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When soggy conditions
threatened to bog down earthmoving operations for one of his contractor
customers this past spring in Calgary, AB, Boyd Folden with Ramco
Sales Inc. came up with a way to keep the project on schedule. He
brought in an 18-yard pull-type scraper sporting rubber tracks instead
of conventional wheels.
Folden, a Bell tractor
and Ashland scraper dealer in nearby Pincher Creek, describes the
muddy conditions at the residential development project. “The
site was a slough bottom,” he says. “It was like walking
on a giant marshmallow. The ground moved whenever you took a step.
Not only were scrapers getting stuck, but they even had to pull
a D7 dozer out of the mud.”
Not long after that,
Folden showed up with an Ashland I-180TS LGP tracked scraper equipped
with a 36-inch-wide rubber track system made by ATI. Pulling it
was a 422-horsepower Bell 4206 D/T tractor, also equipped with ATI
track modules.
“I’ve been
in the industry a long time, and I’ve seen lots of equipment,
so I don’t get excited about many things,” Folden says.
“But, after the second load, I was absolutely amazed at the
way this track system, which produced a ground pressure of less
than 11 psi, kept the scraper on top of the mud and working productively.
In conditions like this, the tracked tractor and scraper were absolutely
a must.”
This latest development
in scraper options and accessories is just one of many choices for
customizing scrapers to fit your own specific needs and desires.
The selection ranges from hook and bail systems, which can increase
productivity by enabling two self-propelled scrapers to work as
a single unit, to disc brakes, which supplement tractor brakes,
especially when towing the combined 45-ton or more payload of some
double pan rigs.
An Adaptable System
The tracks used on the Calgary projects were an off-the-shelf
modular track system made by ATI Inc. The modules, which weigh about
6,000 pounds each, can be retrofitted to scrapers and a number of
other types of off-road machines, like tractors, soil stabilizers,
and vibratory compactors. Applications range from construction and
mining to forestry and geophysical exploration, reports the company.
The modules can be installed at the factory, at the dealer, and,
in most circumstances, in the field. Each unit is equipped with
an adapter assembly to mate the track system to the machine’s
drive assembly. Mounting each module takes about 90 minutes.
The ATI track system
features positive drive and Goodyear 36-inch-wide rubber tracks.
The system is designed to cushion the ride with rubberized idlers
and bogies and auto-tensioning to absorb impact. Permanently lubricated
sealed bearings eliminate maintenance throughout the expected 10-year
life of the system. A low center of gravity results in increased
stability, according to ATI.
The key to the performance
of the track system is a much larger footprint of each track compared
to a typical tire for much greater load-bearing capacity. The 86-inch
length of the 36-inch-wide track produces about 3,000 square inches
of ground contact. In addition, the bigger footprint of the tracks
means more traction, less compaction, less damage to soil surfaces,
and a smoother ride.
The Benefits of a
Bigger Footprint
Equipping a scraper with tracks is worth the expense in the
conditions his customer faced, says Folden. He points out that the
only other alternative in this case was a bailing operation, using
an excavator to dig out the mud and load it into rock trucks and
building road to support the large trucks in hauling the mud away.
“There’s no comparison in terms of cost,” he says.
“The track system was a much less expensive option.”
He notes another benefit.
The smooth ride of the tracks eliminates the constant bouncing of
wheel scrapers on haul roads. That, plus the greatly reduced ground
pressure of the track-equipped scraper, eliminated maintenance requirements
for the separate haul road, which was built for the tracked scraper,
because of quicker cycle times. In all, the scraper made about a
hundred round trips on that road. “The road stayed smooth,
and there was no need to run a grader on it,” Folden reports.
What’s more, he
adds, the smooth riding tracks allowed the operator to travel faster
on the haul road to improve productivity even more because of the
faster cycle times.
Working in conditions
like those at the Calgary site requires an ejector-style scraper
to unload the mucky dirt, Folden says. It also requires plenty of
tractive effort to pull a pan through such soil. “The tractor
we used has 62,000 pounds of pull and was a very good match for
this scraper,” he says.
