Aero display on bike?

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dquirk29
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Aero display on bike?

Post by dquirk29 »

How do i see how aero i am while ridding on the bike. I thought was was an option
TriBike
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Re: Aero display on bike?

Post by TriBike »

If you are riding with a DFPM(Direct Force Power Meter), you have the option of viewing your CdA real time. To turn this feature on, go into the SetUp of the Newton+ and scroll to rACr(yes)->CdA(on). You will then see your Cda in the lower field of the iBike Display, alternating with Cadence(RPM) and HR if you use a Strap. I also attached a PDF Copy of instructions for the Newton+. On Pg.21, I believe it outlines the "Coast Down" Procedure, to help you establish CdA(and optional Crr) measurements without the use of DFPM.
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Newton_Instructions_Jun_12_red.pdf
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dquirk29
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Re: Aero display on bike?

Post by dquirk29 »

So you need a direct power meter? I thought you could look at it while coasting

DQ
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Russ
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Re: Aero display on bike?

Post by Russ »

OK,

One of my favorite features :-)

Go into racer prefs and make sure CDA is turned on.

When going down hill stop the cranks and after about (more or less) 15 seconds you will see CDA displayed after calories and it will redisplay from time to time (more or less periodically).

Wind changes and cars going by and road surface changes will cause changes in the CDA as does wind cal and wind scaling so these must be dialed.

Russ
dquirk29
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Re: Aero display on bike?

Post by dquirk29 »

Can it be looked at in the download later so I can look at the road while descending?
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Russ
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Re: Aero display on bike?

Post by Russ »

Hi dquirk29,

I wish it could! Hint hint --- feature request!!!

That said, the best way, I think, to use Cda display without a direct reading power meter along with the iBike (with one it does get post analysis) is to do hill repeats on the same hill selected for smooth pavement, low traffic and ideally straight or long straight sections so that you can observe. Repeats so that you can look for an value that crops up predominately for verification.

Steady or no wind conditions help a lot. Remember that you need a good wind cal, wind scale and hopefully an accurate CRR for that type of road. Although if you are simply looking to optimize Cda then relative changes downward would be meaningful.

Russ
travispape
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Re: Aero display on bike?

Post by travispape »

Russ wrote:Hi dquirk29,

I wish it could! Hint hint --- feature request!!!
Granted for Newton and iDash+Power devices. Look for it in the next build of Isaac.

Travis
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Russ
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Re: Aero display on bike?

Post by Russ »

Thanks Travis and Velocomp!

Looking forward to the new goodie(s?) !

:D
Russ
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Russ
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Re: Aero display on bike?

Post by Russ »

Travis,
"Granted for Newton and iDash+Power devices. Look for it in the next build of Isaac."

Today I downloaded Isaac 1.0.8 with this new feature for the Newton+ (and Dash, I think).
Looks great but....
I tried the CDA analysis tool that has been expanded to the standalone Newton.

I zoomed in on a downhill section that I ride on the bars and then the uphill on the hoods, they displayed exactly the same CDA (as a number value exported to the clipboard), I expected a lower value on the bars and a higher value on the hoods.

Next I tried changing the CRR, just for kicks and the CDA numeric exported values still stayed the same, I expected a higher analysed value for a lower CRR case and a lower CDA value for a higher CRR with the same ride portion selected.

Am I misunderstanding something here or is it not yet working?

If I am correct, it looks quite promising!

Thanks,
Russ
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Re: Aero display on bike?

Post by travispape »

Russ wrote:I zoomed in on a downhill section that I ride on the bars and then the uphill on the hoods, they displayed exactly the same CDA (as a number value exported to the clipboard), I expected a lower value on the bars and a higher value on the hoods.
I'm not sure what 2 values you are comparing. Note that if you don't have a DFPM, the CdA is only calculated for sections where you are coasting. It would take some pretty special circumstances to be able to coast uphill.
Russ wrote:Next I tried changing the CRR, just for kicks and the CDA numeric exported values still stayed the same, I expected a higher analysed value for a lower CRR case and a lower CDA value for a higher CRR with the same ride portion selected.

