Aerodynamics of Triathlon Cockpits & Handlebars

Earlier this year I was approached about working on a collaborative project to improve the aerodynamics of triathlon cockpits between VeloVetta – my company known for making aerodynamic cycling shoes, SpeedBar – a manufacturer of high-end aero extensions for triathlon and time trial bikes, and professional triathlete Trevor Foley, all coordinated by the founder of Wove bike saddles.

Front-end aerodynamics can be highly affected by not just the choice of aerobar, but also if and how you add a water bottle to it, how it interacts with your particular bike position, and a host of other factors. Add in a raft of new rules from World Triathlon and Ironman about water bottles attached to aerobars, putting together a system that is going to a) be aerodynamically slippery, b) meet your hydration nutritional needs, and c) fit into ever more complicated rules gets more difficult.  It seemed like a good time to see if there was any way to simplify things. Specifically, could we make a set of aerobars that were fast whether or not you had bottles mounted?

The SpeedBar extensions are already really fast. That is why they are used by  pro tour teams like Lidl Trek, Quickstep and Cofidis as well as triathletes like Trevor Foley and Rudy von Berg. But in triathlon there is a wider variety of ways aero extensions may interact with the rest of the bike setup and just because a set of bars are fast on their own doesn’t necessarily mean they are fast in all possible setups. In fact, there are so many variations of setups it would be impossible to test and design for all of them. But if we could ensure that a bar tests fast both with and without a BTA water bottle, that would go a long way towards giving us confidence that it’s going to be fast in most situations.

I used extensive Computational Fluid Dynamics (CFD) modelling to design our shoes at VeloVetta, My background is in mechanical engineering and I have experience working in aerospace as a contractor to NASA as well as in the engine and powertrain industry. CFD is essentially a computerized wind tunnel, but it gives us a lot more information than what you can get from a tunnel. For instance, it shows us in detail how the air puts pressure on all surfaces, and from the geometry of those surfaces you can calculate things like drag, lift and thrust. You can see exactly how the interaction of the air with the objects in the test changes the speed and direction of the wind and how that might change the way it interacts with things further downwind. We started the project by making a computerized version of Trevor Foley, matching his dimensions and bike position. We left out the bike and lower legs to lower the time required for the computer to run the simulations without affecting the results that we cared about. We then added in a computerized version of the standard SpeedBar design and put this into our virtual wind tunnel to get a baseline for the drag of this setup. We also tested the same setup with a water bottle added in the location that Trevor frequently uses in racing.

The results showed that adding the water bottle added 61 grams of drag. So we made two more designs, testing them both with and without water bottles. One design connected the aero extensions with a flat carbon plate turning them into a single “monocoque” system. The other design modified the monocoque system with a “strake” that helps with two things: It provides some structural integrity to the otherwise flimsy carbon connecting plate, potentially eliminating the need for a metal connecting bar between the extensions, and it manages the direction of the airflow downstream of the bar.