Medium Wheel Loaders - Foundation of the Cat Wheel Loader Range for 50 Years

Fri January 22, 2010 - National Edition
CEG


In December of 1959, the first production Cat wheel loader was driven off the assembly line at the Caterpillar plant in Aurora, Ill. — the 944 wheel traxcavator.
In December of 1959, the first production Cat wheel loader was driven off the assembly line at the Caterpillar plant in Aurora, Ill. — the 944 wheel traxcavator.

In December of 1959, the first production Cat wheel loader was driven off the assembly line at the Caterpillar plant in Aurora, Ill. — the 944 wheel traxcavator.

The 944, fitted with a 2-cu. yd. (1.5 cu. m) bucket and available with either a 105-hp (78 kW) gas or diesel engine, was the culmination of a seven-year development effort.

The 944 was joined in 1960 by two additional models, the 80-hp (60 kW) model 922 and the 140-hp (104 kW) model 966, using buckets of 1.25 and 2.75 cu. yds. (0.92 and 2.1 cu m), respectively. A 1960 Caterpillar press release stated “these machines are operated by conveniently located controls, have a two-speed forward/two-speed reverse power-shift transmission and attain a maximum reverse speed of 30 mph.”

The release also quoted W. S. Zeigler, domestic sales manager, who summed up Caterpillar’s goal for developing the new wheel-loader line: “These new traxcavators will enable operators to perform their work quickly and well, and give them safer working conditions.”

Time changes most everything, but the basic qualities Zeigler noted about the first Cat wheel loaders have remained constant through 50 years of continual refinement and through the placement of more than 100,000 Cat medium wheel loaders in the hands of customers.

Although the Cat wheel loader line today ranges from the 55-hp (41-kW) 904B to the 1,577-hp (1,176 kW) 994F, the eight-model lineup of medium wheel loaders — 938H, IT38H, 950H, 962H, IT62H, 966H, 972H and 980H — remains the foundation of the line and serves the largest market segment. These models offer standard buckets from 3 to 8 cu. yds. (2.3 to 6.1 cu m), can be fitted with a diversity of work tools and take on the toughest jobs in applications as varied as material handling, scrap yards, quarries and forestry.

Five Decades of Refinement

Developing new products in the 1950s was a long, laborious process, necessitating many prototype models and thousands of hours of in-the-dirt testing. Today, of course, the power of computer-aided design allows testing virtual prototypes, and today’s engineers can perform more evaluation in hours than could their 1950s counterparts in months of field testing.

But the basic philosophy of Caterpillar’s product development process has not changed; when designing the 944, engineers asked customers what features they wanted in wheel loaders — and Caterpillar engineers are still asking that question. The 944 engineers learned, for instance, that wheel-loader users wanted loader arms and hydraulic cylinders positioned forward of the operator’s compartment. Good idea — because the side-mounted loader arms of the day’s competitive designs brushed past the operator’s elbows with every bucket load.

Front-mounted lift arms were included in the 944’s design and became a Caterpillar exclusive. Through the decades, the design of Cat medium wheel loaders has reflected customer input and the best technology to yield efficient, durable, safe machines that operate at low-costs, according to the manufacturer.

The 944’s pre-combustion-chamber diesel engine, for example, gave way in the early 1980s to more efficient direct-injection engines, then to electronically controlled engines, and finally to the Cat ACERT diesels that deliver a combination of fuel efficiency, emissions control and power density that 1950s engineers would have thought impossible.

Likewise, early-loader hydraulic systems, using gear-type pumps and mechanical controls, have been refined into the Cat medium wheel loaders’ load-sensing systems that use variable-displacement pumps and Caterpillar-designed pressure-compensating valves to reduce horsepower draw and save fuel. In the cab, long-throw hydraulic control levers gave way to lower-effort pilot controls, then to intuitive electrohydraulic joysticks that provide Cat machines with precise hydraulic response in all operating situations.

The list goes on: Caterpillar was an early pioneer of articulated steering, using proprietary center-hinge designs that greatly improved maneuverability — and today’s optional command control steering allows lock-to-lock articulation through just plus/minus 70 degrees of wheel turn. The 944’s drum brakes gave way to more efficient disc brakes, then to internal multiple-disc brakes in the Cat four-piece axle, which is a component in every medium wheel loader.

Power-shift transmissions, once controlled by mechanical linkage, are now electronically managed and feature variable shift control to match gear-change patterns to the application. Belt-driven cooling fans have given way to fuel-saving on-demand fans; loader linkages have been strengthened and simplified; and the stark operator stations of early loaders are now the ultimate in operator comfort, convenience and safety (even allowing hands-off operation when the optional Aggregate AutoDig system automates the loading process).

And compared to the 944, today’s Cat medium wheel loaders really do think for themselves. The Cat monitoring system continually checks machine health; product link, a satellite-based system, provides two-way information exchange between onboard machine systems and the Caterpillar network operations center; and the equipment manager system places product link data on the owner’s computer screen, allowing efficient management of machine utilization, maintenance/repair decisions and security risks.

W. S. Zeigler’s words are still true of Cat medium wheel loaders; these machines still “enable operators to perform their work quickly and well, and give them safer working conditions.”