Am I misunderstanding something here or is it not yet working?
What you are actually seeing is a reconstruction of the data as it happened on the road. The underlying sensor data is being used in the CdA calculation, which enables you to see in Isaac what happened on the road. It is similar to what happens when you select, "Analyze -> Return to Original Download', so the edits you made to CdA and Crr are being ignored in the CdA Analysis window. If you need to update your value of Crr and CdA, go ahead and update your profile then do another ride. In other words, this tool isn't intended for editing your profile.
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Russ
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Re: Aero display on bike?

Post by Russ »

Travis,

Thanks for the new features in Isaac! I guess I was hoping you had some of that secret sauce, perhaps using some of that proprietary data to calculate Cda under power or something.

Anyhow, I think i am starting to understand the use of this Cda tool. I started Saturdays ride a bit cold so I dawned a windbreaker and it was too warm soon. So instead of stopping and removing it I unzipped it about 2/3 until my first regular stop. Well I noticed on the realtime dynamic Cda display (while coasting) some very high numbers and that portion of my ride was about as slow as I have ever done it but I worked harder.
So I thought about it and at the end of my ride I did four coasts downhill on smooth pave though my Crr was set for an average of smooth and rough, so the actual numbers may be a tad skewed. I did the first two coasts with my jersey fully zipped and on the drops. I did the last two after stopping to put the windbreaker back on and unzipping it again about 2/3.
This is on a cross bike with 700x32 Gaterskin hardshell tires and full winter kit. My Cda was measured at just below .4 for the jersey in the drops and nearly .6 for the windbreaker on the hoods, cool thing is it seems that the Cda increases as the windbreaker billows out and catches more wind. I guess the slightly high Crr may contribute a bit to the rise as well, or do I have that reversed?

It would be nice to have a print capability other than screen print for that screen. I think a cursor like the one on the base screen that would display all the values would be a nice touch if you can do it.

Russ
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Re: Aero display on bike?

Post by travispape »

Russ wrote:I guess the slightly high Crr may contribute a bit to the rise as well, or do I have that reversed?
No, I think you have it right. If the entered Crr is too low for the actual riding conditions, then that would cause CdA to over-report. Adjust your Crr up for the Gatorskins and you should see a more accurate value of CdA.
Russ wrote:I think a cursor like the one on the base screen that would display all the values would be a nice touch if you can do it.
I think that what you actually want it already in there. If you highlight a portion of the ride such as the particular descent you are interested in, the average CdA for that portion of the ride will be shown in the plot label.

Travis
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Russ
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Re: Aero display on bike?

Post by Russ »

Travis,

This is really nice! I love it and it, for the Newton+ without the second power meter, will be very useful for many. Thanks!

You said:
"I think that what you actually want it already in there. If you highlight a portion of the ride such as the particular descent you are interested in, the average CdA for that portion of the ride will be shown in the plot label. "

Somehow I had missed that little plot label in the upper left, that works fine!

Thanks again!
Russ
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racerfern
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Re: Aero display on bike?

Post by racerfern »

Umm, I think it's that forest for the trees thing. I select a downhill non-cadence section. Not using a DFPM then click on Tools > CdA Analysis on Selection. I have a flat CdA line of .375 and I don't think the line should be dead flat. Am I looking in the wrong place?

I now see the plot label but why is it flat?
Fernando
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Russ
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Re: Aero display on bike?

Post by Russ »

Hi Racefern,

I am not positive if it is needed, but I select zoom in after selecting the portion. I assume you did that.

Even if everything is dialed, I would expect a small hint above or below the profile Cda value. Usually the wind is not dead steady or dead calm so some slight perturbations should show, I would expect. Also, if you highlight a section in the Analise Cda tool itself then the value for the highlighted section appears to the right of the Cda panel label up top left.

Also, you can right click and export a couple of types, including excel. I did a quick and dirty export of the other choice - I think it was text, anyhow not the excel choice and pasted it into ms word. There I scrolled through (for the whole ride file in my test export) reams of the profile number to see the occasional coasting sections where the numbers varied. Point is you can see minute changes there if you dig them out but you have to look carefully if it is a the whole ride.

I guess this is why I got interested in contrasting the zipped up jersey in the drops to the unzipped windbreaker on the hoods, so I could see a drastic depiction of change, just to feel out the tool. Try something like that to see that is definitely works in an easy to see drastic case :-)

Regards,
Russ
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Russ
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Re: Aero display on bike?

