Engineering News 7519Engineering News 7519

Cycling electronics deliver hot fun

Newton, MA--Computer applications continue reaching further into consumer sports and recreation. Nowhere is this highlighted more than in developments geared to fine tune the man-machine interface inherent in various forms of bicycling--from cyclist power measurement to the latest heart rate monitors (HRMs) and real-time-tunable suspensions.

Until recently, only Olympic-class cyclists had access to computerized training systems to monitor performance, allowing athletes to tailor training regimens and plan event strategy. Now Schoberer Rad Messtechnik (SRM, Welldorf, Germany) has available for amateurs, at 3,499 DM ($1,990), a system based on one it provided only to national teams two to three years ago. An even higher-end version is sold for precision laboratory research on roller tracks or mounted on an ergometer.

No strain, no gain. The SRM system monitors power produced by the rider during actual outdoor cycling, thus measuring aerodynamic effects and accounting for environmental influences, such as temperature, and course conditions and terrain. At the heart of the system, says company founder Uli Schoberer, is a 7075 aluminum-alloy disk fitted with strain gauges supplied by BLH Electronics (Canton, MA). This disk is the only bike component changed and mounts in the power train connecting the pedal cranks to the chainrings, or gears. Sealed in the disk, the strain gauges provide torque readings along with a magnetic pickup to determine crank rpm (cadence). The amateur version has two strain gauges, the professional model four, and the scientific version 20. The more gauges, the greater the exactness of measurement, according to Schoberer. Measurement accuracy for the three is plus or minus 5%, plus or minus 2.5%, and plus or minus 1%, respectively.

Schoberer says the original concept was to place the strain gauges on both pedal crank arms. However, the influence of non-torque forces and other effects prevented accurate adding and averaging of the strains over the crank cycle.

With the disk, data are inductively coupled to the handlebar-mounted Powercontrol unit, which computes the rider's power output--the product of torque and cadence. A Polar Electro (Kempele, Finland, and Port Washington, NY) heart rate monitor strapped to the rider's chest transmits heart rate by radio frequency to the Powercontrol. Another magnetic pickup on the front wheel determines bicycle speed. An LCD screen displays data to the cyclist. On-board memory stores up to 128 kbytes of data. With sampling from once per second up to once every 30 seconds, data logging can be keyed to the length of an event. At a rate of every five seconds, the unit can store more than 36 hours of information.

Athletic analysis. The software developed by SRM for the system can calculate and display instantaneous, average, and maximum values of power, speed, cadence, and heart rate. Also available are intermediate times (splits) and cyclist characteristics such as energy efficiency, recuperative capacity, and aerobic and anaerobic training ranges. An RS-232 interface is used to port stored data, via Polar Electro's Polar Interface^TM sender unit, to a PC. Thus an athlete's training history can be compiled. Champion cyclist Greg Lemond, an SRM user, comments: "I can ask for an exact statistical output of how many minutes I did in each power range."

Dan Golich, a sports-science training consultant with the US national team and Javelin bicycles, notes the team originally used the method for investigating bike-racing aerodynamics. "We used the SRM system to evaluate individual cyclist positions, attempting to find cyclist/bicycle setups requiring less power for a given speed," says Golich. The device was also used in assessing the effects of drafting and the power required to maintain a given pursuit line speed. It showed that just monitoring heart rate (which increases) did not accurately correlate with power produced (it remained constant) during long races.

For those who cannot spring for the full-blown SRM system, Polar Electro also produces a sophisticated series of heart-rate monitors that can be linked using the Polar Interface to a PC. The Polar XTrainer Plus^TM is not just for cyclists but any athlete. Such modern HRMs use coded, digital transmissions to link the ECG pickup on the athlete's chest to the wrist or handlebar pickup, storage, and display unit--thus avoiding crosstalk from other users' monitors. An elastic strap keeps the electrodes in the sealed monitor close to the skin, where a voltage differential caused by the body's triggering each heartbeat is detected.

In addition to basic heart rate, system functions include maximum heart rate, average rate, rate per lap, and, afterward, recovery heart rate and recovery time. System sensor options are available for cadence, speed, and altitude. Software tracks training progress of individuals and team members as well, and offers training guidance based on fitness levels and goals.

