power 'should' remain the same) 
- Cadence Ramp Test ERG disabled (Cadence increase, power increase)







Data: https://analyze.dcrainmaker.com/#/pu...9-ffdaaa8cd18c


Test 10 - PowerTap P1 | Tacx Neo

Everything IDENTICAL to Test 9, except for the pedals. I skipped the 2nd 3minute block I used in Test 9 after disabling Cycling Dynamics (showed no change)



Data: https://analyze.dcrainmaker.com/#/pu...0-abf3212b6abe



The raw data files should be accessible on Ray's site for download / further review. 

In summary and for clarification - I really want the Vector 3 to work, just as well as the P1, it not better. I won't rule out the Neo, my testing protocol, my wonkyness at higher RPM on L/R, maybe the moon phase.... I just can't explain or resolve what I'm seeing with the readings. 

Grabbing at straws...

- Installation torque? I'm snugging them on just as tight as the P1.
- Interface between the pedal and the cranks? I've tried with and without the 2mm washers, no change on the Ultegra 6800 cranks. 
- Cleats?.... I'm running 6deg float on V3, 0deg on the P1. I have the 0deg Exustar ones here in a box I'm yet to install. 
- Sample rates.... well beyond what I've got access to see/review/know about. I'll leave that for the engineers. 

Stay tuned..... again! 


Thursday, 7 December 2017

Tour of Bright heads indoors as race cancelled due to severe weather




This time last week saw the cancellation of the 2017 Tour of Bright stage race in the Victorian high country. With severe weather warnings and predictions of up to 300mm of rain, the decision by Alpine CC was a tough one, but was the correct one to make. If anyone has descended Mt Hotham in the wet, you'll agree wholeheartedly with their decision.

Rewinding back a few years to my blog post on the 2008 edition of the Tour of Bright

"Up Rosewhite the pace was gentle and steady. At one point an O2 rider beside me asks how many watts? My reply being "too many", watts and speed up a hill is all dependant on weight, so its of little relevance to anyone other than me. I have a chat to him and find out its Mr CyclingTips himself, Wade Wallace. I've followed his web site for a while, and know of him, but never met him. No better time for introductions than up a climb in a bunch of 90 riders!"

Wade Wallace (founder of CyclingTips) and I both have a fondness for this race. We'd initially crossed paths in the bunch, and in following years we'd both managed to pull on the Yellow jersey in the Masters 1/2/3 and Masters A categories after the final sage.

A post from 2013 on Cycling Tips "Tour of Bright: A Legend Two Decades in the Making" covers the history of this race and some of the successful names in the sport who've pinned a number on at "Bright" over the years.

My last memory of racing Bright were back in 2014, finishing the extremely wet Stage 3 Mt Hotham ascent curled up in a ball on the side of the road after crossing the finish line. I've given the race a wide berth in the following years while trying to block out that experience. I'm sure I'm not alone there, it was quite a memorable stage.





Upon hearing the news the 2017 edition was cancelled, a number of people joked on social media that we shouldn't let all the race preparation go to waste and we should hold a "Virtual Tour of Bright" using Zwift. I liked the idea, however I took it as light humour knowing the effort it would take to make that happen.

Within a few hours the wheels were in motion to make it so. Wade had grabbed this idea and had run (ridden, I guess) with it at full steam!

With the approval of the organisers, sponsors, Zwift, a number of parties, and 62 emails later - The Zwift Bright Brewery Tour of Bright was in place.

Two stages, no official prizes, no entry fees, just log in, clip in, race! I was in! So were over 200 others on the start line of each stage.

– Stage 1: 9am AEDT, 55.7km (London Preztel - Somewhat Hilly)
– Stage 2: 9:30am AEDT, 72.2km (Watopia Pretzel - Really really hilly!)

Was this the official Tour of Bright? No. Was it almost as hard? Yes! A message from Wade after Stage 1 mentioned the word "Brutal" more than once I'm sure. :)

The offical 'virtual' results are over on ZwiftPower if you'd like to see where you ended up or how the riders went in each stage or in the overall GC standings.

