In 2005 MAN was able to meet the needs of the first customers demanding traction from the front axle at the “touch of a button,” with MAN HydroDrive which was the first to bridge a gap in the market for those customers who drive largely on roads, but in some situations require additional traction from the front axle without having to purchase an all-wheel drive truck.
Vehicles often operate as fire service vehicles, refuse collectors, construction vehicles and tankers – all of which need to respond in a timely manner even in adverse weather conditions and on mountainous terrain. They may also be working on unsurfaced forest tracks as timber transporters.
If rain has softened the surface, then rear-wheel drive alone is sometimes not enough, especially if the truck is loaded and the rear axle is unable to generate full traction. An example of this is entering and leaving unsurfaced construction sites with a building delivery vehicle, tipper or truck mixer. A HydroDrive truck which can avoid getting stuck in such everyday conditions in a quarry means increased uptime. In addition to this, the driver is also spared the inconvenience of having to be towed out in bad weather.
Steering on a slippery surface also becomes more difficult when a fully-laden truck pushes over the non-driven front wheels. A traditional selectable all-wheel drive is what is required here and MAN’ solution was the HydroDrive. The HydroDrive provides additional traction and safety but doesn’t need a transfer case, a front-axle differential or a front drive shaft. This helps to save fuel and decrease CO2 emissions day in day, out.
In comparison with a traditional all-wheel drive truck, a HydroDrive truck weighs around 400 kilograms less. This also means that HydroDrive vehicles are able to transport a much greater payload. A truck with HydroDrive thus expands the operational range of on-road vehicles: for many businesses this means the acquisition of an additional all-wheel drive truck is unnecessary.
MAN HydroDrive is the only all-wheel system that can get traction on to the front axle of a normal and medium-height truck. The advantage lies in the fact that this is the only possible way to implement all-wheel drive on certain vehicles: This is the case, for example, for container bodies in which standing height is necessary, for swap-body vehicles for fire-fighting and rescue services. The reason for this is that only normal-height vehicles can carry high swap bodies and still remain within the statutory height limits. Normal height also means easy access to the vehicle and a low centre of gravity, resulting in better driving stability.
Another advantage is the small turning circle. A HydroDrive truck has a smaller turning circle than vehicles with a mechanical front axle drive. This is an important benefit, for example for fire-service vehicles, which are then able to turn in one attempt.
MAN HydroDrive drives the front axles using a hydrostatic motor on each wheel. This is fed by a hydraulic pump with pressure of up to 420 bar. The drive can be engaged by simply turning a rotary switch, both while driving and under load – the driver can thus master gradients safely without having to stop.
The additional traction is also available in reverse and when coasting. On the one hand, this increases the brake output of the continuous braking systems – in particular of the MAN PriTarder. On the other hand, it significantly improves the vehicle’s manoeuvrability on slippery surfaces and therefore driving safety.