Shocking. In addition to monitoring athletic performance, electronics are allowing mountain bikers to tailor their mounts as they ride. Cannondale (Georgetown, CT) has developed a patent-pending computerized Surface-Mapping Active-Response Technology (SMART) suspension-fork damper as part of its Headshok line.

A single damper in the "head," which is below the handlebar stem, supports the fork holding the front wheel. A frame-mounted microprocessor controls electric motors that adjust the damper's valving for compression and rebound speeds, as well as the bottom- and top-out characteristics. Each of these four functions is matched to a performance curve stored in the microprocessor. Together the curves define an individual damping-characteristics map.

The microprocessor stores up to five of these maps that provide the best ride for different conditions and terrain, such as bumps. While riding, the biker selects the desired map by turning a knob on the processor. Position and speed sensors on the damper provide feedback to the microprocessor for control input. For example, if the damper is already highly compressed, increasing damping will prevent bottoming out.

Using Windows software developed by Headshok and an infrared link to the microprocessor, a laptop computer can adjust the SMART damper without any disassembly. The software also contains additional maps for downloading into the microprocessor.

For further ride customization, the four performance curves in each of the maps are adjustable with the computer. "The mouse just grabs the curve and moves it, just like a drawing program," explains Tom Armstrong, Cannondale media-relations director. Some of these specialized damping settings might include tightening compression to eliminate suspension bobbing--as when a rider enters a flat area and stands on the pedals. Here, downward pedal loads, as he or she tries to increase speed, cause the front wheel to hop.

A series of "stutter bumps" may call for fast rebounding so the damper doesn't bottom out from the stream of compression impulses. The laptop can also store map preferences for different course venues and the microprocessor test program includes adjusting the suspension to support a given rider's weight at the proper damper-travel position.

Microprocessor-based electronics have allowed these small, lightweight systems to be used by bikers and other athletes without interfering with movement or function. The performance gains possible from training and using these devices, along with cost reductions with volume production, should cause many more athletes to become "wired."

Composite targets night-vision scope

Dallas--When designing a portable weapons sight to military specifications, Texas Instruments needed a material that could withstand cleansing with a chlorine solution in the event of contamination from a nuclear, biological, or chemical attack. It found that material in a glass-fiber-reinforced modified polyphenylene oxide (PPO) composite.

The NIGHTSIGHT^TM scope uses longwave infrared technology to sense differences in heat emitted by objects in its field of view. It separates people and other objects from cluttered backgrounds and foliage, in either full daylight or the darkness of night. Because it emits no light or RF energy, the scope cannot be detected by enemy forces.

The composite, Thermocomp(R) ZF from LNP Engineering Plastics (Exton, PA), is used for the scope's lens housing, knobs, and battery door. It replaces metal components used on earlier versions.

"The problem with metal is that it added a lot of weight. Since the sight is attached to weapons like the M-16, it is important to minimize the extra weight that troops have to carry," explains John Vasarhelyi, TI materials engineer. "Thermocomp ZF allows us to reduce the weight and make the sight a truly portable unit."

Because it is portable, good impact resistance was another major requirement for the component material. The composite, with its glass-fiber reinforcement, provides the strength and stiffness needed to survive drops and other harsh treatment.

The sight is also available for commercial applications, including marine and automotive, and is used by law enforcement and government agencies throughout the country. "Even though these applications do not have the same requirements as the military, we chose to stay with the same material for these customers," says Vasarhelyi. "By switching to Thermocomp ZF, we realized significant cost savings by eliminating the need to perform secondary machining."

Indium phosphide amplifier sets speed record

Redondo Beach, CA--Working as a team, engineers from TRW Electronic Space and Technology Div. and JPL Microwave (Pasadena, CA) recently fabricated and tested a low-noise amplifier chip that delivers 12.5-dB gain at 155 GHz. Described at the Indium Phosphide & Related Materials conference held in Massachusetts recently, the device is reportedly the highest frequency solid-state amplifier ever demonstrated.

