Komatsu's Hydrostatic System Offers Greater Control

Sept. 28, 2010

Komatsu WA200-5
Komatsu has fundamentally changed the design of its WA200-5 wheel loader by using a hydro

Komatsu has fundamentally changed the design of its WA200-5 wheel loader by using a hydrostatic drive system which, in conjunction with a high-torque engine, results in reduced fuel consumption. (CE's test of Komatsu's WA250-5, in the January 2004 issue, found the new model, on average, 31 percent more fuel-efficient than its predecessor.)

Local 150's Jim Minyard commented favorably on the visibility from the WA200-5's cab. Komatsu has added rear-quarter glass panels to enhance over-the-shoulder sight lines, and all glass in the cab is flat to facilitate replacement.

Komatsu's Post, left, and Minyard discuss the WA200-5's design details. The machine's cooling package (radiator, air-to-air cooler and oil cooler, placed side-by-side) is isolated from the engine compartment. The system's swing-out, hydraulically driven fan draws air from side intakes and is credited with a 10-percent gain in cooling efficiency and lower sound levels.

Just aft of the loader-lever wrist support is a panel that houses controls for the WA200-5's Traction Control System and Variable Shift Control, which allow operators to tailor machine performance to the application.

The WA200-5 received good marks from Minyard on its load-and-carry performance. The hydrostatic system's dynamic-braking capability, he said, helped control the machine in turns.

Minyard was impressed by the WA200-5's Traction Control System, which allowed the machine to push through a stockpile with no wheel spin.

Jim Minyard, who for the past five years has been an instructor for Local 150's Apprenticeship and Skill Improvement Program, has worked for several contractors as a member of the International Union of Operating Engineers, including 12 years running cranes and loaders for an international foundation contractor. Today he serves primarily as a trainer and certifier of crane operators, but since he still likes to get on loaders, he seemed a good choice to run Komatsu's new WA200-5 wheel loader for this installment of Hands-On Earthmoving.

Komatsu product manager Bob Post graciously arranged the loan of a virtually new WA200-5 for our evaluation, and it arrived at Local 150's Plainfield, Ill., facility with a 2.6-cubic-yard stockpile bucket, 20.5-R25 tires and optional couterweight. Our Hands-On evaluation began, on an exceptionally cool mid-August day, with a machine walk-around.

Post explained to Minyard that the new loader, announced earlier this year, uses a hydrostatic transmission in lieu of the powershift transmission and torque converter used in its predecessor, the WA200-3. The hydrostatic system, he said, uses a variable-displacement hydraulic pump (driven directly by the engine) to supply fluid to a pair of variable-displacement hydraulic motors. The motors, in turn, drive into a transfer case, from which the WA200-5's conventional axles are powered by drive shafts.

In situations that might cause the WA200-5's wheels to slip, said Post, that is, when too much torque is delivered for the traction available, the operator can activate the machine's Traction Control system. When activated, if the system's computer senses that conditions are conspiring to cause wheel slip, it can reduce output from the pump and motors, thus reducing torque to the wheels.

While Minyard adjusted the seat to his liking in the WA200-5's new cab, Post pointed out the Traction Control switch and the two dials for adjusting the WA200-5's Variable Shift Control system. The upper dial, with four positions, limits the machine's top speed, he said, similar to the ranges in a powershift. The other dial lets you fine tune ground speed within the limits of the "1" speed range on the dial above. Post encouraged Minyard to experiment with the system.

"We tell operators if they dial in their ground speed to match hydraulic speed," said Post, "then they can do V-cycle truck loading without ever lifting the throttle—just touch the brake when approaching the truck. Or, if you are more comfortable coming off the throttle at the truck, then the hydrostatic system's dynamic braking gives a soft stop, usually without braking."

(The WA200-5's brakes respond initially like a proportional transmission disconnect before applying the service brakes.)

Loader turned dozer

While waiting for Local 150's articulated dump truck to arrive, Minyard began digging in a tightly compacted bank and making a sizeable stockpile off to the side. He then pushed through the pile, bucket flat, and moved the material back to the bank.

Curious, we stopped him and asked about this exercise.

"When I worked for the foundation contractor," he said, "the big caisson drills would create spoil piles that had to be pushed away and stockpiled. This was an easy way to do it."

We noted that the WA200-5 muscled though this tough application in good fashion, but Post observed that it exhibited some wheel slip in the process.

"Try the traction control," he told Minyard.

The demonstration was convincing. Minyard pushed into the pile until the wheels began to slip, stopped, switched on the Traction Control system, then continued with all the tires now exhibiting a solid bite.

"I'm impressed," he said, after cleaning up the area. "The tires didn't spin with the system on, and I really didn't notice that the machine had any less power. It picked up the load from a dead stop and walked away with it."

When the truck arrived and Minyard had loaded it several times, we asked what he thought of the WA200-5 as a truck loader.

"It has a lot of pushing power and a lot of breakout power. The only thing I noticed was that the boom seemed a little slow coming up through the bank—at least compared to larger loaders I've run."

Given the WA200-5's high tractive effort, said Post, it's easy to pin the bucket in the pile, which might account for Minyard's observation. He suggested applying just a bit of rollback to break loose the material before raising the boom.

We were also curious about how Minyard had set the machine's speed-control adjustments?

"I had the upper dial in the first position, then tried the lower dial at its quarter, half, three-quarter and full positions. In the full position, I was getting to the truck before the boom was where I wanted it, so I had to dial it back. But I did get to the point where I didn't use the brakes, even though I had to keep reminding myself to stay off them."

Notice any difference between this loader and one with a conventional drive train?

"One thing that stands out is that you don't feel it shift when you switch directions. I also like the rocker switch on the loader lever for making directional shifts. It lets you work faster, and you never have to take your hand off the steering wheel. And I noticed, too, that you don't have to reset the system if you inadvertently use the shift lever on the steering column."

But Minyard was not completely sold on the single-lever, joystick-type loader controller.

"I realize this is a standard feature on many loaders, but I actually prefer two levers, because in my opinion, you have better control when you're doing finish work. But, the single lever is a time saver when you're loading trucks."

Do you have any comments generally about the operator's compartment?

"Nice cab. Plenty of foot room. Good seat, good visibility all around. And I like the push-button operation of the air conditioner—you don't have to look up to adjust a dial. The walk-through design is good—two doors are handy—and I like the positioning of the hydraulic lockout lever."

How about sound levels?

"The cab's very quiet, but you can still hear the engine. That's important, because you can hear if you're in a bind."

But, with good humor, Minyard said he could pick on a few items in the cab. In his opinion, the left armrest should be a bit longer and higher, and he questioned why the wiper switch was positioned on the left side of the steering column's tilting section. Would he bump his knee on it? A couple of test swings of his leg under the lowered steering column seemed to assure him that the switch was safe.

Although he liked the WA200-5's tilting steering column, which articulates at dash level to allow easy entrance and exit without jeopardizing foot room, he did have a concern.

"I'll use the tilt feature every time I leave the cab," he said, "so is the latch durable enough to take that kind of use?"

Post said it was a simple ratchet mechanism that should perform without problem.

Minyard concluded the evaluation with a few load-and-carry runs, which included climbing and descending a fairly steep berm, both with the bucket empty and loaded, and with the ride-control switched on.

"No complaints about power or the ride," he said. "What I really like is the dynamic braking—especially on turns. It didn't slow the machine as much as I anticipated going downhill, but you can lift the throttle in turns and it slows just right. Normally I'd have to use the brakes."

Any last comments?

"If I ran this machine long enough, there might be some things I'd like to change. But, right now, if you gave me this loader, I could easily run it every day—no problem."