Typically, articulated dump truck (ADT) drivers are among the last positions filled on a jobsite and they may not be the most experienced employees. The latest advancements make ADTs easier to operate. “We can fill that role efficiently, safely and effectively with a person who may be new to the industry, new to the workforce,” says Scott Thomas, articulated truck application specialist, Caterpillar.
An ADT driver’s job description rarely changes. “Your job is to get loaded and drive from Point A to Point B,” says Thomas. The majority of the workload for the driver occurs at Point B, where the driver has to stop the truck, set the brake, raise the bed to dump the load and then lower the bed and place the truck back in gear. Caterpillar is now incorporating software to simplify operator workload at Point B.
Automated Features Reduce Workload
Automated functions on the Cat 725 require less operator input and accommodate a range of operator experience levels. An assisted automatic hoist places the transmission in neutral, applies the waiting brake and hoists the truck bed to the maximum tipping angle at high rpm, requiring up to 50% less operator input. The system lowers the bed with a controlled descent to prevent “body slams” and increase component life.
Most personal vehicles today have power windows. “This one-touch approach is now being applied to the entire dumping process,” says Thomas.
There is an assist hoist switch next to the joystick. When the switch is on and the operator is stopped or travelling below 2 mph, the dump sequence is automated with one finger. The truck neutralizes the transmission automatically. The gear shift can still be in park, reverse, neutral or drive; it doesn’t matter where it is located.
“Then we apply the service brakes, elevate the engine [speed] and raise the bed. The only thing the operator did was initiate that with their finger, much like raising the power window on your car,” says Thomas. “It’s one of the best received features that we put on these trucks in many years.”
Bell ADTs include a hill-assist feature so the truck doesn’t roll back when stopping on inclines and pulling away again. “This is all automated for the operator [which reduces fatigue], as is the tipping function, I-Tip, where a push of a button places the transmission in neutral, puts the park brake on and lifts the bed, increasing the rpm to speed up the tip function,” says Robin Pett, product manager, Bell Equipment North America. “The operator no longer has to work the service brakes on decline. The retarder system is powerful enough to manage the braking of the vehicle and the intelligent engine software will maintain the downhill acceleration to optimum safe speed.”
Safety is the top focus on any jobsite and manufacturers have addressed roll-over concerns with technology that monitors the attitude of the ADT.
“John Deere ADTs use automation and technology to enhance safety and help customers do more for their employees and bystanders,” says Cory Ouellette, product marketing manager, ADTs, John Deere Construction. “For example, we use sensors on the machine to monitor side-to-side slope percentage in the rear chassis. When a pre-determined slope percentage is exceeded, the machine recognizes this and will prevent the dump body from being raised. This slope percentage can be set based on the demands of the jobsite or operator skill.”
Volvo Construction Equipment incorporates many safety features into its current ADT line. “The two most notable are Hill Assist and a dump support system,” says Rob Palermo, product manager, articulated haulers. “Hill Assist holds the hauler in place on steep slopes without the need to engage the parking brake. The feature automatically activates when arriving at a complete stop on a hill and is disengaged when the operator accelerates.”
The Volvo dump support system allows the operator to see the percentage side inclination of the truck and set allowable parameters for safe dumping operations. “This feature can be configured in three ways: off, on with an alarm, and on with an alarm and a complete bed stop,” says Palermo. The Volvo dump support system compliments the load and dump brake technology. “The tipping lever has an automatic hold in the lower position, which provides precise control for faster cycle times.”
Caterpillar offers Detect with Stability Assist to help prevent machine roll-overs by giving the operator audible and visual alerts when moving and inhibiting hoisting if the machine is at an unsafe angle while dumping. The system uses an inertial movement sensor on the cab and another inertial movement sensor on the bed to monitor the relationship of the cab to the bed.
“It will warn the operator if he is in an unsafe situation,” says Thomas. This is particularly important when traversing side slopes. “If the side slope is greater than 15%, you’re going to get a level two alarm in the cab.” This includes an audible warning and a message on the display screen to change the method of operation. “As long as they change their method of operation, that alarm will go off.”