The engineers who made the amplifier employed TRW's patented indium phosphide high electron mobility transistor microwave/millimeter wave IC (HEMT MMIC) process. According to a technical paper by principal author Richard Lai and associates from TRW and JPL, devices made using this technology have demonstrated the highest extrapolated cutoff frequency and maximum oscillation frequency attained by any three-terminal device. The new chip represents the results from a program that began in 1989, when TRW produced its first indium phosphide HEMTs.

Indium phosphide can provide higher operating speeds and lower noise than gallium arsenide. These capabilities make it an important next-generation semiconductor technology for microwave communications and digital signal processing. In addition, indium phosphide components can operate at approximately half the voltage of gallium arsenide devices. They could permit significant reductions in the size, weight, and cost of power supplies used in personal communications systems.

Results obtained during the testing of the new amplifier reportedly demonstrate the maturity of the production process. Further, the design team's members state in their paper that indium phosphide low-noise amps should provide useful gain to 220 GHz.

Dwight Streit, manager, microelectronics technology at TRW's Electronics Systems & Technology Division, says: "The original application for this technology is radiometers and very specialized space applications. But the impact on device development is for all types of communications circuits." He describes the technology used to produce the new chip as at the prototype production stage. "We're committed to supplying commercial parts to our commercial customers by the end of 1997," says Streit. "Indium phosphide is in production but it's not really high-volume compared to gallium arsenide. But it's following the same curve that gallium arsenide followed, with a time delay of a few years."

Filter stops both high- and low-voltage spikes

Houston--Small, "invisible" spikes and surges that pass unseen through a surge suppresser can wreak havoc on microprocessors and other electronic components. The result? Frozen screens and lockups, data loss, component failure, and system crashes.

"The major source of low-voltage disturbances is common equipment such as air conditioners, beverage machines, elevators, computers, copiers, laser printers, and coffee makers," says Bahram Mechanic, president of IEPS Electronic Inc., a manufacturer of power-system protection devices. "These common appliances produce transients which migrate through building wiring into electronic equipment."

The Transformer-Based Power Filter (TBF), developed by IEPS, combines the high-voltage protection of a surge suppresser with low-voltage protection that filters spikes at a safe level for sensitive circuitry. The device provides conditioned, computer-grade power free of disruptive low-voltage spikes.

Industry analysts estimate that dirty power is responsible for up to 80% of all electronic/microprocessor-controlled equipment electrical failures. Studies by IBM and Bell Labs have shown that 88% of problems in computerized machines are caused by spikes and surges of less than 200V. Most of these fluctuations are as small as 5 to 10V.

Normal-mode noise between hot and neutral is generated by lightning and causes circuit-board or power-supply blow out. Common-mode noise between a ground wire and other wires is generated by the above-mentioned office equipment.

The TBF includes a patented processor control board that directs the transformer and other components within the TBF to filter any noises and spikes which are in the common-mode area down to less than 1V. The TBF 1000 LM combines power-filter technology with an additional separate filter function to eliminate electrical noise and transients from data-communications lines. Using a standard RJ-11/RJ-45 telephone jack, customers can protect their modems or FAX machines with the same ease. An optional coaxial jack can be used for protection of LAN devices.

Gas-assist molding produces lightweight bumper

West Des Moines, IA--By replacing an aluminum front bumper on Arctic Cat's ZR-series snowmobiles with a hollow-core-molded, long-glass-reinforced thermoplastic bumper, engineers reduced the component's cost by 73% and its weight by 37%. This part is one of the first components successfully produced by combining gas-assist injection molding and long-fiber-reinforced thermoplastics, according to Mid-Central Plastics Inc. (MCP), which made the part for Arctic Cat of Thief River Falls, MN.

Engineers at Arctic Cat realized that a plastic bumper would provide significant savings in both weight and production cost. However, early attempts to make such parts did not produce satisfactory components. Then Gary Keeney, process engineering manager, and his colleagues at MCP became involved. Under a license from Cinpress Ltd. of Staffordshire, England, MCP employs gas-assist molding to produce parts. Combining that process with Celstran(R) long-fiber-reinforced thermoplastics made by Polymer Composites Inc. (PCI), Winona, MN, (a subsidiary of Ticona, formally Hoechst Technical Polymers) whipped the problem.

