Heavy-duty truck chassis and trailers used to haul equipment to the job site are machines of means.
Truck chassis and trailers used to haul the grading and excavation contractor’s machines to the job site are key elements in operational profitability. Chassis and trailer specification requires an intimate knowledge of the physical dimensions of the contractor’s equipment and may also require some forecasting to allow for company growth and changes in the market. By taking these factors into account, the contractor can optimize both the performance and payload capacity of the chassis-trailer combination.
Leading suppliers of chassis and trailers to grading and excavation contractors were asked for their views of what the current marketplace is demanding from this equipment, as well as how their ultra-heavy-duty equipment is meeting these demands.
More than ever, chassis manufacturers are focusing on axle configuration flexibility for adherence to weight laws, frame integrity, horsepower, fuel-economizing transmissions, dependable engines that meet stricter environmental standards, and keeping drivers operating safely and comfortably. Trailer manufacturers are prioritizing low profiles, low weight with no sacrifice of structural integrity, and easy machine loading.
Truck Chassis
International Truck and Engine—The new Class 8 vocational on/off-highway PayStar 5900i Set-Back Axle (SBA) has a wide-track, set-back axle designed to address contractors’ needs for front-axle load distribution and improved maneuverability, and a sloped hood allows for better visibility.
 |
Photo: International Truck and Engine |
| The PayStar 5900i SBA has a standard 12.25-inch frame rail chassis. |
Powered by Caterpillar or Cummins diesel engines up to 15 liters and up to 625 horsepower, the PayStar 5900i SBA also has a standard 12.25-inch frame rail PayStar chassis. It also is said to provide the highest standard strength-to-weight ratio at 2.3-million-RBM inch-pound ratings. An optional double frame rail provides an increase to 4.7 million RBM. The heavy-duty front bumper with front tow pin is capable of pulling up to 150,000 pounds.
The 5900i SBA reportedly has the widest aluminum cab in the industry and comes with a standard Whisper Cab sound insulation package for a comfortable environment. Outside air cleaners are available for improved air intake in high-horsepower applications.
Kenworth Truck Co. —The Kirkland, WA, manufacturer recently released guidelines for customers to optimize trucks for hauling loads above 110,000 gross combination weight (GCW) pounds, emphasizing that overspecifying can actually end up costing the operator more in fuel mileage and maintenance.
According to Kenworth, primary considerations should include the truck’s wheelbase and the number of axles, which are dictated by local length and weight regulations. But making the truck’s wheelbase longer than necessary reduces maneuverability. Proper positioning of the fifth wheel is critical to ensure full use of the rated capacity of all axles, especially the front. Front axles rated at 20,000 pounds are the most common, but a 22,000-pound rating is available for extra-legal loads.
At those ratings, wide-aspect front tires are needed to not only handle the load but also meet some states’ tire-width requirements. The rule is typically 600 pounds per inch of tire width, but it can get as low as 500 pounds per inch of width. Mounting 425/65R22.5 tires on the front will be good for up to 22,000 pounds on the steer axle in most states. Wider 445-section tires are also available to maximize tire width and improve flotation over loose surfaces. Drawbacks of wider tires include restricted steering geometry and limited turning circles. Kenworth has addressed this trade-off with its T800, which is reported to have a wheel that’s among the best in its class. Kenworth uses dual steering gears on front-axle ratings of 16,000 pounds and above, in contrast to the single steering gear with an assist ram offered by competitors, and also recommends an oil cooler on the steering system to maintain safe operating temperatures.
 |
Photo: Kenworth |
| Kenworth has developed a 1,780-square-inch radiator and a wide hood for the T800. |
Because newer engines run hotter than the pre-2007 engine offerings, Kenworth has developed a 1,780-square-inch radiator and a wide hood for the T800. The company also recommends dual, 15-inch cowl-mounted air cleaners to give the engine cooler air than an under-hood air cleaner.
Also recommended is focusing on transmission ratios to allow improved startability and driveability. In heavy applications, a two-speed auxiliary transmission or a two-speed rear axle are alternatives to the typical 18-speed manual transmission. A two-speed axle works well up to about 190,000 pounds of GCW, but above that an auxiliary transmission is recommended.
The rear-axle-ratio choice affects startability but should be chosen carefully to ensure a good balance between cruise speed and low gearing. Kenworth recommends a startability of 15% to 20% for most heavy-haul applications. Typically, a 4.11:1 gear ratio is advised unless the truck has a two-speed rear axle or an auxiliary transmission. For haulers running long distances at highway speeds, the ratio should be as low as possible without undermining startability; the rule of thumb for gearing is that which will achieve a 1,550-rpm engine speed at 65 miles per hour.
