Spierings SK477-AT4

The Spierings SK477-AT4 was developed to serve contractors who require a capable mobile tower crane with greater reach and load moment than compact three-axle machines, while avoiding the transport complexity of larger five- or six-axle models. Built by Spierings, the SK477-AT4 follows the company’s long-established design philosophy of combining true tower crane working characteristics with the flexibility and mobility of a road-going carrier.

Mounted on a four-axle chassis, the SK477-AT4 strikes a practical balance between maneuverability and operational capability. The four-axle layout keeps transport length and axle loads within manageable limits, making the crane suitable for city-center access, narrow streets, and sites with restricted logistics. Multiple steerable axles provide good maneuverability, and road travel speeds of up to approximately 80 km/h allow efficient relocation between projects without the need for additional transport equipment.

The crane superstructure is equipped with a lattice jib designed for trolley operation, offering a working radius typically in the range of around 45 metres, depending on configuration. At short radii, the SK477-AT4 delivers lifting capacities in the region of 7 to 8 tonnes, enabling it to handle concrete buckets, formwork panels, reinforcement cages, and prefabricated elements commonly encountered on urban construction sites. At larger radii, the crane maintains practical capacities for general material handling. By operating the jib at steeper angles, increased hook heights can be achieved, allowing the crane to efficiently service multi-storey residential and commercial buildings.

A defining feature of the SK477-AT4 is its fully automatic, one-man erection system. Erection is performed at the push of a button and follows a compact, controlled assembly curve that requires minimal space around the crane. This makes it possible to set up the crane close to existing structures or within tight site boundaries, a major advantage in dense urban environments. Once erected, the crane can remain standing between work phases without dismantling, improving productivity on projects with intermittent lifting requirements.

All crane working motions—including hoisting, slewing, trolley travel, and erection—are electrically driven. Electrical power is supplied either by an onboard diesel generator or via an external site power connection. When connected to external power, the SK477-AT4 operates with low noise and zero local emissions, making it well suited for city-center projects and noise-sensitive locations. The electric drive system provides smooth, stepless control, enabling precise load placement comparable to that of a conventional top-slewing tower crane.

The crane is supported by a four-point hydraulic outrigger system with automatic leveling and electronic inclination monitoring. Different outrigger base widths can be selected to suit site constraints, balancing available space with required lifting performance. The stable four-axle carrier and well-balanced superstructure contribute to predictable handling and consistent performance across the crane’s working range.

The operator’s cab is designed to tower crane standards, offering good all-round visibility, ergonomic controls, and a comfortable working environment for extended shifts. Integrated monitoring and safety systems provide continuous feedback on crane configuration, load conditions, and wind limits, supporting safe and efficient operation.

Overall, the Spierings SK477-AT4 can be described as a versatile and efficient mobile tower crane that delivers reliable lifting performance without the transport and setup complexity of larger axle configurations. Its combination of four-axle mobility, fast self-erection, electrically driven crane functions, and tower-crane-like precision makes it a strong choice for urban and regional construction projects where flexibility, speed, and efficient use of space are essential.