During plastic injection molding, polymer flows from the inside out and rolls to the wall of the mold. In gas-assist injection molding, "you shoot a given amount of material into your mold as a short shot--you don't completely fill the mold. Then you start the gas," explains Keeney. "In place of more polymer coming in behind, gas comes in. As it does so, it pushes the molten polymer from the center core in front of it." The polymer flows as it normally would, and fills the mold, but leaves a hollow core in the part. This process allows the use of very dense material to make hollow-core parts. Doing so retains the excellent properties of the material without incurring a weight penalty.

After two years of work, Arctic Cat engineers have their thermoplastic bumper in production. "Long-fiber-reinforced plastics are well suited to the gas-assist molding process," says MCP's Keeney. "There are fewer strand ends than with short-fiber, and it tends to lay down on the wall better than short-fiber materials. With 40% short-fiber filler, the fibers tend to rake the polymer on the side wall, and thin the wall."

Actively tuned masses cut cabin racket

Burbank, CA--Anyone who has ever sat in the back of a rear-engine airliner knows the noise can make the trip feel like one to the dentist-- without the Novocain. Imbalances due to wear of the rotating turbine machinery can generate conversation-busting, fatiguing vibrational noise on the order of 1 to 2g acceleration through the structure.

But a low-cost, simplified solution is on the way for passengers and operators of twin-engine McDonnell Douglas aircraft. Barry Controls Aerospace has developed a vibration-cutting system based on continuously tuning a set of mass dampers throughout a range of engine rotational speeds. Previously, vibration control was attempted with tuned mass dampers. These are attached to the engine mounts and kill vibration by absorbing energy at the natural frequency of the mass and its mount. Obviously, only one frequency or harmonic can be canceled, thus the reduction is good at only discrete rotational speeds.

Active noise control for quieting cabins has also been done. Here microprocessors drive speakers to generate noise 180 degrees out of phase with offending sounds, canceling them. Such installations are more complex, involving custom designs for each cabin type. Microphones pick up noise and provide for feedback to speakers that produce the out-of-phase signals. These systems are most useful for turboprop aircraft that produce nonstructurally conducted noise.

Steve Nowak, Barry Controls Aerospace engineering manager, says the Active Tuned Mass Absorber (ATMA) is a proprietary electromechanical device that changes its frequency to continuously absorb and tune out noise as engine rpm varies. These can-like devices, two of which are bolted to the front of the forward engine mount and two on the aft side, react to harmonics at the engine, sopping up vibration close to its source.

"A base sensor picks up structural vibration on the engine support structure," Nowak explains. "These data are combined with engine tachometer readings which provide the cold spool (engine fan and low-pressure turbine) tonal frequency (N₁) and its counterpart (N₂) for the hot spool (compressor and high-pressure turbine)." The forward ATMAs absorb the N₁ vibrations and the aft ones the N₂. Sensors on each ATMA provide feedback to the processor electronics for closed-loop control.

Test results indicate aft-cabin noise reductions over 20 dB using the ATMA system. Since the devices absorb energy rather than generate vibrations, the system consumes an average of 30W of electrical power. With minimal wiring, no aircraft cabin modifications, and no engine removal, installation can be completed by six workers in one shift. Being a "non-essential" safety system, only routine health monitoring and on-condition maintenance is needed.

Midwest Express is installing the system in its DC-9s. Northwest Airlines, boasting the largest DC-9 fleet in the world, will have 173 planes equipped by mid 1998.

Nowak reports that business jet makers are also looking at ATMAs. These luxury aircraft now use generous amounts of heavy lead-impregnated vinyl in cabin walls to cut noise. Noise reduction with ATMAs will permit reducing the empty weight of aircraft for greater payload and range.

Composite faces off with steel at Kodak

Rochester, NY--As a cost-reduction project, Kodak engineers designed a high-performance, metal/plastic composite gudgeon, or end cap, for the fuser roll assembly of the company's 3100 Duplicator high-speed copy machines and Lionheart Power Printing systems. The patent-pending part consists of glass-fiber-reinforced thermoplastic polyimide injection molded onto a powder metal insert made of 303 stainless steel.

