Wilbert began to manufacture tower cranes in 2002. Four years later, the German’s firm had made 50, and, as this article was being written, the 100th Wilbert crane left the factory. His tower crane rental and manufacturing company has recently built a new factory for series production of the flat-top hammerhead WT e.tronic range close to its Stromberg, headquarters.
The design of the cranes was informed by a list of 280 points of how a tower crane could be made better, compiled over the years by Franz-Rudolf Wilbert, managing director and co-owner of Wilbert Turmkrane GmbH.
That viewpoint informed the choice of components in the flat-top hammerhead WT e.tronic range’s choice of hoist rope winch assembly. “For me it was decisive that we only use well-proven, standard, components from large series production,” Franz-Rudolf Wilbert says. Should something go wrong, spare parts are easy to find around the world, so the crane can be back up and running quickly.
Wilbert’s clever use of standard components has enabled the cranes to raise loads quickly, without huge motors. The smaller cranes lift a 1t load at a maximum speed of 140m/min, and the two larger models lift 1t at a maximum speed of 225m/min. The hoist rope winch assembly needs to be small to allow the counterjib to be lifted into place in one piece, without having to add the winch assembly—motor, gearbox, clutch, holding brake and rope drum—to the assembled tower separately.
High rope speeds require high motor speeds, especially in Wilbert’s case. Its maximum drive speed is 6,000rpm, four times higher than conventionally-controlled cranes, the company says. “In this way a high speed can be achieved without having to use an expensive variable gearbox,” the company explains (although these are rarely used in tower cranes).
The Woelfer motor has a special winding to be able to cover the wide speed range. Such a large speed range also requires a powerful frequency converter, the company says, to drive the motor to its highest speeds. It says that its SEW Eurodrive unit’s output frequency, as high as 200 Hz, is “state of the art.”
Wilbert chose a Simatic S7 crane controller and Siemens Flender K4FH gearboxes to transfer power from the motor to the rope drum. There are two sizes of K4FH horizontal gear units for the Wilbert range. The frame size 7, which has a rated torque of 20,500Nm, is used for the WT 150, 200, 300, 320 and 420 e.tronic models. The frame size 11, with rated torque of 60,000Nm, is for the WT 560 and 650 e.tronic. (Wilbert tower crane model numbers refer to the tonne-metre class of the crane). Siemens also installed a filling/drain ball valve to change the oil.
