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Biomimicry, And What Humpback Whales & Electric Motorcycles Have in Common

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Lost in a story about testing for this year’s TT Zero, the all electric motorcycle race on the Isle of Man, was an image that portends great things for the future of long-range, high-speed battery-powered biking.

A trick learned from two giants: the Boeing 787 and the Humpback whale.

2009 was a watershed year for motorcycling. Globally sales of new bikes vaporized, forcing the giants to shut plants and kill brands.

The major brands, like Honda, Yamaha, Suzuki and Kawasaki all pared down to the bare minimum, while European brands clung to life by their fingernails. In America, Harley-Davidson quietly asked for a loan.

But 2009 was also a touch-point for the modern electric vehicle. Tesla unveiled its first car; governments invested billions to support EV development; and the TTXGP, the world’s first all-electric motorsport event was held at the historic Isle of Man TT.

Within five years, street-legal electric motorcycles were commercially available and the annual TT Zero race (as it was called after 2010) became the place to watch the amazing potential of battery-powered vehicle technology.

(Above: The Motoczysz E1pc broke every mold and TT Zero record)

Within five years, the average speed of the electric motorcycles advanced 50%, coming to parity with lap times of 650cc gasoline powered models. The onward march of battery technology is the principal reason for this.

Since 2009 the energy density, the amount of energy per unit of weight, of lithium batteries has increased by the same amount (about 50%).

The initial gains have slowed dramatically, though. While those years saw dramatic and often radical electric motorcycle designs in an effort to define the standard, recent years have been decidedly less adventurous.

Mugen, the winner of the last four races has stuck to a simple formula of adding more batteries to a conventional layout, while refining the overall execution to slim it down. The weight of the machine is monstrous, the power ever increasing, but the overall increase in performance has slowed.

Has the evolution of the electric motorcycle, as a performance concept, reached an evolutionary dead-end?

Fighting Nature

All vehicles spend most of their energy overcoming air resistance once speeds exceed about 20 mph. While cars and even large, blunt-shaped objects like trucks and twin-aisle passenger jets can cheat the wind with smooth, enclosed body shapes, the motorcycle is an aerodynamic nightmare.

No amount of bodywork can overcome the aerodynamic disaster that is the exposed human body draped over the machine.

A typical modern car today has a coefficient of drag (a value commonly expressed as Cd) of less than 0.3, but even the most sleekly bodied racing motorcycles is at best 0.5. The difference may not seem like much, but a 0.1 increase in drag coefficient translates into a geometric increase in energy lost fighting air pressure.

For an electric powered motorcycle, already hampered by limited range of the very large battery, this means even more precious energy that cannot be used to go faster.

Completely enclosing the rider of a motorcycle in an aerodynamic shell has been toyed with for nearly 100 years, but it is completely impractical. Openings for entry and exit, and provision for balancing at rest introduce huge challenges in terms of technical complexity and cost.

More critically, enclosed single-track two wheelers tend to be highly unstable in crosswinds and difficult to steer. These factors mean that aerodynamically, the rider must remain largely exposed.

As the average speed of the TT Zero electric motorcycles passes 120 mph, the law of diminishing returns has set in: each additional unit of speed must be bought with an order-of-magnitude increase in energy on-board.

With the motorcycle internals out of space and lithium batteries reaching their theoretical maximum energy density limit, added speed and range appear hopeless without a major battery technology breakthrough that can deliver the power needed to punch through the air at high speeds.

Slice. Don’t Punch.

A next generation energy storage breakthrough will happen, but there is a better, cheaper way forward. If air cannot be gently smoothed aside by sleek bodywork, it can be tricked into doing so using advanced air management devices.

(Above: Vortex generators on an airplane wing)

Airplanes and racing cars have used aerodynamic devices such as air fences, strakes and vortex generators for decades, each of which intentionally manipulate the air.

Some are useful when you need to force air into a cooling duct, or to avoid a part of the vehicle to reduce drag. The more sophisticated devices intentionally create micro-turbulence (a form of drag) to create invisible air fences that guide air past vehicle surfaces.

It’s a kind of alchemy that when done right can reduce overall drag and dramatically decrease the amount of energy needed to move ahead. Best of all, because it is accomplished using shape, it is incredibly cheap.

Since 2010, Ducati has been advancing motorcycle aerodynamics in this direction with the introduction of winglets.

Last year every major brand in MotoGP motorcycle racing experimented with aerodynamic devices, mostly to increase downforce on the front wheel, but also to cheat the wind beyond the edge of the body and over the rider’s rumpled figure.

By using a repeating pattern of tiny winglets, tiny vortices of turbulence force following air to pass over the rider’s legs in a smooth way as though the plastic bodywork extended far further to the rear. These techniques add a little initial drag but pay it back many times over by reducing overall drag.

In the press release photo of the 2017 Mugen Shinden Roku racer (top four images) the trailing edge of the body clearly features the pointed waveform familiar to anyone who has looked closely at the engine nacelle of a Boeing 787 (bottom).

This device allows two streams of air, the one outside the body and the one inside, to mix smoothly, combining their energy.

In the case of the 787, the stream inside the white outer casing is moving faster than the outside air. Blending them together well reduces turbulence and drag.

With the Mugen, it not clear if there is any internal air flow (battery cooling?); but if not there, is still the largely static air pockets surrounding the rider’s legs, which are being sucked out by the fast moving air outside causing enormous uncontrolled turbulence and drag.

The waveform will at lest help mix these uneven air speeds.

The Humpback whale’s fins (described above) show how the wave form on the leading edge reduce turbulence and extend smooth, unidirectional flow.

Studies have shown that this is one of the many tricks that allow the whales to range tens of thousands of miles across the world’s oceans so efficiently. The same technology has been adapted to wind turbines to reduce energy loses and noise.

(Above: A wind turbine blade with a humpback whale inspired design)

The electric motorcycle is reaching a point in its development where a major step-increase in overall performance will only come with a new battery chemistry, something that is surely coming.

But in the meantime, regular incremental advances in performance are possible at little added effort, in terms of both cost and complexity, if new fluid dynamic theory is applied to motorcycle body design.

The motorcycle industry has been spoiled. Gasoline motors have achieved almost unimaginable levels of power, well over 2hp per litre, making advanced aerodynamics unnecessary.

Electric powered bikes have equally impressive levels of power and superior torque, but the limited amount of expendable energy available onboard requires designers to be more economical.

The electric motorcycle has much to benefit from the limits of current battery technology. Human ingenuity is always at its best when presented with a seemingly insurmountable challenge, when some limitations for us away from the obvious path of least resistance.

With electric motorcycles, creatively reducing air resistance has the potential to revolutionize all forms of motorcycle to the benefit of all.

He is also, together with partner Kevin O’Neil, behind the Amarok Racing team, and the P1 electric motorcycle experiment. He lives with his family in Halifax, Nova Scotia, which is about as far away from the center of the motorcycle universe as one can get. This may or may not be a coincidence.