2/17 update A lot of things have happened in the three weeks since the original posting. It appears that Aerolab will make it into Golden Cheetah 1.4, where it will be a complete alternate view instead of a tab. The extra real estate will fit Greg Steele's interface, which has a tab for calculating air density (including an option that pulls data from a weather service), as well as tabs for creating and overlaying laps.
The abilty to overlay tabs is especially interesting as barometrically derived altitude is far from perfect, so the option of comparing a slow virtual elevation lap with a fast virtual elevation lap should be even more revealing.
I got the idea to incorporate the iBike's wind data into Aerolab's calculations (the original version assumes that air speed matches ground speed). Froncioni got me a patch in 24 hours, and the result was stunning.
Here's a short interval I did analyzed by the original version of Aerolab. There was nothing I could do to make the plots fit. I was starting to wonder if I had grabbed the wrong interval, one where I sat up instead of staying in the aerobars.
Here's the same file with the iBike adjusted plot in red. There was a headwind that slowed me down, which Aerolab interpreted as an increase in pitch. With the headwind accounted for, the plots line up almost perfectly. This, to me, is a real testament to the iBike, and I'm more convinced that anyone who wants to play around with the Chung Method should do so with iBike paired with an ANT+ power meter.
Of course, none of this accounts for the effect of crosswinds. So could there be Aerolab hardware in the future?
Aerolab is Andy Froncioni's brainchild, a virtual wind tunnel freeware tool that utilizes the Chung Method. A basic explanation of the Chung Method is here, but for now suffice it to say it's a mathematical tool that lets you measure your aero drag with nothing but a power meter. Froncioni is still refining Aerolab, and hopes that it will be integrated as a tab within Golden Cheetah version 1.4 (1.3 is to be released soon).
Aerolab does a few cool things. First of all, it simplifies the Chung Method. Instead of manually extracting your power data and pasting it into an Excel spreadsheet, you can simply upload your data from your computer head into Golden Cheetah, or import an existing ride file. Aerolab creates the virtual elevation plot automatically, and you can tweak the plot with sliders for Cda, Crr, air density, and rider + bike weight.
Aerolab also adds another layer of data to the Chung Method. Whereas original Chung Method users had to do loops or out-and-back courses and level repeated landmarks on the course, Aerolab superimposes the course profile generated by your computer head over the virtual course profile, so you can compare the plots along the entire course. While the elevation plot generated by the altimeter in your computer head isn't necessarily 100% accurate, it does provide more detail with which to analyze your ride.
The blue line is virtual elevation generated by Aerolab, the green line is actual elevation from my iBike's altimeter. Tweaking the sliders will make the two lines match better.
Here's the same file, with better Cda/Crr estimates. Note how the VE plot is steeper on the last climb. I sat up at that point of the race, and the extra drag slowed me down. Since the Chung Method assumes consistent positioning, this slowing down is interpreted as a steeper gradient.
Aerolab is still in its infancy, and Froncioni is adding new features at a rapid rate. In cooperation with the eponymous Robert Chung, plans are currently in the works to include special views for superimposing loops and out-and-backs, as well as other course features. Provisions are also underway for tagging course segments with special attributes such as wind, road roughness, or a CdA multiplier. All this extra data will significantly help in finding the unique pair of parameters (Crr,CdA) that make the elevation profile 'work'.
Further features include additional sliders for elevation offset and drivetrain efficiency, as well as a table of wheels that will allow you to correct for the extra momentum you get from the rotational inertia of your wheels. An auto solve feature will generate Crr and CdA values mathematically instead of graphically.
Here's the next build of Aerolab, with sliders for drivetrain efficiency and elevation offset.
So why does Robert Chung think Aerolab is a 'game changer'? Aerolab brings the Chung Method out of the realm of engineers and aero geeks and into the hands of anyone who can download a power meter file. Once Aerolab is complete you'll be able to go out for a training ride, do an interval in one position, do another in a second position, and go home and find out which is faster. Want immediate feedback? Bring your laptop and analyze each run as you complete it. Breakaway artists can easily see if it's faster to ride in the drops or with their elbows on the tops. Considering a new wheelset? Borrow a friend's and see if it's as fast as the manufacturer claims. And best of all, this will all be measured in real world situations while you pedal at race intensity, as you're getting your training done.
You can download a PC version of Aerolab here and try it out for yourself. Just dig up an old TT file and import it (use files with little or no braking and no changes in position), and leave suggestions in Froncioni's comments section. Once Golden Cheetah 1.3 is released, Froncioni will have Mac and Linux versions available for testing as well. Check back here or at his blog for updates.
On cannot ride on water and mightiness alone, and as I age, I find that I have to pay more attention to my nutritional needs, lest I become an empty husk of veiny gristle.
The fall is here and winter will soon be upon us.
I've been playing around with the Chung Method for a while, and I've found a way to use it to pry apart Crr and CdA from a ride file.