Σάββατο, 16 Απριλίου 2011

Students Shoot for 2,500 MPG. Seriously

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The car runs, so there is that.
But as the Cal Super Mileage Vehicle Team loaded its ultralight carbon-fiber three-wheeler into a trailer for the long haul from Berkeley to Houston, Murphy was definitely in the driver's seat. Anything that could go wrong did — and did so in the last 12 hours before the team was to leave for the Shell Eco-marathon.
The Eco-marathon is a race, of sorts. The only goal is doing 10 laps around a Houston park at an average speed of 15 mph while consuming the teeniest, tiniest amount of energy possible.
Last year's winners, from Laval University in Quebec, achieved a phenomenal 2,487.5 mpg with a futuristic streamlined three-wheeler that weighed less than the engine in your hoopty. The University of California at Berkeley is among 70 teams — from 31 universities and 18 high schools throughout North America — slated to compete in this weekend's race.
If Murphy will let them, that is.
Above: Team leader Clarissa Harrison and her father David load the chassis of UC Berkeley's supermileage car, Bearly Burning, onto the trailer Tuesday morning. (Jim Merithew/Wired.com)

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The Eco-marathon started in 1939 with a friendly wager between scientists curious to see who could eke the most miles from a gallon of gas. The winner saw a whopping 50 mpg, a figure any hypermiler worthy of the name can achieve these days. The modern version of the race started in France in 1985, then jumped across the pond to the United States in 2007. Last year saw a third event introduced in Malaysia.
Competition is divided into two classes. Prototype cars are futuristic and sleek, usually with three wheels. They comprise the bulk of the entries, with 62 on the roster this year. Urban-challenge vehicles look a bit more like conventional cars. Well, sorta like conventional cars and sorta like the cars in Cars. There are 15 entered this year. (Some teams enter more than one car.)
Internal combustion remains by far the most popular means of propulsion, and the cars run on everything from gasoline to diesel to ethanol. Some may find it ironic that Shell introduced an "E-Mobility" division this year. The 23 cars with cords include battery-electric vehicles, hydrogen fuel cell vehicles and even half-a-dozen solar cars.
Above: Three hours before departing for Houston, Harrison crosses one more thing off the to-do list. (Jim Merithew/Wired.com)
Above: An urban challenge entry during the 2010 Shell Eco-marathon. The rules state vehicles in this category must be "close in appearance to today’s production-type passenger cars." (Shell)
Above: A driver shoehorns himself into a prototype racer at the 2010 Shell Eco-marathon. Protoype cars are more futuristic and streamlined than the urban-challenge entries. (Shell)

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As is so often the case with college projects, construction of Cal's car, Bearly Burning, went down to the wire even though work had started months before. Still, things were going swimmingly, and the team even took the car for a spin earlier this week.
That's then it all went sideways. The bracket holding the transmission — a simple gear reduction — slipped out of alignment, causing the car to throw its drive chain.
An electrical gremlin found its way into the kill switch that the rules say the car must have. A bearing on the starter motor shaft seized.
"All of that's happened in the past 12 hours," Harrison, a senior who's headed to Fisker Automotive when she graduates, said with a sigh Tuesday morning. "Something breaks every time you look at it. The horn may be the only thing that works. But it's the backup horn. We broke the other one."
Still, Harrison and her teammates were consumed by the confidence of youth as they left for Houston, convinced they'll get everything sorted out, with time to spare.
"All the major components are done," she said. "Now it's string and duct-tape stuff."
Above: The team troubleshoots an electrical problem a few days before departing for Houston.
Above: Small victories.
Photos: Jim Merithew/Wired.com

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Bearly Burning, like all prototypes in the Eco-marathon, features fully enclosed aerodynamic bodywork.
Well, sorta aerodynamic. The Cal students didn't have access to a wind tunnel, so they used Solidworks flow simulations to design the car's carbon-fiber bodywork. The rules say prototype cars must be no more than 100 cm tall, 130 cm wide and 350 cm long. For the metrically challenged, that's roughly the size of a large conference table.
Many cars are smaller than that, though, to maximize aerodynamic efficiency and fuel economy. Harrison said Bearly Burning, which looks a bit like a carbon-fiber tear, was "pretty much designed around the smallest person on the team." That would be driver Mia Criner. She'll squeeze herself into a cockpit about 3 feet tall and not much wider.
"There's not much room," said Criner, a junior mechanical-engineering major. "It's kinda tight. And we're racing in Texas. In April. It's kinda hot, and you're wearing a fireproof suit. And a helmet. It's not bad, but it's not comfortable."
Above: In January, the team works on the mold for the lower half of the body.
Above: Blueprints and templates of the car's cross section.
Photos: Jim Merithew/Wired.com

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Bearly Burning rides on three 20-inch wheels. The hubs, rims, spokes and brakes are bicycle components, which are sufficient for the speeds and braking forces typically experienced by the car. (The rules state the brakes must be capable of keeping the car stationary on a 20 percent incline). The tires are low rolling-resistance jobs designed by Michelin for solar-car racing. Why use just one wheel at the back?
"Because it's easier to drive one wheel than two," Harrison said.
It also creates less rolling resistance and drag, which further increases efficiency. It's the same reason the Aptera 2e electric car rides on three wheels instead of four. You may not think so, but three-wheelers can be remarkably stable, even when the front wheels are shoulder-width apart.
"It's really hard to flip," said Criner (left). "Unless you design it poorly."
Above: The rear-wheel mounting bracket is tested earlier this spring on a wood mock-up of the chassis. The actual chassis is made of Nomex and carbon fiber. (Jim Merithew/Wired.com)

