Things that creep and crawl in the dirt

October 2000

Dozers Article December 28, 2000
Printer-friendly version





When Case Corp


When Case Corp. wanted to design a new series of dozers, the company gathered a cross-section of its customers, as well as users of competitors’ equipment, last summer at the Case proving grounds in Burlington, Iowa. Case, based in Racine, Wis., has turned a couple hundred acres of the rolling hills of Iowa into a testing area where customers and prospective customers can try on Case equipment and see how it fits for doing various tasks, such as backfilling a trench, cutting a V-ditch, doing slope work or slot dozing.


The customers participated in classroom discussions and hands-on operation of prototype dozers, rated the dozers’ various quantitative and qualitative features and ranked those features by importance. Case personnel were available to answer questions and listen to comments and suggestions.


"We try and draw representative samples from those various applications proportional to what we know the current machines are being sold in," Rusty Schaefer, Case marketing manager, told ROADS & BRIDGES. "So we get a weighted score according to the market for the input."


The result of summer 1999’s customer input was the Case H Series of dozers—five machines ranging from 67 hp to 119 hp—whose features include a redesigned transmission and Case’s exclusive PowerTurn system. PowerTurn provides full power to either track during a power turn. "What that allows us to do is, say, perform better in heavier duty applications," said Schaefer, "whether you’re doing heavy slope work or tree removal. At the same time, we’ve put modulation into the system, so that it can be very smooth for fine grading and landscaping applications."


Some of the modifications are less weighty. Customers liked the new flip-up access to the engine dipstick and fill points on the prototypes, but they suggested lengthening the fluid ports to make them easier to fill.


Another modification that came out of the customer evaluations is a narrower dashboard. "On the previous design, the dash was wider," said Schaefer. But customers said they wanted a better view of the blade, so Case made the dashboard narrower and sloped the hood. "That allowed better visibility down to the corner of the cutting edge and even behind the blade without the operator’s leaning."


And the dashboard is only one comfort enhancement. "We’re putting more comfort and ease of operations into the machines," added Schaefer, "whether it’s quieter cabs or lower lever efforts."


It is possible to be too comfortable, though. "Taking all effort away is not good, because the operator needs a certain amount of feel, so combining low efforts with feathering ability and control location is critical. We rely on a lot of customer input to decide whether we’re on the money or not."


A high-backed seat provides additional back and neck support for the operator. An optional ROPS-located heater provides more comfort in cold weather. Fingertip controls provide easy, precise control.


Engine emissions are another area of improvement. Emissions requirements continue to get more stringent, and Case must keep up. The H Series is equipped with a new component Schaefer called a waste-gate turbocharger, which allows more even emissions whether the engine is running at full throttle or partial throttle. "What it does basically is it has a valve to relieve or limit the maximum turbo boost pressure in the system," he explained, "which makes for more even combustion throughout the operating range of the engine."


Schaefer was optimistic about the market for the newly designed H Series dozers, especially in road and bridge construction markets. "We are seeing a shift with the highway programs to a little bit stronger activity in roads and bridges than what we had in the past. It’s part of the project to upgrade our roads and bridges."


All H Series dozers are available in long-track, wide-track, and low-ground-pressure configurations. They can be equipped with Case Lubricated Track or Case Extended Life Tracks to increase track life and overall machine performance in abrasive conditions.


High-tech giant


A major emphasis in dozers, or track-type tractors, from Caterpillar Inc., Peoria, Ill., is sophisticated electronic controls. The D11R Carrydozer, for instance, features low-effort fingertip controls and semi-automated blade functions, such as auto-carry and auto-dump, which increase machine productivity by reducing the burden on the operator.


The D11R also is equipped with an electronically controlled, 850-hp engine; AutoShift, which automatically shifts the transmission from first forward to second reverse and vice versa when the operator makes a directional change; Automatic Blade Assist, which automates some of the more common blade functions; electro-hydraulic dozer and ripper controls; and the Caterpillar Vital Information Display System, an advanced diagnostic and equipment management tool that provides feedback to the operator, detects abnormal machine health conditions and simplifies troubleshooting.


With an operating weight of 246,500 lb and a blade capacity of 57 cu yd (with a carrying capacity of 6 cu yd), the D11R is a large machine. The somewhat smaller 26,000-lb D5M and 35,000-lb D6M track-type tractors (rated at 110 hp and 140 hp, respectively) also offer state-of-the-art improvements, including rapid engine response, electronic power train control, an advanced load-sensing hydraulic system and new variable-pitch power angle tilt blades.


An extended-length undercarriage option provides optimum track on the ground for finish grading. A low-ground-pressure undercarriage provides better stability and flotation in swampy conditions.


The planetary power shift transmission has three forward and three reverse speeds. The design delivers fast, smooth speed changes while distributing loads over multiple gears for long life.


The instrument panel is available with the optional Caterpillar Monitoring System, which includes a scroll-through digital display for gear selection, engine speed, hour meter, diagnostic codes and other vital information, such as coolant, transmission and hydraulic oil temperatures and fuel level.