ZwiftPower Tour of Bright Results

Stage 1 Wrap Video:


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Stage 2 Short Video:


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From an event cancellation to the global collaboration between CyclingTips and Zwift - all in only a few hours to provide riders an opportunity to race their bikes, albeit virtually, and for nothing more than to chase other pixel bike riders on their screens.

This is everything I hoped this new world of connected technology would be. It's not a replacement for the joy and excitement of racing or riding our bikes outside. That'll never be matched indoors. It's an opportunity to still get that heart rate up, to get those legs burning, and to race that rider next to you for 1st or 101st place rather than sitting on the couch looking out the window wishing you were on a bike.


Sunday, 26 November 2017

Zwift on Apple TV - The Full A to Z User Experience


Released just last week, Zwift on AppleTV just might be the game changer people have been waiting for. The AppleTV 4K packs a huge amount of processing power for the 3D rendering required for a solid Zwift experience. In short, nothing comes close in terms of price/performance.

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Friday, 10 November 2017

Strava Insights - TCS New York City Marathon 2017



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-----------

::: TCS New York City Marathon 2017 (November 5th) - STRAVA Summary Stats ::::

Records:     5389 (~10.77% total participants)
Event Entry Estimate: 50,000


GPS / Device Brand Used:
   4070  75.5% Garmin
    678  12.6% Strava Mobile App 
    245   4.5% *Unlisted*
    163   3.0% Suunto
    112   2.1% Apple
     78   1.4% Polar
     30   0.6% Fitbit
      7   0.1% vívosmart
      3   0.1% Huami
      1   0.0% Soleus
      1   0.0% Samsung
      1   0.0% Android Wear
   5389 100.0% Total (12)

GPS / Device Used:
    866  16.1% Garmin Forerunner 235
    592  11.0% Strava iPhone App
    427   7.9% Garmin Forerunner 920XT
    407   7.6% Garmin fēnix 3
    361   6.7% Garmin Forerunner 735XT
    310   5.8% Garmin Forerunner 230
    293   5.4% Garmin Forerunner 935
    245   4.5% *Unlisted*
    231   4.3% Garmin Forerunner 220
    161   3.0% Garmin Forerunner 225
    131   2.4% Garmin Forerunner 630
    128   2.4% Garmin Forerunner 620
    120   2.2% Garmin fēnix 5
    110   2.0% Garmin Vívoactive HR
    103   1.9% Garmin fēnix 5X
     95   1.8% Garmin Vívoactive
     91   1.7% Garmin fēnix 5S
     91   1.7% Garmin Forerunner 35
     85   1.6% Strava Android App
     76   1.4% Apple Watch Series 2
     52   1.0% Suunto Ambit3 Peak
     46   0.9% Garmin Forerunner 910XT
     45   0.8% Suunto Ambit3 Sport
     41   0.8% Suunto
     39   0.7% Polar V800
     34   0.6% Apple Watch Series 3
     31   0.6% Polar M400
     28   0.5% Garmin Forerunner 25
     15   0.3% Garmin fēnix 2
     14   0.3% Suunto Spartan Ultra
     13   0.2% Garmin Forerunner 10
     12   0.2% Garmin Forerunner 15
      9   0.2% Fitbit Surge
      9   0.2% Fitbit Blaze
      7   0.1% vívosmart HR+
      7   0.1% Garmin Forerunner 310XT
      6   0.1% Suunto Ambit2 S
      6   0.1% Garmin Forerunner 410
      6   0.1% Fitbit Ionic
      5   0.1% Polar M600
      5   0.1% Garmin vívoactive 3
      4   0.1% Suunto Ambit2
      4   0.1% Garmin Forerunner 110
      4   0.1% Fitbit
      3   0.1% Polar M200
      3   0.1% Huami Amazfit Pace
      3   0.1% Garmin Forerunner 610
      3   0.1% Garmin Forerunner 210
      2   0.0% Fitbit Charge 2
      2   0.0% Apple Watch 1st Generation
      1   0.0% Suunto Spartan Sport
      1   0.0% Strava GPX
      1   0.0% Soleus GPS
      1   0.0% Samsung Health
      1   0.0% Garmin vívosport
      1   0.0% Garmin Forerunner 405
      1   0.0% Garmin Forerunner 305
      1   0.0% Android Wear
   5389 100.0% Total (58)


