Reinventing the Wheel

A flywheel may be the key to a car that's both powerful and efficient.

By Will Hively|Thursday, August 01, 1996
RELATED TAGS: GADGETS, ALTERNATIVE ENERGY
Azure sky, calm air, crisp sunlight--it’s a gorgeous day in Newbury Park, California. Jack Bitterly, the 77-year-old chief scientist of U.S. Flywheel Systems, sits by a window in his cheery office. Somehow the scene is not reassuring. For one thing, he resembles Vincent van Gogh; his eyes pierce the space between us like a pair of rivets. Against one wall, his masterpiece rests on a shelf--a colored mechanical drawing, simple and yet cryptic. As Bitterly paces and talks, he moves a sheet of blank white cardboard away from the drawing, points out details, and then casually leans the cardboard in front of it again. When I ask, he confirms my suspicion: he wants to ensure that the glance of a passing industrial spy shall not linger near that spot.

He’s been called a classic paranoid inventor. Also a genius. By most accounts he’s a brilliant, all-American engineer. During World War II, Bitterly was part of a top-secret Lockheed team that designed, built, and delivered the xp-80, an experimental jet fighter, in just 143 days--37 ahead of schedule. During the glory years of nasa, in the fifties and sixties, he pushed the envelope again, working on life-support systems for spacecraft that could travel to Mars. In the seventies, troubled by life- support lapses on spaceship Earth, Bitterly took up a homier challenge: the automobile. He envisioned vehicles with motors more powerful than gasoline engines, yet with zero emissions and no toxic wastes. Twenty-two years later--longer than expected, but still ahead of competitors--Bitterly has finished his engine prototype. He has not yet announced this fact. Almost no one outside the company has seen it. I am the first journalist to be granted permission even to play peekaboo with the plans.

At the heart of Bitterly’s new engine, taking up a quarter of the space in his drawing, sits what appears to be a ludicrously simple device. When Bitterly invites me to inspect the genuine item, partly disassembled and resting on a lab bench, I can see that the drawing is accurate. The wonderful secret is a flywheel--a plain disk, semitranslucent like milky glass, with a hole in the middle for an axle. True, it’s only a wheel, a gadget that in one form or another has been around since the Stone Age. But the man who made this wheel stands beside me convinced that it’s capable of snuffing internal combustion.

Twelve inches in diameter, three inches thick, Bitterly’s magnum opus rotates inside a tubby aluminum canister that looks thick enough to stop bullets. The complete flywheel system, including container, weighs 90 pounds. The wheel alone--a hefty platter--weighs 50. It’s made of densely packed carbon fibers similar to the high-strength graphite used nowadays in everything from golf clubs to Stealth bombers. Bitterly’s wheel needs that strength. The idea is to spin it fast enough to run a car. For that purpose, fast enough turns out to be 100,000 revolutions per minute. Every second, in other words, this wheel turns 1,700 circles. Matter on the rim screams around at 3,700 miles per hour--roughly the speed of a bullet. But the screaming is only virtual, because the flywheel spins in a vacuum. There’s no air to slow it, and no other friction to speak of. The wheel floats gracefully in empty space, collared in magnetic bearings that never quite touch its whirling axle.

U.S. Flywheel Systems is now testing a flywheel system prototype for automobiles, which the company plans to demonstrate in an actual car by year’s end. It puts out a steady 25 horsepower and can kick up to 50 in short bursts. Four flywheels would have the oomph to run a standard-size car, but not for long distances. You would need 16, Bitterly says, to travel 300 miles, the distance many drivers now cover on a tank of gas. Don’t worry about finding room in a car for that many flywheels. Bitterly would clear out everything from under the hood--engine, battery, and radiator--as well as transmission, gas tank, muffler, and tailpipe. Floor a 16-flywheeler and you’d get a rush of 800 horsepower. Bitterly taps out some numbers on his pocket calculator, then looks up at me and grins. It could peel the rubber, he says, right off the tires.

First, though, you would have to get those flywheels spinning, all 800 pounds of them. You could do it overnight using ordinary household current. Electric motors inside each canister bring the wheels up to speed. Each wheel stores 4.1 kilowatt-hours of energy; you could rev up 16 for about six dollars. The next morning you could glide quietly (or peel madly) around town, commuting or shopping all day. The flywheels would keep you going without touching any part of the automobile. Magnets on each flywheel’s axle generate electricity as they whiz past wire coils; current would flow to motors at the car’s four wheels as soon as you closed a circuit by stepping on the accelerator.

