Can someone explain the shit results in this GTN show video using the Notio? Guy on a TT bike gets a CdA of over 0.300???? Like, WTF. No way that thing is setup right. I would hope though a triathlon channel would bother to setup the device correctly if doing an aero test video! There is no way that his CdA is as high as .315 for that video.


I get that it still gives a delta........but aren't we always talking about getting these to "actual" numbers? Did they not do something right before displaying those results? If so, for $1000 the thing should be more automatic in the post-ride display than a $30 anemometer and GC. Mind you, the Notio is over $1000 device. It ought to give me a post ride massage while it is at it.

I just keep seeing stuff like this:
https://www.youtube.com/watch?v=8RfSqOUsZvs

Screencap:

Every happy aero test is alike; each unhappy aero test is unhappy in its own way. Even if you see the data it can sometimes be hard to know but without examining the data it's impossible.

True. I can't really infer "something" from "nothing".

Just that if I was putting up a video as a triathlon network using a fancy device, and was going to display data or results........I'd be cleaning that stuff up first.

In the run-up to "Ollie's hour" attempt, he visited a wind tunnel and GCN did a video showing various watts at different airspeeds for various equipment setups. You could, if you knew what you were doing, calculate his CdA from the data in the video, and it was way higher than what it would have needed to be for a successful attempt with his power. You'd think they would've cleaned that stuff up first. We're obviously not their target audience.

In no particular order of probability

- He is left leg dominant and he was using a single side stages power meter that he didn't calibrate
- He forgot to set parameters and use the defaults for a 16 year old girl that weighs 90lbs
- He forgot to calibrate the device.
- He plans to show that the next informercial, which will be a helmet that brings his CDA to 0.22

Again no particular order of probability

BTW, I hadn't see that video. Seems kind of informercialish IMO.

There are so many ways to screw up a test.

Yes, you want a good estimate; but if you can't get a good estimate the next best thing is to know that the estimate isn't good.

Until we get the magic device that'll fix (or prevent) all screw-ups, we have to do a better job of teaching people how to recognize that an estimate isn't good.


Yeah. I thought so too. At the end he could've added, "...but wait, there's more! You get this free set of allen keys, too!"

I kinda figure that any company that has confidence in their product would be happy to demonstrate in detail what it's capable of... before they start selling it.

I agree that manufacturers should be publishing some type of specs/expectations so people know what to expect and decide if that spec meets their needs. However it is REALLY hard to document this stuff in a way most can understand/appreciate.

IMO ditching air pressure for elevation is key to this working.

Accurate high speed inclinometer?

Sometimes barometric elevation is laughable. Sure, design your runs well.....but....I bet an inclinometer paired to a speed sensor that has the tire rollout input to it right before riding would beat a baro hands down.

Each sensor has it's challenges

Barometers, gyroscopes and accelerometers. Drift, Bias, vibration challenges, noise,all the specifics of cycling...the list is long.The PITA is no sensor is perfect. The beauty is they all complement each other.

The key is not using one sensor, but a fusion of all sensors. Barometric pressure absolutely has it's place in the mix. The right sensor is key. Sometimes I think Garmin chose the worst sensors it could find for their head units.

Knowing how to use the barometer to remove bias from the accelerometers, that complements the gyroscope....how to use the mag and GPS to get better values. It's tough math with a ton of experimentation.

I actually never got to test it. They weren't happy enough with field tests to send me one. And, yes, it was elevation that was the problem.

I do have a friend who's supposed to get me something "soon" though.

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Are you back on the track ? Your friend will send you something, "very soon"😜

iBike has been using an accelerometer for many years and it works well. But it's hard to deal with vibration and weight shifts, tire pressure, etc affect the zero point. So on a 5 min rolling basis it gets calibrated using the barometric sensor!

Elevation is definitely the biggest issue if you want a JRA measurement, but the need for it disappears if you use a good protocol... which you would do in any case if you were testing! Field testing in wind is already a very difficult problem to solve without making it harder by shooting for a "realtime" design.

Yes I know... the pool of potential customers willing to put in the time to do good testing... even with an excellent device and software!... is very small. So no one can make $$$ with that. A JRA sensor can have mass appeal even though its numbers will always be inferior.

It's hard to document a saleable testing protocol and spec if it doesn't work well. Otherwise it's easy... since it would have been done hundreds of times in all sorts of conditions in the device's development.

Have you actually tried it yourself ?

Yep, lots. The old ones.

When you say old one are you referring to before the aeropod?

Though I have experience with the older Velocomp products I can not say they are the same as the aeropod (or the power pod for that matter) which seems to be using a pitot tube sort of probe and maybe better internals.. I am curious if anyone has any real world experience with the aeropod (though it does not interest me as a thing I would buy) and if it does give any usable data in respect of CdA?

You had an ibike ? no wonder you're so sceptical of devices and have more bias than a noisy gyroscope. LOL, I kid..I kid...

Yes, way before Aeropod. But I've looked at Aeropod data and it's a JRA device that suffers from the same elevation measuring issues.

The best thing to use a this point for testing is the CdACrr app plus anemometer. If it had a dedicated out-back mode in the software, and maybe a better airspeed device it would be pretty awesome.

As a triathlete without the PhD in aero testing, most of the discussion is "interesting, but not useful". Finding a testing ground without any wind involvement always seemed good, but not great. Since my CdA will change based on the apparent wind from a crosswind, I really need to test with wind present to find out what is best with wind around because every race I do has some wind at some point. True wind tunnel testing is nowhere near home and is not exactly cheap.

So folks need to solve the second by second elevation change issue and we would have something that could run real time. Isn't this the point of the aerolab product? To allow me to go and perform aero testing with different setups on a known elevation loop when wind is present? Seems the most useful. Kind of like a better output then what Best Bike Split currently produces for $20/month.

Brian

---

"We don't inherit the Earth from our ancestors, we borrow it from our children." --Chief Seattle

If you test on the same course, then you don't need to measure elevation. It's Chung VE with wind measurement. It's better if you build and use an elevation map of that course, which can be done without using an external device to measure it. To allow calibration of the wind measurement while testing, use an out-back course where you ride near the middle of the road in both directions.

Pierre (bugno) has said he will soon add an out-back mode to his CdACrr app. That app and the anemometer is the best thing available IMO, and cheap too.

Thanks

---

"We don't inherit the Earth from our ancestors, we borrow it from our children." --Chief Seattle