Shoes:

    281  14.9% ASICS
    265  14.1% Brooks
    260  13.8% Nike
    217  11.5% Saucony
    206  10.9% adidas
    186   9.9% Hoka
    177   9.4% New Balance
    102   5.4% Mizuno
     48   2.5% On Cloud
     43   2.3% Altra
     99   5.3% Other (25)
   1884 100.0% Total (35)

Gender:
   3586     66.5% Male
   1518     28.2% Female
    285      5.3% *Unlisted*

Overall: 
Heart Rate Monitor Usage: 61.64%
Average Heart Rate: 159bpm
Average Pace: 05:52/km (9:26/mi)
Average Finish Time: 4:07:32 

Male:
Heart Rate Monitor Usage: 64.47%
Average Heart Rate: 157bpm
Average Pace: 05:40/km (9:07/mi)
Average Finish Time: 3:59:06
Winning Time: 2:10:53 (3:06/km, 4:59/mi)

Female:
Heart Rate Monitor Usage: 54.61%
Average Heart Rate: 162bpm
Average Pace: 06:20/km  (10:11/mi)
Average Finish Time: 4:27:14
Winning Time: 2:26:53 (3:28/km, 5:36/mi)


Summary Pace Distribution: 
      4   0.1%  Minute Pace (no data)
     95   1.8% 3 Minute Pace
   1151  21.4% 4 Minute Pace
   1978  36.7% 5 Minute Pace
   1352  25.1% 6 Minute Pace
    549  10.2% 7 Minute Pace
    166   3.1% 8 Minute Pace
     59   1.1% 9 Minute Pace
     26   0.5% 10 Minute Pace
      4   0.1% 11 Minute Pace
      2   0.0% 13 Minute Pace
      1   0.0% 15 Minute Pace
      1   0.0% 17 Minute Pace
      1   0.0% 25 Minute Pace
   5389 100.0% Total (14)


Detailed Pace Distribution: 
      4   0.1% :0/km Pace (no data)
      1   0.0% 3:20/km Pace
      8   0.1% 3:30/km Pace
     24   0.4% 3:40/km Pace
     62   1.2% 3:50/km Pace
    118   2.2% 4:00/km Pace
    127   2.4% 4:10/km Pace
    165   3.1% 4:20/km Pace
    191   3.5% 4:30/km Pace
    259   4.8% 4:40/km Pace
    291   5.4% 4:50/km Pace
    275   5.1% 5:00/km Pace
    295   5.5% 5:10/km Pace
    366   6.8% 5:20/km Pace
    413   7.7% 5:30/km Pace
    311   5.8% 5:40/km Pace
    318   5.9% 5:50/km Pace
    283   5.3% 6:00/km Pace
    259   4.8% 6:10/km Pace
    234   4.3% 6:20/km Pace
    190   3.5% 6:30/km Pace
    205   3.8% 6:40/km Pace
    181   3.4% 6:50/km Pace
    140   2.6% 7:00/km Pace
    120   2.2% 7:10/km Pace
    103   1.9% 7:20/km Pace
     66   1.2% 7:30/km Pace
     60   1.1% 7:40/km Pace
     60   1.1% 7:50/km Pace
     46   0.9% 8:00/km Pace
     40   0.7% 8:10/km Pace
     29   0.5% 8:20/km Pace
     19   0.4% 8:30/km Pace
     17   0.3% 8:40/km Pace
     15   0.3% 8:50/km Pace
     12   0.2% 9:00/km Pace
     15   0.3% 9:10/km Pace
     10   0.2% 9:20/km Pace
      7   0.1% 9:30/km Pace
      9   0.2% 9:40/km Pace
      6   0.1% 9:50/km Pace
      9   0.2% 10:00/km Pace
      2   0.0% 10:10/km Pace
      6   0.1% 10:20/km Pace
      3   0.1% 10:30/km Pace
      5   0.1% 10:40/km Pace
      1   0.0% 10:50/km Pace
      1   0.0% 11:00/km Pace
      1   0.0% 11:10/km Pace
      2   0.0% 11:20/km Pace
      1   0.0% 13:20/km Pace
      1   0.0% 13:30/km Pace
      1   0.0% 15:10/km Pace
      1   0.0% 17:00/km Pace
      1   0.0% 25:10/km Pace
   5389 100.0% Total (55)


Device on pace.....

