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Back 12.19.2016

How Zipp Embraced Biomimicry

Curiosity led Zipp Engineers to Study Humpback Whale Flippers in Development of Zipp 454 NSW

Photo by Beardy Mcbeardy

GERMAN VERSION OF THIS ARTICLE

FRENCH VERSION

Zipp engineers had a radical idea: Design a wheel that’s not exactly round… at least not along its inner diameter where the spokes attach. They had a hunch undulating humps of carbon could improve aero efficiency and stability.

That premise became reality in the form of the new 454 NSW Carbon Clincher, with its Sawtooth™ rim architecture featuring Hyperfoil™ nodes and Hexfin™ dimples. The four-year journey to get there was made possible by the engineers’ embrace of a design concept that looked to nature – specifically to humpback whale flippers – to develop the most innovative and highly efficient wheel in Zipp’s 28 year history.

Zipp Advanced Development Director Michael Hall, back in his days working in motor sports, had seen undulating shapes on car airfoils and around sunroofs. He was eager to test a similar concept on bicycle wheels. His fellow Zipp engineers shared that curiosity, so they produced prototype wheels with unconventional up-and-down shaping along the inner diameter of the rim. The first results in the wind tunnel weren’t great. Hall’s team kept trying new shapes, yet the engineers still lacked a full understanding of how to evolve those undulating carbon humps.

So, as he did back in his college days, Zipp Advanced Development Engineer David Morse went on a studying binge.

That’s when “tubercles” and “biomimicry” first entered the Zipp engineering lexicon.

Tubercles are small rounded projections on the surface of a plant or animal. Morse’ research on undulating shapes and fluid dynamics took him to academic studies of the effect of tubercles on the flippers of humpback whales. The introduction of one article in the journal Integrative and Comparative Biology read: “Humpback whales utilize extremely mobile, wing-like flippers for banking and turning. Large rounded tubercles along the leading edge of the flipper are morphological structures that are unique in nature.”

 

Biomimicry is the subject of numerous reserach articles including "The Tubercles on Humpback Whales' Flippers: Application of Bio-inspired Technology" in the journal Integrative and Comparative Biology. 

Nature, of course, does many things extremely well. But how can that apply to bicycle wheels? The same article stated the potential of an approach to innovation known as biomimicry – looking to systems in nature to solve human challenges. “Nature is now being considered as the template for improving mechanical devices and operations, and developing whole new technologies,” wrote the study’s authors, which included noted biomimicry researcher Frank Fish of West Chester University in Pennsylvania. As it turns out, humpback whales, despite weighing 25-40 tons (22,000-36,000 kg), are nimble and acrobatic swimmers when it comes to corralling the krill they feed on thanks in large part to tubercles at the leading edge on their flippers.

Tubercles into HyperFoils

Zipp engineers had a new reference point for experimentation. Tubercles yielded design cues and inspiration, such as tubercle-like shapes being used to increase the efficiency of windmill blades.

“We tried to find out why that shape works in other industries. How did it come about? The idea didn’t come from the humpback whale, but once we studied the research done on the humpback whale we made the idea better,” Zipp Advanced Development Engineer Ruan Trouw said.

Zipp engineers tested and rejected 35 prototype rim designs before discovering the shape that would become known as the 454 NSW's Sawtooth rim technology. 

Progress took time. The 454 NSW – its Hyperfoils refined from studying tubercles – was four years in development. It included 36 prototypes and 252 hours in the wind tunnel. Zipp engineers also used a wind sensor for on-road testing. The result is a wheelset with aerodynamic efficiency and crosswind stability that far surpasses conventionally shaped wheels. The result is a wheelset with aerodynamic efficiency and crosswind stability that far surpasses conventionally shaped wheels. For example, under the yaw angles in the most common riding conditions, the 454 NSW offers a 5 percent reduction in grams of delta side force.

Zipp engineers developed wind sensors for on-bike testing. 

Hall, Trouw and Morse work in a restricted-access lab and mini-factory tucked away in the corner of the Zipp facility. Hall nicknamed the room The Nest because of Zipp’s history using bird species as internal project names (Firecrest was an internal name that became the official product name). The Nest is its own mini-factory with a carbon-cutting table and wheel press capable of producing prototype wheels quickly without disrupting production on the main Zipp factory floor. Hall’s team is charged with looking two to four years out in product development. The best ideas are handed off to Zipp’s larger design and manufacturing engineering teams and test lab techs in the same building in Indianapolis.

The isolation of the Nest allowed the Advanced Development team to be nimble in changing course, including the embrace of biomimicry. Hall, Morse and Trouw may agree on what makes a good latte, but their varying backgrounds prompt them to debate most everything else. Hall’s background was motorsports. Trouw’s focus was aerospace and manufacturing. Morse has been in the bicycle industry his entire career.

Under Hall’s leadership, Morse focuses on aero efficiency and stability, and Trouw on the structure and manufacturing techniques required to turn these concepts into actual products. Zipp Master Wheel Builder Nic James also is part of Hall’s team, adding invaluable experience for how to best build prototype wheelsets for stiffness and durability.

Zipp Director of Advanced Development Michael Hall at the carbon-cutting table. 

‘Science Fridays’

The trio of Nest engineers regularly host informal “Science Fridays.” Daily tasks are set aside for a free-flowing discussion on any hot engineering topic on someone’s mind. It could be focused on a new carbon layup process or rim shape. “We are not afraid to throw something crazy at the wall because if it doesn’t work, everyone understands it was a crazy idea,” Morse said.

Those discussions include ways to apply biomimicry in additional Zipp products. Nature offers endless possibilities for inquisitive engineers. Articles published by the American Institute of Aeronautics and Astronautics includes “Maple Seed Performance as a Wind Turbine” and “Experimental Design of a Flapping Wing Micro Air Vehicle through Biomimicry of Bumblebees.”

When looking to nature to engineer speed, a dive-bombing falcon or sleek shark may immediately come to mind, not a hulking humpback whale. However, aero answers can be counterintuitive – a fact Zipp demonstrated in 2010 with the introduction of wider, more blunt rim shape with Firecrest wheels. Conventional wisdom held that the “V” shaped rim was faster.

Zipp's advanced development team, from left, David Morse, Ruan Trouw, and Michael Hall. They work out of The Nest advanced develoipment lab in Indianapolis. They're also commonly found in the wind tunnel or out on the road.  

“You can’t really apply the aerodynamics of a falcon to a bicycle because a falcon goes way faster and its way smaller. The physics of the fluid going over a falcon aren’t the same as the physics of air going over a person on a bike,” Morse said. “While the idea behind the 454 shape is best embodied by a humpback whale fin, in development we made sure to pay attention to the research papers that experimented with tubercles in air in the same range of Reynolds numbers that a bicycle wheel operates in.”

Just as a hiker can navigate by using natural landmarks as guideposts, biomimicry can provide clues for innovative engineering. “The next product that we’re working on has ties to nature as well,” Hall said.

As to naming what specific natural system his team is now studying, Hall remains as stealthy as an owl. 

More information on Zipp NSW and the 454 NSW