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Engineering News 7664

DN Staff

April 8, 1996

23 Min Read
Engineering News

Detroit mounts its latest charge toward electric cars

General Motors' EV1 is the first of the new electric vehicles to reach production, but battery concerns remain

When the first gasoline-powered cars rolled on stage at the New York Auto Show of 1900, showgoers were said to be appalled. The sight of them prompted Albert Augustus Pope, a manufacturer of electric cars, to proclaim: "Man will never sit on an explosion."

Nearly a century later, man is again pondering the wisdom of sitting atop an explosion. Efforts to resurrect the electric vehicle (EV) have reached a frenzied peak, as manufacturers react to new legislation. In January, General Motors rolled out the EV1, a two-seat electric vehicle to be marketed by the Saturn Corp. starting this fall. Meanwhile, Ford plans to offer an electric version of the Ranger pickup truck for its 1998 electric-vehicle program. And Chrysler has introduced the EPIC minivan, a battery-powered vehicle with an unspecified release date.

For automakers, the biggest motivator behind the furious EV development programs can be expressed in a single word: California. Sales of zero-emissions vehicles are mandated by the California Air Resources Board (CARB): Two percent of total state sales must be zero-emission vehicles in 1998; ten percent must meet the same criteria in 2003. California officials hope EVs will help ease that state's air-quality problems.

But California mandates aren't the only motivator. General Motors' recent efforts in electric vehicles pre-date the CARB regulations. And the U.S. government has launched initiatives of its own. Through such programs as the Partnership for Next Generation Vehicles, federal officials are encouraging automakers to prepare an alternative to gasoline-powered cars, partially as a hedge against dwindling petroleum reserves and dependence on foreign oil. "We're exploring different alternatives while we have the time to do proper scientific studies," notes Dr. Donald Hillebrand, SAE technology administration fellow at the U.S. Department of Commerce. "The electric car is one of the alternatives we're looking at."

Electric alternative. For now, however, the electric vehicle is the only alternative capable of meeting zero-emissions guidelines. That's why General Motors rolled out the EV1 at the Los Angeles Auto Show.

The EV1--first of the new electric vehicles to reach production--proves that EVs have advanced dramatically in recent years. It accelerates from 0-60 mph in an extraordinary 8.5 seconds and offers an electronically governed top speed of 80 mph. Cruising range is 70 miles in the city and 90 miles on the highway in good weather. That's a significant advancement over most competing test EVs, which typically offer 0-60 mph acceleration times of more than 30 seconds and driving ranges of less than 50 miles.

Twenty-six 12V lead-acid batteries supply the power for the EV1. They drive a three-phase ac induction motor that cranks out 137 hp. A power electronics module connected to the motor contains inverters that change the batteries' dc current to ac.

GM's Advanced Technology Vehicles group says the ac induction motor could push the vehicle to a top speed of 110 mph if it were not intentionally limited as a way of preserving the battery's energy. At 80 mph, they say, the motor spins as fast as 14,000 rpm. "That's one of the strengths of the ac motor," notes Bruce Zemke, a staff development engineer at the Advanced Technology Vehicles facility in Troy, MI. "It offers a wide range of speed capabilities."

General Motors' vehicle also offers the types of features now necessary to earn buyers' interest. With standard antilock brakes, traction control, and dual airbags, its safety is comparable to that of the best vehicles on the road. It also offers such luxuries as cruise control, power locks, power mirrors, power windows, automatic transmission, air conditioning, and a CD audio system.

Battery is key. For all its impressive performance specifications, however, the EV1 still falls far short of gasoline-powered vehicles in terms of convenience. Unlike gas-powered cars, which typically need a brief fuel refill every 300-400 miles, the EV1's recharges are frequent and lengthy. After about 90 miles of highway driving, EV1's batteries need a boost. Recharging takes about eight hours on a standard 110V socket, and two hours on a 220V line.

