Equipment Type

Cat 950K Transformed by New Linkage, Overall Refinement

Optimized Z-bar linkage, power-train changes, and a redesigned cab make this new wheel loader more productive, more efficient, and equally adept at loading or lifting

May 31, 2012

Seldom do we see such fundamental differences in design between a new model and its predecessors as between the new Cat 950K wheel loader and the models it replaces.

The jewel in the crown of the 950K’s design, so to speak, is its loader linkage, which allows the new model to competently replace not only the 950H with its conventional Z-bar linkage, but also the IT62H tool carrier with its eight-bar, parallel-lift linkage. The new patent-pending linkage also has been carefully designed for optimum visibility—to the hook points on the coupler when changing work tools and to the tips of pallet forks.

“The 950K is designed to dig like a conventional Z-bar machine, but also to provide the parallel lift and tilt force of a tool carrier,” says Don Weinhold, product application specialist for Caterpillar’s Global Construction & Infrastructure group. “The design also focuses on visibility when using forks; some machines have good visibility to the tips at ground level, others at truck-bed height—but it’s difficult to get both at the same time. The 950K delivers both—that’s part of the unique character of this linkage design.”

950H vs. 950K Production, Fuel Study

Machine Configuration

  • 950H: Power Package option; Cat Fusion coupler; H-Series bucket rated @ 4.3 cubic yards
  • 950K: Power Package option; Cat Fusion coupler; Performance-Series bucket rated @ 4.3 cubic yards

Test Events

  1. Moderate Truck Loading (MTL)
    + part throttle
    + 30-second cycles
    + 60-minute-hour production; no idle time
    + material: 2-inch limestone; 2,400 lb./yd³ avg. weight
    + material moved per machine: exceeding 700 tons
  2. Batch Plant Load-and-Carry (BPLC)
    + flat load-and-carry segment
    + short ramp at “hopper”
    + 60-minute-hour production; no idle time
    + material: 2-inch limestone; 2,400 lb./yd³ avg. weight
    + material moved per machine: exceeding 300 tons
  3. Sand & Gravel Load-and-Carry (SGLC)
    + load-and-carry segment included 350-ft. climb @ 12% grade
    + 20 mph maximum downhill speed
    + 60-minute-hour production; no idle time
    + material: 2-inch limestone; 2,400 lb./yd³ avg. weight
    + material moved per machine: exceeding 200 tons

Results

  1. Production (Tons/Hour)
    + MTL: 950H & 950K production equal
    + BPLC: 950K exhibited 7% advantage
    + SGLC: 950K exhibited 6% advantage
  2. Fuel-Efficiency (Tons/Gallon)
    + MTL:   950K exhibited 10% advantage
    + BPLC: 950K exhibited 3% advantage
    + SGLC: 950K exhibited 5% advantage

Source: Caterpillar Test Engineering

For a close look at this new model, Construction Equipment editors recently worked with Caterpillar at the company’s Peoria Proving Grounds, where we learned about the 950K’s new features in detail—and where a production/fuel study placed the 950K in a bucket-to-bucket comparison with the 950H, allowing us to put numbers to the new model’s performance.

Our hosts were Weinhold, Wayne Harshberger, performance engineer, and Jason Hagedorn, product application specialist for medium wheel loaders.

Linkage test

With the 950K, 950H and IT62H parked side-by-side and each equipped with a coupler and 72-inch pallet forks, the operators simultaneously placed each machine’s loader control lever in its boom-raise detent and took hands off.

The IT62H’s forks came up dead level from bottom to top, just as its eight-bar linkage is designed to accomplish. But the 950K’s forks did exactly the same, and as the booms moved up, you couldn’t help noting the striking difference between the relative simplicity of the new model’s linkage and the comparative complexity of the IT62H’s linkage. The third machine, the 950H, fared not so well, with forks already tilting forward at truck-bed height and ending at the top in a steep downward angle.

“It’s not that the 950H can’t be manually adjusted to provide level lift,” said Weinhold, “but it’s one more item the operator has to think about.”