New and improved (now with less mud)


John Deere Construction Equipment Co., Moline, Ill., added to its crawler dozer line with the C Series II, available this year. More than 250 major improvements have been made to the C Series dozers since their introduction in 1995, according to the company, the most significant of which is the pinned front crossbar that eliminates the track frame diagonal braces and greatly reduces trapped mud and dirt from the undercarriage area. The pinned crossbar also contributes to more precise control of the blade for easier grading.


For the first time in the C Series, Deere has combined the ground speed, steering and direction controls in a single lever at the left hand of the operator. The operator also can select a reverse speed ratio expressed as a percentage of forward travel speed. This feature allows the operator to select the most efficient reverse speed.


Controls for the C Series II transmission and steering are intuitive and easy to operate, according to the company. The response rate for changes in steering, direction, ground speed and deceleration allows smooth and precise control.


The 850 C Series II (185 hp) is available with an optional power angle tilt six-way blade on standard long-track, wide-track and low-ground-pressure models and provides improved visibility, strength and balance for improved grading and durability. The 750C (140 hp) will continue to have a factory six-way blade available on both the standard and low-ground-pressure models.


The C Series II dozers sport turbocharged diesel engines that meet all applicable U.S. Environmental Protection Agency, California Air Resources Board and proposed European Economic Community emissions standards for off-road diesel engines. The dozers also feature quiet, dual-path hydrostatic transmissions.


Deere’s H Series includes the new 550H (80 and 84 hp) and 650H (90 hp), offered in long-track and low-ground-pressure configurations. These crawler dozers have an optimized center of gravity, according to the company, which gives them greater balance and stability.


The four-cylinder, wet-sleeve diesel engines of the H Series are connected to a drive train featuring a dual-path hydrostatic transmission that provides full power in turns, unlimited counter-rotation, automatic load sensing and infinite speed control.


A single lever controls forward/reverse travel and steering. A separate lever controls travel speed. By setting the maximum desired speed, the load-sensing feature will "shift" automatically. As loads change, the drive train powers up or down to maintain peak engine revolutions and efficiency without stalling.


With no preset gears, an infinitely variable range from 0 to 5 mph allows the operator complete flexibility to choose the best speed for the job.


Blade movements are controlled with a T-bar at the operator’s right hand. Generous hydraulic flow and precise metering deliver a natural feel, according to the company. Blade pitch can be set at 52°, 56° or 60° to adjust to the terrain. Blades are available in three choices from 105 in. to 128 in.


Turbocharged dozing


The dozer lineup from Komatsu America International Co., Vernon Hills, Ill., includes the D155AX-5. The 86,420-lb, 310-hp turbocharged dozer features a hydrostatic steering system, which enables the dozer to maintain power on both tracks, regardless of whether it is moving straight or turning. When the dozer turns, a hydraulic motor drives the outside track faster and the inside track slower for smoother turns. This feature keeps more material on the blade during turns.


The D155AX-5 is ideally suited for construction, highway, forestry, landfill, small to mid-sized quarry and woodchip and coalpile applications, according to the company. Its power transmitting system uses a three-element, single-phase, single-stage torque converter, which provides three forward and three reverse speeds.


The D155AX-5 is available with two blade options: a 11.4-cu-yd semi-U tilt blade and a 15.3-cu-yd U tilt blade.


Komatsu dozers also are equipped with a Resilient Equalized Undercarriage, which uses an X-bogie design that helps the dozer hug the terrain for better contact and maximum drawbar pull. On soft or level ground, the X-bogies perform like a hard-bottom undercarriage to help keep the track flat on the ground for better traction. On uneven or rocky surfaces, they flex to absorb shock and maximize traction. A rubber shock absorber is mounted on the X-bogie, decreasing vibration and shock.


Steering and blade control systems on the D155AX-5 incorporate a proportional pressure control (PPC) system, which provides precise and responsive hydraulic control by applying engine power to the tracks and blade in direct proportion to control lever movement. All steering movements are controlled with a single wrist-action lever mounted in the left armrest. If the operator wants the dozer to move forward and to the left, he simply moves the joystick forward and to the left. Lifting and tilting operations of the blade are controlled with a similar wrist-action lever at the operator’s right hand.


To improve operator comfort, the cab rests on oil damping mounts to minimize machine noise and vibration, and instrument displays are large and easy to read.


Komatsu’s D41-6 crawler dozer, with 105 hp, features optimized blade control and engine responsiveness provided by the closed-center load sensing system, which maintains blade speed proportional to the lever stroke to ensure the best control over simultaneous lifting, angling and tilting.


The D41-6 also is equipped with a hydroshift transmission, which converts engine power to tractive effort via a direct-drive, powershift transmission. According to Komatsu, the transmission system also produces more efficient gear shifts and lower fuel consumption.


The D41-6 comes with a standard 3.4-cu-yd blade or with an optional 3.8-cu-yd blade.


Komatsu’s "Plus" Series includes six new dozers, with horsepowers ranging from 70 to 90. According to the company, these crawler dozers have powerful and easy-to-use controls, larger blades, reliable engines and a comfortable operating environment for a variety of applications including construction, forestry and land clearing.


