Conquering Inner Space

Today’s compact excavators offer many of the ergonomic features found on their bigger brothers, including pilot controls, suspension seats, and enclosed, air-conditioned cabs. But providing plenty of elbowroom inside the cab of the smaller machines has required some inventive engineering.“The biggest challenge is the sheer volume of space available to work with,” says Tom Connor, Bobcat excavator product specialist. “You have a smaller envelope in which to fit all of the necessary components for operating the machine.”Stretching that envelope in one direction alters the dimensions in another. “Compressing the width or length of an excavator often forces it to grow taller to accommodate the operator,” Connor says. “However, in the case of compact excavators, there’s a desire to keep the total height under 8 feet to fit inside buildings.”

When designing the previous D-Series line of Bobcat excavators in the mid-1990s, engineers replaced the conventional thick-cast rear counterweight with a heavy engine-access tailgate made of die-formed 0.25-in. steel. This in turn allowed them to move the engine farther back, for more rear forces to counter the front work group and for freeing up extra operator space in the cab.Squeezing the engine and other components into a smaller package adds to the challenge of dissipating heat. For example, heat generated by the hydraulic valves under the cab can radiate up through the floor. So, in designing the earlier D-Series line, the engineers moved the valve bank on most of the models to the firewall on the right side of the cab.Speaking of cab floors, compact excavator manufacturers have increased foot room by installing two-piece foot control pedals that fold forward when not needed. Some have even eliminated foot pedals altogether in favor of joystick or instrument panel switches.Zero-tail-swing models also require some resourceful approaches. Keith Rohrbacker, product manager for Kubota Construction Equipment, explains how Kubota engineers have found ways to counterbalance the front end despite a shorter tail.“They redistributed the weight that used to hang on the back to different areas of the frame,” he says. “For example, the belly pan that protects the engine and the hood and the side panels has been made heavier.”To keep the size of the engine compartment from encroaching on operator space on its two zero-house-swing excavators, Bobcat has replaced a conventional water pump and fan cooling system, which is connected to one end of the engine, with a hydraulically driven cooling package that can be mounted away from the engine in another area of the compartment. The result is a shorter engine package and more efficient use of already-limited space.Says Connor, “It all boils down to creative packaging.”