Virage project revisited
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Renault's latest concept vehicle spotlights innovations including an aluminium chassis, hydraulic discs and a radical gearbox.
by Colin Sowman • Renault has unveiled its second Virage project vehicle, designated the VE20. The original Virage, which broke cover in 1985, was a 6x4 tractor: this time round the te.stbed is a 6x2 which incorporates a new concept on chassis design and construction; an 11-speed automated manual gearbox, and hydraulic disc brakes. It is rated at 44 tonnes.
The chassis has 300mm-deep extruded aluminium side rails formed from symmetrical double-box section with T-slots towards the top and bottom. The cast aluminium cross members and suspension can be attached at any position by bolting through to a steel plate inserted in the T slots. This allows a single non-drilled side rail to be used on both sides of the chassis which can easily be adapted to 4x2, twin steer or double drive.
Torsional rigidity
Renault VI's technical manager, Pierre Lecoq, says the new chassis has five times the torsional rigidity of current models with no weight penalty.
It bends downwards towards the front, allowing a fifth-wheel height of 1,100mm while affording extra protection to car drivers in the event of a head-on crash. The Magnum-based cab is supported on pillars fixed to the chassis; the engine and transmission fill the space between the two. Cab innovations include a single door and a spiral staircase.
Semi-active hydraulic suspen sion keeps the vehicle level; it can be lowered for coupling to semi trailers. An independent Macpherson strut arrangement is used at the front. Wishbones secure the top of the rear axles with outboard leading and trailing arms at the bottom Electronically controlled hydraulic rams govern the vertical movement of each wheel and transfer weight to the drive axle if the ABS/ASR system detects wheelspin.
Prototype Bendix
hydraulic slidingcaliper, twin-piston discs allow dual-circuit brakes with minimal brake lag. Each circuit controls one piston in each front calliper and all the calipers on one of the rear axles. Load sensing works off the pressure in the rear suspension; a hydraulically mod ulated control valve adjusts the air supply to the trailer, which has air-operated discs.
Michelin supplied the prototype wide, low-profile (425/55) tyres and cast-aluminium 19.5in wheels. With no need to twin the rear tyres the brake is left exposed for cooling. This also increases the potential load space. The front discs are compact enough to fit within the small wheel.
Power-assisted rack-and-pinion steering has dual, parallel circuits with automatic compensation if the primary, open-centre, circuit fails. A warning shows on a monitor in the cab.
The VF.20's gearbox is tucked in beneath an almost horizontal engine, allowing forward control with a non-tilting alb.
A torque converter delivers power through a retarder to the gearbox, which drives the hubreduction rear axle. The prototype retarder has two "electrohydraulic interfaces" in place of an accumulator. It develops 1,2501bft (1,700Nm) of stopping power but is said to have minimal drag when not in use. The retarder can communicate with the cruise control. Inside the gearbox the drive is transmitted via one of two paths, each of which is engaged by its own clutch. Gears 1, 5 and 9 are on one path: 3,7 and ll on the other. Gears 2, 4, 6, 8 and 10 are engaged by activating both paths and using a differential arrangement to give a ratio between the two.
Gear changes
This means that the truck is under power even during gear changes. Steps in the box are a constant 1.2 between each ratio.
Gear shifting is automatic but the electronic control allows the drivers to override the ratio selected unless his choice would damage the engine. Renault says the 8.2000 has only 10% the drag of a conventional five-speed automatic transmission.
Early trials indicate fuel savings of up to 30%.
The VE20 will not be a production vehicle but, says Renault, it has proved the value of a number of concepts which may be incorporated into future models.