Each Plus Series dozer is equipped with an engine-mounted torque converter that enables the operator to throttle down to a finely tune track speed while still maintaining hydraulic flow to the blade. The torque converter also helps the operator perform complicated tasks with greater ease, because it absorbs shock, multiplies engine torque, reduces engine lugging and provides better control of power.


The Plus Series dozers also incorporate Komatsu’s PPC joystick steering and blade controls. Speed is controlled with foot pedals. With the countershaft transmission, the dozer’s gears are in constant mesh and are selected through the operator’s lift-hand joystick. The hydraulic flow to the clutches is automatically controlled to provide smooth, low-shock shifting.


The new D87E-2 crawler dozer incorporates many of the features of the other Komatsu dozers in a 52,885-lb, 230-hp package. The D87E-2’s two-speed, geared steering module al-lows gradual turns while maintaining full power to both tracks, plus a conventional clutch-brake for pivot turns. The steering system is coupled to a three-speed torqflow transmission and torque converter for six forward and six reverse speeds.


All 12 transmission gears are controlled with a single lever. Steering is controlled with hand levers located to the left of the operator. The blade and ripper are fully pilot operated.


An "L" of a dozer


The new DD80(L) dozer, from Daewoo Heavy Industries Corp., Suwanee, Ga., incorporates many features designed to improve its performance. The 90-hp dozer weighs in at 17,000 lb in a package 13 ft 8 in. long and 8 ft 10 in. wide including the blade.


To ensure efficient performance and smooth operation, an electronic control system adjusts the variable-displacement hydraulic pump and motors that drive the DD80(L) to produce the ideal speed and horsepower output for the working conditions. With a built-in self-diagnosis and data communications system, the micro-controller allows external monitoring of the machine’s performance.


The electronic control system also allows each track to move independently for smooth, effortless and precise steering. The DD80(L) can rotate in a full circle within its own length.


To protect the hydraulic system, a cartridge filter is mounted directly on the hydraulic pump and filters oil being discharged from the charge pump. Oil discharged from the drain port flows through a cooler, which is connected in parallel with the bypass valve back to the oil tank.


To provide greater durability, Daewoo used computerized stress analysis in the design and manufacture of the dozer to eliminate potential stress points in the frame.


For better performance in dozing and fine grading, the blade has a tilt height of 16.1 in. and a tilt angle of 25°. The blade capacity is 1.95 cu yd.


The operator’s cab is designed for comfort and convenience. Right steering, left steering and braking are controlled with three separate pedals. The travel and blade levers are ergonomically designed for effortless operation. An ROPS canopy is standard equipment; an ROPS cab is optional. A centralized instrument panel in the cab displays status information for engine oil, hydraulic oil, coolant and fuel, as well as electronic control information.


To increase the durability of the track system, Daewoo used sealed and lubricated track links. An internally mounted wet multi-disc brake system and floating seals prevent leakage. The DD80(L) also is equipped with a final reduction gear with each drive motor. The gear transfers power to the sprocket via a two-stage planetary gear reduction system.


Crawling PAT


The Power Angle and Tilt (PAT) blade of the 72-hp H70 crawler dozer from Hyundai Heavy Industries Co. Ltd., Elk Grove Village, Ill., is designed and manufactured for superior efficiency and strength, according to the company. The solid structure and focused hydraulic power of the blade provide maximum work capacity.


The split master link-type sealed and lubricated track chain is designed to enhance reliability and maintenance accessibility. The rollers and idlers are lubricated for life. The sprockets are segmented, allowing for the replacement of the sprocket teeth without removing the tracks.


The centralized dashboard allows the operator to check all major systems at a glance, including engine oil pressure, water temperature, transmission fluid temperature, fuel level and hour meter.


The H70 employs wet-disc steering and braking systems. The operator controls the steering and braking with foot pedals, leaving the operator’s hands free for other tasks.


Equipped with a powershift transmission, the H70 can reach up to 7.3 mph in forward and 7.4 mph in reverse. The driving gear system has an electronic transmission controller and safety lock lever for reliability and safety.


King of a generation


The PR 752 crawler dozer from Liebherr Construction Equipment Co., Newport News, Va., completes the company’s Litronic generation of equipment. The PR 752 is the most muscular of Liebherr’s crawler dozer offerings, sporting a newly developed turbocharged, intercooled Leibherr diesel engine that generates 330 hp.


The running gear of the PR 752 is of modular construction and attached to the support frame by means of forward-mounted pivot shafts and a swinging beam. The running gear assembly is completely maintenance-free. The resilient connecting elements on the pivot shafts and the swinging beam suppress shock loads, thereby reducing stresses on the machine and the operator.


The PR 752 provides peak traction down to 0.7 mph. Its traction capability makes it ideal for applications involving a ripper, according to the company, where it develops ripping forces that "are of a magnitude usually associated with larger machines."


The cab of the PR 752 has been redesigned to allow a more relaxed sitting position and to reduce noise.


Accessories for the PR 752 include a semi-U blade, a U blade and a mechanically pivoted blade


About the author: 
Overlay Init