Like most major EV programs, General Motors' EV1 group settled on lead-acid batteries as a power source. Ford and Chrysler made the same selection for their new electric vehicles. "We chose lead-acid because it was available, affordable, and because it provides excellent power," explains Zemke of the company's decision. Specific power of the EV1's battery pack approaches 230 W/kg, a figure that engineers say is responsible for the vehicle's remarkable acceleration.

Lead-acid's limiting factor, however, is its low energy density. This causes it to need frequent recharges. Many experts believe that EV use will not grow until those limitations are overcome. "Until battery technology advances considerably, selling EVs in volume to a more widespread consumer base is not feasible," says Mike McCabe, manager of Ford Electric Vehicle marketing and sales. "Our market research shows that prospective EV drivers want at least 100 miles between charges or they won't pay much more than they would for a regular car." Currently, Ford plans to sell its electric Ranger for around $30,000. GM's EV1 will have a pricetag in the mid-$30,000.

Lead-acid alternative. At General Motors, engineers are trying to deal with those limitations by working with another company to develop an alternative battery. In 1994, GM entered into a joint venture with Ovonic Battery Co., Troy, MI, to develop a nickel-metal-hydride battery that would have better energy characteristics.

Nickel metal hydride was selected in 1992 for accelerated development by the United States Advanced Battery Consortium, which includes the Big Three automakers, the U.S. Department of Energy, and the Electric Power Research Institute. In tests, it has achieved specific power levels as high as 250W/kg and energy density of 165W-hr/lb. Its energy density is of particular interest to GM engineers, who say that it could double the range of the EV1 vehicle.

The key for nickel metal hydride, however, will be affordability. And until production volumes increase, the price can't decrease, say engineers. "The dilemma is how to climb up the technology tree while we're going down the cost tree," says Zemke.

EV1 sets the stage. Whether or not a better battery is available, GM engineers say that they are in the electric-vehicle market to stay. GM's Delco Electronics Corp. already has developed an innovative inductive charging system for the EV1. The unique system employs a plastic paddle containing a coil, which transfers charge to a small module containing two more coils located under the front bumper.

As a result of all this effort, GM officials hope to meet requirements in California, as well as new quotas in New York and Massachusetts. It should also help them address federal laws requiring larger percentages of fleet vehicles that use gasoline alternatves.

In retrospect, the EV1 could be seen as an important step in weening industrial society from fossil fuels. Says GM Chairman John F. Smith, Jr: "When auto historians look back, they will see this car as the first in the new generation of vehicles."

--Charles J. Murray, Senior Regional Technical Editor

After two decades and 2 billion miles, engineers exult at Galileo's success

In this era of ever-shrinking design cycles, it's not often that engineers have to wait more than 17 years from a project's start to see if it actually works.

Not to mention designing a device to survive forces up to 238 Gs and temperatures of 28,000F.

But that's what faced Galileo engineering teams when they developed an unmanned spacecraft and atmospheric probe to study the solar system's largest planet, Jupiter. Not only did the little craft's probe have to survive its 106,000-mph entry into the jovian atmosphere; it needed to make scientific measurements and transmit the data back.

Challenges ranged from shielding the delicate scientific instruments inside, to making sure that the batteries on board could sit for six years and then "wake up" the craft's instruments six hours before atmospheric entry.

The probe's mission was to transmit scientific data for 48 minutes after entry into the planet's atmosphere. In fact, it lasted for 57.6 minutes before searing temperature and crushing pressure destroyed its communication system.

"It was unbelievable joy and relief simultaneously," says Bernard Dagarin, program manager at Hughes Space and Communications Co., which developed the probe for NASA. "I didn't know whether to laugh or cry. There were some people in the operation center who did both."

Scientists hope that Galileo data will help explain the mystery behind Jupiter's formation--and, ultimately, the origins of our solar system.

