The John Deere 764 High Speed Dozer redefines a finish grader, with a long, stable platform driven by rubber tracks.
Quickly achieving tight tolerances is the objective of any earthmoving contractor. To accomplish this goal, you need equipment that gives you a competitive edge, and many manufacturers have stepped up to the plate with their current finish dozer designs.
"A machine design that allows for good visibility and control will make it easier to manage applications such as spreading expensive topsoil - saving owner and operator time and money," says Paul Wade, brand marketing manager, New Holland. "A sound combination of length of track on the ground, track gauge, track shoe width and operator comfort are key features of all small dozers, but are particularly significant when it comes to selecting finish dozers. A good balance between ease to maintain the grade and maneuverability is crucial."
Mike Murphy, New Holland's global product marketing manager - dozers, adds, "The relationship between tracks and blade base will determine visibility and controllability. The blade needs to be far enough out from the machine so the operator can see behind it. At the same time, the distance to the blade can't be too long, since it will have a negative impact on the machine's controllability."
Often, the application is what constitutes a finish dozer. "The size of a finish dozer can vary greatly across different applications, ranging from backfilling along a finished curb line to spreading stone to grade on a large commercial development," says Scott Bayless, product consultant - High Speed Dozer, John Deere Construction & Forestry. "Generally speaking, across all sizes of a finish dozer, you want a relatively long track frame to provide a stable platform from which the operator can work. Typically, this longer undercarriage is found on a Long Track (LT), Extra Long Track (XLT) or Low Ground Pressure (LGP) machine."
Yet, it's really a combination of balance and blade control that defines a finish machine. "Machine balance and blade response are what really allow an operator to perform fine grading," says Joel Fritts, building construction products - market professional, Caterpillar. "The customer/operator wants 'motor grader on track' performance."
Primary factors to ensure a smooth finish while working on grade are a dozer's responsiveness to the operator when steering, and the ease with which the operator is able to control the blade, says Murphy. "The ability to control all functions of the blade with one hand comfortably is crucial to ensure the highest level of accuracy," he adds.
"You need responsive, intuitive and predictable controls," Fritts agrees. "The operator has to feel comfortable that, when he moves the control handle, the blade movement is predictable and consistent."
Caterpillar D3K through D6K dozers provide a thumb wheel mounted on the control handle, so the operator's thumbs can actuate the blade angle with low effort. "Other machines require twisting the control with wrist action, resulting in operator fatigue at the end of the day," says Fritts. In addition, a blade shake button allows the operator to remove material from the blade at the end of the doze cycle.
The controls are mounted to the seat above the seat suspension, Fritts continues. "This allows the operator to be isolated from ground-induced vibration, reducing operator fatigue," he points out.
Six-way blades are popular on finish dozers. "Generally speaking, all six-way blades perform the same function, with specs varying slightly by the amount of angle, tilt and pitch," says Bayless. However, a design difference that is often overlooked is blade pitch. "Most makers of dozers with six-way blades have some way to adjust blade pitch, but some manufacturers make it much easier to adjust."
"A good six-way blade needs to provide power in all dimensions," Murphy notes, "in particular when it comes to angle blade forces. It also needs to offer adjustable pitch capability and a good curvature of the blade to allow material to roll. Last but not least, the blade design, along with other machine design elements, needs to account for good visibility to both sides of the cutting edge."
There has been a fundamental shift in finish dozers toward hydrostatic transmissions.
"While old-style machines only provide three-speed transmissions, hydrostatic drives allow the operator to set the exact ground speed needed for the specific application, and thus complete the job more accurately," says Murphy. Hydrostatic drive is not required, but it offers benefits such as power turn capability - the ability to turn the machine in an arc without dropping the load on the blade.
According to Fritts, "Hydrostatic drive allows the operator ultimate control of the machine, from ground speed to exceptional steering maneuverability with power turn. Maintaining constant ground speed is key to fine grading."
There are many contractors still using dozers with conventional transmissions for this type of work. "With that being said, the operator simply doesn't have the overall machine control without a hydrostatic transmission," Bayless comments. "There are too many parameters that can be adjusted for the operator and job conditions with a hydrostatic drive to boost productivity. These simply can't be done with a powershift-style transmission."
Hydrostatic drive also has an advantage when using an automatic grade control system. "Grade control systems are calibrated to each machine with the engine throttle set at high idle. Because of this, the grade control system will deliver its best performance at that same engine speed," Bayless explains. "John Deere hydrostatic machines have the ability to run the engine at high idle while using the decelerator pedal to only control ground speed. This simply isn't possible with a powershift transmission found on some finish dozers."
