The Liebherr TI 274 mining truck, first unveiled in 2007, has returned to the stage with new developments. Although some of the technologies are still in R&D, it is estimated to be available in 2010.
The truck was designed with emphasis on reducing its empty weight while maximizing payload and making the vehicle more efficient to run. Second largest in the Liebherr line, the TI 274 has a capacity of 320 ton (290 t) and features diesel-electric drivetrains designed for specific customer needs.
The body of the truck is an integral part of the load-bearing structure and, thus, does not rest on the chassis. This change, along with moving the hoist cylinder connections to the front of the chassis, enables the payload forces to be directed into the ground. As a result, the chassis and body are lightened and carry the load weight more evenly. Moving the hoist cylinders has changed their role to one of continuously supporting the payload and dump body.
To support these stresses, external supports direct many forces and load impacts away from the internal components of the cylinders, while guides prevent damaging lateral movement.
Further turning the dump body into an integral part of the load-bearing structure is a transverse beam at the rear of the body, which functions as a rear crossmember would on a conventional frame. Castings are used in areas of the frame subjected to particularly large stresses.
A variety of diesel powerplant options are available, each matched to specific customer needs. The largest is a 16-cylinder Detroit Diesel producing 3000 hp (2237 kW) with a top speed of 40 mph (64 km/h).
Rather than having two large electric motors at the rear of the truck, the TI 274 has two rear axles and four rear wheels, each fitted with an individual ac motor for independent control of the speed of each wheel. Liebherr says that feature improves traction, prevents tire overloading, and reduces tire wear as it can minimize scraping in corners.
The two independent rear axles can oscillate 4° left and right to maintain tire-to-ground contact on uneven terrain, reducing excess wear and allowing smaller tires to be fitted without reducing capacity. Having two axles also makes the vehicle more stable, thanks to more distance between the support points on the body and the rear suspension.
The cab is designed for safety and usability, balancing comforts such as air conditioning with roll-over protection, sound insulation, and an easy-to-read instrument layout. The truck stores operational data onboard for access when servicing or managing use.
Liebherr developed the IGBT (insulated-gate bipolar transistor) ac-drive system with digital controls, as well as the suspension and gear systems, in-house. The new design of the TI 274 resulted in an empty weight of 187 ton (170 t), for a ratio between empty and capacity of 1.71, ahead of the typical 1.33 to 1.39 seen on comparable mining trucks, it claims.