Cat Stability Assist will determine if a machine is being operated outside of the safe zone to raise the bed, and will limit whether or not the bed will come up. If the system determines it is not safe to lift the bed, the operator will receive an audible alert and a message on the dash.
“This is one of those systems that come standard on all of our trucks,” says Thomas. It simplifies operation while protecting the operator. “The great part about Stability Assist is there’s no operator input required.”
“An area of significant risk for roll-over is at the tipping site where the truck reverses into a pile of dirt and the bin is raised while the rear chassis is at an excessive angle,” says Pett. “To prevent this, all Bell ADTs have an inclinometer on the rear chassis (bin), and displays [angle] as a percentage on the CDU monitor. If the chassis leans over by more than 15%, the operator is alerted and the truck will not allow the bin to be tipped. The 15% is recommended, but this can be changed by the customer, and also be turned off.”
Active Suspension Smooths the Ride
Many manufacturers offer active suspension systems that adapt to payload and ground conditions.
Volvo’s full suspension model, the A45GFS, uses hydraulic cylinders in place of the mechanical connections, putting a hydraulic cylinder connected to computers and actuators at every tire. “Those six sensors monitor the frame movement in relation to the axles and signal the hydraulic system to adjust the suspension, optimizing stability during travel,” Palermo explains.
The A45GFS is designed for heavy hauling in severe off-road applications. “The front suspension is equipped with a set of accumulators and adapts to payload and ground conditions, making the ride smoother for the operator,” says Palermo. “The rear suspension is equipped with two high-pressure accumulators for loaded operations and two low-pressure accumulators for unloaded operations. Cross flow between the hydraulic cylinders stabilizes both trailer and tractor.
“Due to the ability of the full suspension machine to drive faster over challenging terrain, cycle times are reduced by about 20%, on average, compared with a conventional hauler, which means productivity is increased,” he continues. “With faster cycle times, you can reduce your fleet size and move the same amount of material. The full suspension system also improves operator comfort, which maximizes drivability and reduces the level of maintenance required for haul roads on the jobsite.”
A loaded truck handles much differently than an empty truck. “John Deere ADTs come equipped with standard adaptive suspension that is designed to provide the most comfortable ride possible whether the ADT is fully loaded or empty,” says Ouellette. “Designing suspension for any load-carrying vehicle is always a compromise between designing for the empty weight and risking bottoming out when loaded, or designing for the loaded state and having a ‘stiff’ ride when empty. With our adaptive suspension, we keep the struts at the optimal ride height no matter the payload, which means that you get the maximum compressive and rebound strut travel whether loaded or empty.
“The other benefit is it helps eliminate cab lean when turning, which keeps the operator level and more comfortable,” he adds.
Drivetrains Offer Simplified Operation
All manufacturers have concentrated on simplified operation with automatic traction control and improved retarders.
Earlier this year, Volvo updated its G-Series haulers with cruise control, downhill speed control and Optishift. “All three are operated with simple switches and make work easier and more comfortable for operators,” says Palermo.
Optishift facilitates quick, smooth directional changes in both dynamic and stationary conditions. “When moving the gear lever in the opposite direction of travel, the machine automatically slows down in a smooth transition and the accelerator works as a brake pedal instead,” explains Palermo. “If you push the accelerator more, the machine slows down faster for the directional change. The function works in both directions. This feature is especially useful for maneuvering during loading and dumping, resulting in shorter cycle times and less operator effort when changing direction.”
Dynamic drive and dynamic Volvo Engine Brake (VEB) systems are also incorporated on the latest models. “Dynamic drive provides an improved gear shifting strategy that takes into consideration both the payload and the gradient of the slope,” says Palermo. “The machine will automatically detect when to choose a higher starting gear or when to upshift earlier. When conditions require, the machine will prolong the gear, ensuring maximum rimpull.
