High vibration
frequency or high amplitude?
Pavers have never had such a rich spectrum of options.
If there was any doubt about the importance of high-vibration-frequency
tandem rollers in North American paving, it was washed away at the 2002
Conexpo-Con/Agg show when four manufacturers rolled out a total of 11 new
high-vibe models at that event alone.
That trend will only continue in the months to come, say industry
experts, and the reason is as simple as productivity. All other things being
equal, the faster the roller’s drums vibrate, the faster the roller can
compact thin-lift asphalt.
“To get a smooth pavement,” explains Ingersoll-Rand’s Dale Starry,
“the industry rule of thumb is, you want to get 10 to 14 vibrations per
foot. For the sake of example, let’s say your mix requires 10 vibrations
per foot. If your roller is operating at 2,000 vibrations per minute, your
rate of compaction will be 200 feet per minute; if your roller is operating
at 3,000 vibrations per minute, your rate of compaction will be 300 feet per
minute — 50% faster.”
Of course, that’s assuming the high-vibration roller generates enough
compaction energy to achieve the desired mat density.
“Just because you have high frequency doesn’t mean you automatically
achieve density in fewer passes,” cautions Steve Wilson, manager of
marketing services for Compaction America. “Even though this machine might
have a high travel speed, that doesn’t mean it’s going to be putting out
enough energy to give you the density you want.”
Wilson is referring to the importance of amplitude in compaction.
Amplitude is the vertical distance the drum travels in its vibratory mode.
The greater the amplitude, the more powerful the impact — and the greater
the compaction “energy.”
Today’s technology demands a tradeoff between amplitude and frequency
— the drum’s eccentric shaft bearings cannot take the stress of both
high vibration and high amplitude. So when a roller runs at a high vibration
frequency, it has to run at lower amplitude levels and may not have enough
compaction force to achieve desired density in a thick or difficult
pavement.
Wilson also makes the point that not all 4,000-vpm rollers — the
highest frequency currently available — generate the same amplitude, so
paving professionals should pay attention to the specifications when
selecting a machine.
Matching job requirements
There is general industry agreement that
high-vibration-frequency/low-amplitude compaction is the preferred
application for most thin-lift pavements in North America today, though
there is some debate about what constitutes a “thin” lift. To
Ingersoll-Rand’s Starry, it’s 3 inches or less, while Michael Wyss,
marketing manager for Caterpillar compaction products, thinks more in terms
of 2 inches or less.
The point is a significant one because, as Starry points out, most states
are limiting pavers to 3 inches or less per pass to achieve optimum
smoothness and rideability. Each layer gives the paver a chance to improve
smoothness by 75%, notes Starry, so more thin layers rather than fewer thick
ones, is the trend.
There is general agreement that thick lifts require high amplitude —
and, consequently, lower vibration frequencies — to achieve desired
compaction density.
One of the main areas of debate among factory compaction experts is how
best to approach Superpave mixes. Sakai, the company that brought the first
4,000-vpm compactor to North America, believes high frequency compaction is
ideally suited to Superpave because its rapid rate of coverage allows
optimum breakdown compaction to be completed before the mat cools. “During
compaction, Superpave mixes have shown a tendency to act tender at mat
temperatures around 265 degrees F,” says Dick Draper, Sakai vice president
and general manager. “This means applying a vibratory roller, or any
roller, at this temperature will cause displacement and marking of the mat,
which in turn necessitates additional rolling after the mat temperature
cools.
“In order to get more compaction work done before the mix cools, it is
necessary to speed up the compaction process,” Draper concludes.
While experts generally agree on that point, Caterpillar says that not
all Superpave mixes fit that mold. Some mixes — coarse mix designs in
particular — can make compaction more difficult and require higher
amplitudes to achieve density, says Cat’s Wyss. In these cases, high
amplitude may be required, even if it means putting more rollers on the mat.
Ingersoll-Rand’s Starry agrees that there are times when higher
amplitudes are needed, but he estimates that high-frequency rollers are
appropriate for somewhere between two-thirds and three-fourths of today’s
paving applications.
