Advances in components are allowing fleet managers to maximize effective operation and profitability in refuse haulers.
You might say that specifying equipment components for refuse trucks is more of an art than an exact science. That’s from the customer’s or the chassis dealer’s point of view. Manufacturers of such components as suspensions, retarders, and tires would tell you that the increasingly prevalent use of “science” in their equipment makes the art of specifying more effective as far as designing a truck with maximum durability.
Whether the truck is front-, side-, or rear-loading, few off-road vehicles take the kind of beatings to which refuse trucks are subjected. Even in rural areas, their application necessitates a great deal of stop-and-go driving; the wear and tear on the truck only increases in urban settings. Tight turns with heavy loads are routine, as are extremely bumpy off-road surfaces in many landfills, transfer stations, and recycling facilities. These operating situations, combined with some of the heaviest loads on any vehicle, put a lot of strain on the refuse body. Heavily loaded stops—and plenty of them—stress brakes severely. And those heavy loads and rough surfaces make tire durability a high priority.
MSW Management recently spoke with refuse truck experts to identify truck-specifying approaches and equipment that can provide MSW managers with the highest possible return on investment and service life from their steel workhorses.
Heavy-Duty, Low-Maintenance
Weight capacity, clearance, minimal maintenance, and minimal vibration are some factors that the fleet manager should prioritize, according to suspension experts.
John Rossi, vice president, equipment, procurement and maintenance with South San Francisco (CA) Scavenger Co. Inc., says the company runs front loaders, rear loaders, and rolloff trucks. He overdesigns his trucks because, he says, even though they normally dump at transfer stations instead of rougher landfills, they take abuse from such hazards as potholes and railroad tracks. Because the trucks operate in hilly areas and the front-loaders’ front suspensions experience tremendous shock loading when picking up a container, he specs heavy frame rails and suspensions.
Dylan Frank, marketing analyst with Hendrickson Truck Suspension Systems, points out that more payload capacity provides refuse companies with more efficient routes. Reduced maintenance requirements on a suspension not only increase truck utilization but also aid durability, while maximum ride quality means the chassis and body sustain less vibration, thereby keeping drivers more comfortable and less fatigued. Traction, which is aided by wheel articulation or constant contact between the wheels and the road surface, is also a boon to overall durability, Frank adds.
Most of the time, Frank says, weight laws and payload capacity dictate a suspension with a 46,000-pound capacity on the rear axle and an 18,000- to 20,000-pound capacity on the rear axle. Properly combining the front and rear suspension is important, he adds. For example, specifying a rear-loader with a front suspension rated for heavier loading than necessary can result in a severe ride.
Weight capacity on the axles can vary according to the type of truck body, adds Frank. Side-loaders have the most evenly distributed axle loading. Front loaders put a great deal of weight on the front axles and the need to account for this, stability concerns and a high center of gravity affect the specification process. Rear-loaders experience significant load shifting toward the rear axles, and this should be taken into consideration, he says.
Hendrickson’s main refuse suspension is the Haulmaax, which features a rubber spring system that is designed to provide stability under loaded conditions and reduced vibration when the truck is empty. Frank notes that the suspension is also designed to reduce vibration to levels provided by air-ride suspensions that typically are not used in refuse or off-road applications in general because of dangers of damage from rough surfaces and debris. The rubber springs are incorporated into the suspension to approximate the durability of steel springs at a lighter weight, contributing to a higher payload capacity. The suspension includes equalizing beams designed to evenly distribute weight between axles. High diagonal wheel articulation is designed to provide off-road traction.
Truck dealers can work closely with customers to maximize payload while adhering to state weight laws. “Both our body manufacturer and chassis dealer put blueprints over blueprints to make sure everything comes out OK,” says Rossi. Tom Van Roekel, national sales account executive for suspension manufacturer Silent Drive, notes that the suspension design can interfere with the operation of the truck body, so collaboration during the specification process is crucial. For example, weight laws might allow specification of a tag axle in conjunction with the drive axle to boost weight capacity, but if the customer is specifying a rear-loader, the tag axle will likely get in the way of the low-profile rear hopper. If the customer is specifying a rolloff truck, the suspension might interfere with the large cylinders on the outside frame of the side-loader truck body.
The occasional conflict of configuring axles for the purpose of gaining payload capacity versus truck body operation necessitates close collaboration among the customer, dealer, and truck body manufacturer, Van Roekel stresses. “In a lot of eastern states, the distance between the rear and front axle, and the number of axles determine [gross vehicle weight] capacity,” he says. “Sometimes the rear axle can be moved back a bit and you gain significant capacity, but you need to make sure that it doesn’t affect operation.”
