By Paul Abelson
senior technical editor
No, I’m not talking about your physique or attitude, although there is merit in lightening them up. I am talking about lightening your truck. The reasons for doing so are obvious.
For those who load to 80,000 pounds, less truck means more payload and more revenue. But even if you “cube out,” lighter weight translates directly to increased fuel mileage. A few hundred pounds net savings from a 72,000-pound rig may not seem like much, but the equation for fuel use tells us mpg is in direct proportion to weight. One-percent weight savings becomes
1 percent less fuel used.
Even with diesel now averaging about $2.50 a gallon, the approximately 150 gallons saved per 100,000 miles means you’ll have $375 more to spend at Christmas time, or that much more year-end profit.
Those who “gross out” tell me that each pound of added payload could equate to as much as $10 per year increased revenue. Save 800 pounds and your top line could increase $8,000 a year. With expenses remaining constant, that revenue goes straight to the bottom line.
How, then, can you realize these weight savings? Let’s go around the truck and examine what manufacturers and suppliers offer.
The base of any truck is its chassis. When I entered our industry, the only option was to specify aluminum. Aircraft-quality aluminum was used in place of steel on the Army’s favorite battle taxi, the M-113 armored personnel carrier. Just a bit thicker, but much lighter than steel, aluminum chassis save weight on fuel tankers in urban delivery service and other high gross weight, lightly stressed operations.
When Mack introduced the Advantage Highway Chassis, it engineered weight-saving options with a choice of frame rails. OK, this gets pretty hairy, but here’s the short version – using a computerized method of determining and adjusting stress points on an object, engineers developed a 7 mm frame rail with greater resistance to “bending moment” than the 8 mm rail it replaced. Depending on wheelbase, savings can be 100 pounds.
Other options are 6 mm,
8 mm and 9.5 mm. Severe-duty applications use inside channel reinforcement or double wall frames, but the 9.5 mm frame thickness saves significant weight with no loss of strength.
Up front, nothing says classic truck like a shiny front bumper. Heavy chrome-plated steel bumpers have given way to aluminum bumpers clad in stainless steel. New models from Hendrickson offer aerodynamic curves to help fuel economy. Stainless bumper inserts provide good looks while maintaining the aerodynamics and light weight of polymer bumpers.
Big bore diesel engines are undergoing a weight reduction revolution. Higher specific outputs – horsepower per displacement – allow power and torque previously available only in 13- to 15-liter engines to be achieved with 12 liters or less.
Smaller engines weigh less, saving hundreds of pounds. Even in large engines, improved metallurgy, design and manufacture are dramatically lowering weights.
International’s MaxxForce, due for release in late 2007, uses compacted graphite iron. The company reports that the 13-liter engine will produce “more than 450 hp” but weighs less than 2,200 pounds. While many 13- and 15-liter, 450-plus hp engines today weigh 2,900 pounds or more, the 13-liter, 450 hp Mercedes Benz MBE 4000 engine weighs in around 2,200 pounds.
Do you really need 18 speeds in your transmission? Do you need 13? Sometimes you do, to adapt to terrain or improve fuel economy. But with the new engines producing torque over a much wider rpm range, 10-speed transmissions have proven their worth. Eaton Fuller 18-speed transmissions weigh in at 738 pounds for a 1,850 lbs.-ft. torque rating. The comparable 10-speed weighs
82 pounds less.
Aluminum isn’t just for frames and hubs anymore. An aluminum clutch housing can save 50 pounds compared to cast iron. Aluminum axle hubs on all axles can save 120 pounds or more compared with more traditional ductile iron hubs.
Holland has a forged aluminum fifth wheel with polymer “no lube” upper surface plates. Savings are 100 pounds compared with a traditional steel fifth wheel. Another 100 pounds can be saved if and when Alcoa finds a partner to market its aluminum landing gear. An added benefit is the inherent corrosion resistance of aluminum.