NASA awarded the Galileo's probe contract to Hughes in 1978. The main craft was developed at NASA's Jet Propulsion Laboratory, which manages the overall mission. General Electric designed the probe's heat shield. The Galileo spacecraft and its probe left Earth six years ago; the probe separated from the main spacecraft in July, 1995. Then, last December, Galileo's probe penetrated Jupiter's atmosphere to measure radiation, temperature, pressure, density, and atmospheric composition.

The probe was made up of two parts: a 4-ft-diameter descent module, and 2.8-ft-high, 750-lb probe. Heat shields consisted of a carbon-phenolic shield on the forebody and phenolic-nylon shield on the aft cover. That wasn't new for spacecraft design, according to Charlie Sobeck, probe engineering manager at NASA; "but the environment it was going into is so much more severe." Engineers tested the design in high-speed arcjet and laser facilities, but it was impossible anywhere on Earth to truly simulate the harsh conditions of hurtling through Jupiter's atmosphere. Designers therefore performed "an awful lot of computational fluid dynamics," he says.

To ensure that the probe's batteries could sit idle for six years, and then "wake up" as scheduled, designers chose lithium-sulfur-dioxide batteries--then a new technology. Sandia National Laboratory developed a glass ceramic insulator for the batteries--now also being used in pacemaker batteries today, Dagarin notes. The on-board clock featured an innovative power supply requiring a 1.36-mA worst-case load with 27-mA pulses for 20 ms every 256 seconds. With an efficiency of more than 98%, this power-supply design is being reused, he says.

While Galileo's probe has finished its spectacular descent into Jupiter's atmosphere, the orbiter continues its exploratory mission. Its next major milestone comes on June 27, when the orbiter is scheduled for its closest encounter with Ganymede, Jupiter's largest moon.

Reinforced composite simplifies door assembly

Detroit--The design of modern automotive door assemblies goes far beyond simple entry and egress. Now, thanks to a glass-reinforced composite blend, engineers have consolidated 60 parts from a complex door design into one unit.

The "Super Plug(TM)" door is a pre-assembled module that controls everything associated with door operation in some GM vehicles. The design accommodates locking lever support, armrest supports, window motor attachments, window guide channels, and speaker mounts.

To create the module, engineers at Delphi Interior & Lighting Systems/GE Plastics, Pittsfield, MA, chose a 30% glass-reinforced polycarbonate/polyester blend from Owens-Corning, Toledo, OH. The material's chopped strand provides the required strength and stiffness for the application, say Delphi engineers.

The module snaps into the door cavity. Because it reduces the need to assemble 60 parts at the final automotive assembly site, it cuts total system costs. For automakers, the reduced assembly-line length, parts inventory, and parts scheduling add to its benefit. They estimate a manufacturing cost savings of 5% and system-warranty cost reduction of up to 25%.

The module weighs approximately three pounds (1.5 kilograms) less than the previous design--further contributing to cost savings.

The unit has fewer component interfaces than a conventional door, thus reducing vibration and noise, Delphi engineers claim. It meets normal and abusive load and durability requirements, such as door slams, as well as dimensional tolerances and dimensional stability criteria. When disassembled using approved techniques, the module also meets European recyclability requirements.

Composite putter head may lower golf scores

Portsmouth, RI --A new golf putter head, recycled from scrap in the production of high-performance military materials, applies the advantages of thermoplastic composites to lower the average golfer's score. The putter, part of the QuadForce line of golf clubs introduced last year by the Quadrax Sports Golf Div. of Quadrax Corp., has maximum heel-toe weighting in the form of brass inserts at both ends of the head.

The Quadrax thermoplastic composite has a higher strength-to-weight ratio than materials previously used in putter heads, such as casted metal (brass, steel) and phenolic. As a result, the composite provides strength and stiffness that permit more weight to be distributed on both ends of the head than is possible with conventional materials--without requiring as much material in the head's center to prevent breakage or bending.

Putting control is improved, because the head's weight distribution keeps golfers from unintentionally twisting the head as they stroke through the ball. At the same time, the head delivers a "soft" feel, due to the vibration-damping capabilities of thermoplastic composites, as well as a distinctive sound. Another feature: extra material jutting like "ears" at the putter's heel and toe.