As the flywheels give up their energy, they lose speed, so after driving 300 miles or so, you’d need to spin them up again, usually at home. On longer trips away from home, you could rev up your wheels in 10 to 20 minutes at recharging stations much like the ones Southern California Edison has been building for electric cars.

A flywheel-powered car is, in fact, an electric car. It would work in virtually the same manner as the battery-powered electrics now entering mass production. The main difference would be the energy source-- flywheels instead of chemical batteries--and vastly improved performance. The General Motors ev1, for example, a peppy two-seater scheduled to make its debut in California and Arizona this fall, carries 26 conventional automotive lead-acid batteries. It’s the finest electric car in the world, says Bitterly, with a terrible energy-storage system. The ev1’s 1,100 pounds of batteries give it a practical range of just 70 to 90 miles, and those batteries will die within 100 to 200 rechargings--one or two years of typical commuting. You can replace them for about $1,800. Bitterly’s flywheel system, by contrast, stores four times more energy per pound than lead-acid batteries; a simple same-weight conversion to 12 flywheels would boost the ev1’s range beyond 200 miles. Those flywheels would spin up more quickly than the batteries recharge. Also, they contain no toxic materials like lead, and they run just as well when it’s hot or cold. And you would never need to replace them.

None of this general blue-sky thinking is news. Bitterly has no fear that anyone will steal his idea for a flywheel battery. People have been trying to build flywheel batteries for decades. One rival company, in fact, owns patents for an older system Bitterly designed. Other flywheel companies in the United States and Europe, along with researchers at universities and government labs, are investigating the same concept. All of them continue to struggle, however, with problems Bitterly says he has solved. Many have lowered their sights to flywheels spinning at slower speeds, storing less kinetic energy in a greater volume of space.

They can do that because the largest single market for flywheels is not the automobile industry but the power industry, where size and compactness don’t matter very much. Electric utilities are interested in putting flywheels in buildings and way stations, where they can soak up surplus energy for use during hours of peak demand. Flywheels distributed in this manner would also serve as emergency power backups to supplement the diesel-electric generators now used in hospitals and other facilities. Whereas the diesels take 30 seconds to kick in after a power failure, an eight-flywheel system being developed by Trinity Flywheel Batteries of San Francisco, for instance, delivers one megawatt of power in a few thousandths of a second, fast enough to save computer data.

Automobiles pose a much tougher technical challenge: they require extremely compact, high-energy wheels that can be mass-produced for a reasonable price. Chrysler, Ford, and General Motors are all proceeding cautiously with flywheel companies other than Bitterly’s, including Trinity; United Technologies Automotive in Dearborn, Michigan; and SatCon Technology in Cambridge, Massachusetts. In a few years, they aim to put modest flywheel systems into hybrid cars as power-boosting supplements to smaller, more fuel-efficient gasoline engines. Bitterly doesn’t think all that much of their approach.

This is absolutely not necessary, he scoffs. Why use a hybrid car if you don’t have to? It’s like saying, ‘Let’s go for a piston airliner.’

So far, no one except Bitterly is close to demonstrating a flywheel that’s both compact enough and powerful enough to run a car. But the wheel by itself goes nowhere. You might think all you’re doing is spinning a wheel, he says. The flywheel is a worthless concept unless you can tie it in to a complete system.

The system Bitterly has devised includes not only high-strength fiber wheels but also heavy-duty bearings. He has levitated all kinds of spinning wheels above custom-made magnetic bearings and tested them without touchdown--a term engineers use to describe a crash landing on old- fashioned ball bearings. (Though, just in case, most magnetic bearings include a backup set of touchdown bearings.) His bearings also avoid, he claims, the eddy currents that bedevil some other designs. These useless swirls of electric current, generated in metallic components, sap energy from the flywheel. Even if your car’s flywheels had perfectly frictionless magnetic bearings, you could still, conceivably, park overnight and return to find 16 clunkers, stopped dead by eddy currents. Bitterly says such energy losses will be very minor in his system.