Whatever the breakout, the major manufacturers are covering all their
bases. Market-share leader Ingersoll Rand offers high frequency versions of
its production rollers, as does Compaction America and Dynapac. Sakai and
Cat both offer rollers that let the contractor choose between high-vibration
frequency or high amplitude with the flick of a button or two, and that kind
of versatility option is likely to be offered by other brands in the coming
months.
New This Year From Caterpillar Paving
High vibration or high amplitude in one machine
 Caterpillar Paving’s new 67-inch CB-534D and 79-inch CB-534D XW tandem
rollers are available with the company’s optional “Versa Vibe”
vibratory system which allows the machine to operate in a
high-vibration-frequency (3,800 vpm)/low-amplitude mode for fast compaction
of easy pavements, or high-amplitude/low-vibration-frequency (2,520 vpm)
mode for thick lifts or difficult mixes. Cat says the feature can save
fleets the cost of a second machine and gives jobsite managers more
flexibility in finding the optimum combination of amplitude and vibration
frequency for each job.
Introduced in January, the new D-series asphalt compactors are
recommended for breakdown and intermediate rolling because of their high
compactive forces, and can be used in the static mode for finish rolling,
according to Caterpillar. Cat also recommends the machines for base and
sub-base compacting. Typical applications are highways, city streets, county
roads, lane additions, overlays, airport runways, and other production-size
jobs.
With 67-inch-wide drums, the 534D weighs 22,050 pounds and is designed
for both large commercial jobs and mainline paving applications. The 534D XW
has an operating weight of 24,917 pounds and its 79-inch-wide drums are the
ideal size for compacting 10-foot-wide lanes, according to Caterpillar. Both
models are powered by a 130-horsepower engine.
Standard features on the D-series rollers include automatic speed control
with impact spacing indicator, 50-50 articulation, five amplitude settings,
and a new drum spray system. With the Versa-Vibe option, there are four
amplitude settings — two for each vibration speed.
To enhance sight lines front and rear, the D-Series rollers have one
large, 290-gallon polyethylene water tank positioned inside the machine’s
front frame. Spray bars and nozzles are shielded from wind and sun to
provide consistent coverage across the drum surface and small lights allow
the operator to see that the spray bar is working during night paving jobs.
Operator station features include a seat that slides from one side of the
machine to the other and also pivots to let the operator work at either a
90- or 45-degree angle to the road.
Click 22 on ROADFAX card
Bomag
Newest high-frequency tandem works fast
 Bomag announced its 84-inch 4,000-vpm BW205 roller late last year for
Superpave applications. With an operating weight of 26,500 pounds, the
205-horsepower tandem produces 34,665 pounds of centrifugal force in low
amplitude, and 41,235 pounds in high amplitude. The machine has large,
54-inch-diameter drums to help minimize shoving.
Operator efficiency has been addressed in the new machine, too. It uses
Bomag’s joystick control system, which provides one joystick for steering
and a second for travel control. Button switches at the tops of both
joysticks engage and disengage drum vibration and provide manual control of
the water-spray system. Maximum roller speed and vibration-frequency values
are electronically adjustable for optimum performance.
The BW205 has two water tanks with a combined capacity of 340 gallons,
and an independent secondary pump/spray bar system that continues water
spray functions if the primary system fails.
Click 13 on ROADFAX card
Ingersoll-Rand
Four high-frequency highway compactors
 Ingersoll-Rand entered the high-vibration-frequency roller competition a
year ago, with the introduction of four highway-class, double-drum models,
the DD-70HF, DD-90HF, DD-110HF, and DD-130HF. The company says the high
frequency enhances production capabilities and smoothness potential, and is
especially useful with Superpave mixes where they are capable of breakdown
rolling in the tender zone.
All four new models feature IR’s patented impact meter which measures
the number of drum impacts per foot, allowing the operator to select the
right rolling speed to meet compaction requirements. Amplitude can also be
adjusted by means of an eight-position control.
Each drum has a separate water tank, and the water system is unique in
providing primary and secondary water spray with independent controls.
