HEXR's aerodynamic performance

HEXR is powered by millimetre precision, both in our head scanning and in our 3D printing. This is how we’ve been able to create a helmet that can break records.

Aerodynamics is the study of how air interacts with a moving solid objects. Over 80% of what slows you down on a bike is wind resistance and of that, approximately 20% is due to your head and helmet. So what you have going on up top plays a critical role in aerodynamics.

To make you go faster, we needed to design a helmet with the lowest possible drag force, and so we partnered with TotalSim, a group of experts in aerodynamics. TotalSim have produced Team GB’s helmets for the 2008, 2012 and 2016 Olympics. In total those helmets went on to win 21 gold medals.

"Drag is caused by shape not size. This is why a big fish can move quickly without using much energy."

Rob Lewis OBE, MD of TotalSim.

Would it surprise you to know that both shapes in Figure 1 have the same drag force? Clearly shape is just as important, if not more important, than size.

Figure 1. Both shapes have the same aerodynamic efficiencyFigure 1. Both shapes have the same aerodynamic efficiency

With maximum aerodynamic efficiency as a key priority, together with TotalSim we ran tests on our helmets against four high-end road helmets: the Giro Aether, POC Ventral, KASK Protone and Giro Vanquish. We ran tests in two rider positions, and three yaw angles (the angle between head and cross winds) shown in Figure 2.

Figure 2. Rider positionsFigure 2. Both rider positions tested. Both of them on the drops, head up & head down.

Figure 3 shows the average time difference between HEXR and the four rival road helmets in riding position 02.

The time difference was calculated assuming the rider is travelling at 35 km/h over a 40 km time trial. The full report here details all finding.

Figure 3: The average time difference between HEXR helmet and four other leading road helmets over a 40 km time trial.Figure 3. The time difference between HEXR helmet and four other leading road helmets over a 40 km time trial.

HEXR outpaces all four of the helmets when riding in position 02. Position 01 represents a rider sprinting, it is not a position that can be sustained for a full 40km ride and hence such an analysis isn't appropriate.

Why HEXR is faster:

The reason for this speed increase is that the removable shell of the HEXR helmet is designed to be as aerodynamic as possible. We worked through hundreds of iterations before testing and retesting again. Figure 4 below shows how we reduced the tail of the helmet to prevent separation of the air flow.

Figure 4. How the HEXR helmet evolved in its aerodynamic shape.
Figure 4. How the HEXR helmet evolved in its aerodynamic shape.

Further, by scanning pro-cyclist Simon Gerrans we were able to understand how the helmet performed in a professional riding position. The helmet designs are superimposed onto Simon’s head. Each helmet was then put through a sophisticated computational fluid dynamics software that simulates the consistent riding conditions, seen in Figure 5. We chose to use this method instead of wind-tunnel testing in order to eliminate external factors like changes in the rider’s position.

Figure 5: Aerodynamic analysis of HEXR helmet.

We then studied the wake distribution: that is, how the air flow changes from laminar (consistent and without turbulence) to turbulent around the helmet. By altering the shape of the helmet we could significantly reduce the drag force, saving you serious watts as seen in Figure 6.

Figure 6. Aerodynamic analysis of HEXR helmet.Figure 6. Aerodynamic analysis of HEXR helmet.

This painstaking attention to aerodynamics in our testing begets uniquely precise helmet design, making HEXR not just the safest, but also the fastest helmet in its class, and a recognised innovator in the industry.


AUTHOR

Henry

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