During the development stages, insert molder Pixley Richards, Plymouth, MA, supplied about 200 of the composite gudgeon prototypes for life testing in Kodak machines, with one lifetime equivalent to about one million copies. Pixley Richards also had to address manufacturing issues.

The primary concern centered on the development of an interface between the thermoplastic polyimide, called AURUM, produced by Mitsui Toatsu Chemicals, Purchase, NY, and compounded by RTP Co., Winona, MN. Pressures, temperatures, and fill rates were adjusted to achieve the correct balance to produce a solidly knit part, without overstressing the stainless steel insert that forms a significant part of the cavity. Care was needed during these trials to ensure that the process would withstand high-volume production.

The concerns proved warranted. The end cap had traditionally been an all-plastic component molded from a high-heat-resistant polyimide--most recently AURUM. In an electrostatic-type copier, the end cap attaches to each end of a fuser roll core made of a thermally conductive material, such as aluminum. The aluminum core is heated internally by a quartz lamp. The actual fusing surface that permanently fixes the toner to paper or transparencies typically consists of a thermally conductive polymer, such as silicone rubber.

While in operation, the gudgeon transfers rotational motion and provides support to the machine's frame. In addition, it acts as a thermal barrier to protect an expensive steel bearing positioned between the gudgeon and frame from excessive heat transfer. Moreover, the component provides a low-friction, wear-resistant surface that extends the life of the bearing. In operation, the part is subjected to temperatures of 450F, with spikes as high as 480F, and torque levels of 60 ft-lb.

"There are limits when processing high-performance materials," says Ian MacLeod, vice president of engineering at Pixley Richards. "AURUM seems to allow you to stretch those limits better."

Allen Kass, product engineer for roller development and manufacturing at Kodak, adds that AURUM was selected over an extensive list of other engineering plastics, including PPA and PPS, "because of its good stability when exposed to high operating temperatures, and its high tensile strength at room temperature." Once positive performance results were confirmed for the initial 200 AURUM/metal composite samples, Pixley Richards produced another 800 test samples.

Pixley Richards molded the original all-AURUM gudgeons, a direct replacement of a glass-filled thermoset polyimide. However, the end product was not optimized to utilize the unique characteristics of AURUM. That's when Kodak's Kass and fellow engineer Robert Lancaster came up with their AURUM/powder-metal insert design. Alpha Sintered Metals, Ridgway, PA, produces the powder-metal insert.

P/M part wins automotive innovation award

Detroit--The first P/M part ever made using the warm-compaction process received the Automotive Innovation Award at this year's Society of Automotive Engineers International Congress & Exposition. Delphi Automotive Systems/Seixal Portugal Operations produced the winning part, an ignition coil, for General Motors vehicles built in Europe.

The Metal Powder Industries Federation presented the award to Hoeganaes, Delphi, Cincinnati Inc., and GM's International Operations. Hoeganaes, Riverton, NJ, produced the P/M materials using its insulated powder (IP) process. In the process, each particle comprises a composite of iron coated with a nonconductive thermoplastic. The process requires warm compaction to obtain high density.

"One of the many advantages of the IP process is design flexibility," says William H. Michael, vice president business and product development at Hoeganaes. He points out that the process allowed Delphi to make a round ignition coil, compared to the traditional square or rectangular part.

The new design added performance characteristics to the coil and eliminated the need for several parts in the ignition system. It also did away with sharp corners, allowing for the direct application of the primary ignition windings to the round stock.

"These benefits derived from the process helped to streamline the manufacturing process and reduce costs," Michael adds.

The IP process is a derivative of Hoeganaes's ANCORDENSE^TM warm-compaction process. The process improves green strength, with the nonsintered parts achieving up to 15,000-psi tensile strength.

GM plans to use the new technology on its U.S. vehicles in the near future.

Forms give climbing wall a facelift

LeTouvet, France--Climbing walls has become an increasingly popular recreational activity. However, the same routine could make climbing less appealing after scaling the walls several times. The French company ENTREPRISES believes it has a solution for taking the boredom out of climbing.

Inventor of the "bolt-on" hold and builder of the international competition wall used in the 1996 Summer Olympics in Atlanta, the company makes 15 different Macro-Systems designed to suit the needs of both top competitors and beginners. Using simple wood screws, the systems' forms attach to an existing wall to produce new shapes and a new climbing environment. Constructed of polyester resin, each Macro contains built-in features and insets for added bolt-on hand or foot holds.

