Omega, pt 8: White Paper
- First of all, you can download the Omega White Paper in its entirety.The paper was written entirely by Dr. Andrew Coggan, based on data from his mini wind tunnel. He developed the testing protocol, and conducted nearly 1,000 separate runs, including tests of early Omega prototypes, to generate his test results. The final paper is based on 481 test runs, including the Omega, nine other brakes, and tests of the bare fork without any brake installed. I asked him to write the white paper entirely on his own, so that it would be unbiased, and as transparent as possible. My goal was to avoid coloring it with any marketing lingo, or an unfair perspective. So Dr. Coggan got free reign to write it however he wanted, and tell it like it is. For his part, he said that his goal was "to set a new standard" for test reporting.
- Second, I've attempted to provide my own perspective, and summary of the paper, in this article.As mentioned, I avoided providing any input for the white paper, so that it would stand on its own as an independent, unbiased evaluation. Instead, I knew I'd have an opportunity to present my own thoughts and opinions, and that's the point of this article. It's my interpretation of the white paper, and what I think the Omega is all about. Hopefully it's a little easier to read than the white paper, but it's still pretty comprehensive. The Omega is product with a lot of thought behind it, and I want to make a good case that it's really as good as I've just told you it is. So here we go.
Validity of the Data
Usually the first thing that people will wonder when you tell them about the concept of wind tunnel testing is "does the data apply to the real world?" The short answer is that yes, it absolutely does, at least when we're talking about full-sized tunnels with complete bikes. And I'll assume the reader believes at least that much. The real question before us here is whether this small tunnel, which doesn't have a complete bicycle inside it, is still valid.
Dr. Coggan already addressed the validity of his tunnel in general, in the separate paper linked above. But what we want to know is whether truncating a fork and putting a brake on it, sans spinning wheel, is a reasonable proxy for a complete bike with a spinning wheel. The bad news is that we can't know for sure. There is a chance that the spinning wheel changes the results so dramatically that our results are meaningless. But I'm inclined to believe that isn't the case. And fortunately, we have a little bit of data that suggests the mini tunnel is valid. Dr. Coggan talks about that data in the paper, but it basically boils down to the fact that in certain other data we've had access to, there are a couple apples-to-apples comparisons conducted in full-size tunnels that compare very closely with the same comparisons in the mini tunnel. You can hunt down the specifics in the white paper.
But even if the results are reasonably similar to what you'd see in a full-size tunnel, there are going to be some changes just based on the fact that the wheel is missing, because at yaw, it shields the brake shoes to some extent. That is, at 15 degrees of yaw, the brake shoe on the lee side of the wheel won't see as much frontal air as it does when the wheel is missing. That could have some interesting results I'll discuss later, when we talk about testing we did with some out-of-production brakes.
My takeaway is that while we might not see a 1-to-1 correlation between the results of Dr. Coggan's tunnel and what you'd get in a full-sized tunnel, they most likely represent a very good picture of what works and what doesn't. Although I'll have a small caveat again when we talk about the testing of out-of-production brakes with shorter, non-standard pads. Moreover, the results also seem to bear out what you'd guess intuitively - that the smaller, sleeker shapes test faster than big, clunky ones that stick out in the wind. So we'll proceed with caution, and a little bit of educated skepticism. My assumption is that that the rank order of the brakes is roughly correct, even if absolute drag differences will vary somewhat in a full-sized tunnel. Whether you believe that assumption is totally up to you. But the data is presented as plainly as possible, so you can make up your own mind.
Test Results
For many aero junkies, the only important news in this article is the final product, and how fast it tests. But for those of us behind the scenes, one of the the most exciting parts of this journey was refining the shape, and seeing the wind tunnel results improve from one iteration to the next. Interestingly, the first Omega prototype wasn't very good. Even though it looked cool, it actually tested fairly slow, only a bit faster than a standard sidepull brake. Using tunnel data was crucial in figuring out the difference between looking fast and being fast. The more we learned, the faster the Omega got.
What are those crucial secrets? Well, it would be silly to reveal them all and make it easy for others to copy, but there are certain things that are rather intuitive. You want to reduce frontal area, and you want to keep shapes smooth where you can. Even though those are fairly obvious aerodynamic concepts, it's surprising that no other brake has really taken them seriously until the Omega. There's probably still improvement to be made, and yet the Omega is already better than anything else on the market today.
But of course, the million-dollar question is how much time will the Omega save you? The short answer is, compared to a standard sidepull like a Shimano Dura-Ace, you're going to save about about two Watts, which translates to about six seconds per 40k. So in an Ironman-distance race, you'll get back close to half a minute. One interesting way to put a little perspective on that savings is by calculating dollars spent per Watt of savings. The Omega costs $175 and saves about 2 Watts, yieding 87.5 dollars per Watt. By comparison, a nice set of Zipp Firecrest Carbon Clinchers costs $3000, saves about 30 Watts, yielding 100 dollars per Watt. So you could say that the cost-benefit analysis makes the Omega as good or better a purchase than the very best wheels out there today.
But how did it do compared to the other brakes in the test? As noted, it beat everything currently in production. The Omega quite handily beats any sidepull brake we tested, even the very small Mach 2 brake originally stocked on some Cervelo bikes. But it also bests the few brakes on the market that are supposedly good aero performers, including the Tektro and TRP centerpull offerings. The closest competitor is the Simkins aero brake, but the Omega still tests faster, and is also lighter and less expensive. But what's perhaps even more interesting is the shape of the drag curves. Virtually every competitor in the test exhibits the exact same profile, with drag increasing dramatically at yaw. The Omega, on the other hand, is almost flat. Drag goes up from zero to five degrees, but goes uniformly down from five to fifteen degrees. Not a single other brake tested exhibits this behavior.
Moreover, the Omega is super easy to adjust, and built to work with every rim on the market today, without breaking a sweat. It will open out to about 34mm, meaning the Omega is future-proof, in case manufacturers decide that a 30mm rim is a good idea. And yet, despite the fact that it was really built for function first, and form simply followed, I think the Omega is a rather beautiful piece of hardware. Sure, this has nothing to do with aerodynamic performance, but a lot of athletes would prefer it if their aero gear didn't also look like a bizzare science project. For me, the Omega achieves its aero goals, and still retains a beautiful aesthetic, especially when examining the frontal profile of your bike.