Next to the flywheel, built around magnets spinning on the axle, Bitterly has mounted a remarkably compact motor-generator; it’s the size of a coffee mug and weighs only 3.4 pounds. He calls this little machine, which gives his system its extraordinary kick, pretty much of a breakthrough itself. It is, essentially, a tight bundle of wire coils and magnets. When plugged in to an external source of power, it acts like a motor to spin the wheels up; when unplugged, the same magnets and wire coils become a generator. This device converts electric power into flywheel rotation, or vice versa, at 96 percent efficiency. At that rate, it doesn’t get too hot, Bitterly says--a common problem with motors. An internal combustion engine, by contrast, belongs to the aptly named heat engine family. Most of the energy in gasoline makes engines hot; less than half gets converted to forward motion.

When we started, Bitterly says, none of this technology existed. Each one of these major subsystems had to be brought to full maturity. And that’s the secret he is hiding: a complete, integrated flywheel system. He has specified every mass-producible part, down to the last threaded bolt, in a two-inch-thick book of manufacturing drawings. Right now his system is up and running, which makes it rare. And it stores enough energy in a small enough space, he thinks, to run a standard, assembly-line automobile--which makes it, as far as he knows, the first of its kind.

Bitterly measures his words carefully, weighing how much to reveal. Sometimes he pauses so long between nuggets that it’s difficult to tell when he has finished talking. I sense, at this moment, that he has definitely stopped talking. He’s looking at me with that Van Gogh stare. Finally, he blurts out a request. Would I please show some identification? At least two visitors in the past few months, he says, were not who they pretended to be.

Earlier in the day, Bitterly showed me a pamphlet from the Deutsches Museum in Munich. The museum houses a 17-foot- tall cast-iron flywheel that tempered the rotation of a magnificent steam engine. Such flywheels, Bitterly said, made the industrial revolution possible. Large engines required a heavy rotating mass to carry them smoothly through pauses between jerky piston strokes. Automobile engines today have smaller flywheels that perform the same essential task. The concept goes back at least to the potter’s wheel, a stone massive enough to keep turning between kicks from a human foot. None of those flywheels had to store much energy-- only enough to keep the works spinning, without too much loss of speed, until the next kick.

Over thousands of years, the materials used in flywheels changed dramatically, and stone eventually gave way to steel. But ideas about how to use them didn’t change much until 1973. That was the year Richard Post, a nuclear fusion physicist at Lawrence Livermore National Laboratory in California, published a wake-up article in Scientific American. Flywheels, he pointed out, could store far more energy than most people realized.

Post based his argument on the promise of materials such as fiberglass and Kevlar, a new polymer fiber made by Du Pont. Some of those fibers were lighter than steel, yet stronger. They could be difficult to work into parts: manufacturers had to whip cobweb-thin filaments into useful shapes, often by weaving them or winding them on spindles, and then bond the fibers into one solid mass, usually by curing them with epoxy resin. The effort clearly made sense for exotic applications needing superstrong, extralight parts, such as jet fighters or bulletproof vests. But as Post demonstrated, the lowly flywheel, of all things, deserved equal consideration. In flywheels, as a matter of fact, a high-tech remake could pay off in spades.

For an energy-storing wheel, two properties are crucial: a material’s strength and its density. To understand why, imagine particles of matter in the wheel as monkeys taking a hell-for-leather ride on a merry-go-round. If they let go, they’re shrapnel; the wheel shatters. As the merry-go-round spins faster and faster, the rotating monkeys gain more and more kinetic energy. The amount of stored energy increases rapidly, as the square of velocity. But at some speed the monkeys’ arms give out; centrifugal force rips them away. The stronger those monkeys’ arms, the faster you can spin them, and the more kinetic energy they can store.

Obviously, strength in a flywheel is good. Density, however, is a mixed blessing. A denser material has more mass packed into a given volume. The advantage is this: kinetic energy increases with mass. Steel is denser than carbon fibers, so steel monkeys have more energy than fiber monkeys when they are moving at the same speed. The disadvantage: steel monkeys have a harder time turning in circles. Their greater mass gives them a greater tendency to keep going straight--to fly off the wheel on a tangent. Their arms, pulled harder by steel’s denser mass, let go at lower speeds than the stronger arms of the lighter fiber monkeys, which gain more energy as they spin up to higher speeds.

When engineers work through the trade-offs involving strength, density, and speed, they get astonishingly simple results. Neither strength alone nor density alone is decisive. To maximize the energy you can store in a flywheel, you should maximize its ratio of strength to density. This ratio makes it easy to compare the energy-storing potential of different materials. Engineers use the Greek letter sigma (s) to represent a material’s tensile strength, and rho (r) for its density. The quantity they are seeking to maximize is s/r. This simple ratio became the mantra of the flywheel revolution.

