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When RJ Kromer first went to the Ohio State University in the first grade, he went to math class one day and went halfway. He was attracted by the advertisement of a student science team. The students were designing fuel. Battery car. Previously, he was the most up to assembling a LEGO robot kit, but in any case, he sent an e-mail application to join. Unexpectedly, the members of the group immediately gave him a response. "I thought there would be various requirements," Cromer recalled. "But they said, nothing, you come."
So, Crommer came to this group's work site at the Center for Automotive Research (CAR). When he arrived here, he quickly learned that the most important member of this alternative team, the Buckeye Bullet series of fuel-replacement vehicles, which has repeatedly set a world record, is a unique team with a childish look. First of all, he must test his dedication. Kromer started with engineering-related chores. For the first few months, he used most of the time to organize a variety of Tools, spare parts, or cleaning sites. However, in addition to being confused, senior members began to teach him circuits, control systems and other things. Soon, what he learned here is more than what he learned in class. In the second year, two senior students graduated, and Clomer began to take charge of electrical engineering. “Actually, if you can't sleep, you can quickly become familiar with things.â€
The Buckeye Bullet team is full of similar stories. David Cooke, the team leader, was accidentally added as a freshman. When senior engineer Evan Maley joined, he was a naive high school student who was fascinated by high-speed cars. Cooke said that when the team evaluates new volunteers, they value their initiative rather than IQ. Cromer conscientiously stays up late, this is the team's iconic act, and they often work until the very first morning light comes in from the 30-foot-high garage door at the end of the shop. Sometimes they sleep on the floor of the conference room, occasionally using the test drive lane. At weekends, when other students indulge in beer, they are cutting metal, testing batteries, or designing their own suspension systems.
These are not karting suspensions. This team has already built several of the fastest alternative fuel vehicles in history. In 2008, the top speed of hydrogen fuel cell cars that attracted Krommer's interest reached 286 miles per hour. Two years later, they transformed the hydrogen fuel cell car into an electric car that broke 300 miles per hour. Team members firmly believe that in September this year, on the Bonneville Salt Flats outside of Wendover, Utah, their redesigned electric vehicles will be the first electric car to exceed 400 miles per hour.
To date, only nine gasoline-powered wheeled vehicles have reached such a high speed. "The span from 300 to 400 miles per hour is too big," Cook said. At nearly 400 mph, aerodynamic drag increases geometrically. The motor needs more current, which means that more batteries are needed on the car, adding extra weight to a car that would otherwise need to be lightweight. Moreover, the tires rotate at extremely high speeds and centrifugal force may tear the tires. The challenge is enormous, and even a team of experienced engineers can be daunted, not to mention a group of graduate students and half-adult students.
The past and present of electric speed cars
In 1993, Giorgio Rizzoni, the director of the Center for Automotive Research at Ohio State University, formed the first student team to take part in a college electric car competition. The student team made a car called Smokin' Buckeye. In most of the games, the car won the title. But in a few years, this event was canceled for some reason, and Rizzoni felt that the project may have come to an end. Unexpectedly, two students told him that they had reached a sponsorship agreement with a local company and they wanted to create the fastest electric car in history. "I looked at the students and said, 'You guys are really crazy'," Rizzoni recalled.
In the next decade, this student team created three cars that broke the world record. Rizzoni has almost never questioned the team members' ambitious goals, engineering capabilities and negotiation skills. When Cook and team members decided to break the 400 mph limit, they knew that to achieve this goal, they might seek sponsorship. So they turned to Gildo Pallanca Pastor, the 45-year-old owner of Monaco's electric vehicle manufacturer Venturi Automobiles. Paster, who used to be an amateur racing driver, is a real estate giant in Monaco. He is also involved in the catering industry. He has been following this student team for several years. In 2010, he signed a sponsorship contract to support this student team to attack 400 mph.
Two years later, on a wet Wednesday in August last year, at the CAR headquarters - a two-story building of a very different shape, with a brick structure on the front and a few cave-like hangars on the back, it stayed at the age of 26. Beard's Cook said that the overall design of "Speeding Car" was basically completed. The two electric vehicles, the Venturi Buckeye Bullet 3 (VBB3), are 38-foot four-wheel drive. Since the power required to accelerate the car to 400 mph was too great, the team planned to share this task with four motors. Each motor produces 400 horsepower, with a total power of 1,600 horsepower (1 horsepower, approximately 0.74 kilowatts).
