Aerodynamics played a key role in this project in the US, and PowerTorque’s European Correspondent, Will Shiers crossed the Atlantic to bring us a glimpse into the aerodynamics of a SuperTruck.
The team developing the Volvo SuperTruck2 focused on making both the prime mover and trailer as slippery as possible. This explains the large number of gap closure fillers, including around the wheel arches, and a lack of door handles.
Bond explains that windscreens are one of the worst offenders in terms of destroying a truck’s aerodynamics, so the decision was made to give it a curved, wrap-around shape. Giving it the same sweep and rake as the wedge-shaped cab minimises swirling air, and instead sends it from the front of the truck to the top of the trailer as quickly as possible.
“Having done that, Eric Bond, project manager and principal investigator for Volvo SuperTruck 2, and his team then had the challenge of trying to get the windshield wipers to work,” says Keith Brandis, Volvo Trucks vice president of partnerships for North America.
Also helping to reduce drag is Volvo’s Camera Monitoring System, which replaced conventional external mirrors with cameras and screens. While not yet legal in the US, Volvo has permission to use the system on test vehicles.
The truck rides on air suspension, which adjusts automatically depending on speed. It drops by 7.5cm at highway speeds, and raises for low speed manoeuvring.
Another easy win in terms of aerodynamic savings came from closing the gap between the back of the cab and the front of the trailer. Brandis explains that every 300mm of space between the truck and trailer equates to a loss of between one per cent and two per cent in fuel efficiency. SuperTruck 1 had a 1,000mm gap, but SuperTruck 2 is 180mm less.
Acknowledging that the trailer has a significant impact on aerodynamics, SuperTruck 2’s Wabash tandem-axle semi-trailer features numerous custom aero aids. It’s also significantly lighter than a regular production trailer, rides on low-profile tyres, and features a collapsible boat tail at the rear end.
Michelin was one of the project’s partners, and supplied lighter, low-rolling-resistance tyres for the prime mover too. They’re on 19.5in wheels, which not only reduces weight, but lowers the ride height in order to improve aerodynamics.
Together, all of these aerodynamic enhancements have made SuperTruck 2 20 per cent more aerodynamic than its predecessor, and drag is 50 per cent less than the base 2009 class 8 truck.
“You don’t usually see these kinds of breakthroughs in our industry, as typically improvements come in small evolutionary steps,” says Bond.
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