The best steels have a tensile strength of 280,000 pounds per square inch and a density of .29 pound per cubic inch. For steel, s/r is at most 966,000. Carbon fibers have a higher tensile strength, up to 1 million psi, and a much lower density, around .06 pci. For these fibers, s/r is 17 million, about 17 times better than steel. This means that carbon fibers only 3.6 times stronger than steel can store almost 17 times more energy per pound. Sigma divided by rho is the payoff in spades.

People don’t realize this potential, says Bitterly. You get astounding numbers, and it keeps improving. Carbon fibers that researchers are now making in labs have three times the strength of fibers Bitterly can buy off the shelf, which are themselves more than twice as strong as the best fibers available when Post wrote his article. The energy-storing capacity of long-chain carbon molecules, Bitterly says, represents the biggest golden egg that anyone could conceive.

Post not only predicted that fibers would keep improving, he also envisioned the major components a kinetic-energy storage system would need, such as magnetic bearings and a vacuum container. He even suggested new designs for wheels, to accommodate the stringlike, one-dimensional strength of fibers. A friend read the article and showed it to me, says Bitterly. I was enthralled.

By that time, Bitterly had started his own R&D; company. He was inventing, among other things, efficient techniques for recycling air, water, and nutrients inside a manned spacecraft--pioneering a new field called bioastronautics. At the same time, living in southern California, where the smog seemed to thicken every year, he was particularly receptive to the potential of electric cars for reducing pollution from the burning of fossil fuels. Power plants burn fuel more efficiently than internal combustion engines--or no fuel at all, in the case of nuclear and hydroelectric plants. The challenge was to store this cleaner energy in zero-emissions vehicles. Some thought chemical batteries might be improved to do the job. Bitterly never believed that. To make a major breakthrough, he says, you’d just about have to reinvent the periodic table.

With high hopes, Bitterly founded U.S. Flywheels--the first incarnation--in 1975. He brought in his son Steve, a recent college graduate, to do some research and hired Post as a consultant. It was an exciting era, Bitterly says, because we started from scratch.

As the Bitterlys spun up wheels in tests, they found it difficult to reach high rpms. Tiny, pointlike flaws would propagate through the bonded fibers as a crack. Also, layers of material in the wheel would separate from one another, like hoops. Other times, even without fiber separation, stresses would deform the spinning wheel, throwing it out of balance. Obviously, flywheel practice was not flywheel theory; sigma- divided-by-rho was a mantra that worked only for flawless monkeys perfectly joined as a seamless whole. These wheels would never be possible, Bitterly realized, without powerful computers that could model complex problems in rotor dynamics.

The wheels themselves turned out to be only part of the problem. Magnetic bearings, says Bitterly, were just not there, and neither were the electronics those bearings would need. In automobiles especially, the magnetic bearings in a flywheel system would have to withstand a lot of pounding. On a rough road, a flywheel’s axle might touch down every few seconds; it would quickly rub to a standstill. To prevent that from happening, Bitterly, like most automotive flywheel designers, planned to use active magnetic bearings, which respond to road shocks by boosting the power of electromagnets--a few thousandths of an inch from the spinning axle--just in time to prevent touchdown. Active bearings need fast electronics, since sensors should check the axle’s position several times per rotation. They must therefore work faster than the flywheel turns. A processor must then evaluate this information faster than the sensors send it, and figure out--pronto--how to jiggle the bearings’ electromagnetic currents. What this 1970s-era flywheel system needed was the industrial equivalent of a 1990s Pentium chip to handle the data flow. Carbon fibers, in short, were ready; the supporting technology was not.

Those things, Bitterly says, came to pass in the eighties. Unfortunately, his company passed away in the eighties as the new Reagan administration cut funding for flywheel research. We were forced to do other things, Bitterly says. Everybody was. Jack revived his consulting work. Steve went to Rocketdyne, where he worked on lasers for the Strategic Defense Initiative, better known as Star Wars. Post stayed on at Livermore.

