Design details “The cooling system in 500-frame-size models is the same as that in the 600-frame-size,” says Hoesel, “which means it’s oversized for the smaller machines. Depending on ambient temperature and conditions, the T590 has about 20 percent more cooling capacity than the T190, so it can work in more severe conditions and at higher elevations. We’ve basically taken a cooling system designed for a 74-horsepower machine and installed it in a 66-horsepower machine.”
Trenching
The machines in the comparisons used a 66-horsepower (net) turbocharged diesel, high-flow hydraulic system, Bobcat’s Selectable Joystick control system, enclosed cab, and Bobcat’s standard undercarriage. For standard- flow trenching, the machines were fitted with Bobcat’s LT-313 trencher having a chain width of 6 inches. High-flow comparisons used the 6-inch-wide LT-414 trencher. All trenches were 3 feet deep.
During the comparison, we timed the operators as each used each machine in both its standard- flow and high-flow mode to open an equal amount of trench with each machine. In total, the comparison involved 500 linear feet of trench. Results: In the standard-flow comparison, the T590 was 26 percent more productive than the T190, and in the high-flow comparison, 14 percent more productive.
Cooling system details that have changed with
the M-Series, says Hoesel, include replacing the “squirrel-cage” type fan with a more efficient axial fan, changing oil-cooler and condenser mounting from a lift-out design to a more convenient pivoting arrangement that allows easy access to the radiator, and designing new intake screens that stop finer debris, yet have contours that discourage material build-up and are easier to clean. Among the T590’s more obvious engineering enhancements is a new lift-arm design, which includes a sizeable increase in cross-section, both width and height, as well as a new “inset” configuration that places the lower portion of the arms in a different (narrower) plane than the upper section. According to Bobcat, the new design results in a more rigid, more stable structure that contributes to the machine’s increased lifting and breakout forces. The lift-arm design, when combined with a flatter vertical-lift path, says Bobcat, also contributes to the T590’s higher rated operating capacity (ROC), 2,100 pounds versus the T190’s 1,900 pounds.
Drilling
For the auger comparison, the machines used a 30-inch-diameter Bobcat standard-flow auger. Each operator used each machine to place 11 holes to a depth of 3.5 feet, drilling until the spoil just touched the auger’s upper hub. We timed the operators as they worked. Results: Based on the time required for each machine to place 22 holes, we found the T590 to be slightly more than 19 percent more productive than the T190.
The new M-Series’ main control valve also features tilt-priority, allowing a stalled attachment to be repositioned with the tilt cylinders. This feature, says Bobcat, eliminates having to stop the attachment and reposition the machine during a stall.
With the T590 having about 20 percent more cooling capacity than its predecessor, our observation was that its variable-speed cooling fan ran at a slower speed than that of the T190 during this exercise.
Construction Equipment | January 2013 Reprinted from Construction Equipment, January 2013 17