Bucket-wheel excavators are mechanical behemoths that churn up the earth at a staggering rate. They are used in large-scale open-pit mining operations to clear what is known as "overburden" - the material that lies above valuable mining seams. These continuous digging machines are marvels of complex engineering that can take up to five years to construct, and cost as much as $100 million (£80 million). But once they get to work, look out!
Record title: Largest land vehicle, Heaviest land vehicle (both Bagger 293)
The first bucket-wheel excavators were developed in the early 20th century, and evolved from water dredgers. The machines may be massive, but the basic principle is very simple: when the huge wheel at the front of the excavator rotates, it turns buckets that scoop up earth and drop it on to a conveyor belt to be carried away. Modern bucket-wheel excavators perform this operation on a literally earth-shaking scale: the biggest of all is Bagger 293, a 14,196‑tonne (31.3‑million-lb) monster that is simultaneously the Largest and Heaviest land vehicle.
Launched in Aug 2016, the LEGO® Bucket Wheel Excavator comprises 3,929 pieces, making it the Largest commercially available LEGO Technic set. Its approximate dimensions are 28 in (72 cm) long, 16 in (41 cm) high and 11 in (29 cm) wide. Thanks to a number of motorized elements, including caterpillar tracks, conveyor belts and a rotating bucket wheel, the model works just like a real mining vehicle.
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As powerful as bucket-wheel excavators are, they are unlikely to win many races. Moving on three rows of caterpillar-track assemblies, Bagger 293 has a top speed of around 0.33 mph (0.53 km/h). Any roads it crosses have to be rebuilt afterwards, as its sheer weight is enough to crush the concrete.
The Bagger 293 has 18 buckets, each with a volume of 6,600 litres (1,743 US gal). Working continuously, the excavator is capable of shifting 240,000 m³ (8.475 million cu ft) of earth in a single day. This is the equivalent of around 3 million bathtubs’ worth of soil.