Double drums, double play
Brooke Wisdom | July 1, 2010

In addition to the two groups of roller brands serving the asphalt compaction market, the “split” now extends to drum technology available to U.S. contractors

By Mike Anderson

When it comes to double-drum vibratory compactors, the world is split. And, further in that vein, it’s split in two ways.

With its split-drum design and wide offset capability, the Caterpillar CD54 double-drum vibratory compactor can be both a 67-inch-wide primary roller and a 118-inch-wide finish-pass unit. The split-drum design reduces tearing and pushing of the mat, says Caterpillar.

First, the manufacturers who serve the North American market are generally grouped in two camps. Of the 13 brands responding to Equipment World’s queries, seven offer full lines of tandem vibratory rollers, specifically models ranging in base drum width up to 84 inches – Hamm, Dynapac, BOMAG, Sakai, Volvo, Caterpillar and Hypac. The other camp focuses on offering compact and mid-sized roller lines topping out in the 40- to 55-inch drum width range, and includes such brands as JCB, Case, Stone, Terex, LeeBoy and Multiquip/Rammax. These OEMs generally offer fewer models, from six to as few as one.

The most recent technology trend in the U.S. market is the emergence of split-drum technology. Released this year, the Caterpillar CD54 “aligns alongside our CB54 articulated model with a drum width of 67 inches, but with the added benefit of increased offset, split drums and a high level of maneuverability,” explains Bryan Downing, global sales support consultant, Cat Paving Products.

When the CD54 is turning, the split-drum design allows the outside drum to rotate faster than the inside drum; the design is intended to eliminate the potential for the shoving and tearing of the mat that, says Caterpillar’s Brian Kopff, can occur while turning with standard solid drum designs. “The main benefit is in the turns,” says Kopff, marketing communications specialist, global paving products. “The split drums turn at different speeds, so if you’re maneuvering around a corner, the outside drum will move faster. What that does is provide a better mat quality – it doesn’t tear it – versus a solid drum across the machine.”

The CD54 features an axle-type vibratory housing design with robust tapered roller bearings supporting each half of the drum, to avoid contact between the two. The wide offset feature delivers an additional 51 inches of mat coverage for higher production on thin mats or when rapid heat loss is a concern. With the machine not offset and operating in the coordinated front and rear drum steering mode, it offers an inside turning radius of 110 inches.

“As we introduce the CD54 in the United States, there’s definite interest in a machine that offers 1.3 meters (51 inches) of offset and this level of maneuverability. Heads turn when you talk about a machine that’s 1.7 meters (67 inches) wide, then expands to 3 meters (118 inches). That is definitely is something people start asking further questions about,” says Downing. “Oftentimes while you’re performing compaction, you’d want to keep the drums in alignment with each other, at a minimal offset. While performing the final or any static pass, the machine will demonstrate its versatility in expanding to the full 3-meter-wide coverage.”

Along with dedicated front and rear steering, the 99.5-horsepower CD54 asphalt compactor can be operated in crab mode. With the machine in crab mode and at full offset, the electronic steering system provides an additional five-percent steering angle for “maximum maneuverability,” says Caterpillar. The electronic steering system has the feel and performance of a hydraulic system, with additional operator feedback when the drum encounters resistance, the company says. The CD54 is advantageous in applications requiring maneuvering tight spaces, such as cul-de-sacs, round-a-bouts, parking lots and city streets, but “a machine of this size can easily be transferred to highway jobs and do very productive work there as well. The machine has a high level of versatility,” says Downing. “In addition, the machine is equipped with a standard cab. Equipped with unique top hinging windows, the spacious cab provides the operator with optimum sightlines to the drum edge, the drum surface, as well as the jobsite. Also, the cab can be equipped with air conditioning for the hot, long days of asphalt compaction.”

More established in Europe and even Canada, the split-drum technology is rolling into product lines available to U.S. contractors. Among three double-drum vibratory rollers introduced this year by Dynapac, the 59-inch CC234HF and 68-inch CC334HF models are equipped with the split front and rear drums that prevent cracking and stretching the mat, the company says. These machines, along with the 68-inch CC384HF introduced in January, are part of Dynapac’s 16-model double-drum product line that ranges from the 31-inch CC800 to the 84-inch CC624HF and likewise CC722. With the company’s new rollers, the absence of over-the-drum water tanks in combination with the asymmetric cab ensures continuous visibility of the drum surfaces, sprinkler nozzles and drum edges.

Split-drum configurations are also among the options available on the new 66-inch HD+ 90 and HD+ 110 models from the Hamm Compaction Division of Wirtgen America.

Big rollers

Among the brands serving the U.S. construction market with double-drum vibratory compactors from top to bottom are those renowned worldwide for compaction.