Although most smaller dozers are hydrostatically controlled, Bayless believes controllability goes much deeper than just having hydrostatic drive. "Because each operator is individual in the way they operate, having the ability to fine tune the machine to their style [is beneficial]," he says. "Adjustable parameters such as steering rate, steering modulation, decelerator response, shift rate, transmission aggressiveness and blade response are all areas that will determine how effective a dozer is in the hands of an operator."
It is difficult to achieve a finish grade if you can't see the blade. "A key area that is important for an operator on a small dozer is the corner of the blade," says Fritts. "This is the area the operator looks to determine what blade control adjustment is needed. Also, the bottom of the blade cutting edge is key. This is important when grading up to concrete surfaces, etc."
Many manufacturers, such as New Holland, have redesigned the engine hoods and cab and ROPS structures to enhance visibility. "The sloped, tapered engine hood and the narrow, slanted nose provide excellent visibility to the cutting edge," asserts Wade. "In addition, cab and ROPS models feature seat adjustment capabilities that can accommodate different types of operators to further enhance visibility."
The John Deere 764 HSD offers a unique view for the operator. "The cab of the 764 has been located at the very front of the machine to position the operator right over the blade," says Bayless. "This allows the operator to see not only the back of the blade, but also the ends of the blade and everything in front of the blade. This is especially important when placing finish material in and around existing infrastructure."
The 360° visibility around the machine is also an important consideration. "These machines are typically working around an entire grade crew with laborers on the ground," Bayless points out.
Track on the ground
"The biggest asset to a good finish dozer is the overall machine balance and its ability to hold a steady grade," says Bayless.
Admittedly, John Deere's 764 HSD is a "bit of a departure" from a traditional finish dozer. However, Bayless cites several features that allow it to excel over a traditional steel track machine.
"Because it is slightly over 22 ft. long with four individual track frames, each on its own pivot shaft, it does not exhibit the same fore/aft pitching motion similar to that of a steel track machine," he explains. "The long length provides a stable grading platform, while the rubber tracks remove virtually any blade hop that a steel track machine may exhibit on compacted material."
It is also easier on finished surfaces. "The rubber undercarriage and articulated steering aid with newly graded surfaces, because the machine does not leave grouser marks or ridges when turning that must be taken out later," says Bayless. "The articulated steering also allows the machine to carry and place material much easier than a traditional steel tracked machine."
But the advantages of this undercarriage in finish grade applications come with drawbacks in other tasks. "In order to maximize rubber undercarriage life, the High Speed Dozer should avoid working in large angular rocks or land clearing tasks that include heavy tree stump removals," says Bayless.
With more conventional finish dozers, track selection is the key to stability. "Both Caterpillar XL and LGP dozers provide the same fore/aft stability, with the LGP providing more flotation in soft underfoot and better side to side stability," Fritts notes. "Either tractor will provide good fine grading. The LGP undercarriage is best suited for working in soft material conditions."
Murphy adds, "The longer the tracks, the easier it is to maintain grade, yet the harder it becomes to maneuver the machine, particularly when turning. The LGP track configuration often provides the best grading track. However, it makes it more difficult to turn the machine.
"In soft, swampy terrain, LGP is used almost exclusively, as it provides better flotation," he continues. "However, in areas with rocky ground conditions, LGP is not a good choice; the wide shoes make it more likely for the chains to get twisted and the tracks to be damaged. It is, therefore, more important to have enough flexibility to choose the best track configuration for the specific application and soil conditions. Flexibility in terms of varying gauges, track widths and length of track on the ground is crucial."
"Customers are keenly aware of how grade control can improve their profitability through improved machine productivity, less material cost and less surveying time, resulting in faster job completion," comments Joel Fritts, Caterpillar. "Our job is to make that feature as easy as possible for customers to get and use on our machines. The Cat AccuGrade concept was integrated into the machine design from the very beginning."
In fact, a display is integrated into the dash of smaller Caterpillar dozers. And machines can be ordered from the factory with all necessary wiring required to run the AccuGrade Control System. "Whether the customer needs laser or GPS technology, it?s as simple as plug and play," says Fritts.
John Deere also emphasizes compatibility with grade control systems. "Because the use of automatic grade control systems is becoming more prevalent in the marketplace, it's important to understand how a finish dozer is set up to easily accept the customer's choice of control system," says Scott Bayless. "For example, with Deere's Integrated Grade Control (IGC) option, the machine is delivered from the factory with all of the necessary connections to plug and play the customer's choice of grade control system.
The IGC system is available on John Deere's entire line of finish dozers. "The 764 HSD actually includes the hydraulic portion of the IGC kit as standard equipment included in the base price of the machine," Bayless points out.