Convoys operate with two complementary types of machines for this task: traction machines and grooming machines, which allow the traction machines to work efficiently by running on a levelled and reasonably compacted track.
Choice of grooming machines
In 1989, as the first studies for the new station were taking shape, the project selected the Kassbohrer / Pisten Bully groomers (PB xxx) to meet grooming requirements, for reasons relating both to the brand’s reputation and to its strong existing presence on the continent. These machines are of course designed to travel over all types of snow, even though, by design, groomers were originally intended for ski slopes. Grooming work on convoy routes in Antarctica is different. Here, the machine grooms continuously through snow hardened and compacted by wind and micro-melt, at the speed of the tractors (around 12 km/h for the MT 86x series).
in operation between Dumont d’Urville / Concordia
Dealing with a sastrugi
Evolution
The first Pisten Bully machine to be trialled was the PB 270 model. This machine, although powerful (200 kW), had its limitations and was quickly replaced by the PB 330. The PB 330 was in turn (20 years later) replaced by the PB 300. The naming is misleading: the PB 300 is a modern machine with power output above 350 kW. With the introduction of this model, several weaknesses in overall chassis strength, blade mounting and track tensioning were also corrected.
Track belts and windscreen
Specifications
The PB 330, or now the PB 300, are powerful machines – from 240 to 350 kW. Their weight is 9,000 to 11,000 kg. Their ground pressure is low (80 hPa). Transmission is via hydrostatic pumps and motors, with electronic controls. The blade, very easy to manoeuvre, is purpose-built for snow. Maximum speed is around 20 km/h unladen. In operation, the PB xxx machines consume, like the tractors, around 6 litres of diesel per kilometre. Fuel consumption varies little with the density of the snow being moved.
Adaptations and modifications (known as “winterising”)
As with the tractors, the machines undergo a set of adaptations (winterising) to suit both climate and environment. These modifications and adjustments allow the groomers to operate effectively and reliably in an environment where average summer temperatures range between -20 and -50°C, on an ice sheet (limited ground bearing pressure) and under minimum atmospheric pressure equivalent to an altitude of 3,600 m. Preparation and polar service adaptations are similar across all models.
Unlike the tractors, the groomers are not fitted with winches, electrical generators or cranes — significant accessories fitted to the tractors. Generators and floodlights are too heavy and too bulky. Winches and cranes could be fitted, but the loads the machine can bear remain too low for this to be effective.
Notes
As an alternative, the Kassbohrer groomers can be used as traction machines, but these machines, like bulldozers, were not originally designed for this task. They have the same power output, but remain light, fragile machines which, compared with the much heavier tractors, require a great deal of care when towing loads of several tens of tonnes on sledges. Jerky pulling must be avoided (steady effort required), and loads must not be allowed to push against the machine, and so on.
While they were ruled out for towing the loads generated by transport convoy operations, they do have their place on a scientific convoy, where the requirements are different and where, in particular, it is prudent to standardise equipment to simplify maintenance and reduce the amount of spare parts carried.
