Doosan Construction Equipment literature makes the point that “while Doosan is a relatively young brand in the North American construction-equipment market, the organization has a heritage in equipment manufacturing that goes back to 1937.” Doosan, in fact, lays claim to being the fifth largest construction-equipment manufacturer in the world, marketing excavators, wheel loaders, and articulated trucks in North America, alongside the Bobcat, Geith, and Doosan Portable Power product lines. The company has become a strong contender and continues to develop products designed to appeal to North America buyers.
One such example is the company’s new DL200-5 wheel loader—the first hydrostatic model in the line. Aaron Kleingartner, sales and marketing development manager, Doosan Construction Equipment, explains that the new 159-horsepower model was designed to fill what the company saw as a market niche for a nimble, 2.5-cubic-yard machine that offers the choice of either Z-bar or parallel-lift (DL200TC-5) linkage and that can efficiently handle powered attachments with its ability to modulate ground speed independent of engine speed.
Recognizing that equipping the DL200-5 with a hydrostatic transmission in lieu of a conventional drivetrain was a significant departure in design for Doosan, Construction Equipment asked for the loan of a new model, which we turned over to the expert operators at Local 649 (International Union of Operating Engineers), Bartonville, Ill., for their opinions about the DL200-5’s design and performance.
Brad Walker and Terry Slater, instructors for Local 649’s apprenticeship program, spent the better part of a sunny, mid-November day with the virtually new (36 hours) DL200-5—loading trucks, working stockpiles, running load-and-carry cycles, and using forks to move concrete pipe. The loader arrived with a standard 2.6-cubic-yard general-purpose bucket, a set of forks, optional hydraulic coupler, and optional ride-control system.
Power and traction
Both Walker and Slater said they had limited experience with hydrostatic loaders, but after an initial round of truck loading with the machine’s engine-mode selector set to “Power Mode” (other choices are “Normal” and “Economy”), both agreed that the DL200-5 had ample power, and they gave the machine high marks for traction.
Kleingartner explained that the machine’s hydrostatic transmission uses a single, high-capacity, hydraulic pump that powers a pair of piston-type hydraulic motors—one low-speed, the other high-speed—that drive into a common gear case mechanically connected to the axles.
“The drive line can be powered by one motor or the other, or both motors can work together if the situation demands,” said Kleingartner. “An electronic control system makes those choices automatically to ensure optimum power to the wheels in all applications.”
In addition, said Kleingartner, the hydrostatic system uses a three-mode traction-management system that allows the operator to match traction to the job site in order to prevent wheel spin. Operators can select “Max” for 100-percent torque transfer to the wheels, “Slip” to reduce torque by 50 percent when working in softer ground conditions, or “Traction Control,” which provides three more choices, ranging from 70 to 90 percent torque transfer.
Both of the Local 649 operators liked the idea of being able to control traction.
“Most of the time you’ll probably run the machine in the max setting,” said Walker, “but it’s a plus to be able to reduce power to the wheels in situations that would otherwise cause wheel spin. I experimented with the various settings and did everything I could to make the wheels slip, but couldn’t do it. The machine seems to keep positive power to the ground in any situation—which is something operators appreciate.”
Slater agreed. “I tried all the traction settings pushing material up the stockpile, and the machine never spun any holes. With the loose underfoot material on the stockpile, you’d expect some wheel slip, but it maintained traction.”
Whatever the machine’s traction setting, the operators could instantly return to “Max” by pushing the kick-down button on the loader lever or on the directional-control lever. Also adding to the tractive ability of the new model in any of its traction settings, said Kleingartner, are standard limited-slip differentials, front and rear.
Although both operators had limited experience with hydrostatic loaders, they adjusted quickly to the Doosan system. “It feels almost like a conventional drive train once you’re under way,” was Walker’s observation. Slater’s initial impression of the system was its smooth acceleration. Both operators commented, however, that one feature they missed when loading trucks was the conventional drive train’s transmission-disconnect pedal.
“I had to get used to the hydrostatic when coming up to the truck,” said Walker. “Initially, I was letting off the throttle too much, and when the dynamic braking took hold, the first few approaches were a bit jerky. You soon learn, though, that it’s just a matter of keeping the power up and applying a little brake to smooth things out.”
The transmission can be controlled from either the loader joystick or the directional control lever left of the steering column. Both operators preferred the lever, “simply because we’ve been using it for 30 years,” said Walker. Slater did mentioned, however, that using separate buttons for F/N/R functions on the joystick, instead of a commonly used rocker switch, does make inadvertent shifts less likely when operating in rough terrain.
Neither operator found the dynamic-braking characteristics of the hydrostatic system objectionable, saying that braking was smooth and applied gradually enough to avoid harsh stops.
“This feature [dynamic braking] would be a benefit when working on slopes,” said Slater. “You don’t have to be concerned so much about using the foot brakes.” (The DL200-5 does have two brake pedals for the convenience of operators accustomed to that arrangement in conventional-drive-train machines.)
