Still, all-wheel drive is not suited to every situation. "We have looked at the all-wheel drive and maybe someday it would be nice," says Teates. "We would like to have it when we are handling sand or loose gravel, but that also has a price tag."
According to Abernathy, all-hydrostatic AWD means more power and control at the slowest speeds. "You don't find a situation where you want to turn the tandems off to finish the grade," he says. "You can take advantage of all the added traction and tracking that AWD offers, no matter what the operating speed."
Automated grade control technology can also lead to tighter tolerances. "Automatic grade control systems give contractors the ability to control blade action to precise tolerances on jobsites with in-cab controls using laser or GPS technology," says Lee. "These systems can operate without stakes and grade to an accuracy of 20 to 30 mm (0.1 ft.)."
Even the most experienced operators can benefit from automated controls. "The automated system actually cuts a better grade than a well-trained operator on his own," says Autry. But this is not a substitute for a highly skilled operator. "The skilled operator just doesn't have to see grade as well if you are running automatics with GPS. But he still has to understand the fundamentals of what to do with the dirt."
Porter adds, "Automated blade control systems will ensure the tightest accuracies for finish grade applications, but can only control the blade as quickly and accurately as the hydraulic system is capable of responding."
In the case of Caterpillar M Series graders, a time-proven load-sensing system has been combined with proportional priority pressure-compensating (PPPC) electrohydraulic valves. "PPPC valves have different flow rates for the head and rod ends of the cylinder," Porter notes. "This ensures consistent extension and retraction speeds for each cylinder, and gives the operator consistent and predictable response every time an implement control is moved."
Load-sensing hydraulics can be a real advantage by reducing heat and power demands. "Load-sensing hydraulic systems are almost a given on the modern motor grader - it is the design of the systems that is key," says Lowe.
Side slope work
Having the ability to correctly position the blade is almost a given with motor graders.
"Most, but not all, modern full-size graders in North America can back slope to 90°," says Lowe. As such, blade positioning isn't that important - except you must consider not only the position of the blade, but where the heel of the blade is positioned. "Ensuring that a grader can cut a 2:1 fore-slope without also cutting the traveled portion of the roadway is an important consideration."
The criteria used to evaluate the side slope performance of a grader depends on what you are trying to accomplish. "For cutting side slopes, power and traction will be important," says Lee. "Features such as all-wheel drive, front-wheel assist, articulation for angles and a low profile for stability will increase efficiency."
Porter adds, "If you are talking specifically about side sloping, then the contractor should concentrate on machine weight balance and target a front to rear weight split of 30% to 70%. AWD systems can also help a motor grader hold a slope and achieve better traction, depending upon soil conditions and slope angle.
"Articulation capability will also enable a motor grader to hold a steeper slope and provide better overall machine balance and traction capability," he continues. "Caterpillar motor graders mount the cab on the front frame, in front of the articulation joint, to maintain maximum blade visibility when in an articulated mode."
Bank sloping or ditch cutting performance is closely tied to moldboard positioning. "Heel clearance is another criteria to measure, which will dictate the motor grader's ability to reach up the slope and increase the width of pass, translating into increased productivity," says Porter.
Operator comfort also becomes an issue when cutting side slopes. Lowe asks, "Does the seat offer good lateral support? Can the operator brace himself and still actuate the controls properly, so he is not overly tired by the end of the shift or suffering from muscle strain?"