Formula E racers zap expectations (video)

  • 30-Jun-2014 12:06 EDT
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The Spark-Renault SRT_01E, with its aerodynamic shrouds ahead of its wheels, strongly resembles the current Indycar, which is also built by Dallara.


On a global scale, racecars burn an irrelevant amount of fuel, so racing series’ interest in fuel-saving technology has nothing to do with saving the planet from racecars’ environmental impact.

Transporting teams to the tracks burns far more fossil fuels than any fuel actually consumed at the track. In fact, transporting sports teams of any sort by air to distant competitions burns more fuel than cars competing in a race will use.

Consider the example of race drivers wearing seatbelts encouraging skeptical people to consider wearing belts in their own cars. Or the winning diesel-powered racers at Le Mans helping boost the image of diesel cars that were widely considered sluggish and dull.

So it is meant to be with Formula E: sleek open-wheel racers slicing through the streets of 10 glamorous cities worldwide, putting lie to the notion that EVs are boring transportation modules for people who hate cars.

"We expect this championship to become the framework for research and development around the electric car, a key element for the future of our cities," explained Alejandro Agag, CEO of Formula E Holdings. "We have done research that shows that people watching a championship of electric cars will be more inclined to buy electric cars."

So battery electric racers like the new Formula E racing series will not make a difference in the planet’s ecological balance. But that isn’t their purpose. Racecars pioneer new technology for broader use in production, and they serve as thought leaders, encouraging fans to think differently about the technologies they use.

To minimize conflict with existing series and to take advantage of a global scope that means it is always summer somewhere, the series’ season will commence Sept. 13 with a race in Beijing and conclude June 27 in London. Between, they will visit Putrajaya, Malaysia; Rio de Janeiro; Punta del Esta, Uruguay; Buenos Aires; Los Angeles; Miami; Monte Carlo; and Berlin. All of these will be conducted on city streets rather than on dedicated circuits.

Because racing EVs struggle with the same issue of battery capacity as conventional EVs the series will start with 1-h races. Even that is too long for today’s batteries, when driven at race pace, so drivers will pit mid-way through the race and jump into a waiting fully charged car to continue.

So each of the 10 teams entered in the series will have four cars, two for each driver to use during each race.

The cars

Those cars will be Spark-Renault SRT_01E single-seaters built using a carbon fiber and aluminum monocoque chassis provided by Italian Indycar constructor Dallara, with assembly and drivetrain integration by Spark Racing Technology in France. They are constructed to pass the 2014 FIA crash tests applied to Formula One cars.

Speaking of Formula One, the electric powertrain and control electronics as well as data logging systems come from McLaren Electronic Systems, and the lithium-polymer batteries come from Williams Advanced Engineering, both subsidiaries of well-known Formula One teams. The sequential gearbox is provided by longtime Formula One supplier Hewland Engineering, and its ratios are fixed for the season, so there will be no changing ratios by teams to suit each circuit.

Esteemed racing constructor Dallara built the carbon fiber chassis using know-how earned from building cars for Formula One, Indycar, Le Mans, and other venues over the decades.

“We have designed the structure of the car, which means, starting from the front, the nose, front wing main plane, monocoque, safety structure—survival cell, battery box, bellhousing between battery box and gearbox, and everything inside the monocoque—the pedals, steering system, and uprights of the suspension,” said Luca Pignacca, Dallara Chief of Design.

The company did this in consultation with Spark, which has integrated the various components into working racecars, he added. “It has been a co-design. We have been working as a team.”

When the components arrive in France at Spark’s headquarters, Renault Sport taps that company’s EV experience to help them work together on “the architecture of the electronic system, the reliability, the safety,” said Patrice Ratti, Director of Renault Sport Technology. “We are helping with the design and the integration of all of the elements.”

While the series initially specifies only the SRT_01E, eventually teams will be able to build their cars in search of a performance advantage.

The powertrain

McLaren provides the Formula E electric motor and its control systems, putting it at the heart of the car’s difference from ICE-powered racers. It is an evolution of the 130-kW electric motor the company uses as a hybrid-electric motor in its P1 super sports car. In the SRT_01E, the electric motor’s output is limited by the allowable energy from the battery, which is 200 kW, giving the Formula E power that is comparable to that of a Formula 3 racer.

It can work at this higher output level because the duty cycle of a racing component is shorter and the service environment is less punishing than road service, explained Peter Van Manen, Managing Director of McLaren Electronic Systems.

In the SRT_01E, the electric motor is optimized to run between 13,000 and 18,000 rpm because of the use of the five-speed Hewland gearbox, an unusual feature for an EV. Most EVs connect their electric motor directly to the wheels, but the racecar’s broad dynamic range and the benefit of tuning the motor’s output for a narrow range made using a gearbox appealing for this car, Van Manen explained.

As the early astronauts had to learn techniques to deal with the near-infinite inertia of zero-gravity, so McLaren engineers have had to learn techniques to deal with the near-zero inertia of the electric motor.

“The biggest thing for us has been not having the inertia you get having an IC flywheel,” said Van Manen. “It is electric; as soon as you ask something to happen, it happens,” he said. “There is no inertia to smooth it out.”

When does this matter? “Every time you change gears. A gear change on a racing car is quite a dramatic event—it is a jolt that you get,” Van Manen explained. “Without the inertia, you have to deal with that in software how you control the motor to get a decent shift and not end up with a lot of ringing around the gearbox.”

