When it comes to moving massive amounts of dirt or material nothing beats a 40-ton articulated or rigid frame dump truck – they can move mountains in a matter of days.
But when the job calls for the placement of smaller quantities of material and maneuvering on turf, built surfaces or forests and bogs, you don’t have many options. Komatsu builds a machine called a crawler carrier that runs on a rubber-track undercarriage and offers a rotating upper structure like an excavator. And while there is no single machine that you can directly compare it to, we thought it would be useful to see how the crawler carrier stacks up to other machines that carry materials in other ways.
Weight/capacity
The Komatsu CD60 crawler carrier will hold 13,230 pounds/4.2 cubic yards of payload, says David Caldwell, product marketing manager for the crawler carrier line. Its bigger brother, the CD110, holds 24,250 pounds and 8 cubic yards. This puts the CD60 in the same category as a Class 4 dump truck and the CD110 in the range of a Class 6 or 7 dump. Articulated trucks hold considerably more, with the smallest (a JCB 714, carrying 28,660 pounds) and all the rest ranging from 40,000 to almost 80,000 pounds.
Some of the crawler carrier’s applications are also performed by wheel loaders, such as backfilling or pipeline padding. But other than mining machines, most big wheel loaders top out at 8 cubic yards and the majority range from 2 to 6 cubic yards in capacity. The biggest tracked skid steers carry just half a cubic yard in their buckets.
Advantage: The crawler carrier hauls more than most tracked skid steers and wheel loaders, roughly the same as medium-sized dumps and less than big dumps and artics.
Ground pressure
While the big dumps and articulated trucks can haul massive amounts of material, their tires inevitably tear up the ground. Artics fare better with their fat, radial tires, but even these can generate ground pressures of 30 to 60 psi. By contrast the CD110, even when at a fully loaded GVW of 58,000 pounds, exerts just 6.1 psi thanks to its rubber tracks and bogie-style undercarriage, Caldwell says. Unloaded the CD110 floats across the ground at 3.6 psi; the CD60 registers a featherweight 3.1 psi.
Advantage: If you need to tread softly and leave behind undisturbed ground it’s hard to beat the crawler carriers’ light-footed ways.
Maneuverability
Any kind of dump truck has to back up and turn around, either to load or to dump or both. Same with wheel loaders. The crawler carriers, thanks to their rotating superstructure (which includes both the cab and the dump body), don’t even have to counter rotate, Caldwell says. You can drive into a confined space cab first, rotate the superstructure to dump and drive out cab first having never changed the orientation of the tracks. This makes the CD60 and CD110 ideal for placing materials in a crowded construction site, along roads where traffic and congestion pose safety hazards and anywhere you don’t want to disturb sensitive surfaces.
Advantage: The crawler carrier by a longshot.
Speed
Being tracked machines, the crawler carriers are slow, with the CD60 going from 3.7 to 5.3 mph, the CD 110 from 2.8 to 6.2 mph. By comparison, dumps and artics roar along at speeds up to 35 mph or better. Even wheel loaders routinely hit 20 mph in short runs.
Advantage: Trucks and wheel loaders.
Verdict
Because of its unique design, the crawler carrier falls into a niche market in the earthmoving world, but sales and interest in the machines continue to grow, Caldwell says. Contractors use it to do stream and river restorations, roadbuilding on forestry lands, lake reclamation, hauling and dumping in and around wetlands, work on slopes and on pipeline jobs that require minimal environmental impact.