A decade later, flywheels resurfaced--bizarrely attuned to a new funding environment. In 1990, Ed Furia, formerly a regional director in the Environmental Protection Agency, got a call from Tim Kent, his former press secretary. Two California inventors, Kent told him, had done work for the Army on a new nuclear-biological-chemical protection suit, a completely sealed outfit that combat soldiers could wear. Now Iraq was threatening Kuwait, the Gulf War loomed, and fears of nuclear, biological, and chemical attack made nbc suits quite interesting. These inventors clearly knew how to manage a sealed environment. But the reason Kent liked their outfit was its power pack. Instead of batteries, they had recommended a small flywheel system to be worn in a backpack.

We had a very good reputation with the U.S. Army, Bitterly says. That was for the lean periods. In 1988 he and Steve began a feasibility study on flywheels for the Army because we felt the supportive technology was matured. They could now lay hands on faster electronic components and powerful new workstations for computer-assisted design. But all this for a souped-up moon suit? Furia, who was then international president of Earth Day 20, in Seattle, instantly recognized one other huge possibility, which the Bitterlys, of course, already knew. I saw that flywheels, Furia said, might be the way to make zero-emissions vehicles work. So the Bitterlys, Kent, and Furia formed a new company, called American Flywheel Systems, and decided to set that as their goal.

With Furia as president and chief executive officer, and with former cabinet members like Elliot Richardson and James Schlesinger on the board of advisers, the very existence of American Flywheel, based in Bellevue, Washington, revived the prospects of flywheel-powered cars. Then, too, the climate of opinion was shifting back toward environmental protection. These things go in cycles, Bitterly says, like the stock market.

Furia, a veteran organizer, knew how to galvanize public interest. The first thing he did was pursue a patent, granted in 1992, for a flywheel system that Bitterly and his son had designed; the patent claimed more than 90 innovations. A second patent, nearly as extensive, followed in 1993, and a third in 1995. Press releases came hot on their heels. Drawings of the patented flywheel appeared in dozens of major newspapers and magazines. It was featured several times on cnn. An exhibit made the rounds at trade shows: a small demonstration flywheel, spinning at a few thousand rpm, powered a ten-minute video that touted the coming flywheel revolution. At the 1994 Los Angeles auto show, American Flywheel stole the spotlight with a surprise entry, a flywheel-powered concept car (with no engine). The very notion generated rave reviews and more publicity for the flywheel idea. The strategy, Furia says, was similar to the Earth Day plan: create a groundswell of public interest that would overcome institutional inertia.

The Bitterlys, apparently, preferred a different strategy. Sometime in the early 1990s, before all the hoopla, they left American Flywheel Systems. Jack refuses to discuss the split, saying only that we parted amicably. Furia explains it as a disagreement over R&D; style. He was exploring a business alliance with a large company, hoping to use its resources to develop a prototype. Jack wanted none of a big aerospace corporation, says Furia. He wanted to recruit his own lab. The Bitterlys asked to be bought out and go their own way. In departing, they sold their technology to American Flywheel, giving up all rights to everything covered in the patents.

Many in the flywheel business question the value of the patents the Bitterlys left behind. One particular the Bitterlys came up with, for instance, was to mount two counterrotating wheels on the same axle so that each wheel partly canceled the other’s gyroscopic force. (This force causes a rotating flywheel, like a top, to maintain the same orientation unless an external force is applied. Imagine a soldier carrying only one flywheel in a backpack, trying to zigzag across a field.) The single axle supporting those two flywheels was stationary, so magnetic bearings had to be embedded in the wheels themselves, at the hub--a potential source of flaws where different materials would join. Critics have since torn apart this and other innovations in the Bitterlys’ first patent. Of course, they have their own technology they would rather promote.

One result of the Bitterly-Furia breakup is beyond dispute: the patents from this collaboration launched a company that the Bitterlys are now racing to surpass. What’s more, the patents did not prevent others from entering the race; instead, they seem to have inspired them. Joe Beno, who manages the electric-vehicles program at the Center for Electromechanics at the University of Texas at Austin, which is developing flywheels for power utilities, buses, and trains, offers this opinion: You can’t patent the flywheel itself, but only a particular design or fabrication technique. The final irony, perhaps, is that no one is likely ever to manufacture exactly the system those patents describe anyway. Even if it would work as designed--a disputed notion--better designs now exist.