Models ranging from 31.5 to 84 inches in drum width, with assorted technologies available at the various sizes, place Hamm among the full-line leaders in the tandem asphalt compactor market. The new “Plus” models, including the 78-inch HD+ 120 machines, offer the Hammtronic management control system as standard.

Hamm continues to roll out its next tier of product as part of an extensive compactor offering that includes 27 different variations of HD vibratory/oscillation asphalt rollers alone. Coming 18 months after the introduction of the HD “Plus” models in 78- and 84-inch sizes, Hamm this spring introduced a new 66-inch tandem roller, available in two weight classes. The HD+ 90 and HD+ 110 have operating weights of 20,327 and 23,215 pounds, respectively. Each offers operating options that include conventional vibration, high-frequency compaction, Hamm Oscillation compaction and a combination of those technologies, as well as the split-drum configuration. The new “Plus” models offer Hammtronic operation as standard, providing engine management control, programmable speed control and the ability to independently control vibration frequency and amplitude to either drum.

A Hamm exclusive, the “non-aggressive” oscillation technology is designed to compact with a gentle rocking motion. Whereas conventional compaction works by “bouncing” the drum on the ground, oscillation ensures the roller drums maintain constant contact with the surface for faster, more effective compaction, says Hamm. The company explains: Two eccentric masses turning in the same direction in the oscillation drum cause movement around the drum axle. The movement changes its direction of effect during one turn, so it generates an oscillating or rocking movement of the drum. Horizontal forces are transmitted from the drum to the pavement, and the result is better compaction in fewer passes, with less vibration-related wear and tear on operators and surroundings.

Full-line manufacturer BOMAG has continued to expand its offering at the larger end of the product line, most recently rolling out a second 78-inch BOMAG model featuring the company’s proprietary intelligent compaction system. The Asphalt Manager system automatically optimizes the BW278AD-4 AM tandem vibratory roller’s compaction performance during operation, continuously measuring the stiffness of the asphalt mat and adjusting compaction force where needed. A real-time display allows the operator to constantly monitor asphalt surface temperature, material stiffness, roller speed and amplitude. Proof-rolling with the system allows base work to be inspected prior to paving.

The BW278AD-4 AM debuted at World of Asphalt 2010 this February in Cincinnati. BOMAG, which offers close to 20 models of double-drum rollers ranging from 35 to 84 inches in drum width, first introduced Asphalt Manager to the market with the BW190AD-4 AM model, rolled out during the middle part of the past decade.

The Hypac compactor brand, under the umbrella of Fayat Group-owned BOMAG Americas, likewise now offers a 78-inch model equipped with Asphalt Manager. The C778D model, available with Asphalt Manager, is part of a five-model Hypac double-drum product line ranging from the 47-inch C747C up to the 84-inch C784A.

“Using intelligent compaction like BOMAG’s exclusive Asphalt Manager system, contractors can optimize their compaction, being confident the asphalt will meet specifications and pass inspection,” the company says. “That is because the system measures stiffness of the mat, and the operator knows when the required level of compaction has been met. This helps to eliminate over-compaction and under-compaction, allowing contractors to provide superior results.”

Further increasing the efficiency of the BW278AD-4 AM and other Ecomode-equipped BOMAG and Hypac rollers, engine performance is automatically optimized, matching output to the power required for compaction. Ecomode reduces fuel costs, emissions and jobsite noise, says the company.

With the four largest models rolled out in the past 18 months, Caterpillar offers a double-drum compactor line of 15 current variations ranging in drum width from 31 to 84 inches and gross engine output from 22 to 137 horsepower. Among the new offerings, the 67-inch CB54, 79-inch CB54 XW and 84-inch CB64 models are powered by 137-horsepower Cat C4.4 ACERT engines turbocharged to operate at altitudes up to 8,200 feet without derating. Vibratory systems with a range of amplitudes and frequencies include the optional Versa Vibe, built to handle a variety of mix designs: high amplitude/low frequency is suited for Superpave designs; high frequency/low amplitude matches higher paving speeds. Four amplitudes are adjustable with a hand wheel at the drum; two frequencies can be selected from the operating console for on-the-go customization. When equipped with optional AccuGrade Compaction system, Caterpillar rollers record pass-count and temperature mapping data usable for both quality control documentation and job planning.

Topping off the eight-model SW Series of double-drum vibratory rollers from Sakai is the 84-inch SW990 boasting 4,000 vibrations per minute, capable of 10 to 12 impacts per foot at a travel speed of 4.55 miles per hour. Powered by a 166-horsepower Deutz engine, the SW990 is capable of proper compaction at faster rolling speeds, particularly suiting it for county, state and interstate highway projects, as well as airport runways, says Sakai America. A dual-drum drive system, separated from the vibration system to minimize wear and tear, eliminates bow wave build-up in front of the machine. The drive motors are cross-mounted with the vibration motors to balance weight from front to rear, as well as left to right.