Devices used for <= 3 minute pace: 
     20  22.2% Garmin Forerunner 235
      8   8.9% Garmin Forerunner 935
      7   7.8% Garmin Forerunner 735XT
      6   6.7% Garmin Forerunner 630
      5   5.6% Suunto Ambit3 Peak
      5   5.6% Garmin fēnix 3
      5   5.6% Garmin Forerunner 230
      5   5.6% Garmin Forerunner 220
      4   4.4% Suunto
      3   3.3% Polar V800
     22  24.4% Other (16)
     90 100.0% Total (26)

Devices used for 4 minute pace: 
    184  16.5% Garmin Forerunner 235
    112  10.1% Garmin fēnix 3
    104   9.4% Garmin Forerunner 920XT
     83   7.5% Garmin Forerunner 230
     82   7.4% Garmin Forerunner 735XT
     77   6.9% Garmin Forerunner 935
     72   6.5% Strava iPhone App
     48   4.3% Garmin Forerunner 220
     47   4.2% Garmin Forerunner 630
     42   3.8% Garmin Forerunner 620
    261  23.5% Other (32)
   1112 100.0% Total (42)

Devices used for 5 minute pace: 
    323  17.1% Garmin Forerunner 235
    232  12.3% Strava iPhone App
    157   8.3% Garmin fēnix 3
    154   8.1% Garmin Forerunner 920XT
    142   7.5% Garmin Forerunner 735XT
    111   5.9% Garmin Forerunner 935
    100   5.3% Garmin Forerunner 230
     74   3.9% Garmin Forerunner 220
     52   2.7% Garmin Forerunner 225
     48   2.5% Garmin fēnix 5
    500  26.4% Other (39)
   1893 100.0% Total (49)

Devices used for 6 minute pace: 
    207  16.2% Garmin Forerunner 235
    168  13.1% Strava iPhone App
     93   7.3% Garmin fēnix 3
     91   7.1% Garmin Forerunner 920XT
     86   6.7% Garmin Forerunner 735XT
     86   6.7% Garmin Forerunner 230
     66   5.2% Garmin Forerunner 935
     57   4.5% Garmin Forerunner 220
     47   3.7% Garmin Forerunner 225
     32   2.5% Garmin fēnix 5
    346  27.1% Other (36)
   1279 100.0% Total (46)

Devices used for 7 minute pace: 
     93  17.8% Garmin Forerunner 235
     72  13.8% Strava iPhone App
     48   9.2% Garmin Forerunner 920XT
     30   5.7% Garmin Forerunner 220
     29   5.6% Garmin Forerunner 735XT
     28   5.4% Garmin Forerunner 230
     27   5.2% Garmin fēnix 3
     24   4.6% Garmin Forerunner 935
     22   4.2% Garmin Vívoactive HR
     16   3.1% Garmin Forerunner 35
    133  25.5% Other (25)
    522 100.0% Total (35)

Devices used for >= 8 minute pace: 
     47  19.0% Strava iPhone App
     39  15.7% Garmin Forerunner 235
     27  10.9% Garmin Forerunner 920XT
     17   6.9% Garmin Forerunner 220
     15   6.0% Garmin Forerunner 735XT
     13   5.2% Garmin fēnix 3
     13   5.2% Garmin Vívoactive
      8   3.2% Strava Android App
      8   3.2% Garmin Forerunner 230
      7   2.8% Garmin Vívoactive HR
     54  21.8% Other (19)
    248 100.0% Total (29)