Each millimeter counts: Energy supply systems for extendable heavy load transporter

"This vehicle has been specially designed for the transport of windmill wings," says Herbert Swoboda, chief designer of the semi-trailer of Goldhofer AG in Memmingen. "With the ability to extend the flatbed semitrailer three times to a total length of 203 ft, it is possible to transport extremely long wings of windmills even in difficult terrain. " The vehicle was indeed designed for the safe transport of long windmill wings. Because of the enclosed cargo area, it can also be used as a universal vehicle with a payload of up to 38 tons. Energy supply systems are used in this customized vehicle to ensure the safe rolling of the electrical, brake and hydraulic cables in the inner tubes. It is the tested and proven "E4-1" series. One of their technical characteristics, the design principle of the so-called tongue and groove, provides a very high stability and structural safety. "That is all that matters to us," says chief designer Swoboda.

This telescoping three-axle semi-trailer truck of Goldhofer AG, Memmingen is extendable from 65.5 to 203 feet. In this picture it transports 180 feet long rotor blades across Denmark.

Energy supply systems are used so that the electric, brake and hydraulic cables can roll safely in the inner tubes. The energy chains are exposed to very strong push-pull forces especially when the vehicle is extended.

Triple-telescopic semitrailer

"We set global trends in the semitrailer sector," says Erich Traub of the marketing division of Goldhofer AG. "Our product range in this segment ranges from semitrailer through low-bed trailer up to combinable semitrailer trucks that can be driven over from the front. " At this year's 'bauma' in Munich, the company introduced, for example, a new flatbed semitrailer with pendulum axles. "For the first time it has succeeded in developing a transport vehicle with a maximum length of more than 203 feet," says chief executive Bernhard Katzenschwanz. The pendulum axles with an axle compensation of +/-300 mm give the vehicle an excellent maneuverability and can compensate for unevenness in both the stroke and in the lateral leveling. Moreover, it can be joined together under load to negotiate narrow passages or bends. This is enabled by the great resilience of the inner tube. "A first vehicle is already at work for a Danish heavy transport specialist; the construction of two more is planned," says Katzenschwanz.

Second, the travel is very large. The loading length of the heavy transporter is 20,000 mm, which can extend three times – by 13,950 mm first time, 14,050 mm second time – to a total of 62,050 mm. "This length cannot be implemented with a single energy chain," explains Herbert Swoboda. "Therefore, two energy chains run side by side with different travel lengths. “
The longer energy supply line is responsible for the first two strokes, thus two expansion lengths. The shorter energy supply line takes over the last stroke, and also lies in a trough. The respective travel is 14,000 mm and 7,000 mm. The radius is the same in both cases, with 150 mm. The modification of the transporter's length is done using pneumatic locks with bolts. "The operation takes place invisibly in the tube and completely automatically," says Swoboda.

The two energy chains lie side by side in the narrow black section. Only a width of 340 mm and a height of 577 mm are available as installation space.

Due to the cable-friendly plastic crossbars, the service life of the cables is increased by factor 4.

The telescope moves under the energy chain

Normally in energy supply lines, the upper run runs on the lower run. It is reversed in this application. The top connection point is the fixed end and therefore rigid. The bottom connection point is the moving end and therefore pivots. When the telescope is joined together, the energy supply system has to negotiate a height difference quickly and safely. For this reason, moving the pivoting mounting bracket downward gives constructive advantages. The telescope thereby moves under the energy chain. There is indeed, in this case, a small ramp, so that this process takes place as gently as possible, but still has to negotiate a projecting edge. There are also the coefficients of friction acting on the energy chains. The tubes are made of untreated steel, and the surface is rough. Dust settles on it. When extending, enormous push-pull forces occur especially on the first two meters and particularly at the fixed end, which are absorbed by the tongue and groove of the "E4-1" chain.