Wirtgen America's Hamm Compaction Division has introduced its oscillatory compaction system to North America with the model HDO90V asphalt roller—a double-drum, articulated-frame machine with 127 horsepower, 66-inch drum and an operating weight of 20,100 pounds. The HDO90V is said to be a "hybrid" compactor using a conventional vibratory drum in the front, but oscillatory technology in the rear drum.
According to Hamm, oscillatory technology creates compaction effort by means of generating forces that move out into the asphalt in a horizontal direction, compared to the vertical forces created by a conventional vibratory system. Oscillation results in a rocking motion in the HDO90V's rear drum, a motion generated inside the drum by two eccentric shafts that turn in the same direction and cause movement around the drum axle.
The overall effect of the oscillatory motion, says Hamm, is faster, gentler compaction—gentler, because the drum remains in constant contact with the mat. This translates, says the company, into higher compaction levels in fewer passes, reduced damage to the pavement and surrounding areas, increased operator comfort, significantly longer machine life, the ability to compact at lower temperatures, and reduced risk of over compacting certain mixes.
According to Stuart Murray, president of Wirtgen America, the oscillatory concept is applicable to new mix designs being used in the United States, such as stone-matrix asphalt (SMA) and Superpave mixes. Actually, says Murray, Hamm was employing the concept some 20 years ago in Germany to compact the then-new SMA mixes. Overall, says Murray, oscillatory technology allows enhanced control over the compaction process, especially in the critical target-density ranges of today's mixes.
The Hamm HD-Series compactors feature a swiveling operator's seat and dual, seat-mounted joystick controls for travel and vibration. According to Hamm, the HD models provide excellent curb clearance and allow a 3.5-inch drum offset to both sides for pinching joints and increased rolling widths. Service features include a tilting operator's compartment and a maintenance-free articulation joint.
The suggested list price is $126,700.