The five-axle, Grove GMK5250L all-terrain crane, with a rated lift capacity of 300 tons, uses a seven-section Grove Megaform main boom (with an egg-shaped cross-section) that provides extensions from 44 to 230 feet. Reach is increased with the bi-fold lattice swing-away jib (with hydraulic off-set and luffing capability), which can be pushed out farther with either a boom extension or two jib inserts—or a combination of both—to yield a total jib length of 121 feet and a maximum tip height for the GMK5250L of 361 feet. The jib can be offset up to 50 degrees. In addition, an integrated heavy-duty jib is available.
The GMK5250L’s super-structure cab uses the Manitowoc Crane Control system, which incorporates the parent company’s Boom Configurator, designed to “make it quick and easy to select the optimum boom position for a specific lift,” according to the company. The Boom Configurator allows the operator to enter lift parameters—radius, load, and distance to be moved, for example—and then the system calculates the best boom configuration. When the operator selects the suggested configuration, the system automatically deploys the boom to the required length.
The GMK5250L uses a single engine to power both the carrier and super-structure—a six-cylinder Mercedes-Benz OM471LA rated at 520 horsepower and meeting Tier 4-Final emissions standards. The new crane features a standard 10x6x10 axle configuration, with three driving axles and all-wheel steering. A 10x8x10 configuration is available.
The new crane’s Mercedes Benz G280 transmission features the VIAB Turbo Retarder Clutch system, a torque-converter-like device positioned between the engine-driven friction clutch and the transmission. When GMK5250L is starting under load, the friction clutch opens and the VIAB system functions as a powerful torque converter to drive the transmission. Once rolling, the friction clutch closes and the Turbo Retarder Clutch drains its fluid, allowing an efficient direct-drive arrangement. When braking is required, the operator activates the Turbo Retarder Clutch, which then floods with oil and functions as a fluid-type retarder. According to Manitowoc, the VIAB system saves wear on mechanical components, reduces heat in the driveline, and improves fuel efficiency.
Manitowoc’s Megatrack suspension system allows the GMK5250L’s ground clearance to be adjusted independently of the unit’s five-position outriggers, and allows the crane to maneuver on site with its full complement counterweight. An optional, self-rigging crane eliminates the need for an assist crane during on-site rigging, says Manitowoc.