And the SW990 is smart, too. Now standard on the model, Sakai’s ExactCompact system measures impact spacing to determine the speed the roller should travel to obtain precise compaction and thus eliminate extra passes. Once the impact spacing has been determined on a test strip, the operator programs the settings into the system. While rolling, the operator simply adjusts ground speed until green lights are illuminated on the meter.

With 18 models ranging from the 35-inch-wide DD14S to the 84-inch DD132HF, DD138HF and DD138HFA, Volvo is among the manufacturers offering a full range of double-drum asphalt vibratory compactor sizes and configurations. At 57 inches, the DD70 starts off the larger end of the Volvo family.

The SW Series ranges from the 39-inch SW300-1 to the SW990. Additionally Sakai the 35-inch CR270 double-drum vibratory roller, two combination drum-pneumatic roller models, the vibratory pneumatic GW750, and the R2H “3-wheeler” with two separated 22-inch drums in the front and one 43-inch drum in the rear for a total compaction width of 83 inches.

In its DD Series, Volvo presents 18 double-drum asphalt compactor models ranging from the 35-inch DD14S to the 84-inch DD132HF, DD138HF and DD138HFA. The latter machine joins the 78.7-inch DD118HFA in a new high-frequency, high-amplitude product family using smart drum technology. Each of eight amplitude settings is automatically adjusted to the highest frequency possible, enabling the operator to use higher amplitude with lower frequency on thicker materials, or lower amplitude with higher frequency on thinner lifts to boost production with less risk of damage to structure or sub-grade. “This flexibility once required two separate compactors,” says Bob Marcum, a Volvo road machinery product specialist. Other smart systems put to work on the DD118HFA and DD138HFA include:

• a vibration system that automatically adjusts both drums’ vibration frequency to the design frequency for the given amplitude

• a propulsion system that automatically controls rolling speed

• a water system that not only shuts off water when the machine stops moving, but automatically regulates water flow to match rolling speed

• and a drum start system that prevents vibration of the trailing drum on cold or hard pavement surfaces at the beginning of each paving operation, or at the transverse joints on bridges or junctions with precast concrete pavement panels.

Compact players

The “split” in the asphalt compactor market leaves a half-dozen brands focused on serving mid-sized and compact rolling needs.

Offering the 45-inch TV1200 double-drum vibratory compactor model, Terex is part of a second group of manufacturers serving the compact and mid-sized rolling needs. The TV1200 has a dynamic braking system that can be engaged either when the six-in-one joystick is in neutral or when the unit is shut off.

With the Vibromax product line it acquired in 2005, JCB today offers six base double-drum vibratory compactor models with assorted variations ranging in drum width from 31 to 55 inches. The smallest model, the 23-horsepower, 1.6-metric-ton VMT160 comes in three different drum-width sizes, 31, 35 and 39 inches; the narrowest two of those are additionally available in total side clearance – or TSC – versions that allow operation close up to edges. Topped off by the 5-metric-ton VMT500 model, the JCB Vibromax product line offers the option of operating only the front, rear or both drums. A single-piece exciter shaft is a JCB Vibromax-patented design.

Now standard on the Sakai’s largest 84-inch SW990 model, the ExactCompact system measures impact spacing to determine the speed the roller should travel to obtain precise compaction and thus eliminate extra passes.

Case is another major equipment brand that continues to concentrate on the compact and mid-sized markets of tandem-drum vibratory compactors. The company offers three models ranging up to 51 inches in drum width. The 27-horsepower DV201 and DV202 have drum widths of 39 and 47 inches; the 38-horsepower DV204 tops the line. High centrifugal forces combined with dual frequencies suit these machines to street, driveway and parking lot projects. With infinitely-variable speeds up to 8.5 miles per hour, the Case machines offer manual or automatic vibration modes and a choice or front or both drum vibration. Recessed hydrostatic drum drives provide high curb clearance.

Topped off by 51-inch models, Multiquip’s Rammax brand offers the AR Series double-drum rollers powered by Yanmar diesel engines with dual working speeds. An offset drum design allows wider rolling width and better maneuverability along walls and curbs, says Multiquip.

With its WolfPac product line, Stone Construction Equipment offers a family of ride-on double-drum compact rollers ranging up to the 40-inch WP4100 and 47-inch WP6100. The two larger models feature a vibratory control that allows the operator to select front drum only, rear drum only or both. Weight and torque drive distribution allows for better grade climbing, says Stone. Also in that market are Terex with the 45-inch TV1200 model featuring six-in-one joystick control and VT LeeBoy with the 40-/44-inch LeeBoy 400. The latter “is not a stand-alone product,” says LeeBoy sales and marketing vice president David Carey, but rather offered as a complement to the paver line. EW

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