RUNNING GEAR &

Extra traction is the attraction

Double drive is usually the non-stick solution for units working off-road. But Kevin Swallow asks whether an independent hydraulically-driven could just as easily get your wagon out of the mire

he rule of thumb for most double-drive bogie that incorporates the standard AddiDrive product uses the bulk transport hauliers who a lift axle. When the articulated power-take-off (PTO) to drive two piston venture off -road is to specify vehicle is empty, the second drive axle motors, each one fi tted to the wheel a 6x2 tractor unit. If a lorry disengages from the driveline and is hubs on a steer or straight-beam axle. gets stuck, the driver has raised, leaving one drive axle. Once Pistons move into the wheel hub to Tmultiple options. First, autonomous reloaded, the second axle automatically turn the front wheels (pictured, below) systems might help; the will lowers. No weight is saved, but it independently of the engine. An automatically start rocking, moving reduces the fuel and tyre bill. electric control unit governs its speed backwards and forwards to try to free Another concept of having a second and use, and it can generate up to itself. Second, deploying the diff erential drive axle when needed has been 108bhp and 12,000Nm of torque per lock to turn both drive wheels in unison available in Europe since 2003. French axle. It operates up to 19mph (30kph). might work to get moving. Third, the company Poclain Hydraulics’ ‘on-road’ Exceed that speed and the system driver could try readjusting the load so product is known as AddiDrive, explains disengages, the pistons withdraw, there is more weight over the drive axle, Yannick Seeleuthner, general manager leaving the axle to free-wheel. which will also increase traction. for its Peterborough subsidiary. Seeleuthner explains: “When the If the off -road environment is At the touch of a button in the cab, system is activated, it transfers – in real known to be arduous, undulating or time and instantaneously – part of the soft, like quarries, forestry haul roads, torque on the front axle, according waste disposal sites, farmyards or to the road conditions and vehicle rural infrastructure projects, to name a behaviour. Traction on the front axle is few, then a savvy fl eet engineer might available at 0kph.” recommend a double-drive bogie on AddiDrive has three basic the tractor unit. functions. In creep mode, However, although this option brings AddiDrive, powered by the utilisation benefi ts, it imposes other hydrostatic axle, off ers very slow penalties. Costing several thousand but constant drive speed. In pounds more, it will also be around 1.5 boosted traction mode, the tonnes heavier than a single-drive-axle system indexes torque on the tractor unit, as well as less front axle to the throttle pedal frugal on the open road. position to provide more It could be viewed as a traction at start-up. In front sledgehammer to crack wheel angle compensation, a nut. the speed of the front wheel is Recognising this, most adjusted according to the angle truck manufacturers off er a information provided by the

26 www.transportengineer.org.uk February 2019 RUNNING GEAR & AXLES

“A normal tipper truck requires around 150 litres of oil to operate the hydraulic equipment on the truck and/or . AddiDrive uses the same oil” Yannick Seeleuthner

truck, to ensure optimal traction in turns. a coolant and fi lter system, electric hydraulically-driven SAF Intra CD Trak, The fi rst OEM to off er Poclain’s control unit, as well as cabling and which uses the truck’s hydraulic wetline systems, in 2005, was MAN Truck pipework. This weighs around 400kg, kit, is connected to a SAF 9.0-tonne axle and Bus. It marketed the system as but Seeleuthner argues that it is much on the trailer, explains Ben McEvoy, sales Hydrodrive, and was available for left- lighter than a double-drive set-up or and marketing manager for UK importer hand-drive only. Fellow German mechanical AWD, and, because it is only IMS (Industrial Machinery Supplies). truck OEM Daimler off ers it as Hydraulic used in certain situations, it saves fuel. The hydraulics are fully housed and Auxiliary Drive, again in LHD only. European truck OEM GINAF are covered by standard service and In 2010, Renault Trucks made the produces vehicles mainly for heavy-duty inspection programmes, requiring no system available in left- and right- off -road transport and construction from additional maintenance. To carry the hand drive, marketing it as Optitrack. its factory in Veenendaal, Holland. It uses hydraulics, SAF Holland has moved from Last year, the OEM consolidated a system with a similar design concept a standard reinforced 11mm-thick beam its Optitrack off er, rebranding it as produced by Bosch Rexroth, based in traditionally used for construction to a Optitrack+. Working with Poclain, it has Germany, which GINAF brands as the 14mm-thick beam. The additional weight introduced new features. First, a new HydroAxle+, introduced in 2010. to the tractor unit-trailer combination ‘boost’ button raises hydraulic pressure Product manager Winfred Hovestad is 149kg. It can only be fi tted to trailers from 420 to 450bar, leading to a 7% says: “Compared to a mechanical all- with disc brakes, but lifting axles can be increase in the maximum wheel torque. wheel drive, the HydroAxle+ system is accommodated. It also runs at higher speeds, from cheaper, lower to the ground, lighter The system provides traction from the 20kph to 50kph (12-30mph). Finally, and uses less fuel. We place the system rear of the , improving disconnection and re-engagment on a 9.0-tonne standard front axle and it the manoeuvrability of the truck. McEvoy now occur automatically, no longer weighs around 450kg.” adds: “It is available for fi tment, usually requiring driver intervention. He adds: “The big advantage of on the rear axle. These are for vehicles IVECO Trucks unveiled its badged HydroAxle+ is that maximum power that work in aggregate quarries, waste version of the system, Hi-Traction (LHD is supplied to the front axle from a and landfi ll sites. There is interest in the and RHD) at the launch of its X-Way standing start, completely independent UK, with several going into production range of construction vehicles in 2017. of the (driven) wheels, so it can work in this year.” creep mode, with the truck in neutral.” FITMENT Fitting it to a vehicle with an existing TRAILER MOUNTING hydraulic wetline kit for tippers and Rather than place all the drive axles moving fl oor trailers means adding a on the tractor unit, last year axle switch box, as the PTO can only perform manufacturer SAF Holland introduced one operation at a time. Seeleuthner the Poclain Hydraulics AddiDrive adds: “A normal tipper truck requires system for tipping semi-trailers. The around 150 litres of oil to operate the hydraulic equipment on the truck and/or trailer. AddiDrive uses the same oil.” Without a wet kit, AddiDrive requires a PTO to the back of the transmission, a header tank with 40 litres in the system,

February 2019 www.transportengineer.org.uk 27