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It's only sundown on
the landfill, but you wouldn't know it from the buckets of rain
falling in the near-dark. It feels like it's been raining like this
for the last three years.
Underneath you are 30 tons of rumbling steel and rubber,
and beneath that is landfill—everything from baby toys to errant
construction-and-demolition materials in a leg-deep, swampy soup.
Just a couple of more runs across the yard, though, a
couple of more tons of the stuff before the day's out. There'll
be moguls, ankle-deep pockets of gunk, and 25% grades, but, hey,
this is what articulated dump trucks (ADTs) are made for. From
their first days in Europe to creating today's giants, their designers
seem to have one concept in mind: Transport anything, anywhere.
Roots of a Giant
Volvo claims to have invented the ADT—also known as an
artic—and be the first to mass-produce it. Known for its ability
to turn or "articulate" the front cabin and tires, an artic is
synonymous with dexterity. Couple it with six-wheel independent
suspension and this off-road dump truck can roll over car-sized
moguls that would bend a rigid-frame truck. With almost 40 years
into the design, these dump trucks boast cargoes of more than
40 tons and turning radiuses as small as 13 feet.
Artics can crawl up 30% grades and reach top speeds of
61 miles per hour, all the while dealing with wet, soggy, off-road
surfaces and low visibility.
There are artics in waterlogged landfills; steep, tight
dam projects; miles of bumpy road construction; and even military
operations. If you have something heavy to haul somewhere and
the artic can't hack it, you might want to consider a helicopter.
One of Volvo's biggest artics, the A40D, is a 37-feet-long
by 10-feet-wide behemoth that will carry nearly 82,000 pounds,
or 20.9 cubic yards, of material and hit top speeds of 55 miles
per hour. The drive train features differential locks, one longitudinal
and three transverse, with a 100% lockup function that's operator-selectable
on the move. That means more wheels stay on the ground and less
spinout.
"Volvo articulated haulers can be found being loaded
with overburden—clay, shot rock, gravel, sand, granite
blocks, or just plain mud," Volvo's Mike Stec states. "Articulated
haulers can run over solid obstacles with a height or depth of
16 inches, without causing damage to the machine. However, it
is recommended that the height of solid obstacles should not exceed
1 foot. Ultimately, the operator really determines how fast he
is willing to compromise his machine, body, and safety to haul-road
conditions."
How often you want to repair your ADT will determine
how far you can take it, Stec says.
"The key to being successful is uptime or availability.
In applications where there are terrible job conditions such as
mud, poor weather, or steep grade, Volvo articulated haulers outperform
all competitors. No one offers a 10% dog-clutch differential lockup
and therefore does not have the capability to travel as dominantly
in submerged or deep-mud applications. Not to say that Volvo haulers
cannot get stuck, but more operators all around the world would
agree that the Volvo has the best traction control, which helps
in winter with ice and snow to rainy and muddy job sites."
Stec also says Volvo's hitch area stands out.
"It's quite different than anyone else in the world.
The fully automatic Volvo transmission provides a higher clearance
distance under the hitch versus the competition, which provides
a lower clearance distance under their hitch. Volvo's will not
plow through mud due to the high hitch area, thus better negotiating
in deep ruts while maintaining better fuel consumption. Also,
the high hitch area will allow the Volvo to climb steep grades
and continue forward at the top without encountering a 'high center'
condition—whereas the competition can drag the hitch at the top
or possibly stop due to the low clearance if the steep grade becomes
quickly flat at the top."
John Deere promises a 40-ton payload on a body weighing
just 63,603 pounds. Deere's 34-foot-long, 11-foot-wide 400D hits
a max speed of 32 miles per hour using a Mercedes Benz 413-horsepower
diesel engine. Absolutely essential to carrying a load off-road,
400D standards include an oscillation frame joint, plus hydraulic
articulating steering, traction-control devices, high-flotation
tires and an automatic transmission.
"The new Model D Series trucks are essentially a clean-sheet
design over the previous generation. As with the previous model
trucks, the basic design philosophy remains the same—focus on
increased productivity, low operating costs, and increased uptime,"
says John Deere Product Marketing Manager Tim Averkamp.
"Depending on the application, it isn't uncommon for
us to see anywhere from 10% to 30% lower fuel consumption and
overall haul cycle times in the range of 5% to 10% better than
the competition. Given today's fuel prices, customers are really
taking note."
Caterpillar's
heavy-hitting 740 and 740 Ejector models—both powered by a
3406E ATAAC engine delivering 415 horsepower—have a rated payload
of 42 tons. The 740 will hold 30 cubic yards (30.2 cubic yards
for the Ejector) of heaped material or 22.8 cubic yards (23.3
cubic yards) struck, and reach a top speed of 34.6 miles per hour.
Komatsu's competing in the 40-ton range with the HM400-1,
a from-scratch design weighing 66,800 pounds. The HM400-1 also
climbs near the 30-cubic-yard range for heaped material and includes
a turning radius of about 28 feet.
Moxy
offers the MT41, capable of payloads of up to 41 tons, and a total
weight, loaded, of 73.5 tons. The MT41 holds up to 29.7 cubic yards
of material and articulates up to 45 degrees in a turning radius
of 13.5 feet.
"Moxy's free-swinging rear tandem bogie and the special
articulation system offer excellent performance and the best possible
ground contact in soft and difficult terrain," the company's Web
site says. "The sloping rear frame, in combination with the track
width, ensures a low center of gravity and best possible stability.
