With a continual drive to lower the fuel consumption of its trucks, Scania has introduced a P 360 8×2 rigid version of the New Truck Generation range, targeted squarely at urban distribution roles. Paul Matthei took a loaded unit for a jaunt over the Blue Mountains west of Sydney and returned with an extraordinary fuel figure.
Old habits die hard, and some truckies can be somewhat stubborn in resisting change to the tried and true vehicle configurations to which they are well accustomed.
Often the aversion can be traced to a long-held belief originating from a negative experience that might have occurred 10 or 20 years earlier; with the memory having become an indelible imprint on the person’s psyche.
For example, it might have been the case that way back when he or she was driving a ‘lazy axle’ truck which became temporarily stranded when trying to negotiate a steep grade in the wet or a deep spoon drain across a driveway entrance. The subsequent frustration and embarrassment was perhaps sufficient to cause the angry proclamation: ‘I’ll never have a lazy axle truck again!’
And back in the ‘good ol’ days’ when a typical lazy axle truck was often little more than a lengthened chassis 4×2 rigid with a tag axle and load-sharing leaf spring arrangement tacked on the rear, that was perhaps something of a fair call.
But time and technology never stand still and the relatively recent proliferation of electronically-controlled air suspension has largely put paid to the steel spring suspension ‘hang-ups’ of the past.
What’s more, with the ever-present impost of fuel costs coupled with typically slim profit margins, what sensible operator can really afford to ignore the prospect of a few percentage points better fuel economy simply by having one drive axle instead of two? Over the lifetime of the vehicle this adds up to some serious dough.
This is the assertion put forward by Scania, a truck manufacturer that has done its utmost in recent years to provide its customers, both present and prospective, with tailor-made solutions designed to give them the lowest possible total cost of ownership for the effective life of the vehicle or fleet.
The P 360 8×2 rigid is a great example of this philosophy. Acutely aware of the need to negate the aforementioned vagaries of early ‘lazies’, Scania has designed the rear air suspension with a driver-controlled load transfer system that during low speed manoeuvring simultaneously increases the air pressure in the drive bags while decreasing that of the tag bags.
This combined with the standard diff lock is designed to provide sufficient traction in any tricky situation likely to be encountered during regular urban distribution driving.
During my time as a professional driver, I recently spent a number of years operating a Scania P 440 6×2 prime mover on primarily urban distribution work. As it has essentially the same rear axle set-up as the P 360 rigid, I have no hesitation in vouching for the effectiveness of the load transfer system.
In my experience, the situation where it was needed most was when starting off from the lights on a steep, wet road with a loaded semi-trailer. In this scenario I found it was vital to flick the switch a few seconds before lift-off to allow full pressure to build in the drive bags, thus ensuring maximum traction. Then it was a matter of feathering the throttle to get it cleanly off the mark.
Upon reaching about 40km/h the system automatically reverts to the equalised pressure setting and by that stage enough momentum has been built to maintain traction, provided judicious use of the throttle is maintained.
Here’s the thing though, drivers who are not prepared to go easy on the accelerator in these conditions will definitely get more wheel-spin in the wet than a 6×4 vehicle. However, the load transfer system clearly mitigates this when used correctly.
This is where driver training needs to be undertaken to ensure drivers understand the dynamics of the 6×2 and 8×2 rigid version of the New Truck Generation configurations and how to get the best out of these vehicles in all conditions.
Speaking of which, there is another situation in which extra caution must be taken with retarder-equipped 6×2 prime movers, particularly when the trailer is unladen.
Again, drawing from my experience driving the aforementioned 6×2 prime mover on the long and steep decline of the Toowoomba Range in the wet and with an empty trailer, I found it necessary to gear down lower rather than rely on the retarder to keep speed under 40km/h, and also to activate the load transfer function.
In this situation the Scania’s powerful retarder used exclusively can actually be counterproductive because the retardation effect operating on one axle tends to lock the wheels on a wet road. When this happens, the ABS cuts in and cancels the retarder so speed builds and then the retarder re-engages and so the cycle continues.
I found the best solution was to engage the descent control system whereby the speed was set at 40km/h and held there by a blend of gearing, retarder and service brakes, with the computer and wheel speed sensors working to ensure the optimum blend of retardation to maintain traction.