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A little embellishment on the steering column support which, like most of the suspension and driveline components, was fabricated from aluminum. (Jim Merithew/Wired.com)

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Power comes from a 150-cc Briggs & Stratton lawnmower engine with a carburetor and no muffler. It sounds a lot like, well, a lawnmower at full wail. The rules state the car can't be louder than 90 decibels when measured from 4 meters away.
"It's loud, but then everyone's loud," Harrison said.
The engine once featured an electric starter scavenged from a 9-horsepower mower. It was more than up to the task, but blew a bearing a few days before the race. That forced the team to install a pull starter with an old-fashioned rope. No one's sure what kind of power the engine is good for, but the ballpark estimate is 2 horsepower or so. That's plenty.
"We only need 1.6 to move the car," Harrison said.
The team had big plans for an engine (shown above) that featured a Briggs & Stratton engine block, Honda cylinder head and homemade fuel injection. The 50-cc engine would have produced around 2 horsepower while burning less fuel than the 150-cc mill. But Murphy had other ideas.
"That one's still in development, and we're hoping to run it at SAE," Harrison said, referring to the SAE Supermileage race slated for June. We just ran out of time to get everything calibrated."
Photo: Jim Merithew/Wired.com
The rubber band is temporary. The team was still sorting out the throttle control a few days before heading to Houston. (Jim Merithew/Wired.com)
Last year's car, shown here at the 2010 EcoMarathon, featured a 25-cc engine with about 1 horsepower. It achieved 312 mpg.
Bearly Burning, like Bear Tracks, is a midengine vehicle, with the engine behind the driver. The engine is bolted directly to the chassis -- essentially a Nomex and carbon-fiber plank -- and the car has no suspension. "It's really loud, really hot and really bumpy," said Criner (front left, with helmet).
Photo: Cal Super Mileage Vehicle Team

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The fuel tank, and the fuel, is provided by Shell. During the competition, race officials fill the tank, then precisely measure how much was used once the car completes the course. The race consists of 10 laps, and the cars must maintain an average speed of 15 mph. The tank is shown here temporarily affixed to the aluminum and carbon-fiber firewall. It's since been mounted with an aluminum bracket.
Photo: Jim Merithew/Wired.com

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The fairing is carbon-fiber, designed to be as aerodynamic as possible. Making the car sleek is key because many teams "pulse and glide" -- accelerate, then coast, then accelerate — to maximize fuel economy.
"You spend a lot of time coasting, which is why aerodynamics and low rolling resistance are paramount," Harrison said.
The rules state prototype cars must weigh no more than 140 kilograms [308 pounds] without the driver, but many weigh far less than that, because lighter cars burn less fuel. The rules also state the driver must weigh at least 50 kilos [110 pounds] ready to race.
"If you don't weigh 110, you have to add weight to the car, which they may or may not have to do with me," Criner said.
Above: Peeling off a sheet of fiberglass to work on a mold. (Jim Merithew/Wired.com)

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Criner tries on the car's seat, such as it is, for size. The seat, like almost everything else, is made of carbon fiber custom fit to the driver's body.
"We poured expanding foam in a box, then I sat in it. It was really fun," Criner said. "It doesn't look comfortable, but it is."

The same could be said of the car, which is 37 inches tall, 50 inches wide at the front wheels and 105 inches long.
"There's not much room. It's kinda tight," Criner said. "I'm not claustrophobic. That wouldn't work so well."
Photo: Jim Merithew/Wired.com

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With lots of work yet to do, the team loaded the truck Tuesday morning. The car had a slightly cobbled-together look, but it ran. It was simply a matter of keeping it together long enough to clear tech inspection and complete 10 laps.
Among the things in the box: the throttle control mechanism. Yes, that would indeed be very important.
Photos: Jim Merithew/Wired.com

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The team arrived in Houston around noon Thursday, having worked on the car here and there along the way. The crew even managed to slap some paint on it.
"We painted it in Arizona. At a rest stop. It looks pretty cool," Harrison said. "We put it behind the trailer and painted it, then put it back in the trailer."
There's still some work to do. But by midafternoon Thursday, they'd fixed the gear reduction, sorted out the throttle linkage and were reasonably sure the electric starter would work. Everyone was dead tired, and the car hadn't even been through tech inspection. But it wasn't anything a few pizzas and a case of Red Bull wouldn't cure.
"We're exhausted, but exhausted in a good way," Harrison said by phone from Houston. "Everyone got out of the truck and just jumped on the car. We have a list of things to do, and we're halfway through it already."
Above: Harrison, checks the car before loading it onto the truck Tuesday. (Jim Merithew/Wired.com)
It isn't the best photo, but then Harrison was running on fumes when she snapped it at 3 a.m. today. It gives you an idea of what the car looks like with the bodywork in place. Tech inspection continues today; racing begins Saturday. Photo: Clarissa Harrison


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