Cook and several team members have been working with Ventura's engineers to design the motors they want. The engineers in the team put forward the ideal size, performance indicators and other detailed requirements. They have been repeatedly scrutinizing the design plan and the engineers of Ventura for a year. Pastor has already started road experiments on a miniature version of the "Driving Motor" on the American version of the Ventura Electric Sports Car. The maximum speed of these electric sports cars is 124 miles per hour. The four motors used in the scooter are slightly longer and more powerful. It will take some time to complete.
However, the main problem at the moment is not yet motor. In the CAR, the VBB3 team of college and graduate students sat in a small office. Among them were Cook, Meli, and a clever, 23-year-old engineer, Ling Wang. When Mellie and Cook entered the house, Wang Ling was spinning the three-dimensional model of the vertical tail of the racing vehicle on the computer. Wang Ling is an aerodynamic expert, and the aerodynamic problem is the biggest obstacle for a car to be raised from 300 miles per hour to 400 miles per hour. The power required to overcome air resistance is proportional to the cube of speed. So if you have to double your speed, you need 8 times more power.
Cary Bork, who had just left the team to work for Boeing, spent two years fine-tuning the VBB3's aerodynamic shape, changing the shape, and covering the wheels with drag-reducing parts such as spoilers. . The flying car uses a steel skeleton and a carbon fiber outer shell, and inside the outer shell, a flame-retardant fiber Nomex (a trade name of aramid fiber) of very light weight and high strength is placed. In addition, there are still some major problems that need to be solved. This is the focus of Wang Ling's work - the rear wing.
Anything that protrudes outside the car will increase air resistance, but in order to protect the safety of the test driver, 62-year-old racer Roger Schroer, the team has to increase the rear wing. All the aerodynamic forces acting on the car can be seen as being concentrated on one point of the car body. This point is called the wind pressure center. When this point is biased towards the rear, and the center of mass of the car is near the front, the two balance each other, making the car capable of keeping a straight line, even when disturbed by cross winds. Although VBB3 installed multiple parachutes and a set of aircraft brakes were used, all these measures did not help when the car was spinning. Cook said, "On the last day, the most important thing is the safety of Schloor."
The question is how to strike a balance between aerodynamics and safety. Wang Ling quickly clicked the mouse and opened the tail, allowing it to flip in a virtual three-dimensional space. He changed the tip of the tail to a structure similar to that of a dolphin's tail. A horizontally placed wing was installed on the top of the vertical tail. Mehley explained that the team tried to find a way to add a GPS module and two cameras (one forward and one backward) to the car so that the data can be obtained when the car is sprinting at high speed. Another purpose of adding horizontal fins is to put these three kinds of equipment into it. He then sent the change plan to Burke, who works for Boeing.
However, Wang Ling soon told everyone that the new design was "Burke" out. The abbreviation used by the team members specifically referred to the fact that Burke often refused to amend the plan on the ground of increasing too much air resistance. "Berke means, 'You guys will make the car slower, so don't do it'," Cook explained.
Wang Ling said with annoyance, "I know this will slow down the speed, but how much slower it will be?"
Wang Ling continued modeling work while Cook began to solve another problem: batteries. Earlier this day, he showed us several battery test chambers for CAR. In the test chamber, the battery cells are continuously charged and discharged according to a set procedure while adjusting the environmental parameters. In this way, CAR's engineers can have a better understanding of the true performance of the battery - sometimes, in some technical indicators, the actual situation of the battery and the advertising is really different. Over the past year, Cook and his teammates have been rigorously testing Nano Iron Phosphate batteries produced by industry rookie A123 Systems. At the time of the formal test run, the coaster must run at least twice to get an official world record. At the end of each 60-second period, Cook pointed out that the battery must be fully discharged. "We plan to use up all of the battery's energy every time we run," Cook said. "If there is excess energy, it means we carry extra weight on the battery."
The design of A123’s battery was partially completed by two former members of the Bullet team. These batteries not only carried more battery power than other batteries on the market, but also had a more compact battery box. Cook explained that they used too much space for the standard cylindrical single cells used in the previous car. When the monomers are put together, there is a lot of space between the cells. The increase in space has led to an increase in the total volume and a corresponding increase in the size of the car, which means that the area of ​​the windward area increases, and the result is a decrease in speed.
