Originally Posted by
Steamer
For most of us this is an athletic and leisure time endeavor. I take off my engineering hat at approximately 5:00 pm every weeknight.
But seriously, I think the simplest way to do it without the benefit of any sophisticated meters (that most of us don't have and simply aren't going to waste money on) would involve the classic coast down test (recording terminal velocity) on a known (constant) gradient. If you have a steady grade that is long enough, and bearing drag can be assumed to be negligable for the sakes of the computation, then what would be better?
Hmmm. Does this mean you *have* measured your CdA with coast downs, or are you giving reasons why you *haven't*? For the record, I do this as an athletic and leisure time activity, too -- but even were that not so I'm not sure why it is relevant to this discussion.
Anyway, I agree that coast downs may be the simplest way. But since you ask what would be better, I'd answer that whether something is better depends on how small of a change you want to measure with reliability. I got lousy precision with coast downs until I got a way to track speed accurately and precisely -- lousy in the sense of, with coast downs I could reliably detect changes in CdA of something around 0.02 m^2. With my current setup precision is now quite a bit better. In one test I added a 5cm cube to my bike and estimated the change in CdA at just under .0030 m^2. I leave it to you to figure out what the expected change in CdA should have been.
BTW, as long as you brought up wasting money on sophisticated meters, in any early experiment I scrounged up a cheap data logger to capture speed with stuff around my house (I did happen to have an ancient and obsolete microcassette recorder that I used to use for dictation). Total cost was zero. Not the most convenient solution but the speed precision was quite good, and with the coast down method that's the key.