For extreme heavy-haul applications, Kenworth offers planetary axles with capacities up to 150,000 pounds. The company also recommends wheel differential locks or a cross lock on at least one drive axle and offers optional automatic traction control on antilock brake systems, a feature that controls wheelspin on slippery surfaces. Kenworth also offers steerable and nonsteerable pusher axles. A 20,000-pound steerable is the most common, but a 22,000-pound nonsteerable is also available if needed. Managers running lift axles may want to consider upgrading their braking systems from standard four-channel antilock brake systems to six-channel systems to prevent flat-spotting of the lift-axle tires.
To haul heavy loads, frame rails typically need to be reinforced. The amount of reinforcement depends on the truck’s wheelbase and axle capacities. An inserted three-eighths-inch frame is usually required for most heavy-haul tractors, but two inserts are available for longer wheelbases and higher axle capacities.
Rear suspensions on heavy haulers have historically been mechanical types, but air suspensions are rapidly gaining popularity. By lowering the air suspension, a driver can back under and pick up a lowboy trailer instead of using skid ramps and ramming into the trailer in order to couple it to the tractor. Kenworth offers different versions of its eight-bag air suspension to suit different applications. The AG460 is commonly used for 46,000-pound tandem-axle configurations, and the AG690 can be used for tri-drive applications.
The company advises heavy haulers to spec as much glass area as possible and plenty of mirrors. Four-way-adjustable, cowl-mounted mirrors stay in adjustment longer than door-mounted types and can be complemented with convex mirrors. It is also recommended to spec low-replacement-cost windshields, when available, because most vocational fleets replace at least one windshield side per truck annually. Two-piece flat-glass windshields with roped-in seals can be replaced in 30 minutes for less than $100.
Mack Trucks—At the 2008 ConExpo event, the company introduced the Titan by Mack, which it describes as the most powerful truck in its 108-year history. The model is designed specifically for heavy-transport and heavy-construction applications and features the new 16-liter MP10 engine, the most powerful engine ever offered by the company with a top rating of 605 horsepower and 2,060 foot-pounds of torque.
 |
Photo: Mack |
| All Mack MP engines come with the V-MAC IV Vehicle Management and Control System. |
Certified to U.S. 2007 emission standards, the MP10 is an inline six-cylinder diesel with a single overhead cam and high-pressure fuel injection. It is available in three ratings, with peak horsepower of 515, 565, and 605, all with MaxiCruise torque rise. Maximum torque ranges from 1,860 foot-pounds to 2,060 foot-pounds at 1,200 rpm. All Mack MP engines come with the V-MAC IV Vehicle Management and Control System. The MP10 is characterized by a “hump” horsepower curve, which gives it more power at 1,500 rpm than at 1,850 rpm, encouraging drivers to operate at lower rpm with greater power for greater fuel efficiency. The engine is matched to the Mack T300ES series 10-, 13-, and 18-speed transmissions.
The Titan offers high ground clearance and a long hood to give the engine plenty of room to breathe, while the cab is moved back and up on the chassis for a heavy-haul position and high driver visibility. The higher cab position is also designed to improve airflow for under-hood cooling. Additionally, the truck is equipped with twin cowl-mounted Growler air intakes designed to provide several advantages over external air cleaner assemblies. These advantages include blocking moisture and debris from the air filter element; smooth, nonrestrictive piping optimized for high-volume airflow; and the location of air filter elements under the cab for easy service.
The unit’s Cornerstone chassis, which has been used on Mack’s Granite vocational truck, is available in three frame-rail thicknesses—8, 9.5, and 11 mm—with optional full or partial 5-mm inside-channel reinforcements and application-specific crossmembers. Frames are rated at 120,000 psi and 2.12 million to 4.26 million RBM.
A short, 41-inch front-axle position is designed to increase load capacity while providing high maneuverability. Front axles and suspensions are available from 12,000- to 20,000-pound capacities, and rear axles and suspensions are offered from 38,000- to 65,000-pound capacities.
A new air-ride cab mounting uses twin wide-spaced air bags with shocks to neutralize bumps. Also, the cab has numerous highly engineered features to reduce noise and vibration. The air-assist clutch pedal is positioned low to help drivers work with less leg effort. A foot pedal adjusts the steering column to an infinite number of positions. The standard instrument cluster features large, easy-to-read displays and gauges, and a standard Mack Co-Pilot display provides drivers with easily accessible screens in the instrument panel to monitor such information as real-time fuel economy and detailed maintenance and fault summaries.
