Bourne, Lincolnshire, UK: Truck aerodynamic kit maker Aerodyne is emphatic about the value of fitting aerodynamic kit to trucks which operate solely in urban areas.
“The reason people are skeptical is that these trucks carry out many short distance, low speed trips and therefore aren’t always subject to the same forces or economies of scale that larger, long-distance vehicles are.”
Aerodyne explains why lighter vehicles need aerodynamic even at low speeds. When a truck moves, the engine has to combat three main forces:
- Drive train friction – the loss of power in the drive train, an area in which all truck manufacturers are striving to improve efficiencies and which our aerodynamic kit cannot help;
- Tyre rolling resistance – this relates to the weight of the vehicle, the heavier it is, the more the power needed to move it;
- Aerodynamic drag – this relates to the shape of the vehicle and how it moves through the air when travelling. This force is easy to test.
As a vehicle doubles its speed, it needs twice the power to overcome its weight and eight times the power to overcome the aerodynamic drag. Put another way, the vehicle behaves as if it is heavier the faster it travels.
For an 18-ton rigid vehicle, the type which would be used on longer, faster journeys. Aerodynamic drag starts to use engine power at around 18km/h. At 50km/h, 40 horsepower (66%) is being used to overcome weight and 20 horse power (33%), aero drag. The key interest is at the 50Km/h point.
Now, look at a 3.5-ton vehicle, more like the smaller urban trucks which this article is focused. At 50km/h, 8 horse power (42%) is being used to overcome weight but 11 horse power (58%) of the engine power is overcoming aero drag.
There is a dramatic increase in aerodynamic drag between 16 and 50km/h, the most common speed range at which these trucks operate. “This evidence leaves no room for doubt that aerodynamics are worth considering even on shorter, slower urban journeys,” Aerodyne says.
“In fact, the lighter the vehicle, the lower the speed required to see a benefit from aerodynamic improvements.” And fleet operators report these benefits achieving a 15-20% fuel-saving in actual operations.
Reynolds Catering, a fresh fruit and veg wholesaler achieved over 20% fuel-saving fitting Aerodyne deflector and side-wing kits to its 3.5tonne vehicles operating at lower speeds than Bidvest.
In 2019 Reynolds purchased five Mercedes Sprinter refrigerated box vans and checked the average fleet MPG over a period of weeks, at this stage no Airkit was fitted. Aerodyne supplied five cab roof deflector and sidewing kits (modified to fit around the fridge).
Once these had been fitted, the average fleet MPG over a number weeks was again checked though the telematics with the Airkits providing a fuel-saving of over 20%, Aerodyne says.
“Due to 3.5 tonners being a light-weight vehicle, most of the engine power is consumed overcoming aerodynamic drag. This means an improvement to the aerodynamic shape of the vehicle will see strong fuel-saving even at lower speeds,” Aerodyne says.
“We were amazed at Aerodyne’s Airkit producing over 20% fuel-saving – they’ve opened further fuel-saving opportunities for Reynolds, helping us to meet our environmental goals,” Steve White, head of national fleet, Reynolds Catering, says.