Click 12 on ROADFAX card
FallLine
Long-wearing drum scraper blades
 FallLine manufactures polyurethane scraper blades for all makes and
models of compaction equipment. The company specializes in making
polyurethane products for construction applications and says its Compaction
Drum Scraper Blade material has been formulated for maximum wear
performance.
Click 21 on ROADFAX card
Multiquip
New compact tandem works anywhere
 Multiquip’s new AR-13H ride-on tandem weighs 3,088 pounds but develops
3,100 pounds of centrifugal force with a 4,000-vpm front drum and a static
rear drum. The drums measure 35.7-inches wide. Powered by an 18-horsepower
gasoline engine, the unit has a top travel speed of 4.8 miles per hour.
Designed for asphalt and for sub-layer granular and mixed soils, the
AR-13H is recommended for parking lots, driveways, and road applications.
The unit has a 1.25-inch clearance on the right side for working close to
walls and obstacles, and a 19-inch curb clearance to allow compacting flush
to the curb.
Multiquip says the front drum’s vibratory assembly is maintenance free.
The roller is articulated for optimum maneuverability, and it has 11 degrees
of oscillation for dealing with uneven surfaces. Multiquip says the unit’s
60-gallon water tank is 15% larger than competing models.
Click 16 on ROADFAX card
Stone Construction Equipment
Compact roller for high- volume compaction
 Stone says its 47-inch-wide WolfPac 6400 asphalt roller is designed for
professionals doing high volume compaction. It has double-drum vibration and
drive and is recommended for base, binder, and finish lifts.
The 6,383-pound unit articulates 30 degrees right or left, and oscillates
15 degrees. It has variable vibration rates in both drums or in the rear
only. At its maximum vibration rate of 3,060 vibrations per minute, the
machine produces 6,518 pounds of centrifugal force.
Standard features include a 26-horsepower diesel engine, a 47.6-gallon,
removable water tank, ROPS, self-tensioning urethane scrapers, a 10-gallon
removable fuel tank, and a 9.25-gallon removable hydraulic tank.
Stone’s WolfPac line includes five asphalt rollers which range in size
from 32 inches to the 47-inch 6400. Service and support features include a
same-day parts response guarantee from the manufacturer.
Click 18 on ROADFAX card
Vibromax
Designed for roads and larger parking lots
 Vibromax says its 66-inch-wide Model 752C has 64% more centrifugal force
and 24% more static weight than the machine’s B-series predecessor.
Recommended for paving and resurfacing roads and larger parking lots, the
752C power train includes a 110-horsepower diesel and a three-speed
hydrostatic drive system which can reach speeds up to 7.4 miles per hour.
Operators can use front, rear, or dual-drum vibration, and a choice of
two frequency and amplitude settings to meet varying job requirements.
Vibromax says the roller’s compact 167-inch length contributes to
excellent visibility and makes the machine easy to trailer.
The 752C features a 216-gallon water capacity, a back-up alarm, and a
four-post ROPS canopy. It is covered by a two-year, 2,000-hour parts and
labor warranty.
Click 17 on ROADFAX card
Sakai
High frequency in mid-size rollers
 The pioneer in 4,000-vpm, high-frequency rollers has applied the
high-vibe technology of its large machines to three new mid-sized units.
Sakai’s SW300, SW320, and SW330 have drum widths of 39, 47, and 51 inches,
respectively, and range in weight from 5,965 to 6,505 pounds. The new models
are designed to handle county and municipal roads, as well as parking lots,
bike paths, and tennis courts.
Sakai says the 4,000-vpm speed allows the operator the choice of
increasing ground speed while still maintaining the customary 10 to 12
impacts-per-foot spacing required for density and smoothness. Alternatively,
the operator can maintain typical ground speed, increasing the number of
impacts per foot, which may allow density to be achieved in fewer passes.
The company says a test strip will tell the operator which technique will
work best, but in either case, productivity will be enhanced.
Sakai claims its proprietary counter-rotational eccentric system in the
compaction drums always directs forces downward into the material, promoting
a smooth surface. Other features of the new machines include dual drum
drive, drum-edge visibility, and a patented isolator system which protects
machine components and virtually eliminates any shock from reaching the
operator.