From the shelf on his desk, Cook took a black box reminiscent of the car battery, and a silver square bag that looked like an ice pack and was thin and flat. This type of cartridge-like battery has a smaller battery size and produces a stronger current. Each black module contains 25 cartridge battery cells, one close to the other, with no gaps in between. With a total of 80 such modules, the space savings are considerable compared to cylindrical cells. "One-third of the weight and volume are saved," Cooke said. "This is better than the original best battery."
The volume is more than just a battery requirement. The design of the car is mainly to fill in as much as possible in the narrowest possible space. From the area of ​​Cook, you can see the virtual suspension on the Meli monitor. Usually, in order to reduce the weight, a car that breaks records is not equipped with a suspension. However, since the driver only used one mile to accelerate, Melley and teammates decided to use every inch of traction on this mile length. The bumps on the salt-alkaline beaches will cause the wheels to spin, which, though only for a short time, will still cause valuable power to be lost. Mehlis said that the damper in the suspension was originally placed underneath the motor and the drivetrain, and he is now modifying the design. After considering the overall layout of the entire car, he realized that the shock absorber may cause the center of mass of the car to become higher. "Think about the weight of the gearbox and the motor, that's a few hundred kilograms," he said. "For stability reasons, the weight of this piece should be as low as possible."
Then, Cook came to the outside workshop, a long, open warehouse with other CAR student projects. On the racing field, Cook grabs a tire and its rubber is less than 2mm thick. He explained that when the speed exceeds 300 miles per hour, the tires turn quickly and centrifugal force will cause them to expand outward. The more rubber, the greater the mass, and the greater the force separating them from each other. Thinner tires mean lower mass and reduce the chance of tearing at high speeds. The problem is that the car will drive on a rough saline beach. "Is the tire resistant? This is one of the few problems that make me sleep."
Test drive countdown
At the beginning of November 2012, the team started to build a car for just two months. Meili redesigned the suspension to reduce the center of mass of the motor and the vehicle, but it is still undecided whether to use the tail. For security reasons, the team is considering using three or even four deceleration parachutes. This extra equipment makes the rear of the car too long, increasing air resistance. "The number of parachutes has not yet been determined," Wang Ling added.
Earlier this year, battery supplier A123 went bankrupt, but fortunately, the former team member working at A123 delivered the battery needed for the project. "They need everything they need to do, plus some spare parts," Cook said.
The motor has also been completed, but the shape has changed slightly. After further simulation tests, Ventura's engineers believe that the motor may not provide enough power. But Cook is not discouraged. "We learned early that we can't give up easily," he said. "We have to look for the reasons. Why can't we get more power? Is it that the copper windings (the circuit turns of the circuit) cannot pass a stronger current?" After further investigation, it was found that the problem is temperature dependent. Simulation analysis shows that the motor will overheat. As a result, Cooke, Mehly and Luke Kelm, a senior undergraduate, redesigned the motor's cooling system with Ventura's engineers. They changed the flow path of the oil-based coolant so that it would be in contact with more parts of the motor and bring out more heat and lower the temperature.
This is the tradition of the racing project: a series of amazing technological innovations, and the determination of the team to make breakthroughs in the search for the limits of existing technology. “This is a wonderful practice,†said Ventura boss Paster. “When you have to use the power of components to the fullest, you can discover new things and let you think differently.â€
In the end, these challenges became unparalleled educational practices and created a group of graduates with unique experiences. Over the past few years, the racing team has created 50 engineers, most of which continue to work on important technical work in the automotive manufacturing, aerospace and battery technology industries. "They are excellent engineers because they have dealt with these complex issues," Pastor commented.
Cromer, a former freshman, joined the team on a whim, and he said that he had learned a lot more than he had in class. The young man who knew nothing about the car at the time spent the next two years designing the electric center of the electric-powered vehicle. This was a system that could monitor the operation of each component and match it perfectly with the driver. . However, Cromer and others do so not only to earn credits. After all, they are still college students. In September, the prospect of breaking the 400-mile-per-hour mark made them passionate. “We can break the world record,†he said. “How many people can make this statement?†(author Gregory Mone translator Tian Guangyu)
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