Mobile Cranes: Technological Balancing Act
The moment of tilt invariably plays a major role where cranes with long extension arms are deployed to lift and move heavy weights. In docks or railway facilities covering a wide area where, for example, bulk materials or scrap metal weighing several tonnes need to be moved, cranes of this type are nevertheless in their element.
The Belgian company E-Crane Worldwide in Adegem has already been responding to this sophisticated technical challenge for more than 16 years with its special design “E-Crane®” (equilibrated crane): counterweights are used to bring into equilibrium the major part of the moment in the crane that generates the tendency to tilt. The unique feature is the fact that both the weight of the crane’s steel structure and that of the load to be moved are kept permanently in equilibrium. This means that the counterweight will “traverse” into the particular position required due to the position of the crane jib and the weight suspended from it.
E-Crane Worldwide can supply the E-Crane® in five model ranges, the size of which is based on the maximum jib length and lifting capacity. Rexroth in Belgium supply the complete hydraulic control for all five versions of Series 700 as well as pumps and filtration for the larger models manufactured by this crane specialist.
Designed for High Performance
The focal point is the compact hydrostatic gearbox with its case-hardened gear wheels, featuring heat-treated and surface-hardened internal gears capable of withstanding heavy loads. The specialist Belgian crane builder uses the Type GFT17 planetary gear box from Rexroth in its rail-mounted traveling cranes because they are effectively pre-destined for mobile heavy-duty applications: the compact construction saves space, and space is something which is at a premium in an E-Crane®, not least because of the counterweight technology. The gearbox structure also makes it easier to employ hydraulic motors
Here E-Crane Worldwide combines the three-stage gearbox with a size 28 variable displacement “mobile motor” from the A6VE series, thus achieving a transmission ratio of 77.9 (i). The robust structure drive is characterized by a high overall efficiency and features an integrated, spring-actuated multiple-disk brake.
E-Crane Worldwide adopts a totally modular approach to building its balancer cranes so that they can be dismantled within a short period of time. Here too, the GFT planetary gear box is able to capitalize on its strengths because it can be easily fitted and all hydraulic components are well coordinated with each other, including the plug-in motor. This means that an E-Crane® can be quickly transported within a docks area or even by ship to the other side of the globe.
Source: drive&control – The Magazine for Rexroth Customers 2007, 1