Stop-and-go driving in many pickup-and-delivery operations is a money eater, but the stopping may soon be an advantage rather than a liability. Development of hybrid trucks, which capture and recycle much of heretofore wasted braking energy, is coming along so fast that progressive managers are already planning orders and almost counting their savings. Diesel-electric and diesel-hydraulic hybrids are in advanced demonstration stages and some are available to buy now. Although still expensive, greater interest among truck users is expected to lead to volume production, which in turn will bring down prices. It’s already happening with hybrid automobiles from Honda and Toyota, adherents say, and military money is funding development that will spill over into civilian use.

The U.S. Army’s National Automotive Center is spending $150 million US on hybrid developments on one medium-duty truck family alone, “and 80 per cent is on the street, working for you,” Paul Skalny, NAC’s associate director, told civilian fleet managers at a recent meeting of the Hybrid Truck Users Forum (H-TUF), which gathers regularly to track progress.

“We are working with the same set of suppliers that you are,” he said. “We have a heck of an opportunity to work together to come up with data and share it.” To that end, NAC has a co-operative agreement with the Technology & Maintenance Council of the American Trucking Associations.

This T-HUF conference in San Antonio was organized by WestStart/CalStart, a technology advocacy organization in Pasadena, Calif., and co-hosted by Stewart & Stevenson, a major builder of Army trucks, and Southwest Research Institute, whose engineers are doing some of the Army hybrid work.

The Army is committed to hybrids because they can dramatically reduce fuel use, Skalny said. Fuel is the single biggest item shipped to foreign areas of operations. It costs $40 to $400 per gallon to ship JP4, a relative of diesel, which is burned by the Army’s trucks, armored vehicles, and aircraft, and millions of gallons are needed. Saving 20 to 40 per cent on fuel in just one deployment, such as now in Iraq, would pay back the estimated $667-million cost of converting the fleet to hybrids, according to an analysis by Southwest Research.

The Army plans to begin putting soldiers in hybrid trucks between late 2005 and early ’06, he said. The first contracts for class-6 and -7 supply trucks and HUMVEE utility trucks should be let by February or March of ’04. Contracts for hybrid heavy supply trucks will probably come soon after, and NAC has stipulated that the hybrids will have definite commercial application.

Among civilian users, the best-known embracer of hybrids is FedEx Express, which plans to convert its fleet of 30,000 medium-duty parcel-delivery vans to hybrids within 10 years. It has chosen an Eaton diesel-electric system in a vehicle built by Freightliner Custom Chassis.

In Canada, Purolator Courier and Canada Post are testing diesel-electric hybrid vans designed by Azure Dynamics of Burnaby, B.C. Azure is beginning work with United Parcel Service on another electric hybrid system.

Costs are fuzzy and few suppliers want to quote numbers, partly because they’re likely to come down fast. FedEx Express won’t tell how much more an E-700 hybrid will cost over a W-700 (for walk-in, 700 cubic-foot) van, but says the E-700’s life-cycle cost will be lower.
Weight is better known. FedEx says the electric system in its E-700 test van adds about 200 pounds to a standard 14,000-pound-GVW W-700. Systems on heavier duty trucks are much weightier-typically 1,500 to 2,500 pounds. These are likely to be reduced in production versions, and in any case are usually not much of an issue in medium-duty P&D trucks.

The H-TUF meeting included a ride-and-drive session at Southwest Research’s campus on the outskirts of San Antonio. About a dozen vehicles were displayed and some could be driven by participants. Among them:
Eaton/FedEx parallel diesel-electric. This powertrain, now in final development, is slated to replace many of the straight diesel W700 vans in the company’s fleet. The hybrid uses an electric motor and a 170-hp Mercedes-Benz 904 diesel, both running through Eaton’s six-speed UltraShift with an automatic clutch. The motor doubles as a generator during braking, capturing kinetic energy and storing it as electricity in batteries; that energy is fed back to the motor during startup.

Both engine and motor run through the same drivetrain, and can run together or alone-thus the term parallel. In a series hybrid, the engine drives a generator that sends electricity to batteries, as does the motor when operating as a generator during braking. But the engine cannot drive the truck by itself.

In short spin in the vehicle, I found that the electric motor usually launched us while the engine spent most of its time idling, and occasionally revved for running at higher speeds. The engine idles to spin the power steering pump and the alternator, explained Sid Gooch, FedEx Express’ fleet managing director, who is overseeing this project. Idling the engine is simpler than using additional electric motors to run the steering and accessories, which in turn, would allow the engine to shut off.

The engine’s idling and occasional rise in revs tends to mask the sound of the electric motor at work. Partly because of this, the hybrid system doesn’t seem much different than a standard FedEx W700 to a driver. That’s also its beauty, because employees need only about five minutes of instruction before getting in and driving away, explained the Eaton engineers who showed me what to do.

But would a hydraulic hybrid be better for what FedEx Express wants? “Had we started this [project] about a year later, we might have gone the hydraulic path,” Gooch remarked over lunch. “We were technology-neutral when we started it; we had no opinion on which way to go. At that time the electric systems seemed to be further along, so that’s what our contractors recommended. But there’s been a lot of development in hydraulic systems, and now I wonder.” Could the company acquire some electric hybrids and then switch to hydraulics for the rest of its 20,000- to 30,000-unit buy? “That could be,” he said.

