Out and back test protocol

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jules.b
Posts: 16
Joined: Thu Feb 25, 2021 3:06 pm

Out and back test protocol

Post by jules.b »

Apologies in advance for this rambling post! I live in a rural area, where road surfaces are highly variable, often potholed. It's really difficult to find a consistently surfaced road without heavy traffic and where you don't need to brake. If I want to ride a circuit, I have to brake during the laps. If I'm not going to brake during the laps, I need to ride out and back on a single stretch of road, and stop and turn between test laps.

I've had some success with testing on a 3km circuit which has fairly decent surfaces and only two places one needs to slow down or brake, but it's not possible to find a circuit where you don't have to brake at all. The first attachment is a test of two tri bar positions using this protocol and circuit. The runs were in the following order AAAAAABBBBBBAAAAA where A was the lower position. It surprised me as the higher position showed a lower CdA on average by about 0.01m2. The results lap by lap seemed consistent enough except for the first "B" run which read very low whilst riding and then appeared to correct as I pressed the lap button. The first set of "A" runs were from KM 2-21. The "B"s from KM21-39, and the second block of "A"s from km39 onwards.
Velocomp_04_19_2021_1619_55_km.ibr
(530.49 KiB) Downloaded 144 times
I'd be happy to stick with this protocol but I'm afraid the need to slow down for some junctions may be introducing error. Traffic got lighter through the test allowing me to coast through the junctions, with far more consistent results in the final block of "A"s.

With this concern in mind, I decided to try an out and back system. I found a fairly well surfaced stretch of road, and lapped back and forth. I set a lap marker each time I passed the start or end of the stretch, so you have alternating laps on the test strip and at each end where I slow, turn in the road, and get back to speed in the opposite direction. The result are pretty poor: a very high variance in the calculated CdA depending on direction, and a high variation overall which I suspect may be due to the runs being too short. I'm wondering if the need to brake and turn in the road is messing up the calibration.
Velocomp_04_22_2021_1013_13_km.ibr
(116.32 KiB) Downloaded 147 times
When I stopped to switch configurations, the CdA readings were madly low with a consistent high wind speed displayed. I switched the Aeropod off and back on again and got the same outcome so I gave up and decided to seek advice.
Velocomp_04_22_2021_1047_6_km.ibr
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So, my questions are these:

1 How much will the need to brake to the extent needed by the first protocol effect the outcome? Does the Aeropod correct for braking to any extent. If I coast down to 15 km/h before braking will this help in any way?

2 Is there a better way to manage out and back runs, for example stop and pick up the bike at the turns? Should I be having a longer run in at the start and run out before turning?

3 What is going on with the wind speed and ultra low CdA in the third and fourth attachments? Is this caused by the aeropod's calibration changing whilst I alter the tri bar pedestal height. The Aeropod is mounted on the base bar using a QR plate. Should I switch it off or even when I stop to make alterations to the bike set-up? Because it is mounted on a QR plate I can take it off and put it back on without messing up the tilt.
jules.b
Posts: 16
Joined: Thu Feb 25, 2021 3:06 pm

Re: Out and back test protocol

Post by jules.b »

I must be doing some thing wrong. I tried again on the circuit this afternoon after resettting the device (12 second press on the button), but results were similar to this morning. My displayed CdA dropped until it was steady but improbable at about 0.13. The speeds in the ibr file look fine, but the wind speed seemed consistently high. Any ideas where I'm going wrong?
Attachments
Velocomp_04_22_2021_1540_27_km.ibr
(225.81 KiB) Downloaded 143 times
Velocomp
Velocomp CEO
Posts: 7793
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Re: Out and back test protocol

Post by Velocomp »

jules.b wrote: Thu Apr 22, 2021 12:26 pm I must be doing some thing wrong. I tried again on the circuit this afternoon after resettting the device (12 second press on the button), but results were similar to this morning. My displayed CdA dropped until it was steady but improbable at about 0.13. The speeds in the ibr file look fine, but the wind speed seemed consistently high. Any ideas where I'm going wrong?
Your profile is radically changed from your 55KM ride. Wind scaling went crazy starting on your 6KM ride.

I took your 55KM profile and applied it to this ride (Tools/Switch Profile After the Ride). Results are much better.

Corrected ride file and profile are attached.
Attachments
JulesB.ibp
(410 Bytes) Downloaded 148 times
Jules_Corr_Velocomp_04_22_2021_1540_27_km.ibr
(203.91 KiB) Downloaded 147 times
John Hamann
jules.b
Posts: 16
Joined: Thu Feb 25, 2021 3:06 pm

Re: Out and back test protocol

Post by jules.b »

Hi John, it's a Rotor InPower.
Thanks, Jules
Velocomp
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Re: Out and back test protocol

Post by Velocomp »

Reply to your first posting:

1) You're using AP in profile 4, for CdA testing. This is the correct thing to do

2) When using profile 4, it's critical that you click the lap button ONLY when you are at the same start/stop place. In your 13KM ride you don't do this. Therefore, none of the measurements are valid...

3) Your 6KM ride has a new, and completely incorrect, calibration. See post above.

