The new shape is shorter than the previous TT3. The goal, Specialized says, is to increase aerodynamic “robustness,” increasing the variety of positions and wind angles in which the helmet retains its low drag figures. The goal, of course, is to make the helmet work well within a wide variety of positions and wind conditions.
“The new helmet is faster than anything we’ve tested at every wind angle,” said Chris Yu, a Specialized R&D engineer and aerodynamicist who was intimately involved with the helmet’s design and was in Liège to ensure the new lid matched up well with each athlete’s position.
Speaking with VeloNews.com before Saturday’s prologue, he explained that while of course low drag in the optimal position was key, keeping drag low as a rider moves his head around was equally important. That led to the shape changes, and in particular the much shorter tail.
“If you put your head down, which is what a lot of the riders are doing these days, Levi (Leipheimer) included, the gain from the new helmet is actually much, much larger than if you compare the new and old both in their optimal position,” he said.
The perception, particularly with long-tail aero helmets, is that the fastest head position is that which allows the helmet to lie flat on the back. That isn’t always the case, according to Specialized, and it’s rarely a position riders can actually hold anyway.
“The optimal position with this helmet design is to have the tail just above the back,” Yu said. “We have mannequins with multiple positions, and we do design the helmet around a certain window. But the design is such that when the rider puts it on he doesn’t have to stress, because it’s much better across the range of positions than anything we’ve tested before.”
The new helmet also includes a small slit on both sides, a feature Specialized dubbed the Gill Vent, for obvious visual reasons. The feature appears to be intended to aid ventilation, but that wasn’t the original goal, according to Yu.
“The design was first and foremost proposed as a drag-reducing feature,” he said, noting that the details of the Gill design were one of the largest areas of collaboration between the Specialized and McLaren engineering teams.
“In aeronautics, it’s commonly known that boundary-layer suction reduces drag, so as a system when you have the gill vent in the side paired with an exhaust port on the back the exhaust port is creating a lower pressure wake,” Yu explained. “So the entire cavity in the tail is low pressure, which draws in the boundary layer on the side of the helmet. In our testing, if you cover the slots the helmet is actually slower.”
The added bonus is that the slot also works as a vent. You can feel air trickling in, according to Yu, and the riders have remarked on the odd sensation.
“We just have to assure them that that is the helmet doing its job,” Yu said.
Availability and price haven’t yet been nailed down, but the new helmet should be available sometime in 2013, according to Specialized.