In addition, the system adapts for use on a different part of the wall, providing a wide choice in technical difficulty, as well as interesting holds for all levels of use.

Copolyester steams Dream Machine competition

Bloomington, IL--The Eureka Co.'s new Dream Machine Heavy Duty Steam Cleaner converts from rug shampooing to bare-floor care to upholstery cleaning at the flick of a switch.

Where clarity and impact, abrasion, and chemical resistance proved of paramount importance for components, Eureka engineers selected a copolyester resin, EASTAR DN004, from the Eastman Chemical Co., Kingsport, TN. It is used for the leak-proof recovery tank, tank lid, and plate assembly, as well as for the floor-care suction cover and upholstery nozzle and attachment.

"The combination of physical attributes, processability, and cost makes this copolyester the material of choice in these applications," notes Doris Hobbs, business market manger for Eastman's Appliance Business Segment.

Parts made of the copolyester were subjected to in-house impact and end-use conditions testing, including resistance to an array of cleaning solutions. All components met or exceeded requirements.

"Our service group worked with Eureka's designers and molders from the product's inception," Hobbs adds. "We provided critical assistance with part and mold design, and, in some cases, recommended part design changes to improve processing."

Dipsticks go high performance

Gaffney, SC--Dipsticks have long caused headaches for makers and users of motor homes and other rear-engine, diesel-powered vehicles. Due to their length (up to 6 ft) and awkward locations, the dipstick assemblies have traditionally been tough to remove, difficult to read, and even harder to reinsert and tighten properly. Undertorquing or overtorquing the caps can cause oil leakage or "blowby," a messy and costly predicament. However, Freightliner Custom Chassis Corp. believes it has solved the problem with its Fluid Level Indicator.

"We felt that dipstick designs had not kept pace with modern vehicle technology and that there must be a better solution," says Lewis Parsons, a senior designer at Freightliner. "As a result, we set out to find a new idea for a product that would replace the dipstick as we know it."

The design objectives: enhance accuracy, reliability, and ease of use; find a single-source supplier; achieve product differentiation in the marketplace; and do all this while remaining cost-competitive.

Parsons met with representatives of Furon Co., Holmesville, OH, to discuss these initial goals. Though Furon had never produced a dipstick, it felt it had the material and process expertise to tackle the challenge. Freightliner liked what it heard and awarded Furon the assignment, along with liberal design freedom.

Furon assembled a market focus team headed by Product Development Leader Anthony Williams and included 25 other employees from a dozen departments and locations. "We wanted to leverage expertise from as many disciplines as possible to find the best solution, and we started with a blank sheet of paper."

Furon returned to Freightliner ahead of the prescribed timetable with a rough-tooled prototype of the proposed product: the Fluid Level Indicator. It consisted of a lightweight, corrosion-resistant plastic molded cap and spout overmolded onto a polymer tube. The assembly promised to eliminate the multiple components found in typical dipstick systems. Several more prototypes were produced for evaluation and testing.

"We installed one prototype in our own test vehicle and ran full-power wind tunnel testing at ambient temperatures in excess of 100F," Parsons recalls. "We also exposed it to repeated heat-up and cool-down cycles with temperatures from 40 to 110F. We found no signs of deterioration or leakage."

Freightliner placed other prototype Fluid Level Indicators in rear-engine motor homes for field trials. "In the course of this testing, one vehicle owner actually called and thanked us for letting him try the new product," Parsons reports.

Furon also performed extensive heat aging, thermocycling, and other testing to make sure the indicator would provide durability as well as a reliable seal at the cap and engine interfaces. "After experimenting with different techniques for joining the cable to the metal marking blade, we developed a die-cast fitting that greatly enhanced the mechanical strength of this assembly," says Williams.

The final product uses a combination of features to meet all of Freightliner's criteria. The overmolded cap and spout assembly has a controlled turning mechanism to ensure that the marking blade is consistently positioned every time. "Furon's overmolding or 'insert-molding' technique is very innovative for these type of applications," notes Parsons.