Sep 17, 04:52 PM by Steve | CinQo, Take 2
Posted in Cycling & Training
Because I was have calibration issues with my CinQo power meter, the good folks at Quarq sent me a new one. Unfortunately it arrived the day I broke my ribs, and I was not able to test it until the next day. On Thursday I put it on the bike and redid static torque test, taking great care to make sure everything was parallel etc. The results were about 10% low at 10Nm to about 5% low and 30Nm. Interestingly, althought the % error was decreasing, the absolute difference is consistent. That means that the slope is correct and the offset should be accounted for in the auto-zero procedure. Given my crude setup and the nature of the test I would say these aren’t going to be perfectly accurate figures so I think that the results are very promising.
| Actual | Measured | Delta | % Error |
|---|---|---|---|
| 3.79 Nm | 3.37 Nm | -0.42 Nm | -11.07% |
| 7.71 Nm | 6.77 Nm | -0.93 Nm | -12.09% |
| 11.48 Nm | 10.26 Nm | -1.22 Nm | -10.64% |
| 15.24 Nm | 13.78 Nm | -1.46 Nm | -9.61% |
| 19.50 Nm | 18.02 Nm | -1.49 Nm | -7.63% |
| 25.41 Nm | 23.93 Nm | -1.48 Nm | -5.81% |
| 29.75 Nm | 28.21 Nm | -1.54 Nm | -5.19% |
In the chart below I excluded the reslults below 10Nm as they were very non-linear. I also extrapolated out the % error assuming that the absolute error increased 1% for every 10Nm.
Today, my ribs have finally healed enough I took it up OSM for a “live” test against estimated values. I hauled the new CinQo, broken ribs, and a few extra pounds up today with a time of 18:48. I entered into analyticcycling.com is 73.5kg (142lbs + 16lb bike + 4lbs clothes&gear), 0.078 slope (365.7m / 4667m), 4.14 m/s (4667m / 1128s), and got out 255W. The unit reported an average of 245W. I may have been overestimating some of the weights, so if you take 2kg off and use 71.5kg instead, the estimate is 248W. I think it’s pretty clear that this one is much more realistic, and it’s not like I’d expect the numbers to match exactly. This doesn’t account for wind and I used the default rolling and air resistance numbers. Combined with the results of the static torque test, I’d say this one is good, but at some point I’d also like to test it against a PowerTap.
my head hurts. maybe it is better i dont race or use power?? later.
— aham23 at Sep 18, 12:00 PM