Just what was this Biglorryblog editor doing at a decommissioned army testing range in Germany this week? Driving some very large and VERY heavy trucks is what. BLB reported on the launch of the Mercedes SLT Euro 6 range a while ago- but now we have the chance to drive the beasts
Actually beast is the wrong word, while powerful there is nothing beastly about this mammoth mover. with a 120 tonnes load and a gross vehicle weight of 170 tonne it is actually extremely refined. The way the power is transmitted to the wheels is the answer - a new approach very different to the traditional torque converter. The Turbo Retarder clutch, a fluid system, is only used when starting or at very low speeds once the engine speed and transmission speeds match a conventional dry friction plate clutch takes over - but the Turbo retarder clutch has a few tricks up its sleeve- allowing 170 tonne to slow to a stop on a hill, hold it still, let it roll backwards under control, bring it to a stop again and then move off fowards - just by use of the accelerator pedal without the transmission oil overheating this is something a torque converter could not ever achieve - but the Turbo Retarder does this with ease
But it is no "one trick pony" a torque converter has for many years allowed heavy haulage outfits to creep very slowly when very low speed manouvering is required - the Turbo Retarder, by the flick of a couple switches can do this too . The power shift 3 auto gearbox has had its shift times decreased by 20% so even at these weights uphill upshifts are made with ease. Uphill starts from a stand still with the handbrake on are made simple using the hill start operation - quite simply put, the brakes will not disengage until there is sufficient torque to move the vehicle forward. Down hill the same components turn the turbo clutch into a highly effective retarder capable of holding back the massive weights on all but the most steep of hills. Some may feel that this is taking away from the highly skilled heavy haulage driver some control, but Biglorryblog has to report it doesnt, the driver remains the element that chooses the correct mode and makes the decisions, the SLT simply does all the hard work of carrying out the drivers instructions. Thus allowing the driver to concerntrate on the road and hazards ahead. Just how good is the SLT? well in this ex heavy haulage drivers opinion Mercedes have taken the next step and moved on the conventional thinking on a prime mover, its not just good its astoundingly brilliant.
Its not just in heavy haulage that this new concept comes into its own - Biglorryblog also had the opportunity to drive an 8x4 tipper fully laden ( at weights that would have a DVSA weighbridge operator having fits) that was also fitted with a Turbo Retarder clutch around an off road course that would make most 4x4 cars nervous. on a 20% + incline on wet stone the Turbo Retarder system allowed the fully loaded truck to make the ascents and descents under full control without using the brakes- again allowing the driver to concerntrate on what was going on outside the cabin. For this driver , unused to left hand drive vehicles, it meant he could concerntrate on keeping the vehicle on the challenging track while the truck took care of the business of keeping it moving and under control even over the most difficult of terrains
Look out for a full driving report and the technical details in an upcoming issue of Commercial Motor.
After all this excitement this Biglorryblog editor is off on holiday for a few days and is wondering if he can sneak back to Germany for another go with the simply awesome SLT