Furia recruited an impressive new roster of engineers, who quickly moved on to new system designs. The second version was much simpler, Furia says, with 40 percent fewer parts. The third version--the current one--may soon be tested, and with this one, he says, I think we have it. (He, like Bitterly, declines to give details.) His team is also developing stationary flywheel units, and it now has a contract with the firm Allied Signal Aerospace in Teterboro, New Jersey, to build flywheel systems for satellites. The payoff in space, they discovered, is better than on Earth, because a flywheel can act like a gyroscopic stabilizer and a battery rolled into one, saving hundreds of pounds in weight. Also, magnetic bearings should be less challenged in space: they would be levitating, after all, a weightless wheel. But Ed Zorzi, chief engineer at American Flywheel, says his group is still going for the gold medal: a compact flywheel system for automobiles, with no other source of energy on board.

Meanwhile, Jack and Steve Bitterly set out to revive U.S. Flywheels. The prospects looked dazzling. The technology they needed had finally arrived: better magnetic bearings, faster electronics, computer- assisted design. But financially speaking, their company was now a minnow among sharks. Their new rivals were making deals with large corporations; any one of them might get lucky and push a successful design quickly to market. Legally, too, the Bitterlys were handicapped. They could not simply improve the patented system. They would need, literally, to reinvent their wheel, as if those 90-plus innovations had never existed, so as not to infringe on the patents they had already sold.

The Bitterlys had to consider their own energy reserves as well. For Jack, by now, the standard retirement age had come and gone. Steve, a youth in the exciting 1970s, was now middle-aged. In all the years they had worked toward their common goal, the Bitterlys had never expected so many setbacks. How many times can a phoenix rise from the ashes?

U.S. Flywheels’ next incarnation was every bit as far-fetched, in its own way, as flywheel-powered moon suits. This time the script came from Hollywood. The film Waterworld, released in 1995, takes place in a future of melting polar ice caps. The hero is a mutant with gills and webbed feet. Kevin Costner plays this role and also produced the film, which had a record-breaking budget of $200 million. Costner in fact believes the film’s environmental premise: our dependence on fossil fuels may soon change the climate, catastrophically.

To help avert such disasters, Costner invests in new technologies that promise to improve the environment. A few years ago, his brother Dan, who manages these investments, got a tip about a small company, not far away, that was desperate for capital. Perhaps he had also heard the story going around about the engineer in charge, an elderly gentleman, who while talking to potential investors at his office sometimes hopped up on a treadmill--proving he was fit to complete his visionary program. Costner paid a visit to U.S. Flywheels in 1992, checked out the Bitterlys’ credentials, asked his staff to research the feasibility of kinetic-energy storage, and decided the idea was legitimate.

A reorganized U.S. Flywheel Systems, the current incarnation, sprang to life in 1993. It is, Dan Costner says, certainly the crown jewel of Costner Industries. Flywheels could have a greater impact than any other technology he has financed. At the end of the day, he acknowledges, we’re still going to burn hydrocarbons to power electric plants. But he sees flywheels as a bridge to cleaner energy sources. Anything that generates electricity, such as solar panels, can spin up flywheels. Flywheels might, in fact, enable greater use of solar or wind power. Instead of driving machines through pauses between piston strokes, they could carry households, say, through energy doldrums between sunny days.

Despite the apparent head start of competitors--including the veteran Richard Post, who was also up and spinning again, working with Trinity Flywheel Batteries--the Bitterlys felt confident they would soon pull ahead in the race. For one thing, they were now probably better funded. For another, they had already made their first zillion mistakes. As Dan Costner says, The day I hired Jack, we knew more about what not to do than other companies even know. Bitterly, in turn, knew the value of money with no strings attached. There would be no bottom-line pressure to rush a less ambitious product to market, such as a flywheel system for a hybrid car. We chose to make a Cadillac or Mercedes Benz right from the beginning, he says. If you don’t, you end up dropping requirements as you run into problems, and wind up with something not very impressive.

Bitterly began by following a dream he had nurtured ever since starting his career in the Lockheed Skunk Works during World War II. That original team had been housed in a top-secret compound; everyone not involved in the jet-fighter project was told to pretend the compound stank and not even think of going near it. Five months later, a new kind of airplane rolled out the door. Today Bitterly advances a concise theory of skunk-works efficiency. He draws it on a napkin: a simple graph that plots productivity versus the number of engineers working in one place on a project. His graph takes the shape of a bell curve, peaking at 15 to 20 persons. To the left of this peak, you have too few people--not enough ideas. To the right, with more people, his curve actually goes negative. You produce not ideas, he snorts, but dogma.