Both Walker and Slater agreed, also, that being able to control ground speed independent of engine speed was an added benefit for the hydrostatic system, especially when using powered attachments. Kleingartner explained that travel speed can be modulated either via the accelerator pedal or via the machine’s Speed Management system by selecting one of seven pre-set speeds. Both operators tried the lowest Speed Management setting (frequently called a “creep mode” in hydrostatic systems) and found it a useful feature.
“The creep mode is a plus,” said Walker. “I used it when positioning the machine to pick up pipe with the forks. It would be handy in any situation where you wanted to slow everything down, but still have the throttle up.”
From the perspective of one who works with new operators, Slater sees a further advantage. “I liked the speed-management feature—it would be useful when training someone in a congested situation, or when someone might not be comfortable with the machine. You can simply bump things down a little for the novice who’s always in a hurry.”
The implement hydraulic system and front linkage are at the heart of any wheel loader, and the Local 649 operators gave the DL200-5 good marks in this regard.
“I liked the speed of the loader controls, both with the bucket and with the forks,” said Slater. “Sometimes machines of this size tend to be a little slow. I also liked the way the bucket dumps at a steep angle—lets you quickly empty the bucket when you’re loading trucks. It also helps if you’re in a difficult situation and need to push yourself out.”
“The machine seems to have plenty of hydraulic power, and as Terry mentioned, the system is fast,” said Walker. “When you’re approaching the truck, you don’t have to be concerned about slowing down to let the bucket come up.”
The DL200-5 has a closed-center, variable-displacement-pump hydraulic system than can produce flows to 49 gpm and working pressures to 3,190 psi. Hydraulic controls are pilot-operated, and a third (auxiliary) spool and control lever are standard equipment, but piping down the lift arm is optional; a fourth auxiliary also is optional. Standard hydraulic-system features include boom float, adjustable boom kick-out, and adjustable automatic return-to-dig.
Walker asked if the hydraulic system shares oil with the hydrostatic system. It does, explained Kleingartner, but the gear case has its own reservoir. Slater questioned whether the common reservoir for the hydrostatic and hydraulic systems might a potential service problem: “If the reservoir is low, where do you look for leaks?”
Walker thought the bucket loaded well, but did comment (saying it was a minor item) that the “bucket-flat” indicator was a bit small, especially for novice operators. (The indicator is a flat edge on the top of the bucket that corresponds to cutting-edge position.)
In the important area of stability, the DL200-5 received generally good marks.
“Side-to-side stability was very good when I turned with a full bucket and maneuvered over uneven ground,” said Slater. “On a couple of occasions coming out of the stockpile with a full bucket, though, I thought it was just a bit light in the rear.”
“Overall, the machine is very well-balanced when using either the bucket or forks,” said Walker. “Keep in mind when we say that it was a little light—that we were loading from a pile of wet sand and easily getting three yards of material in the bucket. So, we were pushing the machine’s limits with its two-and-a-half-yard bucket.”
Walker asked if added counterweight was available for the DL200-5. Kleingartner said, no, not with standard Z-bar linkage, but additional counterweight is used when the machine is equipped with its high-lift-boom option. That option adds 18 inches of clearance under the hinge pin.
A couple of final performance items—ride control and the coupler—were well received. “I used ride control with both a loaded bucket and with pipe on the forks, and it’s a definite plus for this machine,” said Walker. “Stability when traveling with a load was not an issue. The coupler? It’s a good system.”
The operators said the Doosan’s cabin was well-appointed, quiet, and comfortable—equipped with an air-suspension seat, automatic climate control, and an LCD monitor with easy-to-read digital gauges. The cabin’s low 72 dB(A) rating, says Doosan, results from a variable-speed cooling fan, double-wall muffler, sound-proofing materials throughout the engine compartment, and a tightly sealed, pressurized cab.
Visibility, both operators agreed, was excellent. “We had a cone down there that was only 18 inches high,” said Walker, “and I was able to keep an eye on it and not run over it. The machine has good-size mirrors that help you see pretty much everything going on around you. Visibility to the forks was typical—I don’t think there’s a loader out there that makes it easy to see the forks.” (A rearview camera is an option.)
Doosan obviously kept serviceability in mind with the DL200-5; service features include centralized, remote hydraulic-diagnostic ports; color-coded and labeled hydraulic hoses and wiring; access to stored alerts though the LCD display in the cab; and an integral diagnostics program that gives dealer technicians access to machine information.
The operators agreed that routine maintenance should be easily done on the DL200-5. Sight glasses are used for most fluid levels, easily accessed grease fittings allow reaching difficult points, and remote drains are used for engine oil and coolant. Slater said he appreciates the remote drains, but questioned their placement—just inside the right rear wheel and perhaps vulnerable to damage.
Taking the long view of the day’s events with the new Doosan loader, the Local 649 operators gave the new hydrostatic model good reviews in the important categories—power (both engine and hydraulic), stability, controllability, and traction. Traction, especially, got good reviews—the result perhaps of the new model’s hydrostatic drive system being coupled with an electronic system that allows the operator to modulate rimpull to control wheel spin.