Other areas where you can save trailer weight include aluminum plate or fiberglass composite wall structures. Alcoa also developed Aluplate, an aluminum composite panel material of high-strength aluminum alloy over an extruded thermoplastic core. Lufkin had a trailer with Aluplate at the 2006 Mid-America Trucking Show. Weight savings run from 500 to 1,000 pounds.
Another benefit of aluminum and fiberglass is that they do not need painting. Leaving bare metal can save 20 to 30 pounds, depending on how much paint is normally used. American Airlines saves millions annually with lighter, unpainted aluminum aircrafts.
For years, truckers have been saving weight with aluminum wheels. Depending on size, weight savings can be 35 to 40 pounds per wheel compared to steel.
Drivers like the looks of tall 11R24.5 tires, but the smaller 22.5-inch wheels and low-profile tires save weight. Besides the direct benefits, lighter tires carry less federal excise tax based on tire weight.
Greater savings can be realized with wide-base singles instead of duals. Drivers have been reluctant to use one tire in place of two for the risk of being unable to limp home. The availability of replacement tires is another concern.
Over the past few years, Bridgestone and Michelin have increased distribution of their Greatec and X-One tires to include OEMs, their truck tire dealers and many truck stops. Both lines are 445/50R22.5.
Reliability of wide-base singles has been proven in the field, provided air pressure is checked and maintained regularly. They are 600 pounds lighter than 275/80R22.5s on aluminum wheels and 1,370 pounds lighter than the same tires on steel wheels.
They also save fuel by lowering rolling resistance. There are only eight sidewalls to flex and absorb energy with wide-base singles, compared to 16 in a normal tandem. Other benefits include a 3-inch wider track for a more stable ride.
Air disc brakes used to be heavier than equivalent drum brakes, but in recent years, disc brakes have achieved parity.
When FMVSS 121 is amended to require shorter stopping distances, oversize steer axle and tandem drums will become even heavier, making disc brakes a more attractive, lighter alternative during spec’ing.
Meritor’s SteelLite X30 and Motor Wheel’s CentriFuse drums save weight. Instead of using massive cast iron for strength, the centrifugal casting process fuses gray iron braking surface material to the one-piece steel shell. The steel keeps the drum intact in the event of damage, and the weight savings over cast iron can reach 200 pounds on a three-axle tractor.
Suspensions have lightweight components. Many have optional aluminum spring hangers. Liteflex fiberglass springs can replace steel springs. Savings vary with suspension design, with an added benefit. Fiberglass has a “soft failure” mechanism, so the springs gradually splinter instead of suddenly cracking.
The ultimate composite vehicles are trailers from Martin Marietta, the aerospace giant. They make all-fiberglass trailers, with the exception of the suspensions, lights, wiring and kingpins.
Even their frame rails are composite. Their first model was a transfer trailer for trash hauling, followed by a flatbed. Compared to an all-aluminum trailer, savings are several thousand pounds.
Sleeper cabs are fertile ground for weight-saving ideas. OEMs are competitive with sleeper weights. You have options to help you lighten your load without giving up comfort. Do you really need that big refrigerator or will a smaller one do? Do you need that super-long or super-high sleeper? Every inch adds weight.
Most trucks today come with four standard 625 to 675 cold-cranking amp batteries, or three 900-plus cold-cranking amp batteries. A single super capacitor can start your engine. It can be backed up with one or two deep-cycle batteries to run accessories and hotel loads. Weight savings can be 50 to more than 100 pounds.
A study by Jeffrey Ang-Olson and Will Schroeer funded by the Environmental Protection Agency’s Office of Transportation and Air Quality, says: “We assume that trucks can achieve a weight reduction of 3,000 pounds while still maintaining desired reliability and features.
A 3,000-pound weight reduction improves fuel economy by approximately 0.11 mpg at 65 mpg. This would reduce fuel use by 296 gallons annually for a typical long-haul freight truck.”
On the other hand, what will 3,000 more pounds of payload do for your revenue?
Paul Abelson may be reached at firstname.lastname@example.org.