FedEx Ground, a sister company, is taking the hydraulic path, said Bob Flesher, managing director, vehicle maintenance. He and his team had met with suppliers during the conference and were close to choosing one.

“But our situation is different than Express,” he said. “Their vans are driven by company drivers, and ours are run by owner-operators. We spec them and arrange to have them built, and our contractors buy them. The hydraulic systems seem simpler than the electrics, so would be better for our situation.”

Dana Permo-Drive/Army hydraulic hybrid. Developed in Australia by Permo-Drive Technologies, the system is installed on a 5-ton 6×6 cargo truck. It’s part of a 21,000-unit fleet the Army calls FMTV, for Family of Medium Tactical Vehicles, made by Stewart & Stevenson. The 5-tonner’s standard powertrain includes a 330-hp Caterpillar 3126E and an Allison MD3070 transmission. These are augmented by an axial-piston hydraulic pump/motor motor on the driveline and two high-pressure accumulators hung beside the driveshaft.

Army regs wouldn’t allow unauthorized civilians (even Army vets like me) to drive the truck, so I observed from a jump seat while a Permo-Drive rep demonstrated. The motor became a pump as soon as he took his foot off the accelerator; the truck’s momentum turned the pump to pressurize hydraulic fluid, which is stored in the accumulators at 3,000 to 5,000 pounds per square inch.

The pump made a low-pitched whine as it worked and was powerful enough to stop the truck with no help from its service brakes, even on slight downgrades with an 11,000-pound concrete-block load in the bed. The retarder will stop the truck in half the distance of an exhaust brake, said Simon Baseley, Dana’s director of advanced pumping systems, who described this hybrid prior to the demonstration. When the driver punched the accelerator, pressure from the accumulators flowed back to the motor, spinning the driveshaft and launching the truck.

Torque from the hydraulic system is high at launch, then dissipates as pressure is expended. The system on this truck is oversized, so the power is more than what’s needed, Dana and Permo-Drive engineers said. In fact, it has almost gotten away from several first-time drivers who mashed the pedal too hard. A production system would be sized so it propelled the truck at the same rate as one with the diesel alone. This would let the diesel loaf and effect the desired savings in fuel and, of course, brake linings.

The Army is looking at various types of hydraulic systems with motors mounted in the driveline, as on this truck, and at the wheels, which would give armored fighting vehicles a lower profile. Hydraulic hybrids are sufficient to slow and propel cargo and engineer trucks, while electric hybrids would be useful for trucks that transport missile systems and other equipment requiring electrical power.

A truck’s ability to produce on-board power would eliminate the need to pull and maintain thousands of generator sets now in the Army’s inventory. Electric and hydraulic systems could silently power trucks for short distances in “stealth” mode, useful in many tactical situations.

Civilian public utility and refuse collection fleets are intensely interested in hybrid technologies, and were active participants at the conference. Two of the working groups represent their industries, and each seems headed down different but appropriate paths.
Utility companies believe electric hybrids could operate more economically and quietly than current diesel trucks, said managers from Alabama, California, and Florida. The trucks could use smaller diesels because they’d recycle braking energy during on-road driving and they would be enough to generate power for off-road work. Electric motors instead of an engine-driven power take-off would spin hydraulic pumps to run man buckets, derricks and other equipment. A smaller, slower-running engine would also reduce noise–and related complaints.

Trash collection trucks make repeated stops and starts, so are prime candidates for powerful hydraulic hybrids. One major fleet is ready to acquire some for tryout. Brake linings now absorb kinetic energy during stops and wear out fast doing it; capturing that energy and using it to launch the trucks and power compacting rams could save considerable amounts of money. Brake linings should last twice as long and perhaps more, tests have shown. Such hybrids would also be quieter and emit fewer pollutants.

Eaton Corp. is developing both electric and hydraulic systems because “we believe there are uses for both,” said Sohan Uppal, vice president of technology at Eaton Fluid Power Group. Its HLA, for Hydraulic Launch Assist, produces tremendous torque at startup–600 foot-pounds by a 6-cubic-inch accumulator and 1,000 foot-pounds by a 15-cubic-inch model–and produces energy faster than electric systems.

HLA uses proven low-noise pumps and motors, and proprietary electro-hydraulic controls from Eaton’s Cutler-Hammer division. “Leaks are the single biggest problem in a hydraulic system, and 80 per cent of the leaks are in hoses and fittings, so we eliminated the hoses and fittings,” he said.

What happens if a hydraulic system’s accumulators are punctured? Wouldn’t a high-pressure stream of fluid be dangerous? Dana is looking at armoring the tanks with composite materials, but Eaton has another way. Uppal explained that its system works in a cushion of nitrogen, which would harmlessly escape first; meanwhile, hydraulic pressure would drop fast so fluid can dissipate without harm, except for whatever is spilled on the ground.

Safety can also be a problem with electric hybrids which operate at hundreds of volts, an attendee noted. H-TUF needs to develop standard warning stickers that can be applied to hybrid trucks. The stickers can point to sources of high voltage so rescuers, tow-truck drivers, and passers-by can avoid them.