The Bitterlys recruited all the differing specialists they would need, including several of Steve’s former colleagues in high-energy laser research. You don’t find many people who are trained in flywheels, Bitterly says. They are not nine-to-five types, he adds. Often, they spent weekends holed up in a glass-and-concrete building on a dead-end street off the Ventura Freeway. No one outside the company knew much about it, and Bitterly says he discouraged inquiries from the press. A fait accompli, he and Costner agreed--a working system, ready to roll out the door--would bring the best publicity.

In November 1993 the nouveau skunk-works team began designing a totally new flywheel system. The wheel itself, they decided, would be simple: one flywheel on one axle, without embedded magnets--just a clean fiber disk. To cancel gyroscopic forces, they would simply stack flywheel- containing canisters together as pairs. After they settled on a basic wheel design, a few months into the effort, there was never a major flaw, Bitterly says. Our problems tended to be things like a loose wire in an instrument. The complete, integrated system design locked down, he says, early in 1995. By fall it was up and running.

One key to this speed was computer-assisted design; Bitterly installed three workstations. Another was the well-matched skills of father and son. Steve is a whiz at computer modeling; Jack is a hands-on engineer, with an uncanny feel for materials. He knew, from years of experience, that fiber wheels would not behave like a simple disk when spun at high speeds. The overall shape expands like pizza dough, but the individual fibers stretch at different rates, opening up space between them and stressing the epoxy filler. We didn’t realize those problems in days past, Bitterly says. To design a new wheel, he needed to analyze every spot on the wheel, not just some idealized, disklike shape. There are so many variables, he says, it’s hard to conceive. The Bitterlys’ design program divides a simulated wheel into as many as 50,000 nodes, or elements, while tracking all the stresses on the fiber at each node. In the old days, when the Bitterlys limited their analysis to simple shapes, it took them a week to work through 15 equations. Their new workstations juggle tens of thousands of equations and can finish the analysis in an hour.

While they reinvented the flywheel--different designs for different applications--the Bitterlys also reinvented the machines they would use to build them. Once they settle on a wheel configuration, they feed data from the design program into a separate program, which Steve set up, that figures out how to wind such a wheel from any type of fiber. That program, in turn, sends instructions to a slave computer, which controls tension in the fiber as it unwinds from a reel, the speed of winding, the angle of winding, the amount of epoxy resin fed into the space between fibers, and so on. This computer can in principle run a hundred wheel- winding machines simultaneously. At the end, says Bitterly, there’s a record of every cubic micrometer in a wheel.

With their automated system, the Bitterlys wind fibers much tighter than in earlier days, using a minimum of resin; their wheels are as much as 86 percent fiber by weight, as opposed to 60 percent in most manufactured fiber materials. The weak link in a wheel is the resin, Bitterly explains. You don’t want a lot of resin in there. In fact, the Bitterlys found their wheels were so strong that they did not always need the strongest, most expensive fibers everywhere in the wheel--but the composition remains a trade secret. I’ve seen some other wheels around, Bitterly says, and with the winders they’re using, God help ’em. How long it takes the slave computer to wind a wheel, Bitterly says, is also a trade secret--not very long.

Spin-up tests, Bitterly says, confirmed that their flywheels were working as designed. The whole system, in fact, was soon working as designed. Everything was custom-made, including test instruments. A wheel being tested gets a shiny silver coating; laser pulses reflecting off its surface measure the wheel’s expansion as it revs up to speed. Some 95 data stations, including 100 laser sensors that the Bitterlys invented, monitor wheel growth, temperature, the current flowing through the magnetic bearings, et cetera. These instruments must work at exceptionally fast speeds, like the electronic components in magnetic bearings. This is where we outshine the world, Bitterly says, surprisingly: custom-built instrumentation. He documents every wheel’s performance in exhaustive tests, similar to the ones used for new airplane engines. You don’t just run it up to speed, he says, laughing, and say, ‘Hey, it’s done.’

Watching the data come in from a test, Bitterly can choose to burst a wheel or shut it down before failure. His instruments show him where fibers will start to separate, and the speed at which the wheel will break. Failure, by the way, is difficult to achieve; his wheels survive considerably higher speeds than 100,000 rpm. And Bitterly has never broken one during a test; the equipment is too expensive. Safety, however, requires such tests. It’s common knowledge already, he grumbles, that you don’t get shrapnel from fiber wheels. A fiber wheel’s kinetic energy dissipates, instead, into hot fluff and high-speed dust. But an explosion of hot dust is still a sort of mini-volcano; it must be safely contained.