It isn’t just when the driver changes gears that lack of inertia is an issue. “Any transients, so every time you put your foot on the accelerator,” he said.

McLaren engineers tuned the control software to compensate for this, but it is an area where they had no experience. “A lot of areas where your knowledge and experience is with an IC car, you have to part with that,” Van Manen explained. “Engineering is the most fun when you have to tackle problems.”

Rules dictate that the cars can run at a maximum of 200 kW of power during practice and qualifying sessions. In races, they’ll be limited to 133 kW, with a limited amount of “push-to-pass” mode that releases the full 200 kW of power for brief periods. The resulting top speed is limited by rule to 225 km/h.

Hewland Engineering's five-speed gearbox was specifically designed for the SRT_01E, but which naturally employs many components shared with existing models in the company’s line, according to a spokesman.

It uses a pneumatic paddle shift system, and because the electric motor can reverse its direction, the gearbox carries no reverse gear. The transmission was optimized for durability, with high rpm and high torque in mind. The casing is magnesium and incorporates attachment points for wheel tethers and rear crash structure.

Energy source

Power comes from a Williams-supplied 200-kg (440-lb) 28-kW·h lithium-polymer battery pack providing the 200 kW of available power. The pack dimensions were coordinated with Dallara to fit in the car inside a protective case that provides physical protection from intrusion along with thermal and electrical isolation from the rest of the car.

The lithium-polymer pouch cells are cooled by liquid, and their individual voltage and temperature are watched by cell monitoring units (CMUs). Those CMUs in turn, report their information to the battery management system (BMS) via the car’s CAN bus. The BMS controls state of charge, charge/discharge power limits, cell state of charge balancing, isolation monitoring, and other factors. Maximum bus voltage is 1000 V.

The BMS and CMUs were both developed in 2009 for the Williams Formula One program when that series began using hybrid-electric power. Another, potentially overlooked specification of the battery pack is that, because the Formula E series is global and transports its cars to races using air freight, the battery pack is certified for safe air transportation.

Rubber meets the road

O.Z. Racing provides the 18-in wheels. The tires are treaded Michelins that probably bear stronger similarity to the company’s sports car racing tires than to the ones the company formerly supplies to Formula One, because of that series unique use of 13-in wheels and high-profile tires rather than the larger wheels and low-profile tires used elsewhere.

The treaded tires use a hard enough compound that the cars each use a single set of new tires for the race; a set of used tires may be used for practice and qualifying. Using treaded tires means teams won’t have to stop the cars to switch from slicks if it starts raining during races. In fact, pit stops for tire changes during races aren’t permitted in Formula E, saving teams the expense of pit stop equipment and manpower.

“This tire must have a compromise of running low temperatures, running high temperatures, different concrete, tarmac, pavement, rain, dry, so it will be a much more complete and much more complex tire to develop,” observed Lucas di Grassi, Formula E development driver.

As if that weren’t challenge enough, the series has also specified that the tires be low-profile in the manner of popular street tires.

“For the first time in a single seater racecar, you will see 18-inch tire diameter.,” noted Florent Menegaux, president of Michelin’s car and light truck product line

These tires will have reduced rolling resistance compared to the tradition type, boosting efficiency, he said. “Fuel efficiency in an electric car translates into additional power or additional [driving] time,” he added. That may well be, but it presents one of the many challenges faced by teams aiming to win races in this new series.

On track challenges

“They’ve gone from a 13 inch, which is typical for a formula car, to an 18-in low-profile rubber,” said Graham Moore, chief engineer for Drayson Racing Technologies.

“That’s going to be interesting, because street circuits are normally quite bumpy, so the last thing you normally want is a low-profile tyre, because it’s going to give some interesting inputs into the chassis.”

All of the series’ racer are planned for street circuits, with the idea being that electric cars can run in city centers, in front of large crowds, without offending anyone with their noise.

“In F1 for example, a lot of the suspension deflection is done in the tire [side] wall – but we don’t have that with a very low-profile tire, so that’s all going straight into the suspension. Street circuits are notoriously bumpy, slippery and have a lot of camber changes – the cars are going to be quite a handful with no traction control.”

Drayson Racing Technologies is a British team entered in the series that already has extensive high-performance EV experience as the recent electric-powered world speed record holder. In October, 2013, the team set a world speed record for electric cars weighing less than 999 kg, averaging 205 mph over one mile with a flying start and running once in each direction to equalize for wind and elevation changes.

The team is in the enviable position of being able to simulate the Formula E to some degree using its speed record car, despite their differences, according to Moore. But there is no substitute for testing the real thing when it comes to devising race strategies.

“Once we’ve got a few tests out of the way we’ll know how far we can go and how much we can push the car and for how long – and therefore know its operating envelope and strategy,” Moore explained. That will mean, of course, that the teams are finally really racing, rather than simply demonstrating technology. That development should help overcome concerns about the EV’s lack of exhaust note on the track.

“You have a constant debate about electric vehicles and noise, people say there won’t be any noise and it will be terrible – but noise is a waste of energy,” said Moore. “It will be a different noise. And Formula E shouldn’t replicate the noise of a petrol engine—you don’t want that noise, especially in a city center environment.”

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