Pick up the tempo

By: Allen Zeyher

Roadbuilding is trying to be the silver lining in the dark cloud of an economy that has been particularly rough for the manufacturing sector. Money for building—and rebuilding— infrastructure continues to flow, and projects are moving ahead, but some subsectors can only hope for a recovery over the horizon.

"What we’re seeing is that, even though there is a tremendous amount of work activity going on, the actual purchase of equipment isn’t necessarily as strong as it has been in the past," Steve Wilson, manager of marketing services at Compaction America Inc., Kewanee, Ill., told Roads & Bridges.

Wilson said sales of his company’s BOMAG and HYPAC asphalt rollers were down about 40% from last year, and the rest of the industry is in a similar situation.

One of the drags on the industry is the cost of petroleum products, such as the diesel fuel used to run the asphalt rollers and the asphalt cement used to make the material to compact.

"There have been delays of jobs waiting for the cost of the petroleum products to reduce so they could afford to do the jobs, because the escalation had just been so dramatic," Dick Draper, general manager at Sakai America Inc., Adairsville, Ga., told Roads & Bridges.

At the same time, some states concerned about the cost of gasoline to consumers have scaled back gasoline taxes, which means there may be less money to match the TEA-21 funding coming from the federal government.

Another pull on the asphalt compactor industry is the growth of the rental market. Big rental houses have spent the past couple of years buying equipment, but now they have what they need and don’t need to replace equipment.

"They filled a tremendous pipeline," said Wilson, "so there’s a lot out there that’s available to the contractor base," although it might be last year’s model.

The result of these influences is that manufacturers and rental houses mostly have been working down their inventories rather than making and buying new machines.

But the big talk of the asphalt compactor industry is vibratory frequency. With the use of Superpave mixes on the rise, the challenge for asphalt compactor makers is to increase the rate of compaction so that the contractor can get the hot mix compacted before it cools off to the "tender zone" and becomes unworkable.

Sakai America thinks it has the answer to the Superpave question, and the answer is a roller that vibrates at 4,000 vibrations per minute (vpm). The higher vibration rate means the roller can move over the mat faster while maintaining the same number of impacts per foot of asphalt.

"That translates directly to the bottom line in many cases out on the jobsite today," commented Draper, who said sales of Sakai’s 4,000 vpm rollers are doing well.

Sakai introduced its 4,000 vpm compactors in 1999. The latest model, the SW900, has dual 84-in. drums, delivers 38,800 lb of centrifugal force and offers two amplitudes. At 4,000 vpm and 10 impacts per foot, the SW900 reaches a ground speed of 4.55 mph. The machine features a counter-rotating vibration system, in which the weights in the two drums rotate in opposite directions, so when the weight in the front drum is pulling forward, the weight in the rear drum is pulling backward. The machine also features a patented system for isolating the operator from the vibration of the machine’s components.

Sakai recently opened a new manufacturing plant located in Adairsville, Ga., to build compactors. It is the Japanese company’s first manufacturing facility in the U.S.

The latest addition to Compaction America’s BOMAG line is the BW180AD, with dual 72-in. drums, dual amplitudes and a choice of 2,520 or 3,600 vpm. At 3,600 vpm and 10 impacts per foot, the BW180AD delivers a centrifugal force of 22,500 lb and a ground speed of 4.1 mph.

Unlike traditional tandem rollers with articulated frames, the BW180AD is steered by means of independently pivoting rollers. This steering system provides five steering modes: rear drum only, front drum only, coordinated, crab left and crab right.

The HYPAC C778B and C766C dual-drum vibratory compactors feature an asphalt mat temperature sensing system that measures the surface temperature of the asphalt mat as the compactor rolls. The operator can monitor the mat temperature and adjust machine parameters without stopping or getting off the machine.

The AV/H Series of tandem vibratory rollers from Ammann America Inc., Jacksonville, Fla., offers the Ammann Compaction Expert system for measuring compaction with a device attached to the compactor itself. The Ammann Compaction Expert will measure relative or absolute compaction.

For relative compaction, the system compares two successive passes with the compactor and shows the difference between the two passes. It gives no information on the absolute compaction, stiffness or density achieved.

For absolute compaction, the system continuously measures density and/or stiffness and displays the values at the operator station.

The AV/H Series adds a regulation feature which uses the measured compaction to change the equipment operation to achieve the desired result. The operator sets the absolute compaction target, and the measuring and regulation system adjusts the machine’s working speed, vibration frequency and vibration amplitude to hit the target.

