Transmissions and Connectivity Boost Off Highway Productivity
April’s Bauma construction machinery show in Munich, Germany, highlighted not only the latest – and largest – off-highway vehicles from the world’s leading manufacturers and component suppliers, but also important developments in hybridization, electrification, electronics and networking. These innovations promise major improvements in productivity, efficiency and environmental compatibility.
Common themes running through the presentations were the introduction of connected technologies to improve material handling cost per ton ratios by automating repeated processes, boosting accuracy to require fewer cycles, and lowering fuel use through more intelligent operation of drivetrains and hybrid systems. In addition to hybridization, innovations were on hand to further improve the efficiency of non-electrified drivelines through closer matching of engines and transmissions to the duty cycles of construction equipment and, in particular, the demands of the latest Tier 4 Final and Euro Stage IV emissions requirements.
In February, the National Farm Machinery Show in Louisville, Kentucky already saw the reveal of McCormick’s X7 VT-Drive series of tractors, featuring a continuously variable transmission system from German supplier ZF. The new models, says McCormick, combine the efficiency and reliability of a mechanical gearbox with the infinite speed range of a hydrostatic drive system.
The result is a tractor that can achieve any ground speed, from creeper to maximum transport speed (up to 50 km/h), to match the needs of nearly any job around the farm. “The true benefits of a CVT are found in its versatility,” adds McCormick. “The engine and transmission work together to find the right engine rpm and travel speed for the job at hand: high rpm with low ground speed for draft and specialty applications, or high ground speed with low engine rpm for efficient transport applications.”
McCormick’s application is based around ZF’s Terramatic generation of transmissions; at Bauma, the German supplier launched a new, enhanced series, the cPower CVT. The cPower transmission goes one step further than the familiar hydrostatic powersplit transmissions by ensuring that only a very small proportion of the machine’s duty cycle needs to be accomplished on hydrostatic power. The overwhelming percentage of the machine’s output is delivered through the more efficient mechanical torque path.
“Continuously variable transmissions clearly demonstrate their benefits in all ranges of the typical off-highway machinery operating cycle, such as during bucket-filling, transporting or loading,” says ZF. “In this process, the percentage of hydrostatic power is kept low, whereby an optimal degree of efficiency can be achieved.”
Right from launch, the greater part of output already comes from the mechanical part of the transmission, notes the company, and even in very short loading cycles the utility of the CVT technology becomes noticeable in reduced fuel consumption. The cPower system also enables a reduction in the diesel engine’s rpm and looks ahead to future exhaust legislation steps when constant-rpm running may be required to further reduce emissions.
Among ZF’s claims for the cPower CVT are continuously variable drive over the whole range, as well as hydrostatic-mechanical power splitting across all driving ranges, including the “frequently used range” up to 10 km/h. It also decouples engine speed from driving speed, and reduces fuel consumption by up to a quarter.
The ZF hybrid system, suitable for all ZF transmissions, offers further consumption and emissions reductions; an even more radical program, under development by Oerlikon Fairfield, claims still greater benefits. Hybrid Drive, already being evaluated by a leading construction equipment manufacturer, is a series hybrid system which does away with the entire mechanical drivetrain of torque converter, gearbox, propeller shafts, differentials, driveshafts and hub gears. There is no direct mechanical connection between the engine and the wheels; instead, an engine-mounted generator set provides electrical power to e-motors in the wheels and in the various implements and sub-systems.
An ultracapacitor-based energy storage system allows optimal engine efficiency through constant speed operation, enabling Oerlikon to claim that Hybrid Drive offers an improvement in fuel economy of up to 30 percent as well as increased overall driveline durability. The regenerative braking also contributes to longer operating life by reducing heat load on the wheel ends.
Volvo pioneered the concept of the articulated hauler in 1966 with its DR631. This simple 10-ton machine was essentially a Volvo BM350 agricultural tractor with its front axle removed, permanently joined to a trailer via an articulating hitch; it was soon nicknamed Gravel Charlie.
To celebrate the 50th anniversary of this groundbreaking innovation, Volvo chose Bauma 2016 to launch the latest – and largest – chapter in its catalog of ever more sophisticated articulated haulers. The A60H, with a payload of 55 tons, is by far the largest hauler on the market and represents a 40 percent increase in capacity over its predecessor.
With its automatic transmission, fully automated operation of diff-locks on all six wheels, hydromechanical steering and active suspension all around, the A60H is claimed to be a viable and more versatile alternative to rigid dump trucks — more maneuverable, better on steep slopes and in confined sites, and causing less damage to the jobsite. An onboard weighing system is just one of several innovations that boost productivity, leading Volvo to claim a significant lowering of the cost-per-ton ratio.
The A60H has a 16-liter engine giving 512 hp and 495 Nm torque, and has a dump support system, Hill Assist and load and dump brake to boost productivity and safety. The giant hauler is just one of a clutch of new Volvo models, including the 90-ton EC950E crawler excavator, its smaller 75-ton EC750E companion, and the new compact P4820D ABG paver, designed for inner-city work as well as larger projects.
Further innovations presented at Bauma include Caterpillar’s 730C2 articulated dump truck and 323F excavator with automated boom and bucket movements, as well as the mighty 6015B hydraulic mining shovel, 140 tons in weight and capable of scooping up more than 8 cubic meters in each grab of its standard bucket. The 6015B is often paired with Caterpillar’s giant 775-777 series of rigid super dump trucks, boasting over 1,000 hp and a payload of 100 tons.