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Formula One Racing Gets Toroids, Not Steroids
by Alex Mendelsohn
When it comes to motor sports, contemporary kids think of NASCAR and Dale Earnhardt, but I come from a generation where Formula One open-wheel racing was king, and Jim Clark and Tazio Nuvolari were racing icons. Ah, those were the days. Gasoline at 18 cents a gallon fueled our dreams.
I digress. Though I haven't followed F1 racing since my youthful treks to Watkins Glen every autumn for the genre's US venue, I am aware that technology's impact on racing cars today is every bit as pervasive as its effect on consumer electronics, medical electronics, or just about anything that packs an embedded controller these days.
Mechanical Engineering
Forward-looking F1 car designers are summoning revolutionary changes, but not all innovation relies heavily on electronics. Significant is the development of an energy recovery gearbox, which may very well speed around the world's F1 race tracks sometime next year.
The energy recovery gearbox recovers energy wasted during a vehicle's braking. Unlike regenerative systems that charge a hybrid or electric vehicle's battery, this technique is almost entirely mechanical. Designed by partners Xtrac in Indianapolis and Torotrak in the UK, the Kinetic Energy Recovery System (KERS) comprises a CVT (continuously variable transmission) gearbox that's mated to a mechanical flywheel. The flywheel spins up, gathering energy when a car is braking. This stored energy is then used when the F1 car needs to accelerate beyond the rate it can do with engine alone.
Like a lot of folks these days, Federation Internationale de l'Automobile race officials are going green. The FIA envisions KERS as a way to prove to the world that F1 racecars can be environmentally friendly, too.
"This is an opportunity to show how KERS in mainstream road cars can provide performance, economy, and greenhouse gas emission benefits," says Torotrak chief executive Dick Elsy. "The flywheel recuperates, stores, and subsequently discharges a moving vehicle's kinetic energy, which is otherwise wasted when the vehicle is decelerated."
A toroidal traction drive variator, based on Torotrak's patents, will provide a continuously variable ratio connection between the flywheel and a vehicle's gearbox. Torotrak claims its variator will operate at 90% mechanical efficiency, or better, yet weigh in at a featherweight 11 pounds.
Stop-And-Go Relief
Racetracks aside, the CVT-controlled flywheel is expected to really shine in stop-start driving, where it can assist getting a commuter's car going again after a momentary stop in traffic. In these scenarios, KERS is expected to slash fuel consumption, as well as greenhouse gas emissions.
Inside the variator there are disks and special rollers that transfer power from the input to the output, with changes in ratio accommodated by the design. The system works somewhat like the friction drive on my Ariens snow blower.
Inside the snow blower lash up (and it is a kludge), a lever moves a rubber drive-wheel across a flat metal plate that rotates. If the drive wheel is lowered near the center of the rotating plate, my snow blower moves ahead slowly. If I move the control lever and lift and reposition the drive wheel at the plate's periphery, the snow blower goes faster. If the drive wheel is positioned over the opposite side of the rotating plate, the snow blower goes into reverse.
Similarly, a KERS roller operates at a small radius on its input disk and with a large radius on the output disk. As an example, moving the roller across the disks to a large radius at the input disc and a low radius at the output disk would set a high ratio. This ratio change can happen rapidly, continuously, and smoothly. The transfer of power takes place across a microscopic film of transmission fluid.
Some experts feel a KERS system will be capable of dissipating 80 kW, or more, and help a car meet emissions tests to boot. Complementing CVT developments, Torotrak's IVT (infinitely variable transmission) KERS could get a vehicle moving from rest with no assist from its engine at all. With the transmission ratio continuously varied independent of engine speed (a ratio spread of 6.25:1 is typical), Torotrak expects car designers will be able to establish engine performance at optimum fuel economy points. In hybrid test simulations of a typical SUV, a 35% fuel savings was predicted.
There's no doubt that lots of electronics contribute to vehicular efficiency and safety, and adds myriad creature comforts and amenities to today's cars. But mechanical systems seem poised to upstage electronics in the race to design cars with speed, efficiency, and low emissions. I can hardly wait for 2009 to see a KERS-equipped F1 car in action. Maybe I'll fuel up my timeworn, but beloved, 1946 MG and make the trip to Watkins Glen in the autumn of 2009.
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