One of the main highlights of the Moxy concept is the location
of the turning ring in relation to the swing point. The turning
ring is located in front of the swing point, which always ensures
equal weight distribution to the front wheels in all situations,
also during maximum turning."
But enough of the showroom. Out in a soggy Ohio landfill,
Maintenance Manager Todd Perrine says four or five years of record
rain have contributed to bad ground in the Midwest.
"We mostly use artics on steep grades. A lot of sites
are wetter than normal, a lot of mud, but material still has to
be spread."
Perrine says his employer, Kokosing Construction Company,
currently runs about 25 units, mostly 35-ton Volvos, for everything
from soggy landfills to huge dam and factory excavations to road
repairs.
"We're out in southern Ohio on farm land in low-lying
ground where it's wet and soggy," he says. "Almost too soggy for
anything else."
Perrine says Ford is installing 200 steel-making ovens
in the area, and the work requires digging down through foot after
foot of peat to sand, where the ovens will be situated.
A $200 million West Virginia lock and dam project is
also making for some tight squeezes for the ADTs, Perrine says.
The project requires double shifts six days a week.
"We're running really hard on them, up the center of
these steep grades and moguls."
And when a multimillion-dollar road construction project
has a slip, Perrine says the artics are back out there.
"Talk about bad ground. We had a major slip on a project
and we had to come back in and fill more material. It's too soft,
just bad soil, wet, spongy, and swampy, just full of moisture,"
Perrine says. "You have to dig it all out and dig down to the
good material, then you have to go find and haul material to build
your fill back up."
Bill Minor, a heavy-equipment manager for Waste Management
in Lombard, IL, says the company is running somewhere between
125 and 150 artics in a fleet of 7,000 pieces of heavy equipment
spread out across the United States.
"In bad weather it's the only applicable vehicle to go
out across a landfill with a [heavy] load. You try to do it with
normal highway tractor-trailers and they fail pretty miserably.
They get mired down, stuck," Minor says.
"Primarily we're in the landfill-waste-handling business
and we use them to excavate dirt and haul daily cover for landfills.
We do have one operation where we use special truck frames and
haul containerized garbage from rail siding to the landfill working
face, 20-foot containers that fit right on the back of an artic
and haul it and dump it at the working face."
Greg
Kittle, equipment manager for Ryan Incorporated Central, says
the Janesville, WI,based company uses 60 artics with an emphasis
on 40-ton Volvos and Terex ADTs, all from 1998 or later.
"They've been in some sloppy materials and wet materials
that anything else would sink in," he says. "We use them as a
specialty tool."
"I've seen them go ankle-deep in mud and they will certainly
go deeper, though there's no guarantee that they won't get mired,"
Kittle notes. "It's a significant part of the hauling fleet. There's
nothing quite like what they can do in muck, silt, clay, and other
difficult positions."
Tom Kellerman, chief engineer with Clarkson Construction
in Missouri, says artics have excelled in heavy highway construction
and waterworks infrastructure like channels.
Artics have hauled 40-ton loads out of excavation projects
running deeper than 100 feet, with maximum haul lengths of 1.5
miles, too far for a scraper team.
Kellerman says Clarkson's latest heavy road construction
projects with artics started late July with $145 million in Kansas
Department of Transportation contracts, some of the largest the
state has ever had.
"We've had some situations where they've been going up
10% grades, probably 15% grades. I wouldn't dump them on that
grade unless you want to turn them over." During channel work,
he says, "We run them in pretty tight places where we have to
back in, get loaded, and turn tight corners. We used them in limestone
rock excavations in lieu of rigid frames starting probably five
or six years ago. We felt the artics were better used in other
situations handling both dirt and rock.
"The rough rock and gravel roads can beat up an artic
just as much as a scraper," Kellerman says. "Any haul road that's
not maintained well is going to be rough."
The need for versatility in ADTs' uses has pushed specialty
items and system add-ons to fantastic levels. With equipment like
ejector bodies that can spread fill like a backhoe and complex
container-lifting modules, an artic can do nearly any job, says
LeRoy Hagenbuch of Philippi-Hagenbuch Inc. of Peoria, IL.
Ejector bodies, which push debris out the back, mean
fewer opportunities for the number-one hazard in artics: tipping.
Raise the center of gravity with a bed full of debris and any
slope magnifies the tip potential of the relatively light artic.
Volvo cautions against even driving on certain grades, let alone
dumping.
"Only in exceptional cases should a Volvo A35D be operated
up or down grades steeper than 20% to 30%," says Volvo's Stec.
"The absolute limit uphill is approximately 45%, and downhill
the Volvo A35D can negotiate 50%, but other factors such as the
available traction make it hazardous to work under such conditions.
Only in exceptional cases should the machine be operated on lateral
slopes of more than 15%. The maximum limit for the machine in
travel on lateral slopes is 30%, but other factors such as roughness
of the ground can cause the machine to tip over before this limit
is reached."
Ejector bodies solve the problem of dumping on a dangerous
grade.
"In unstable conditions
you can dump. If you're in an underground area…you can dump
despite the low clearance. With large fleets of ADTs on a construction
job running 20 trucks a week, at least one will tip. The back end
is over unstable ground and there are no rigid connections to the
frame, nothing stabilizing it to the other parts, plus a little,
lightweight frame," says Hagenbuch.
"The rear eject is really a safety issue. The last thing
you want to try and do is spread with a rear body up. It's just
a stability issue."
David Downs is a writer based in San Francisco.
GEC
- September/October 2004
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