The putter head consists of Quadrax Unidirectional Tape, fabricated by embedding carbon fibers in a polyphenylene sulfide resin matrix. Multiple layers of tape placed into specific lay-up plies and angles of orientation achieve the desired strength, stiffness, flexibility, and other engineering characteristics. The layers are fused into a laminate.

Normally, the material going into the putter heads would be occupying a landfill instead of a golf club, according to President and CEO James J. Palermo. Since 1994, the company has converted many materials from military to commercial products. The military contracts include supplying thermoplastic composites for the F-22 fighter aircraft and the Seawolf submarine. In being recycled from scrap, the material is chopped to the actual length of the putter head, then reshaped in a compression mold.

Resin 'changes the rules' in bike-hub design

Olney, IL --Commodity-type bicycle components sold to mass-market manufacturers are subject to tremendous cost pressure, due to an extremely competitive retail market and the influence of foreign competition. In order for a U.S. component manufacturer to gain a toe-hold in this mature market, it must find truly innovative ways of gaining a competitive advantage.

Marwi USA, a supplier of bike components to domestic mass-merchant manufacturers, has patented one such innovation with the introduction of its New-Technology Resin Bicycle Hub. The hub reduces total part count by 75%, and virtually eliminates the number-one cause of quality defects in bicycle wheels. It also outperformed its metal predecessor by 600% in standard industry life tests, according to Marwi President Jim Haley.

The new hub consists of two major resin components: a structural "shell" and two push-in bearings that interface with the wheel's metal spoke flanges. The chief quality problem with hubs is misalignment of spoke holes. The hub design eliminates this problem with a part that can only be assembled in the proper orientation.

DSM Engineering Plastics, Evansville, IN, provided prototype and materials-selection assistance in the project, including the idea to minimize the lubricated area by designing a press-in bearing insert, rather than making the entire component from the more expensive lubricated material. DSM supplies engineering compounds for both the shell and bearing inserts.

"Hubs had been designed and manufactured in the same way for decades," Haley explains. "We could not compete in a commodity market against incumbent suppliers if we did things the same old way. We had to find a way to change the rules."

Tiny memory card holds up to 64 Mbytes

Folsom, CA --A host of consumer-electronics companies are embracing the new Miniature Card digital media specification for storing and exchanging image, text, and voice data. A quarter the size of PC Cards, the Miniature Card can accommodate up to 64 Mbytes of flash memory, DRAM, or ROM based on current chip technology. Other backers include IC suppliers, software firms, and connector companies.

"We believe flash memory is the ideal data storage medium for handheld consumer devices and for bringing that data back to the PC for further use," says Bill Howe, general manager of Intel's memory components division, which will manufacture the cards. "We have several design wins for Miniature Card in-hand and will ship product in the second quarter."

Measuring 38 mm wide by 33 mm long by 3.5 mm high, the Miniature Card is currently the smallest standard form factor available. The unit's rugged, pinless connector suits it for consumer applications such as digital cameras, audio recorders, cellular phones, and handheld computers.

The Miniature Card spec is available from the Miniature Card Implementers Forum now. For more information or a copy of the spec, phone (916) 356-7060.

Toys hold lessons for plastics designers

Summit, NJ --Two successful toy designs might contain useful lessons for OEM design engineers about complex performance requirements and materials selection.

Discovery Toys, Martinez, CA, created Boomerings Links(R) to entertain infants in cribs or carriages; The Rodon Group, Hatfield, PA, developed K'Nex(R) construction sets that enable older kids to build whatever they imagine. Both products required mechanical strength, dimensional stability, and spring action to last. Moreover, they had to meet strict safety requirements for non-toxicity and chemical stability.