The AV 75 T has 55-in. drums and the AV 95 T has 63-in. drums. They both are capable of vibrating at 1,500 or 3,000 vpm with an amplitude of 0.025 or 0.012 in. The AV 75 T produces a centrifugal force of 1,350-8,990 lb ft, while the AV 95 T produces a force of 1,570-11,690 lb ft.

The Hamm HD 130 is the largest asphalt compactor sold in the U.S. by the Hamm Compaction Division of Wirtgen America Inc., Nashville, Tenn. At 30,000 lb, this 84-in.-wide tandem-drum, articulated machine boasts a centrifugal force ranging from 30,000 to 41,625 lb with a frequency up to 3,000 vpm. The Hamm HD 130 in June joined the existing line of small Hamm HD machines (the HD 10, HD 12 and HD 13) and larger HD machines (the HD 70, HD 75, HD 90 and HD 110).

The HD 130 features 50:50 articulation, with an inside turning radius of 203 in. A 117-hp diesel engine powers the infinitely variable hydrostatic drive to both drums. Vibration is available in two frequencies (2,520 and 3,000 vpm), two amplitudes (0.032 and 0.016 in.) and two centrifugal forces (41,625 and 30,150 lb). The machine has a variable working speed up to 3.8 mph.

The DD-70HF, DD-90HF and DD-110HF are specifically designed for high-frequency performance by the Road Machinery division of the Road Development Group of Ingersoll-Rand Co., Shippensburg, Pa. The company said the compactors were built to compact the new Superpave mixes now used in highway, airport and other large paving applications.

The models feature a patented Impact Meter that accurately measures the number of drum impacts per foot.

The DD-70HF, DD-90HF and DD-110HF compactors have operating weights from 15,000 to 25,000 lb, with drum widths of 57 in., 66 in. and 78 in., respectively.

The Dynapac Compaction and Paving Division of Svedala Industries Inc., Schertz, Texas, has increased the diameter of the drums on its asphalt rollers. The larger diameter decreases the asphalt "bow wave" in front of the drum, according to the company, and more easily meets the requirements of compacting a Superpave mix.

The CC 522 has an operating weight of 26,130 lb, a drum width of 77 in., a static linear load of 169 pounds per linear inch, a vibratory frequency of 2,940 vpm and amplitudes of 0.012 or 0.025 in.

The dual drums on the T-Series of Rammax tandem ride-on vibratory rollers from Multiquip Inc., Carson, Calif., are offset to increase working width and allow maximum clearance. The inside turning radius of the T-Series is only 86.6 in. for the largest machine, the T-33, with 55-in.-wide drums.

A high-torque, water-cooled, three-cylinder Yanmar diesel engine offers two working speeds of 2,400 and 2,700 rpm. This allows two different frequencies, centrifugal forces and travel speeds to adapt to different working conditions. The T-33, for example, is a 4-ton machine that offers a centrifugal force of 4,119 or 9,266 lb, a frequency of 3,300 or 3,780 vpm and an amplitude of 0.020 in.

In the area of utility-sized vibratory asphalt compactors, Caterpillar Inc., Peoria, Ill., offers the CB-214D, CB-224D and CB-225D.

The CB-214D is a double drum machine with a 39-in. compaction width and an operating weight of 5,355 lb. The CB-224D also is a double drum and has a drum width of 47 in. and an operating weight of 5,750 lb. The CB-225D is a combination machine with a 47-in. drum in front and four smooth tires in back. It has an operating weight of 5,265 lb. All three models have a drum diameter of 27.6 in.

The models are powered by a three-cylinder, 31.5-hp diesel engine and have a vibratory system that generates 3,600 vpm at a nominal amplitude of 0.02 in.

The WolfPac 6400 compaction roller from Stone Construction Equipment Inc., Honeoye, N.Y., has an operating weight of 6,383 lb, a 26-hp engine and a drum width of 47 in. It is the largest of Stone’s WolfPac line of ride-on asphalt compactors designed to operate in confined spaces. The others in the line are the 2500, 3100, 3600 and 4000.

The WolfPac 6400 delivers a centrifugal force of 6,518 lb.

The Tru-Pac 915 is a pneumatic-tired roller with an articulated design that provides true-tracking and full-width compaction, especially in tight areas. Frame articulation is rated at ±40û. The machine is available from Rosco Manufacturing Co., Madison, S.D.

Ballastable up to 30,500 lb, each of the nine wheels delivers about 3,400 lb of compactive force directly to the work surface.