Peterbilt—The Model 365 has a 115-inch bumper-to-back-of-cab (BBC) dimension and can be configured in a set-forward position—useful in states where bridge law regulations are strictly enforced—or a set-back front-axle position. Available engine options provide horsepower ranges from 280 to 470 and torque up to 1,650 foot-pounds.
Manual, automated, and automatic transmissions are available, as well as numerous heavy-duty axle and suspension options. Available axle configurations are 4x2, 4x4, 6x4 and 6x6, and factory-installed liftable pusher and tag axles are available. Both rear engine power takeoff (REPTO) and front engine power takeoff (FEPTO) are also available. In addition, Peterbilt offers individual frame layout and drilling, combined with one-inch increment wheelbases.
 |
Photo: Peterbilt |
| Peterbilt’s Model 367 is offered in both set-forward and set-back frontaxle configurations. Engines are available from 280 to 600 horsepower. |
The company’s Model 367 is offered in both set-forward and set-back front-axle configurations. A 123-inch BBC, dual front-axle positions, and tag- and pusher-axle options allow configuration of the Model 367 to comply with state and federal bridge requirements.
Engines are available from 280 to 600 horsepower and with torque from 1,150 to 1,850 foot-pounds. The Model 367 also features manual, automated, and automatic transmissions and numerous heavy-duty axle and suspension options. Axle configurations of 4x2, 4x4, 6x4, and 6x6 are offered, as are factory-installed liftable pusher and tag axles and both REPTO and FEPTO.
The hauler can order the model in a special heavy-haul configuration with a high-capacity cooling system and 1,669-square-inch cooling module. The Heavy Haul can accommodate the highest horsepower engines that Peterbilt offers.
Trailers
Eager Beaver Trailers—The company advises haulers specifying trailers to pay close attention to the equipment that is typically transported, the trailer’s loaded height, the ease of loading, the ease of attaching and detaching the neck, and the available features.
Of primary importance are the weight and height of the equipment that will be hauled and terminology relating to these measurements. The company points out that a trailer’s capacity is its rated payload, whereas the gross vehicle weight rating (GVWR) is the payload plus the trailer weight. State load and bridge law limits may effectively reduce the amount of payload a trailer can carry. It is important to understand the state laws where a trailer will be operated, including the state’s axle-spacing requirements. Sometimes a simple increase in distance between axles permits a trailer to haul its rated capacity.
Eager Beaver Trailers notes that whether the trailer is a tag, a rigid-neck single drop, or a detachable-neck double drop, the loaded deck height is a critical factor. As a rule of thumb, the overall height of equipment when loaded on a trailer should not exceed 13 feet, 6 inches. Therefore, a lower loaded deck height results in a higher equipment height that can be hauled. The company’s use of pierced-main-beam construction, low-profile tires, and underslung suspensions is intended to provide the lowest loaded deck height possible.
 |
Photo: Eager Beaver |
| Eager Beaver Trailers notes that whether the trailer is a tag, a rigid-neck single drop, or a detachable-neck double drop, the loaded deck height is a critical factor. |
Ease of loading and unloading is also crucial, especially if only the driver is available to handle this task. For tag trailers that can carry equipment weighing up to 50,000 pounds, ramp weight is always an issue. Eager Beaver Trailers builds ramps with T1 steel for strength and light weight, and the ramps include springs to help lift them both off the ground and off the beavertail. Because many companies and government entities are concerned with potential workers’ compensation injury claims, many haulers have opted for electric-hydraulic ramps as a solution. Eager Beaver Trailers’ use of hydraulics allows these ramps to be 3 feet wide and 8 feet long, permitting easy loading and unloading of equipment with varying track widths. Additionally, hydraulic ramps store in a vertical position without the encumbrance of bars or chains, thus freeing up 6 feet of beavertail for loading additional equipment onto the trailer.
The company also notes that for detachable-neck lowboy trailers, the ease and speed of detaching and reattaching the neck are critical, especially on rough-terrain or ungraded construction sites. Eager Beaver’s self-aligning gooseneck-to-bed trough is designed to allow easy hookup on non-level ground and in adverse conditions. Additionally, a multi-position gooseneck design allows a neck height to be quickly reconfigured to match the height of the tractor’s fifth wheel.
Several standard features designed to reduce maintenance costs and downtime are available on the company’s trailers. These include antilock brakes on air-brake trailers; modulated, spring-brake–equipped wheels; a 100% sealed wiring harness and long-life LED lights; hub-piloted wheels that eliminate wheel wobble and extend tire life; and outboard drums designed to allow quick brake changes and reduce labor costs.