“With dynamic drive, customers can expect a 3% to 10% fuel efficiency improvement, depending upon the model,” he points out.
With the VEB system, the torque and shift points are dynamically adjusted against the current load, inclination and rolling resistance. This improves brake life by reducing the need to use the brake and retarder pedal when going downhill. The dynamic VEB also leads to increases in maximum torque on all models.
Bell TrucksBell ADTs feature Automatic Traction Control (ATC). The trucks permanently drive through all three axles. But when the full ATC system detects wheel slippage, it automatically engages.
“First, the inter-axle diff lock (IDL) dog clutch in the transfer case is automatically engaged if axle slip is detected. The engine is momentarily de-torqued to give smooth, damage-free application,” Pett explains. “In most applications, the IDL will be sufficient. However, in extreme conditions if further wheel slip is detected, the controlled traction differentials (CTDs) are engaged, giving 6x6 traction.
“It should be noted that the IDL, when engaged, changes the torque split to 50% front/rear axles to use the front axle to pull through mud,” he continues. “This is a fully automated function and operates in split seconds to ensure the truck’s momentum is retained during poor underfoot conditions so there is minimum loss of traction and the vehicle can deliver constant production through almost all terrain.”
Caterpillar uses wheel sensor technology to provide automatic traction control. “It is 100% automatic with no operator intervention,” says Thomas. “There are six sensors on the truck that monitor wheel slip, and they will instantaneously automatically reassign torque to each wheel.” This reduces torque to wheels that are beginning to slip and increases torque to those that have traction.
Caterpillar also offers automatic retarding control standard on the 725, 740 Ejector and 740 GC. It is moving toward automatic retarding control as standard on all of its ADTs, which means taking the lever out of the truck. The ADT understands if it is on a grade and how much payload is onboard. Based on these inputs, it selects the most appropriate gear and uses the most appropriate level of retardation. “The operator only has to take the foot off the accelerator; that will engage the automatic retarding control,” says Thomas.
Available on Deere ADTs, standard automatic downhill-descent control provides security on grade and eliminates the guesswork in shifting and applying service brakes while descending. The operator matches the gear to the grade, backs off the throttle and lets the transmission retarder manage the descent safely, while helping reduce service brake wear, operator fatigue and maintenance costs. In tough traction conditions, the interaxle differential lock transmits 50% of available torque to the forward axle and 50% to the two rear axles, simplifying operation. In addition, it can be engaged on-the-fly while slipping for smoother navigation of tough jobsites.
John Deere’s E-II Series trucks, which launched at CONEXPO-CON/AGG 2020, feature multiple drive modes to help optimize the drivetrain and reduce inputs from the operator. Normal Mode provides the same features available on the existing E Series trucks but with up to 7% fuel burn reduction. Traction Mode engages the differential lock more often while automatically eliminating the need for operator involvement. Beyond the normal automatic slip mitigation system, Traction Mode preemptively engages the interaxle and cross-axle differential locks to help minimize slip initiation. Finally, when conditions or customer operations allow, Eco Mode conserves fuel up to 12% by managing the engine power and power delivery.
One way to reduce operator fatigue is with an automated speed control system. With Bell ADTs, the operator has two options available for speed control when driving downhill laden (loaded).
Automatic Hill Descent Control allows the truck to take the speed at which the operator takes the foot off the accelerator and automatically varies retardation to maintain that speed. “Then there is Operator Selected Speed Limit, where the operator can set two different speed limits on the dash panel and activate one of them at the top speed of the decline. The truck will then maintain that speed,” says Pett. “The truck can be set up to control the speed when driving in specific situations so that the operator cannot exceed that speed, such as when the ADT is laden and on a downhill. A speed limit is applied and retardation is varied to maintain that speed. However, if laden and not on a downhill, the normal speed limit applies.”
ADT manufacturers continue to innovate by automating key functions and adding safety systems to keep novice operators safe on the jobsite. ET