Folden, an experienced
scraper operator with Ramco Sales, found that using a track-equipped
scraper required more of his attention, at first. “You need
to be more aware of the type of conditions you’re working in,”
he says. “Initially, you don’t really know what this track
system can do because you’ve never been able to operate in
these kinds of conditions. You’re going where you’ve never
been before with a scraper.”
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PHOTO: HOELSCHER |
The Latest Track System
Scraper manufacturer E-Ject Systems of Elkader, IA, is introducing
its own ground-driven modular track system, called the Track Pack,
this fall. Designed to fit the company’s two scraper models,
a 12-yard unit and a 17-yard machine, the Track Pack is available
with Goodyear rubber tracks in 30- or 36-inch widths. It features
all-Caterpillar components, says John Moyna, the company’s
president of manufacturing.
The 36-inch-wide rubber
tracks can reduce ground pressure of the scraper from about 20 psi
per wheel to about 10 psi, he reports. “It’s a rugged,
lightweight, simple design,” he says. “Four 37-inch carrier
rollers and four 20-inch idlers are used to route the tracks up
and around the scraper’s wheel spindle to allow you to bolt
one of the modules on in the field in about 20 minutes.” The
modules can be purchased for about $35,000 per set or they can be
rented from E-Ject dealers.
The company has been
field testing the track system for the past year on construction
sites, using 500-horsepower 865 Challenger tractors to pull one
or two track-equipped scrapers. Moyna reports that the increased
flotation of tracks produces a smoother, more comfortable ride,
reducing shocks to the scraper and allowing for higher travel speeds.
“In soft ground conditions, where top speed with tires is eighth
gear, we can run the track scraper in 10th gear,” he says.
Field Test Evaluation
Lorin Walz, an equipment operator for C.J. Moyna & Sons,
a grading and excavating contractor that is also based in Elkader,
has been putting the Track Pack through its paces. From his point
of view, the two biggest advantages of the tracks are a smooth,
comfortable ride and the ability to keep working in muddy conditions.
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PHOTO: MISKIN |
“There’s a
night-and-day difference in operation between tracks and tires,”
Walz says. “The flotation of the tracks is amazing. They really
carry nice. The tracks allow us to work in muddy places where we
couldn’t go with a wheel scraper. There’s no bouncing
on rough ground, and I’m not tearing the haul road apart when
I have the tracks on the scraper. Also, because the tracks don’t
sink into the ground like tires, the scraper pulls so much easier.
Since the tractor isn’t pulling as hard, this should save fuel
in the long run.”
In fact, Moyna has found
that fuel consumption of the tractors pulling track scrapers in
soft underfoot conditions drops as much as 15% compared to wheel
scrapers.
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PHOTO: ATI |
The tracks also enhance
operation when cutting or filling. “The operating characteristics
of a track scraper are phenomenal,” he says. “There’s
no side, horizontal, or vertical motion when working. And, because
of the flotation, the scraper doesn’t drag through the muck
and leave ruts in fill areas. When you’re not cutting into
the fill, the job goes a whole lot better and it keeps the inspector
happy.”
The E-Ject Systems tracks
have proven themselves on sites with extremely high subsoil moisture,
Moyna notes. “You can go into the lower, wetter sites on a
project to load the lead scraper and then swing around on the upper
side and fill a rear scraper with drier soils, maintaining production,”
he explains. “This allows you to produce a 50-50 fill blend
of wet and dry soils for the dump sequence. We’ve dumped 4-
to 5-inch lifts of wet soil from the lead scraper and followed a
few seconds later by another 4- to 5-inch lift of dry soil from
the rear scraper. If conditions are really soft, you could put tracks
on the rear pan as well as the front one.”
The extra traction of
the tracks also helps the scraper hold on slopes. That makes it
easier to maintain stockpile areas, Moyna notes. “When stockpiling
topsoil in tight residential projects, the tracked scrapers stay
in place behind the tractor,” he explains. “With wheel
scrapers, the front pan tends to slide off to one side, causing
the rear scraper to veer off and slide down the slope even more.”
Given a choice, Walz
prefers operating a track scraper over a wheel scraper on just about
any day.
“We don’t wait
for muddy jobs to use the track scraper,” he says. “If
it’s on a job site, we run it, no matter what the soil conditions.”
Greg Northcutt writes
frequently on construction and business issues.
GEC
- September/October 2005
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