Calibration Advice (issues with drafting numbers)

[Russ]

Hi, Regarding this:

Postby rruff on Wed Aug 19, 2009 8:52 am
In IB3 go to "Tools/ Tweak CdA" and there you can adjust it until you like what you see.

I have been experimenting, along these lines but with specific criteria in mind.

First I rode a ride on very smooth roads and softpeddled down and partally up several hill/dips and along several level to very slightly uphill segments. My target speeds were high, medium and low.
I wanted high and medium to be for aero and low - to very low speed for tinkering with CRR.

Then back in iBike 3, the softpeddle zones were easily identifiable with fairly steady 40rpm'ish cadence.

I used the Tools/Tweak Crr first on the low speed to make the lower power sections just go to zero watts.
Then, using that Crr, I went to the higher speed sections and did the same with CdA.

Now my high speed sections were above 20 mph (mostly up around 25 or so) and my low speed were as low as I could hold the bike fairly steady, below the 8mph for much of it. I beleave this lets me nearly ignore CdA when doing the Crr part first and then lets the CdA come out more clearly having established the Crr.

I did observer that wind gust sections were best not to be selected and mostly looked for either a steady head/tail wind speed or zero wind speed sections for these tweeks and ignored the bumps in power that seemed associated with the changes in wind conditions (on a second by second basis).

What do you all think of this procedure? I am starting to think it is superior to the CD's.

Another question, about my tires and Crr. I run Conti Gatorskins, the manufacture has published the Crr as .0058 against a four foot diameter polished drum in what looks like a normal work room judging from the photo, so probably at around 70 degrees F. And a list of Crrs that were linked on this list said the same thing. My test came in at .0061 using the above method and the road is not as smooth as a polished steel drum. It was steam rolled tarmac or maybe chipseal but just short of the smoothest that I occasionally find, mostly on major roads. Also I my bike and I weigh in around 235 lbs and I am not sure how this rates against the 'standard' mfg number measured at around 70 kilograms for it's simulated rider load. I run 110 psi for my rides. Also the temperature for my recent tests was a good bit higher than 70F.

Thanks,
Russ

[Russ]

Wow,
I just updated to 3.0.6 iBike 3 for winders.

I took another look at the ride I mentioned above.

First thing I found, looking again at Crr (not related to the upgrade) was that I had a couple of instances of enough tail wind for the relative wind speed to go to zero which meant no aero power.
These instances verified my .0061 Crr. That might be a real useful condition as long as you are not actually being propelled by the wind.

Now for the great thing - what is this new Analyze Dymanic CdA function under Tools?
Well it looks great... After a lot of work with the above mentioned method, I derived a CdA of .321.
Now this new tool says 0.320 with no work at all ! I suppose, it needs the Crr to be dialed and of course the wind cal to be good and all that but what a great tool (if I am using it right) . btw I am using OEM aerobars position during that ride.

Haven't looked yet at any new manual entries for it, will see about that a little later, on to other things !!! Wow Wow Great stuff guys!

Thanks,
Russ

[nigeld]

The Dynamic CdA dialog looks really interesting, but I think I'll get my static values dialed in before messing with that! The rate of updates and enhancements from Velocomp is impressive. I think more documentation is needed on some of these advanced features, and even the core ones. I'm hesitant to employ them unless I know what I'm doing, and it's often not clear from the manual what the effects will be, why and when you should utilize them, and whether they'll be permanent alterations to the file, or to the profile, or what. It seems I'm not the only one having trouble keeping up with Velocomp, the documentation team is too. But prolific enhancements is a good problem to have, good work!

[Russ]

Well I am now thinking I jumped to a wonderful but wrong conclusion about the new Dynamic CdA function. I have looked for new doc on it and don't think that exists yet.

So after poking at it with some older ride files, I have concluded that it seems to be a revamped and improved add second CdA function. It doesn't appear to analyze and so it must have simply come up with what I had allready analyzed, tweeked and profiled

Still big improvement, including now in the 'Pedaling-Tuck' Position you can go below 1 for CdA factor as well as increasing the factor for the 'climbing position' whichever, relative to your profiled position.
The window display of dynamic CdA mystifies me though and looks quite interesting!

Still saying Wow to this all

Russ