To satisfy multiple regulatory agencies--and very unpredictable end-users, the colorful toys were molded from Celcon(R) acetal copolymer from Hoechst Celanese. Although four times more expensive than polypropylene, a mainstay material for toys, "there are certain buying and selection decisions you make that go beyond dollars and cents," explains Larry DeSeguirant, director of quality assurance at Discovery Toys. "In this case, it was the insurance we were buying for both the kids and the parents."

Boomering Links are appealing, deceptively simple C-shaped clips that make colorful chains. They attach themselves and other toys to strollers, car seats, or cribs. Each link measures 2.5 inches high by 1.75 inches wide, with a 0.0045-inch gap on one side that a child can pull or twist open. "The gap couldn't be so tight that small hands couldn't separate it, or so loose that things fall off the loop," says DeSeguirant.

The spring-like links need a "memory" to come back to original shape despite repeated twisting. They also must keep their uniform color, without turning white at stress points. Most importantly, the links, if over stressed, must not break into small pieces that a child can swallow.

Prototype links molded from other materials couldn't withstand repeated abuse. Polyethylene elongated and showed white stress marks at weak spots. Polypropylene had no memory to retain its shape.

The high-mold-flow Celcon M270 selected for the project has a tensile strength of 8,800 psi at room temperature. Sample links proved the copolymer satisfied the stringent toxicity standards demanded of a teething toy, and more than met the 15-lb load-to-failure standard for toys.

The K'Nex construction kit consists of 27 different molded rods and connectors that can make durable motorized models of any shape. Prongs on the connectors engage the rod ends and build rigid assemblies that can be broken down for new projects.

"Our parts make virtually anything and everything," says Robert Sica, Sr., Rondon's vice president of manufacturing. "But they need to snap together smoothly. For children, the fit of the parts can't be so tight that it hurts fingers or so loose that the structure falls apart."

"We were looking for flex modulus in the 375-ksi range--not too brittle and not too stiff," Sica adds. "Celcon acetal copolymer has 8,000-psi tensile strength, and a flexural modulus of 375 ksi. Low-cost materials simply couldn't provide this for our value-added toy."

Trigger helps troubleshoot intermittents

Chestnut Ridge, NY --The toughest electronic problem to debug is one that's intermittent--especially if the shape of the failing signal changes characteristics each time the failure occurs. You don't know when to trigger the scope because the failure is irregularly spaced in time, and you don't know what shape of signal to trigger on because the failure doesn't always have the same characteristics.

What you do know is the shape or period of the normal pulses. Using the new exclusion trigger from LeCroy lets digital storage oscilloscope (DSO) users specify that information so the scope can ignore normal-shaped signals and trigger only on abnormal events. Scopes with this feature can be actively looking for circuit failure nearly 100% of the time.

Analysis and troubleshooting tools include: a time and date stamp for each abnormal signal; the ability to display worst-case analysis of the signal shape, such as maximum amplitude excursion, variations in pulse width, and overshoot; and the ability to draw live bar charts on the scope screen showing which failure modes are most/least common. Users can view each occurrence of the intermittent failure, document the signal shape and worst-case parameters, and save data to a computer.

Plastic puts stabilizer bar rods on a diet

Dusseldorf, Germany --European car makers have achieved cost savings of up to 10% and weight reductions between 20 and 46% on suspension systems by using stabilizer-bar linkage rods made of nylon. The anti-roll bars help resist a vehicle's tendency to roll outwards when cornering. They also improve weight distribution on the wheels, for better road handling.

Linkage rods connect the stabilizer bars to coil-spring struts of leaf springs. Produced by TRW Enrenreich Fahrwerksysteme, the rods, made of Zytel(R) nylon from DuPont Chemical, Wilmington, DE, have several advantages, according to the manufacturer:
- They are lighter than their steel counterparts, which cuts down unsprung weight, contributing to a more comfortable ride.
- They can be injection molded, eliminating the need for finishing operations.
- Various functions can be integrated, saving assembly operations.
- Their vibration and damping characteristics are better than those of metals.