Flywheel designers recently began to pool their experimental information on safety. So far, they agree that the best approach is simply to build adequate containers. Almost any container at all, Bitterly suggests, would make fiber wheels safer than, say, the massive, shrieking steel turbines in jet engines, next to which unknowing airline passengers routinely sit for hours. Even in cars, people blithely ignore a more hazardous material. Gasoline, Bitterly points out, has more concentrated energy than rapidly spinning flywheels, and it is easily ignited.

Only one question that’s technically interesting, Bitterly believes, remains to be answered: How long will his flywheels last? The longer it takes him to find out, the better. We run them up as fast as we can, he says, and then run them down. That exercises the motor-generator and all the components.

What’s to wear out in a frictionless system? Eventually, perhaps, the flywheel might get fatigued from expanding and contracting. Bitterly designed it to survive at least 10,000 run-and-recharge cycles. That would be one complete spin-up, then driving until discharge, every day for 27 years. Bitterly is beginning a comprehensive life-cycle test, funded by nasa and the Defense Department, this summer. He can run a wheel through 70 cycles a day. So if the wheel lasts 10,000 cycles, he’ll know in 142 days, but if it lasts 100,000 cycles, it will take about four years to find out. We think it’s somewhere between 10,000 and 100,000, Bitterly says. That would be an upper limit of 270 years for a system in normal use. We’re not sure. But that’s academic.

In August 1995, at a closed symposium on flywheels held at Oak Ridge National Laboratory in Tennessee, Bitterly revealed, for the first time, some of what his company had already achieved. That event, he feels, was the high point of his career. Afterward, Costner says, our phone began ringing off the hook. Potential customers wanted to see for themselves what the system could do. (Claims made at meetings have been famously optimistic.) We now have contracts for satellites, and we’re talking about trains in Germany, Costner adds. By going after the toughest goal, all of a sudden we woke up and found we’d already passed the goal for two or three other major applications.

The automotive application, Costner admits, needs more testing. We think we have it, but the proof is more demanding. Bitterly seems remarkably nonchalant about providing it. Part of that stems from his prodigious fear of giving away secrets, though he knows some hardware will eventually have to be shipped. In fact, Steve predicts that they will begin testing a flywheel-powered automobile by the end of the year, under simulated driving conditions. The Bitterlys seem to feel, however, that only a big car company has the resources to prove their wheels in actual road and crash tests.

The problem, Jack Bitterly claims, is convincing automakers to risk the money it would take to bring out such a revolutionary product. The Big Three ask, ‘How much can you build it for?’ he says. They want a $500 system for a hybrid car. Bitterly estimates that his system, if mass-produced, will cost $800 per unit--around $10,000, in other words, for 12 flywheels in the ev1, already an expensive car. But when you figure cost per mile driven, he insists that flywheels will be cheaper than lead-acid batteries: $1,800 per year for new batteries, over ten years, adds up to $18,000. Flywheels, over their long, useful, maintenance-free life, should also be cheaper per mile than gasoline engines. If the initial price is too high, Bitterly suggests that dealers might lease flywheels, much as they now lease whole cars. He feels confident that eventually his company will deal with Detroit.

On yet another gorgeous morning, Bitterly sits in his office with his son. A sheet of white cardboard still hides the drawing. What you can see, prominently displayed, is a photograph of Steve and his wife, who were married last year. Bitterly is chauffeuring them in a pink convertible 1952 Chevy. It’s a hobby, he says. He has collected and rebuilt a number of classic cars; he admires them the way a railroad buff admires steam locomotives. To him, they must seem like the dreadnoughts of a bygone era-- the purest, most satisfying family-size blend of steel, oil, and internal combustion ever produced. I wouldn’t drive a modern car, he says, for all the tea in China. Unless, of course, it is powered by flywheels.

There seems to be some interest among foreign automakers, Steve says hopefully. Foreign automakers seem more aggressive. That’s not an idea his father can easily accept. Nowadays, Jack Bitterly knows, we all share the same planet, but still. . . I would rather see flywheels first, he says, in an American car.
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