Murray Trailers—The company reports that disc brakes (on about 65% of the eight- and 16-tire trailers it sells) and light weight are two major distinguishing characteristics.
Murray Trailers recently conducted a road test to demonstrate the integrity of disc brakes and determined that this type of braking system is actually superior to S-Cam brakes. The test involved the use of full brake power on a trailer going down a fairly steep road grade. The S-Cam traveled about 1.4 miles before the brakes burned out, and the disc brakes were effective for about 2.2 miles—roughly an improvement of one-third. Additionally, the company claims that its disc brakes can be changed in about 30 minutes.
Murray Trailers also has two engineers on staff to ensure that its units achieve the lightest weight in the industry. It guarantees equipment loading via simply driving it up the back of the trailer without the assistance of ramps, but the company points out that structural integrity is not sacrificed. This capability is particularly useful when the contractor is working on a muddy site and otherwise would have to go out to a curb to disconnect the gooseneck to allow loading. The company claims the design of the trailers allows them to be loaded and tied down in 15 minutes or less.
Murray Trailers offers several different trailer models. The four-axle, 16-tire, 47-ton Professional is reportedly the lightest yet strongest trailer available for heavy hauling. A three-point suspension transfers weight to each side of trailer for an actual total of six transfer points, in contrast to the industry-standard walking-beam suspension. Because the gooseneck is designed without a floor, an earthmover’s scraper fits right inside the gooseneck. The model is also configured for low maintenance with only a few grease spots and a UHMW (polymer) ball-and-cuff suspension design said to last about two and a half times as long as a metal-on-metal design.
Designed to haul up to 76 tons with a two-axle jeep and 71 tons with a four-axle jeep, the Ambassador has a 16-tire group on the jeep and two eight-tire groups on the trailer. The tail is designed with a well that allows the contractor to fit an excavator boom in it.
The 32-ton-rated Easy Load has an outer deck height equal to that of the Ambassador at a nominal 24 inches. A height of 32 inches over the rear prevents a high center for equipment in most cases. Rear loading ramps store in a rear pocket, or optional air ramps fold up 90 degrees. The air-ride suspension includes a suspension dump valve and a scaling gauge; strain gauges or air-pressure gauges are also available. Optional slide-out outriggers with rectangular tubing can be set at every foot up to 12 feet.
The 32-ton double-drop Easy Tail uses an air-operated tail, eliminating the need for a motor or wet kit that would be required for hydraulic operation. The single-piece tail folds in two sections, meaning the driver does not have to pull out heavy ramps—a particular advantage for older drivers.
The low-profile, 46-ton, three-axle Interstate features an air-ride suspension and all high-tensile-steel construction. The base trailer weight is only 15,500 pounds.
 |
Photo: Towmaster |
| The Titanium series of trailers from Towmaster Trailers features modular-frame construction that allows any Titanium gooseneck to attach to any Titanium deck. |
The Loadmaster, a 16-tire trailer, has a 60-ton capacity when using a 16-tire jeep. This 16-16 configuration has a base weight of only 27,200 pounds. Its patented expandable running gear is 8 feet, 6 inches to 10 feet wide.
The nine-axle M2000 can accommodate 179,000 pounds of payload with a 28-foot deck. The company can lower the trailer profile about 6 inches, allowing a profile of 15 feet, 7 inches at the front of the gooseneck, compared with an industry standard of 16 feet, 6 inches to 16 feet, 10 inches.
The nine-axle Magnum has an 87.5-ton rated capacity. Patented True-Track self-steering is available. This steering system, which was developed more than 25 years ago, is said to turn the trailer wheels within about 3 inches of the jeep’s turn, allowing high maneuverability in tight sites.
Towmaster Trailers—The company manufactures heavy-duty trailers for hauling construction equipment, including grading and excavation equipment. A dealership network across the United States and Canada sells and services the Towmaster and Contrail trailer brands. The company says it has always built trailers a little heavier duty to last longer and backs them with a warranty.
The Titanium series trailers feature modular-frame construction that allows any Titanium gooseneck to attach to any Titanium deck. This detachable-gooseneck-trailer series is designed with features to make loading or unloading quick and easy. The entire trailer is pre-painted before assembly and decking.
The T-100DTG model is rated at 100,000 pounds, and the base weight is only 18,300 pounds. The fully loaded deck height is 24 feet, and air suspension is standard.