“Years ago, when first had tags on our front loaders, ground clearance was a factor,” says Rossi. “To unload the body, we had to go with a smaller tire, a smaller wheel. Our steerable axles sometimes get in the way on some bodies, but most are working beautifully. We use pushers on our rear loaders and roll-offs and tags on our front loaders.”
Silent Drive does provide air-ride suspensions for vocational use. The model most commonly used for roloff trucks is the 14,000-pound-capacity, air-ride/air-lift AA-270FD Non-Steer Air Suspension. Van Roekel refers to a unique design feature: drop axles at the wheel—rather than at the center—that create clearance for roll-off drop axles. A suspension commonly used on front-loaders with tag axles is the 13,500-pound AS-115 Self-Steering Air Suspension, which features lift up to 10 inches, beneficial for front loaders operating in hilly terrain. Another popular steerable is the 13,000-pound AAS-721 Steerable Air Suspension, which is often specified for side-loaders. “The inboard configuration keeps the bags inside the frame, which is good if you need a steerable for a rolloff,” says Van Roekel.
Bruce Barton, director of engineering at Ridewell Corp., echoes the contention that low maintenance and durability are two of the most important attributes of refuse-truck suspensions. He argues that the drive-axle suspension should require little maintenance and have a good durability track record. Additionally, because drivers have enough to deal with, suspensions should not require driver intervention, as do those with an auxiliary liftable tag axle. With this in mind, Barton says, Ridewell is developing a new steerable tag-axle suspension that will be equipped with an air bag for driver comfort and will not require driver intervention to operate.
One Ridewell drive-axle suspension model that has been used in the refuse industry since 1982 is the RD-202S Dynalastic for tandem drive, which has a capacity of 34,000 to 65,000 pounds. It is designed to provide independent axle movement using individually jointed rubber spring-cushioned torque beams. The suspension is designed to transmit the entire axle load from the frame to the center trunnion, where the load is equally distributed along the compensator. Elastomer springs housed at the ends of the compensator deflect according to the load applied and transmit the load to the independent torque arms connected to the axles. Elastomer overload springs attached to independent torque arms assist the main load-carrying springs and engage as the suspension reaches a given load deflection.
Chalmers Suspensions International Inc. offers a suspension system built around a hollow, self-dampening, rubber spring. Livio Luchini, manager of sales administration, stresses that this system provides full parallel and diagonal freedom of articulation. The absence of leaf springs or airbags keeps maintenance at a minimum, he adds.
Watson & Chalin Manufacturing Inc. offers steerable and rigid lift-axle as well as drive-axle suspensions, including the DA-2300 drive-axle suspension, which has a 23,000-pound capacity per axle and suits 25% off-highway use. It features an onboard shock mount that is integrated with the lower axle seat.
Retarders Save Brakes
The emphasis on maximizing payload during the specification process as well as such advancements as more powerful engines and aerodynamics can affect a truck’s safe operation and costs, however. This is particularly relevant in regard to conventional friction brake wear: Refuse trucks are some of the heaviest trucks on the road. One study indicates that brakes applied on a 19-ton truck traveling at 40 miles an hour on a 6% grade reach 750°F in two and a half minutes—and up to 2,000°F in panic stop situations. The resulting danger and cost involved in frequent brake pad replacement is causing some refuse fleet managers to consider taking the stopping burden off of their friction brakes.
One option they can consider during the specification process is that of a retarder, which abruptly cuts the driveshaft rotation with quieter operation than conventional brakes. Retarders, which may be better suited to more rural areas with greater distances between stops, are equipped with rotating parts called rotors that are attached to the driveshaft. A stator transmits electricity through coils, generating electromagnetic fields with alternate polarities. When the rotors pass through these fields, eddy currents are generated that slow the rotors and thus the driveshaft rotation, and heat generated during this process is dissipated through rotor vanes. The entire process slows down the truck and relieves much of the stopping burden that otherwise would be on the friction brakes. These systems can supplant friction brakes as the main braking system on a refuse truck.
Allison Transmission offers ABS-compatible retarders that can be activated by a dashboard switch or hand lever that allows braking power selection, or using a separate foot pedal. Alternatively, the retarder can be configured to activate automatically, when the driver pushes the brake pedal or eases up on the accelerator, and the amount of retardation can be preset according to the operating environment.
Frictionless braking systems from Telma Inc. can be integrated into the axle, driveline or transmission. Control can be incorporated into the brake pedal, off-throttle, or hand control and reportedly handle up to 85% of the braking horsepower needed to slow down or stop the truck. These systems can utilize a driveline mount or focal mounts on the axle or transmission. Depending on the application, the system is said to increase the life of brake linings by up to a factor of 10.