Plus, said Harshberger, the 950K, compared with the 950H, has a 20-percent advantage in tilt force at full lift. Tilt force at full lift is critical when carrying heavy loads, he said—a trench box, for example.

After this demonstration, Weinhold invited us into the 950K’s cab and pointed out two control panels (on the right front ROPS post) that have a number of membrane switches. Among the switches are two that set up the loader linkage for bucket or fork use, and when the latter is selected, the 950K automatically provides parallel lift through a combination of mechanical and electro/hydraulic systems.

View down the boom

Weinhold then asked us to select the parallel-lift mode on the 950K, to note visibility to the coupler hook points, and to raise the boom while tracking visibility to the fork tips from ground level to truck-bed height. The 950K, equipped with the Cat Fusion Coupler, as was the 950H, provided a wide-open view to the coupler’s hook points (where the top of the work tool attaches), as well as to the fork tips in both critical positions.

By comparison, the view down the 950H’s boom was obstructed by the cross-tube (the large casting welded between the boom arms), the tilt-position sensor (contained in a large box-like structure on the boom’s right side), and the routing of hydraulic hoses. Seeing the hook points on the 950H required pushing up in the seat to find a less-obstructed viewing path to the coupler, and the fork tips were difficult to keep in view, both on the ground and at truck height.

The IT62H’s hook points were partially obscured by a pair of linkage cylinders and by a large hydraulic hose adjacent to each cylinder. Visibility to the fork tips at ground level was obstructed, and only by trying to look around the clutter could you catch a glimpse. At truck level, however, the open design on the IT coupler allows a good view to the tips, important for not damaging the material being unloaded—and for staying friends with the truck driver.

Compared with the 950H, the 950K’s new loader linkage appears somewhat different in its design details, but still quite recognizable a Z-bar type (the “Z” being formed by the tilt cylinder, bellcrank and bucket link).

For instance, the 950K’s boom arms are configured with less curve at their midpoint; the cross-tube has a flatter oval cross-section and is mounted higher on the arms (toward the cab); and the lift-cylinder rods are pinned higher on the arms and positioned more vertically, with adequate space around the cylinder body to avoid trapping falling debris.

The bellcrank, which pivots on a thick plate that is integral with the cross-tube casting, is now a heavy fabricated member, versus the single-plate casting used on the 950H. (The bellcrank transfers tilt cylinder motion to the bucket link, causing the link to move in a direction opposite that of the cylinder rod to open and close the bucket.) In addition, the tilt-position sensor has been relocated, hydraulic hoses carefully rerouted, and the windshield-cleaning platform lowered—all in the interest of improved visibility. The overall result is dramatically improved visibility to the coupler and work tool.

Power-train refinement

The 950K’s Cat C7.1 ACERT engine meets Tier 4-Interim emissions requirements and has a net-horsepower rating of 211 in the new model’s standard version and 221 in the Power Package version, which uses a larger counterweight for enhanced tip-load ratings. Net-horsepower ratings for the 950H and IT62H were 195 and 209, respectively; both used the Cat C7 engine.

New for the 950K is a high-pressure common-rail fuel system and the Cat Clean Emissions Module, which is mounted on a platform above the engine and houses a diesel oxidation catalyst, diesel particulate filter and the Cat regeneration system. Our observation was that the module is designed with adequate space to accommodate additional emissions-control hardware if required for Tier 4-Final compliance.

(Although the emissions module results in an 8-inch increase in height to the top of the 950K’s hood and diminishes the hood’s rearward slope, the new model maintains good rearward visibility with a standard, wide-angle, rear view camera.)

Farther along the 950K’s drive train, the new model’s planetary power-shift transmission incorporates a larger torque converter for added tractive effort (rimpull), as well as new friction-disc material in the clutch packs. The new friction material allows a significant, beneficial change in the way the transmission operates.

