Originally Posted by
ks1g
I have a question for RChung about doing this test protocol in real life. I have a long downhill-flat section-downhill around the corner, I will have to check next commute how fast I need to be going to coast through the flat section. It looks like the protocl is get to a desired entry speed, coast through the test section while collecting the time-series speed data. Repeat with identical geometry/body position but at a much different entry speed. Use USGS maps, barometric altimeters, etc. to get altitude/slope data. I assume you use other means than hitting a "lap" button to note when you've entered the test section (since we're assuming no power meter that would indicate coasting).
That's about it. In this example I did only two runs because I was only trying to show that it could be done, and done with pretty minimal equipment. I'd do at least one more in a real attempt, then compare the runs against each other. I don't hit a lap button -- I like to get my position set and start to coast before I enter the test section so I don't have to move my hands or head or anything, even if only to hit a lap button. Instead, I transform speed into distance and from the speed and change in speed and mass I build up a preliminary elevation profile for the course. It's pretty clear where the slope begins, or where it transitions to the flat, and then steepens again; so once that's identified I can count in distance backward and forward to match the test sections. May sound hard but it's not, really, and it frees me up from remembering to mark the sections. Basically, I try to make the data collection as simple and brainless as possible even if it means I have to do an extra calculation when I get home. Many other protocols require that you hit a certain speed at a certain point or hold your speed or equalize mass or something else. I'm usually too stupid to remember all those things when I'm on the bike so it makes sense to account for it later.
I wish I knew about this when my kids were a few years younger - they both did a bike tire rolling resistance experiment for school science fair (I was the "test pilot"). Data collection was limited to stop watches, and my ability (or lack of) to hit a consistent entry speed, lap buttons (gave up on that) and note max indicated speed for each run. I sat up as upright as I could to try to get consistent CdA*rho. No collection of data or adjustments for air density and I forget what we did about wind.
If you're serious about this kind of thing you really need to do it under calm conditions (or else have a way to measure wind on the bike, and that's not easy to do).