For those of you who were curious about Aerolab, there’s now a patched Win32 build for it in a development version of Golden Cheetah 1.3. Thanks to Mark Liversedge for building my patch into GC1.3. Keep in mind that this is a very early version of the Aerolab module and that it is not currently part of Golden Cheetah. Aerolab is just a prototype right now, but it will eventually be a complete suite of aerodynamic tools for virtual elevation work.
Continue reading You Can Test Drive GoldenCheetah/Aerolab on Windows Right Now!
As GoldenCheetah prepares for its upcoming release, I wanted to keep you all posted about the development of the virtual elevation module, Aerolab. Aerolab is not currently in Golden Cheetah, but I’m hoping it may eventually find its way there. There’s tons of work still to be done, but at least we now have a prototype that works.
To recap, Aerolab is a tool for estimating the coefficient of rolling resistance (Crr) and the aero coefficient of drag (CdA) of a bike/rider combination. It does this by reverse-engineering an elevation curve from power data using Newton’s Second Law. With the help of Justin Knotzke, I’ve put together some of Greg Steele’s ideas into a very preliminary tool.
Continue reading Aerolab: A Sneak Peek of GoldenCheetah’s Upcoming Virtual Wind Tunne
Thanks to Adrien Gontier of Roues Artisanales and David Linke, I am able to provide you with a unique database of moments-of-inertia and effective rotational masses of a large number of wheelsets. The data allows greater accuracy for VE, a virtual elevation perl script I wrote.
The big surprise is that the larger wheels contribute more than 2kgs to the inertia of the rider and bike. While it’s not going to make or break the VE calculation, it will add an increment — however small — to the accuracy of the calculation.
Continue reading An Effective Rotational Mass Database for Wheels
The method of Virtual Elevation and all its variants are derived from Newton’s 2nd Law for linear motion, neglecting rotational inertia terms. Do those additional terms play a significant role in elevation-matching? Can we accurately measure the moment of inertia (MOI)? In this post, I’ll describe the terms and provide a method for testing MOI.
Continue reading Virtual Elevation: Does Rotational Inertia Play a Role?
A recent discussion on the Wattage Training Forum got me to hack the VE code to quantify the difference between the exact and small-angle version of the VE calculation.
The columns of the resulting CSV file are as follows:
SAMPLE #: row index
SLOPE_EXACT,SLOPE_SA: exact and small-angle slope
DELTA_EXACT,DELTA_SA: delta-elevation, exact and small-angle
ELEV_EXACT,ELEV_SA: cumulative elevation, exact and small-angle
The final elevation numbers are as follows:
| SAMPLE # |
ELEV_EXACT |
ELEV_SA |
| 2978 |
8.51942653497284 |
8.55456417534516 |
|
Conclusion: The cumulative error on the final elevation of the ride is on the order of about 0.4% error.
Downloadable results and code are here.
I was looking at the convergence of the first version of VE and thinking, “this can’t be right…”. When it’s coded right, Newton-Raphson typically converges extremely well, or not at all.
So looking at the code I realized I made a beginner mistake and used a one-sided numerical differentiation scheme:
sub fy
{
my $x = shift;
my $y = shift;
my $delta = shift;
my $f2 = f( $x, $y+$delta);
my $f1 = f( $x, $y );
return ( $f2 - $f1 ) / $delta;
}
Continue reading VE Update: Improved Stability and Convergence
In trying to create a prototype for Golden Cheetah, I put together this perl script that I submit for your perusal. The script comes with the sample data used by Robert Chung in his recent post to the Wattage Forum, so it may look familiar to many of you.
My aim was to match a known profile by using the exact 2nd-law equations of motion. All the details are contained within, as well as a full set of data. The code is submitted “warts and all” for your healthy criticism. As shown in the header file, the code is fully GPL’d, as it is meant to be used for Golden Cheetah.
Continue reading VE – A Perl Script for Virtual Elevation Calculations
Hi Everyone and welcome to my new website.
Yes, after years of helping others get online I’ve finally decided to publish myself. I’m no one special, but I’ll be sharing some of my experiences and thoughts with you from time to time. There’s no unifying subject or theme for this website except that it’s about the stuff that interests me. When I’ll feel like venting, I’ll vent. When I want to share a special experience with you, I’ll write it down here.
So stay tuned and see what’s up on this site every so often.
