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Notio aero testing in indoor velodrome
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I have a question for those of you who have experience aero testing with Notio in indoor velodrome. Do you keep the same calibration value for the whole test or do you estimate the calibration value for each of the runs and compute the cda value for each of the intervals individually? (assuming the front end does not change)

Latelly, I have been doing some aero testing in an indoor velodrome. At the start of each test day, I perform a calibration procedure as suggested by Notio (2 runs of 3km each, and estimate the average calibration value of both runs). I get a value of 1.39. I then proceed to test whatever gear, position... I want to test. I do 4 runs of 2.5-3km for each position. GC has the option to estimate the calibration factor for each interval and I noticed that as the test day progresses, the calibration factor keeps growing. I start at a value of 1.39 and I get values up to 1.41 for the final runs. These are average values for each 2-3km interval.

I am the only rider in the velodrome, doors are closed. I do the tests at a constant speed of approx. 43km/h, and I start and end them at the same point. From my understanding, if the front end does not change, which in my case did not, the calibration value should not change. My guess is that the air starts circulating as a rider keeps doing laps in the velodrome, but I am not sure.

I have computed the cda values with the calibration value constant and also for each interval with its individually estimated calibration value. In some cases the results change significantly. I assume the latter method is better but I am not sure.
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Re: Notio aero testing in indoor velodrome [casio] [ In reply to ]
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casio wrote:
I have a question for those of you who have experience aero testing with Notio in indoor velodrome. Do you keep the same calibration value for the whole test or do you estimate the calibration value for each of the runs and compute the cda value for each of the intervals individually? (assuming the front end does not change)

Latelly, I have been doing some aero testing in an indoor velodrome. At the start of each test day, I perform a calibration procedure as suggested by Notio (2 runs of 3km each, and estimate the average calibration value of both runs). I get a value of 1.39. I then proceed to test whatever gear, position... I want to test. I do 4 runs of 2.5-3km for each position. GC has the option to estimate the calibration factor for each interval and I noticed that as the test day progresses, the calibration factor keeps growing. I start at a value of 1.39 and I get values up to 1.41 for the final runs. These are average values for each 2-3km interval.

I am the only rider in the velodrome, doors are closed. I do the tests at a constant speed of approx. 43km/h, and I start and end them at the same point. From my understanding, if the front end does not change, which in my case did not, the calibration value should not change. My guess is that the air starts circulating as a rider keeps doing laps in the velodrome, but I am not sure.

I have computed the cda values with the calibration value constant and also for each interval with its individually estimated calibration value. In some cases the results change significantly. I assume the latter method is better but I am not sure.

In your case, the calibration should remain the same.

Your theory of the air circulating may be valid and this could (in theory) explain the different calibration numbers, but if the phenomenon is present, calibration won't be accurate anyways. Calibration is trying to get a net 0 wind from and out and back. In your case, if the air circulation theory is valid, would not be valid, you'd have a continuous tailwind. Again, all in theory.

One thing you could do is keep the factor constant and see if you are getting a gradual tailwind.

But to compare two runs, you should be keeping the value constant. Using a 1.41 will make CDA look artificially better, quite significantly

I always chuckle when I see the 1.39 default value being used, since it's the default value for one particular rider who happened to do a lot of tests.
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