A Wide Variety
One of the most important components for maximizing truck uptime is tires. Manufacturers offer a wide variety with unique features for managing severe-duty refuse operation.
Rossi, who has been in the industry for 33 years, takes geographic factors into account when specifying tires for his refuse trucks. Because the company operates in an urban area and serves many homes in cul-de-sacs and the trucks have to make a large number of tight turns, sidewall scrubbing resistance is at a premium. “I also want a good, strong casing so that I can get tires retreaded for the rear wheels,” he says.
Don Baldwin, product marketing manager of Michelin’s commercial truck tires division, points out that companies operating in different areas of the country should take climate into account when specifying tires. In an industry where durability is a prime concern, heat buildup in hot climates and freeze-thaw cycles in cold climates are key factors to consider in the durability of such a key operating component. He adds that the tire model may vary according to its location relative to the axle and the axle loading.
Selecting the right tire for the driving environment is important, but so is preventive tire maintenance. Baldwin stresses that drivers and maintenance staff can do a few simple tasks consistently to prolong tire life. These include visually checking for sufficient pressure and tread wear; the appearance of metal is a red flag. Making sure that all valves are capped seems simple but is crucial, he says. Also, dealers offer valuable preventive maintenance services with which specialists inspect every tire on the fleet every workday.
It’s also important to keep debris such as pieces of wire off the road surface and fill potholes on company property, Baldwin adds. Finally, the way that drivers operate their trucks can affect tire life, he says. “In urban areas, keep from running over curbs, because you’re putting the entire weight of the truck on a thin portion of the tire—and it’s bad for the curbs, too,” he says. “Also, keep from scrubbing the tire sidewalls against curbs.”
Management should hold drivers accountable for making sure to avoid loose debris on the driving surface and ensure that debris is picked up. Puddles also play havoc with tire durability, so it’s also important to fill puddles as quickly as possible after a storm.
“Our drivers check tires daily and make sure that nothing is lodged between the duals in the rear and make sure that tires matched pressurewise,” says Rossi. “Also, a tire service comes in every day to swing the tires and check treads. We used to have flats all the time, but not any more—this service really helps.” Regarding operating techniques that prolong tire life, “When they come to a stop, I don’t like them to slam on the maxi brake,” he says. I tell them to use the foot brake first. Also, if you get a flat, pull over. And be aware of what you’re running over—stay away from metal products and glass.”
Retreading has become more popular in recent years, thanks to shortages of some tire sizes from booming mining industries in developing countries such as China and because, more than ever, fleet managers are maximizing equipment uptime and return on assets. An effective retreading policy entails regularly rotating the tires and preserving as much as 20% of the cores to allow retreading. It’s also important to work with both the retreader and the original tire manufacturer to get the best possible retreading quality and determine the ideal use of retreads—on the rear wheels of a front-loading truck, for example.
Michelin’s main refuse-industry tires are the XZU S and the X One XZU S, which are specially made for refuse applications. They are designed with more durable sidewalls and high flotation capability for muddy landfills.
The XZU S is designed for urban applications in which sidewall scrub resistance is a priority. It has a higher tread volume and than other Michelin commercial tires and application-specific tread compounds. It is also designed to have reduced operating temperatures in the crown, and the bead design resists high brake temperatures in stop-and-go operating conditions and provides high traction in wet
conditions.
The X One XZU S is designed to provide fuel savings in urban regional operations. It has a flat, stable contact area for long life and quarter-mile of steel cable to eliminate casing growth. Variable pitch groove walls and groove bottom protectors in all grooves enhance protection against stone drilling. A reinforced bead package with a wide metallic chafer provides bead durability and heat resistance.
Goodyear has offered DuraSeal technology, the first built-in, instant tire sealant for commercial truck tires, since 2005. It is available on mixed-service tires such as Goodyear’s G287 MSA and G288 MSA, which are popular in refuse.
The motivations for developing the technology included the difficulty that maintenance staffs have traditionally experienced when trying to apply liquid-based sealants, the fact that they sometimes dry out and lose their effectiveness while in service, and the downtime necessary to apply them.
The system, which works on tread punctures up to one-quarter inch but not sidewall punctures, uses a gel-like rubber compound dispensed from the crown of the tire that instantly surrounds a nail immediately after a puncture occurs and forms an airtight barrier. It is designed to work multiple times without the need for tire replacement until it is time for retreading. Goodyear reports that the system works in temperatures ranging from minus-40°F to 100°F. The technology reportedly adds 5 to 7 pounds to each tire.