Saturday, October 19, 2013

Aero Testing for Dummies

Just lately I've been having some fun with the Alphamantis aerodynamics testing system here in Australia.

In a nutshell, this system enables me to precisely assess changes in a rider's aerodynamics in real time while they are riding their bike.

The rider does not need to do anything special other than ride their bike around a suitable track. Any regular oval-like cycling track or velodrome will do, although an indoor velodrome is preferred as environmental conditions are far more predictable indoors and of course you won’t get rained out.

All that's needed is an ANT+ power meter and speed sensor on the bike, and a clear track to ride around, one where the rider can maintain position and does not need to brake.

Do a handful of laps, and we have your CdA baseline number. Then make a change to your bike position or change a piece of equipment (e.g. helmet or wheel), do a few more laps and we can tell immediately if you are getting an improvement, and by how much. Lather, rinse, repeat.

Test while riding, know if the position is rideable, how it feels at race pace, as well as whether or not it is faster for the power you have, and by how much.


Here's a 7-minute long video showing a sample of it in action, with me explaining in voice over.

That's just a sample of the data capture, there are lots of other things but that's the essence of it.

I've been in a systems testing phase these past couple of weeks, and have successfully tested the system with two riders using different power meters (one an SRM, the other a Powertap) at the Dunc Gray Velodrome. Apart from Rod, who's data was featured in the video, the other rider was my mate Tony. It was only a systems test, not a properly controlled aero test, nevertheless we were able to quickly discern for Tony a difference between two good aero helmets.

The next phase will be to demonstrate for those interested in seeing it in action, in particular those with a professional interest in aerodynamic related cycling performance improvement such as bike fitters, coaches, squad development people, and organisations that have tracks. Australia has over 90 velodromes/tracks to choose from!

The system is portable, meaning I can set it up anywhere with a suitable track, so if there is sufficient interest and access to a clear track, I can travel. All I need is access to a regular 240V power outlet and maybe a table and chair for convenience.

How it works:

Power and speed information from your bike's ANT+ device is transmitted wirelessly to special software on my laptop which, along with various parameters (e.g. rider morphological data, track geometry data, rolling resistance and environmental data) and track timing tape data, calculates and plots charts of power output, speed, CdA, exact track position and so on. It does all this in real time.

There are lots of calculations going on underneath (viewable if desired) such as centre of mass speed, lean angles, precise lap distance actually ridden and so on. And more work is being done to further refine the already sophisticated physics modelling, e.g. modelling the intra lap variation in rolling resistance/tyre scrub, as well as integration with individual track timing data systems for even more frequent precise positional data.

The system also works with the Alphamantis "aerostick" device that can additionally capture the relative wind speed and yaw angles, enabling the software to parse out the effects of any wind during testing.

All the data is also captured for reporting, additional analysis, as well as replaying the data to the rider afterwards if desired.

It is, very, very cool.


Robert said...

Cool, ain't it? Very slick, very sensitive.

Robert said...

BTW, experiment with variable speed (or variable power) protocols.