Last weekend, the MIT Cycling team was able to use the MIT Wright Brothers Wind Tunnel for many hours. Wind tunnels are few and far between, and getting time on them is neither cheap or easy, so we appreciated the 30-minute wind tunnel time slots as the unique opportunity they were. The test protocol was fairly straightfoward: with the wind tunnel running at 30 MPH, we mounted the bicycle (via modified quick-release skewers) on a force-sensitive platform, got a baseline drag reading, and got subsequent drag readings for a rider pedaling in different positions.
I used my wind tunnel time to tweak my position on my time trial bike. My time in the wind tunnel taught me a few things:
- a 30 MPH, 30 degree F wind is quite cold for any period of time.
- once you're already wearing a skinsuit and an aero helmet, body positioning makes the most substantial difference in aerodynamics. Being narrower and lower is ideal.
- lowering the handlebars as much as is feasible is the easiest way to gain an aero advantage.
- keeping your hands flat (by using flat or R/S-bend aero bars) is much more advantageous than keeping your hands raised (using ski-tip aero bars).
As I don't currently have a functional digital camera, we didn't get any pictures of me in the wind tunnel. Mike Garrett, a team mate, chronicled our time in the wind tunnel at http://www.triplepointstudios.com/MIT_Aero.html.
After our time in the wind tunnel, I was able to get a bicycle sizing by Todd of ttbikefit.com. Todd was nice enough to come all the way to MIT on a Saturday morning to assist our team with bicycle fitting. He has an effective system for consistently reviewing bicycle positioning. Todd will have you ride on a stationary bike trainer. He'll use a camcorder on a tripod mount to record your pedal stroke for a minute or two. Then, he'll use what amounts to a glorified image editing program to analyze your positioning on the bicycle. The most brilliant part of this system is the repeatability: since neither the trainer, your bike, or your camera moves between sessions, he can easily compare your position from one tweak to the next.
Todd seems to favor a very aggressively triathlon-biased aero position. He tries to put riders almost over the bottom bracket, with a 140 degree leg angle at the bottom of the pedal stroke. Compared to my road position, he put my saddle much lower and more forward than I would typically ride it. This allowed me to open my hip angle, and assume a lower position on the aero bars. Some experimentation with my road bikes taught me that this was NOT a good road position. Nevertheless, for triathlon positioning, Todd has a workable system and plenty of experience, and I would not hesitate contacting him if you have any triathlon-related questions.
As an important aside, I'm wondering just how useful this TT bike fitting and aero analysis was. Recently, the powers-that-be at USA Cycling decided to ban aero equipment, or specifically, not mass start legal equipment, for race categories below A in the collegiate race season; A-category racers will be able to use aero equipment only if it will be allowed at the National Championships. As I'll be starting the season racing in the B category, with a hopeful upgrade to A, I'm unsure that I'll be able to use a full aero position. (For details, see http://collegiatecycling.org/eccc/wiki/index.php?n=Events.FallMeeting2008.)
What is certain is that my Fuji Aloha CF2's frame, the same that Fuji uses to build their current SST road bike, is a very aerodynamic frame and would make a superb road bike. I have all the parts I need to make it into a great road racing bike, one that may be superior to my Specialized Roubaix, so that may be the way to go. The CF2 road bike, already Ivan Dominguez's choice, would be stiffer and more aerodynamic than the Roubaix, but likely heavier. I'll need a Jtek Shiftmate to allow me to use my spare Campagnolo Veloce shifters with an otherwise Dura-Ace equipped ride, and I wonder if the longer 175mm cranks will be more or less helpful in road races. We'll see.
With all of the thoughts about aerodynamics behind me, I went to the place where aerodynamics hardly matter at all: a cyclocross race. With some residual fitness from the summer and plenty of training this fall, I've been doing well at the local cyclocross races. What I lack in bicycle handling skills, I can compensate with power. So far, I've done reasonably well at the three cyclocross races I've done, well enough to convince me to go to the Collegiate Cyclocross National Championships in Kansas City this December. My race experience this weekend was far from ideal, due to a number of mechanical disasters. I'm just glad that this all happened before Nationals.
What happened, exactly? I was doing well in my race, moving up through the field and maintaining a top-20 position, when I got two simultaneous pinch flats after running over a concrete curb at speed. I rode half a lap on flat tired to the service area. The pit crew was nice enough to loan me a set of Zipp 404 clincher wheels, which served me well until my chain fell off of the chainrings at the major run-up of the course. While struggling to get the chain back on quickly, I managed to twist my derailleur backwards, ripping apart the derailleur cage and bending a derailleur hanger. I ran to the pit, where they gave me a spare bike (an Orbea) with flat pedals, which at least allowed me to finish the race a lap behind.
That was not the first time I had chain issues on the cross bike that I built myself. Using a triple crankset was a stupid idea, but that's all I had. With substantial modification, I was able to replace the three chainrings with a 39-tooth chainring and a chain guard. I hope that works better next weekend. I'd like to race the new configuration at least once before Nationals.
Cyclocross is fun, but I miss the warm weather that makes enjoyable road riding possible.
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