TRW began developing linkage rods made of glass-reinforced engineering plastics in the mid-1980s. Early attempts at using polyacetal (POM), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT) resins showed dynamic loading problems. After testing short-fiber-reinforced PA 6, PA 66, and a blend of both, TRW turned to Zytel 70G43 HSL, a 6,6-type nylon with 43% glass-fiber reinforcement. Additives improve heat resistance and molding characteristics.

U-profile and double-T profile rods made with the resin show stiffness and strength like those of steel rods, yet offer three times the high-dynamic dimensional stability, the manufacturer reports.

New linkage rods of Zytel are now going into production at the TRW factory in Dusseldorf. The new all-wheel-drive Audi A4 is one of the models on which tests are well advanced. The model that will replace the Peugeot 405 also will use the nylon rod. Fiat/Lancia is expected to follow suit in the near future.

Transducer enables maximized stamped-part quality

Dimondale, MI --Delivering continuous impacts of 800 to 1,000 tons, the typical high-speed, high-capacity mechanical stamping press has little tolerance for "sensitive" feedback devices. That was the dilemma facing Pete Walacavage and Jim Black of IDC Corp. when they sought to add a "shut height," or die position, readout to the company's retrofitable TM-80 press-load monitor.

The two men knew they needed a non-contact, magnetostrictive transducer to provide e.001% accuracy and 0.0001-inch repeatability across a range of 24 to 36 inches. The first transducer they tried was easily thrown out of alignment, and often bent.

Their solution--the Balluff BTL-2-F--combined the best of contact and non-contact positioning. The device uses a magnetic positioner to eliminate contact between moving parts. However, the BTL also features a NEMA 6 housing that constrains the positioner's motion between parallel tracks.

Low-friction, wear-resistant rails let the positioner move slowly along these tracks, while a ball-jointed connector eliminates the need for precise parallel alignment with the moving machine member. Says Black, "Setup is easy because the model doesn't have to be perfectly square to the machine. And with the positioner held in place, vibration is no problem."

Before shut-height feedback, the TM-80 user could only return to a pre-determined tonnage value by measuring tonnage on a scrap part, adjusting the die up or down, and repeating the process until the correct tonnage was found. With the shut-height readout from the BTL-2-F, users generally achieve the desired tonnage on the first try, without wasting test parts.

32-bit processor runs on AA batteries

Maynard, MA--Manufacturers would love to be able to put Pentium-class chips in consumer electronics. These chips' computing power would enable better handwriting recognition and true speech recognition for PDAs (personal digital assistants), dazzling 3-D games, interactive TV, and fast Web terminals.

The problems are two-fold. First, the chips are far too expensive to let companies build products consumers would actually buy. Second, the heat these chips would dissipate would cause users to drop their cellular phones.

Digital Semiconductor addresses these problems with its new 32-bit RISC processor--the SA-110. The chip provides the computing power to improve consumer products, and features power dissipation low enough for it to run on AA batteries. The 100-MHz part operates at 1.65V while dissipating 300 mW. The 160-MHz version delivers over 400 MIPS (million instructions per second) per watt, which led Digital to claim that it's the most power-efficient processor available today.

The 200-MHz part operates at 2.0V and dissipates approximately 1W. The company says this version achieves the industry's best performance/price ratio at almost 5 MIPS per dollar.

And at $29 each for the 100-MHz part to $49 for the 200-MHz version in 10,000-piece quantities, the price is right.

In addition to improving consumer products, manufacturers expect the SA-110 to enable new technologies. "Interactive set-top boxes are a demanding product to build--you need twice the performance of a desktop PC at one third the cost," notes Malcolm Bird, chief executive of Online Media, a supplier of set-top-box technology and products. "While the performance of these Strong-ARM processors is impressive, what sold us was the price point. These chips will help make interactive TV a reality."

The SA-110 is the first member of the StrongARM family, which is the result of an architecture license agreement between Digital and Advanced RISC Machines, Los Gatos, CA. Samples are available now; look for production quantities in June.

--Julie Anne Schofield, Associate Editor

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