The Utility Marketing Division of Komatsu America has a pair of new compact crawler dozers that are designed primarily for slope work and fine-grading applications. Both new models, the D21A-8 and the D21P-8, feature long tracks for balance and stability. Komatsu says, "the option of either a rubber or steel track chain allows the units to travel easily over soft ground and mud." The rubber-track option reduces travel noise, minimizes vibration transmitted to the ground, and allows the machines to traverse paved surfaces without planking.
The 8,680-pound D21A-8 is fitted with a standard-width undercarriage that uses 11.8-inch-wide track shoes and exerts a ground pressure of 5.1 psi. Its 9,530-pound counterpart model, with a wider undercarriage and 19.7-inch track shoes, has a ground pressure of 3.4 psi. The D21P-8's wider stance, says Komatsu, improves flotation for added application versatility.
Each tractor uses a six-way, power angle/tilt blade that is controlled via a single-lever joystick, and a push-button on the joystick allows switching between the tilt and angle functions. Both machines also feature single-lever steering control, and the steering system employs wet multi-disc clutches interconnected with dry, contracting-band brakes. The "PPC" (proportional pressure controlled) valve built into the circuit facilitates smooth steering control.
Also adding to ease of operation and precise grading control is the transmission inching pedal, which allows controlled starts and stops, as well as smooth approaches to obstacles and stubborn materials. An optional decelerator is designed to provide infinite speed control.
Both tractors are powered with a Komatsu 4D94LE-2 diesel engine, which is rated at 40 flywheel horsepower and is Tier-II compliant. Both also use Komatsu's Hydroshift transmission—a two-speed powershift that allows top speeds of 2.7 and 3.5 mph, forward and reverse, respectively. The transmission is a planetary-gear type that is hydraulically controlled and force-lubricated.
According to Komatsu, machine durability is enhanced by "lifetime lubricated idlers and track rollers," and "optional lubricated track links reduce power loss that results from pin-and-bushing friction, while improving operator comfort."
Estimated list price is $60,493.
|Main relief pressure||2,200 psi|
|Flow @ rated speed||15.6 gpm|