4) Your 55KM ride seems to be OK.

Your first "A" laps yield an average CdA of 0.228; your B laps 0.241, and your final A laps 0.232
John Hamann
jules.b
Posts: 16
Joined: Thu Feb 25, 2021 3:06 pm

Re: Out and back test protocol

Post by jules.b »

Thanks John.

With regard to point 3 I did not recalibrate. I stopped and changed the bike setup.


Is there any method you would recommend for doing CdA testing on a single stretch of road? The 13km ride was an attempt to do this. I pressed the lap button at the start rode the stretch, pressed the button, turned, pressed the button at the place I finished, rode the other way, pressed the button, turned and repeated. If I can find a way of testing line this it would be ideal

With regard to the subsequent files, I can't understand how the CdA readings have fallen so low. Can you advise me?

Thanks again, Jules
Velocomp
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Re: Out and back test protocol

Post by Velocomp »

Your calibration shifted radically in the 3rd ride. Wind scaling is too high; this causes incorrect high watts, which pushes down CdA.

The profile in your 6KM ride is labeled "Argon 18". The profile in your 55KM file has a generic name.

Do you have two profiles in your device with the same wireless IDs?
John Hamann
jules.b
Posts: 16
Joined: Thu Feb 25, 2021 3:06 pm

Re: Out and back test protocol

Post by jules.b »

I may be over-thinking the instructions for out and back tests incorrectly, specifically the line
"If you’re doing out-and-back loop testing, click the lap button at the end of the test.
Your test result will be displayed for 30 seconds. Turn around and ride back to your
starting point. Click the lap button again to start a new test"


I was clicking at the end of the run I had identified, braking and turning, clicking again as I passed the start point (i.e. end point of the previous run) and so on. I thought this was intended to enable each run to consist of a constant effort without braking, with a short "lap" in between containing the braking, turn and acceleration. Like this:
OOB1.png
Should I click only the once, at the point when I turn, like this, and include the braking and turn in each lap:
OOB1.png
jules.b
Posts: 16
Joined: Thu Feb 25, 2021 3:06 pm

Re: Out and back test protocol

Post by jules.b »

Velocomp wrote: Thu Apr 22, 2021 5:22 pm Your calibration shifted radically in the 3rd ride. Wind scaling is too high; this causes incorrect high watts, which pushes down CdA.

The profile in your 6KM ride is labeled "Argon 18". The profile in your 55KM file has a generic name.

Do you have two profiles in your device with the same wireless IDs?
The 55km ride was a few days ago. After it I adjusted the bike/rider weight and renamed the profile, and re-sent the profile to profiles 3 & 4 in the
Aeropod. I set 4 as active. I didn't touch the wind scaling

The second (13km) and third (6km) ride were done this morning in the same session. I just paused to change the handlebars. Was the wind scaling OK in the 13km file? I don't see how it could switch profiles between the two blocks. It was not connected to a computer or app.

Where do I go from here. How do I start afresh?
jules.b
Posts: 16
Joined: Thu Feb 25, 2021 3:06 pm

Re: Out and back test protocol

Post by jules.b »

Hi John,

I've extracted the profile from the 55km ride and copied it back in to profiles 3 and 4 on the Aeropod, hopefully that will fix the windscaling.

If you could advise on the query on when to use the button on out and back tests (a couple of post above) that would help lots!

Jules
Velocomp
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Re: Out and back test protocol

Post by Velocomp »

jules.b wrote: Thu Apr 22, 2021 5:28 pm I may be over-thinking the instructions for out and back tests incorrectly, specifically the line
"If you’re doing out-and-back loop testing, click the lap button at the end of the test.
Your test result will be displayed for 30 seconds. Turn around and ride back to your
starting point. Click the lap button again to start a new test"


I was clicking at the end of the run I had identified, braking and turning, clicking again as I passed the start point (i.e. end point of the previous run) and so on. I thought this was intended to enable each run to consist of a constant effort without braking, with a short "lap" in between containing the braking, turn and acceleration. Like this:
OOB1.png

Should I click only the once, at the point when I turn, like this, and include the braking and turn in each lap:

OOB1.png
You are using the lap function correctly.
John Hamann
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Out and back test protocol

Post by Velocomp »

jules.b wrote: Thu Apr 22, 2021 6:05 pm Hi John,

I've extracted the profile from the 55km ride and copied it back in to profiles 3 and 4 on the Aeropod, hopefully that will fix the windscaling.

If you could advise on the query on when to use the button on out and back tests (a couple of post above) that would help lots!

Jules
Danger, Will Robinson! (sorry, it's a line from a very old TV show...) If you have two profiles with the same wireless IDs, AP may become confused about which profile to use. If you have selected profile 4 it should remain on profile 4, but if you hard reset for some reason, it might shift to profile 3. You won't know until you finish your testing...
John Hamann
jules.b
Posts: 16
Joined: Thu Feb 25, 2021 3:06 pm

Re: Out and back test protocol

Post by jules.b »

That makes sense, I could have done that whilst reconfiguring the bars. Thanks for the useful advice!
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