Post by Russ »

Racefern,
Here are a couple of screenshots showing what I have talked about. You can see on Cda2 right hand set shows the drag of my windbreaker 2/3's unzipped billowing out. The first downhill achieved full billow earlier and has a bit of a flat top, the second had a more progressive billowing with speed increase and so it shows a ramp due to increasing Cda. At least that is my best explanations.

Set the averaging window to 10 (lowest choice) and see more, the selection section will give averages in the Cda display upper left.

Russ
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Cross Bike, 1st 2 downhills w/jersey zipped up. 2nd 2 with windbreaker billowing 1/3 zipped. !st zipped on the drops, 2nd winbreaker on the hoods. Shows drastic difference.
Cross Bike, 1st 2 downhills w/jersey zipped up. 2nd 2 with windbreaker billowing 1/3 zipped. !st zipped on the drops, 2nd winbreaker on the hoods. Shows drastic difference.
Cda2.JPG (107.85 KiB) Viewed 12534 times
Road bike on the bars, summer kit
Road bike on the bars, summer kit
Cda1.JPG (108.31 KiB) Viewed 12531 times
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Russ
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Re: Aero display on bike?

Post by Russ »

Everyone that is interested,

After playing with today's ride I have a found the following method to be helpful:

Probably first, set the averaging window to minimum (10 seconds currently).

1. When you choose a portion of your ride to analyze, bracket the non cadence section a bit, I mean select a little before over to a little past. No need to zoom in (unless you can't make out the no cadence section).

2. Launch the Cda Analysis tool and select the middle pane for speed and the bottom pane for power.

3. Highlight the 0 power section, this should be the same as the non cadence section if you made sure you were not soft peddling coming into the coasting.

4. Now change the bottom pane to wind wrt road.

5. Observe the wind and if it is changing, perhaps select a sub set portion where the wind is steady. Notice any changes in the Cda that somewhat follow any sudden changes in wind, if there are any. Not sure yet but changes here with wind may indicate a wind offset (zeroing) or a wind scaling issue. Otherwise it may be a sudden change in the wind that iBike can't keep up with for this purpose.

I am suggesting this as a starter set for experimentation. I would love to hear your observations related to this tool.

Also for Travis, I would like to have a 0 filtering option and a default of the lowest value (10 now). The 30 second default caused me to miss the 'flat' top in my first crack at the windbreaker Cda picture above (first crack picture not posted). I think the 10 second filter still makes it a little more difficult to relate the wind/speed/Cda relations for trying to make an intelligent final highlight choice.

Thanks,
Russ
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racerfern
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Re: Aero display on bike?

Post by racerfern »

Russ,

Nice investigative work! Apparently the key is to bracket the coasting selection with a little bit of cadence either at the beginning of the coasting section or at the end.

Attached are three screenshots. One is a short coast in a tight tuck. The displayed CdA was .34 while my base is .374

The other one is regular coasting but with turbulence from traffic, etc. It's easy to see the fluctuations as cars whiz by. With the buffeting from winds it makes sense. It also might be that my CdA is set a bit low since I've been playing with Isaac more than I've been riding :(

The third one is rolling down a hill on and off the brakes waiting for a break in the traffic to make a left turn at the bottom of the hill.

I think 10s smoothing is fine since it's extremely difficult to guarantee better resolution under the circumstances.
Attachments
tight_tuck.jpg
tight_tuck.jpg (94.59 KiB) Viewed 12336 times
coasting_with_traffic.jpg
coasting_with_traffic.jpg (89.6 KiB) Viewed 12337 times
braking downhill.jpg
braking downhill.jpg (97.09 KiB) Viewed 12336 times
Fernando
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Russ
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Re: Aero display on bike?

Post by Russ »

Racefern,

For a basic look at the graphs, yes 10 second works. My thinking, though, is that to use the graph visually to the maximum 0 would be helpful. This is because any averaging changes the shape of the leading edge and trailing edge. Also if you do not have access to a mountain with long descents, the whole descent picture may never have a chance to fully average out.

Again my thinking is that the shape of the coasting section sheds light on the validity of of the Cda measurment because if it is not generally flat, you have diagnosis work to do on you profile, or need a different run for better wind conditions.

I notice that your first plot is generally quite flat. This says that you are indeed well dialed! So in your case, being well dialed, no need for 0 averaging :-)

Russ
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