CdA-measuring AeroPod makes cycling less of a drag
Remember back when cyclists had to travel to a wind tunnel or velodrome if they wanted to get their aerodynamic drag measured? Actually, that time is now. It might not be for much longer, however, if the handlebar-mounted AeroPod reaches production.
The AeroPod was created by Florida-based Velocomp, the same company that previously brought us the bar-mounted PowerPod power meter. Like that product, the AeroPod is capable of measuring the rider's power output in watts, plus it provides an analysis of their pedal stroke efficiency and economy. If paired with a third-party direct force power meter, however, it can also calculate their coefficient of drag times frontal surface area, or CdA.
Upon initially installing the 40-gram device, users utilize custom software to dial in bike and rider settings, then perform a three-minute out-and-back calibration ride. This creates a profile for that bike/rider combo. Four such profiles can be stored on the AeroPod, allowing it to be swapped back and forth between different bikes.
From there, every time the rider goes out with it, the device calculates their CdA once a second. The continuously-updated figure – along with a Time Advantage measurement, telling riders how much time they gain/lose during the ride due to changes in ride position – is displayed on either a pair of Raptor Glasses, a compatible ANT+ Garmin bike computer, or via the company's PowerHouse Bike app on a paired smartphone. That app can also be used to review how the rider's CdA changed throughout a ride.
So, how does the AeroPod work?
"The fundamental principle is Newton's third law: applied forces equal opposing forces," Velocomp CEO John Hamann explained to us. "Traditional direct force power meters measure forces applied by the cyclist. AeroPod measures forces opposing the cyclist. One of the forces opposing the cyclist is wind. The magnitude of opposing wind force is dependent not only on how 'strong' the wind is, but also the aerodynamic sleekness of the rider and bike."
"AeroPod knows the applied force (it reads that from the direct force power meter), and it also knows the other opposing forces (acceleration, hill slope, friction, measured by AeroPod sensors). Wind is the remaining opposing force, and when the measured wind force is 'correct,' applied forces equal opposing forces. Since AeroPod knows all the forces except wind, AeroPod can calculate out, in real time, the value of CdA that makes total opposing force equal to total applied force."
If you're interested in getting an AeroPod, it's currently the subject of a Kickstarter campaign. A pledge of US$349 will secure one for you, if everything goes according to plans. The retail price will be $499.