The new DAF LF 6×2 is all about lifting the pusher and the new model, previewed at the Brisbane Show gets a Diesel News test drive around Melbourne. Here in Australia, we are unused to the concept of a pusher axle that can lift out of the way when not needed. If any axles have been capable of being lifted in the 6×2/6×4 space, they have normally been lifting tags, which are simpler to engineer. However, their popularity has remained limited by issues around overhang lengths, especially when we have to live with the 6.0 to 6.5-tonne front-axle mass limit.
Of course, this kind of configuration is common in Europe due to the fact that, despite the overhang laws being similar, the front-axle weight rules are a lot more liberal, making axle placement less critical. The job of many European truck brand importers to the Australian market is to scour the large number of different configurations on offer in very different truck markets and see if any of them fit the requirements of the Australian truck buyer.
This where the DAF LF 28 6×2 comes into the picture, a useful addition to the DAF truck range aimed at a market which is crowded, offering something a bit different. With the configuration on offer, this truck can load up to its 23.5 tonnes gross vehicle mass (GVM), but as soon as the mass at the back drops below 6.5 tonnes, it can be retracted.
Any operation where the load diminishes during the journey, or where the truck is only fully loaded one way, will have a truck that turns into a 4×2, with all of the fuel use, tyre use and manoeuvrability advantages this will bring. The truck will work at its 23.5 tonnes GVM as long as is necessary and then, as soon as the load gets down to a manageable level for a 4×2, it can be raised and the operator starts saving fuel and tyre wear.
The Traction Question
There is another reason for some scepticism in the trucking industry about 6×2 configurations, namely the potential to lose traction on the single drive axle if and when the pusher takes enough weigh to reduce grip on the drive. Variations in road surface, driving through gutters or even a speed bump can be responsible for causing the drive to spin.
DAF has a solution to hand and it is an effective one. In the event of a loss of traction, the driver simply presses a large, prominent button on the dash and the suspension on the pusher axle lifts, and will stay lifted for five minutes unless the truck gets up over 30km/h, in which case the axle will drop back down and into action.
The lifting system is all part of the truck’s electronically controlled air suspension’s electronic control unit (ECAS ECU), rather than being separately controlled, as it can be in aftermarket systems which are fitted later. The axle can be controlled from within the cabin, or from the outside. There is a key-operated switch actually mounted on the axle itself, the one that is to be used when the driver wants the axle to remain lifted. It can only be lifted if the mass on the axle is weighs under 6.5 tonnes.
DAF recommends that the operator should always load the truck with the pusher axle down, to ensure there is no chance of overloading the drive axle unnecessarily. Once loaded, the driver can switch the axle to lift and, if it does not rise up, they will know that the load is too heavy for the truck to run as a 4×2.
Although on this test around the city of Melbourne, Diesel News didn’t try to get the truck into a sticky (or should that be non-sticky?) situation, our experience in the past has shown that dumping air in a suspension for just a matter of seconds is usually enough to get the truck out of any situation caused by a lack of grip for the drive. Normally, as soon as the rubber hits the road properly, the situation is resolved.