Click 11 on ROADFAX card
Hypac
More efficient 66- and 78-inch tandems
 Hypac has rolled out 3,800-vpm upgrades of its 66-inch C766C and 78-inch
C778B double-drum rollers. With the increase in vibration frequency has come
an increase in centrifugal force — up 10% in the C766C and 19% in the
C778B. Both units can now achieve a working speed of 4.3 miles per hour
while maintaining a minimum of 10 impacts per foot. The combination of
faster speed and higher output means the two units can cover more area in
less time without sacrificing compaction performance, says Hypac.
Both units also feature an asphalt mat temperature system as standard
equipment. It measures the surface temperature of the asphalt as the
compactor rolls across the mat and relays the data to a platform-mounted
display. Hypac says the feature is especially useful for Superpave projects
where compaction must cease when mat temperatures reach the “tender zone.”
Controls include Hypac’s Multi-System Performance Indicator which
allows the operator to input maximum working speed and automatic vibration
start/stop, as well as front and rear drum vibration frequency and
amplitude.
Click 14 on ROADFAX card
Caterpillar
Performance-enhanced production roller
 Cat’s 28,160-pound, 84-inch CB-634D tandem roller received a host of
upgrades last year to enhance productivity and service life. The machine now
has automatic speed control with an impact spacing indicator and five
amplitude settings. Vibration frequency has been increased to 2,640
vibrations per minute, and amplitude choices now range up to 0.041 inches.
Maximum centrifugal force has increased to 35,745 pounds/foot.
The revamped machine’s drum shells have been thickened 3 mm and 22 mm.
Cat says this adds 441 pounds to the overall weight of the machine, and it
will increase the drum surface life by 50%. The CB-634D also features 20%
more fuel capacity, increased water spray coverage, and improved access to
water pumps and filters.
Click 20 on ROADFAX card
Hamm Compaction
New 78-inch model completes the line
 The Hamm Compaction Division of Wirtgen added the 78-inch-wide HD 120 to
its HD series of double-drum rollers last year, filling the gap between the
top-of-the-line, 84-inch-wide HD 130 and the 66-inch-wide HD 110. Hamm says
the new model shares all the technological features of the HD 130.
With frequency ranges of 2,520 and 3,000 vibrations per minute, and an
operating weight of 26,675, the HD 120 boasts centrifugal forces between
38,700 and 29,025 pounds. Hamm says the machine was designed specifically
for the North American market, with a low, compact profile and a low center
of gravity. It has a true 50:50 articulation, and the ability to
hydraulically offset the drums to either side by 3.5 inches — a feature
that enhances maneuverability around curbs or building foundations and can
be used to reduce roller marks.
Like its stable mates, the Hamm HD 120 has water spray bars located
inside the frame of the roller, protecting them from damage from external
forces. Because of this location, water sprays directly on the drum. The
operator is able to see the spray nozzles and the top of the drum, as well
as the drum edges.
Click 15 on ROADFAX card
Wacker
Cybernetic design in a performance compact
 Wacker says the cybernetic design of its RD 11 vibratory asphalt rollers
turns heads and produces large roller results without the price tag. The
one-ton-class roller has dual-drum drive and articulated steering for
accurate control, and variable-speed hydrostatic drive with even
acceleration and deceleration for smooth asphalt finishes.
The RD 11 has a 35.4-inch drum width and develops up to 3,000 pounds of
centrifugal force. It has an 18-horsepower engine and a maximum forward
speed of 414 feet per minute. Wacker recommends it for lifts up to 4 inches
on asphalt and 10 inches on soil.
Sleek styling adds to the ergonomics of the machine, according to Wacker.
The sloping hood affords excellent forward vision, and the operator is
positioned for an unobstructed view of the drum edges. The right-hand drive
control and vibration switch are positioned next to the operator’s seat
for convenience. Removable panels provide complete access to the engine.
Click 19 on ROADFAX card
Reprinted from March 2003 issue Better Roads Magazine
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