To explain, when the 950H’s transmission makes a range shift—say, downshifting from 4th to 3rd on a ramp—the transmission’s directional (F/R) clutch disengages, momentarily interrupting power flow through the transmission. Only when the range shift is completed does the directional pack re-engage; this sequence is designed to protect the engaging range pack from excessive torque. By comparison, however, the 950K’s transmission, with the new friction material, no longer disengages the directional pack during a range shift, thus minimizing torque interruption—especially advantageous on uphill grades—and yielding smoother range shifts.

The 950K transmission also incorporates a new automatic shifting strategy, which, says Caterpillar, delivers smoother shifts, faster acceleration, and better performance climbing grades. Essentially, the new strategy is aimed at optimizing gear selection in all operating situations for the best performance and fuel economy.

“Key to good fuel efficiency and performance is being in the correct gear,” said Weinhold. “The basic rule of fuel usage is that rpm and fuel-burn rate go hand-in-hand; if rpm goes up, so does fuel burn. When operators shift manually, they tend to wait too long to change gears and end up using more throttle than necessary.”

The 950K, Weinhold told us, is designed for use in its automatic mode, which has the logic to evaluate both ground speed and torque demand when selecting the optimum gear and shift points. For instance, he said, the downshift from 2nd to 1st when loading the bucket is now a torque-based decision that the transmission makes based on machine load. The benefit is lower fuel consumption. If the machine does downshift and load in 1st gear, he said, it’s already shifting to 2nd as it backs from the pile, and will move forward in 2nd, because little torque is required.

“We’ve determined from side-by-side tests that fuel efficiency improves about 15 percent when the automatic system does the shifting, compared with the operator shifting manually,” he said.

Operator’s environment

Significant refinement in the 950K’s design continues to the operator’s environment. For starters, the cab structure is now built around a four-post ROPS, replacing the six-post design used on the 950H, but maintaining the same rating. Eliminating the center posts (the left of which was present primarily to hinge the 950H’s rearward-opening door) opens up the cab interior and enhances visibility.

According to Caterpillar, visibility in the horizontal plane is enhanced by 54 degrees, compared with that of the 950H. The seat in the 950K is moved forward, again in the interest of visibility, and this more-forward position necessitated using a convex windshield, which further enhances visibility and actually serves also to attenuate interior sound. The forward position also allows the operator to see when the bucket is full and to come off the throttle immediately, said Weinhold, which saves fuel.

The 950K’s door hinges on the left-front ROPS post and opens to the front, allowing a significantly wider door opening that, in turn, allows using significantly more glass in the door for better sight lines when grading against a curb, or for better seeing (and conversing with) people standing on the left side of the machine. The operator can open the large window in the door with one hand, and also can open and close the door while seated.

Images from the rear view camera (located in a protected pocket on the grill) are displayed on a color monitor in the upper right corner of the cab. The system can be set up to activate only when the machine reverses (to avoid distraction, especially at night), and powerful rear lights illuminate the space behind the machine. So expansive is the camera’s view, said Weinhold, that the operator could actually see all of a 980K (which is more than 32 feet long) when it’s parked directly behind the 950K.

The 950K is available with conventional steering or optional Command Control Steering, which provides full articulation with ± 70 degrees of steering wheel movement. Automatic climate control is standard. Blue-tooth and satellite radio are options.

After spending the day with the 950K and its predecessor models in the expert company of our hosts, and after reviewing the numbers resulting from the day’s comparative testing, we left the Peoria Proving Grounds thinking that the new 950K is an extremely versatile, extremely efficient machine with design features that significantly enhance both its productivity and fuel efficiency, as demonstrated by the on-site test results. The 950K and its K-Series companion models should serve well in Caterpillar’s wheel loader range.

GET FREE PRICE QUOTES

 
 

Comments on: "Cat 950K Transformed by New Linkage, Overall Refinement"

SUBSCRIBE TO OUR NEWSLETTERS

Optional
Optional
Type the characters you see in this picture. (verify using audio)
Type the characters you see in the picture above; if you can't read them, submit the form and a new image will be generated. Not case sensitive.