Most people never think about the aerodynamic drag on trucks traveling at speed, but it’s one of the most important considerations for logistics companies. The majority of fuel doesn’t go into putting the vehicle into motion; it goes into keeping it there. You might know how mounting spoilers, vortex generators and diffusers on cars result in drag reduction but have you ever wondered how do trucks deal with aerodynamic drag?
Air resistance is a real devil. It starts off small but then grows exponentially. The drag force is directly proportional to the square of the speed. So air resistance at 60 mph is more than double that at 50 mph and so on.
Generally whenever we talk about drag force, it mainly comprises of skin-friction drag and pressure/form drag.
The skin-friction drag, as the name suggests is the resisting force because of friction caused between the body and the air flow.
While pressure drag is the drag caused due to significant pressure change between the front and back of the body because of the flow separation. More bluff the body, more the pressure drag. Eg. A flat plate held vertically, a cube, flat faced trucks etc.
Fast-moving vehicles, such as supercars and supersonic jets, get around the aerodynamics problem by adopting certain shapes. For instance, the nose cone of a fighter jet is conical and has a point on the end, allowing it to cut through the air like a hot knife through butter.
By contrast, trucks have a problem. By virtue of their function – to ship goods around the country – they have to be big and boxy. And that’s precisely the opposite of what you want when trying to save fuel.
The Aerodynamics Tradeoff
In engineering, everything is a trade-off. And nowhere is this more apparent than in the world of trucking. You could make a truck with virtually no air resistance at all, capable of zipping through the air at fabulous speeds. But you’d only be able to make it at the cost of reducing its capacity to near zero, just like sports cars.
When it comes to sports cars, the lightness, aerodynamic shape and higher gear ratios, all go along with each other enabling the sports and race cars to achieve high speeds. On the other hand, the main purpose of trucks is to carry heavy loads as opposed to sports cars.
Aerodynamics can do wonders! Did you know, Formula 1 cars generate enough downforce at 160mph that they can even be driven upside down in a tunnel! Unbelievable, right? Read the whole article here to know how.
Solutions To Aerodynamic Drag –
If you’re a trucking company, offering quotes via online load boards, you want to be able to offer customers shipping for the lowest cost, highest margin possible. That’s how you win business.
But the only way to do that is to cut your fuel costs. And the only way to do that is to reduce the coefficient of drag on vehicles in your fleet. Following are some of the solutions –
One of the most effective solutions is to install truck fairings. The word fairing is just an engineering term for features that modify the shape of the OEM chassis. You can add them anywhere drag is likely to occur, such as atop the cabin and around the wheel arches.
The 2 main locations where they could be found is at the end of the trailer and underneath it between the tires. The ones that are at the end are called Rear/Tail fairings. Tail fairings delay the separation of the airflow from the truck thereby significantly reducing form drag! Most fairings are made of lightweight materials and are foldable that don’t increase the energy costs of getting the vehicle up to speed substantially.
2. Rolling resistance
Another solution is to reduce the rolling resistance of the tires. Always make sure that your tires are inflated exactly up to the right amount! Lesser tire pressures lead to higher rolling resistance as well as wear and tear both ultimately resulting in higher operation and maintenance costs.
Also, you might experiment using flexible sealants around and under the vehicle. These have two purposes. The first is to fill in little gaps where air could circulate and create vortices that slow the truck down. The second is to dampen vibrations and reduce energy loss as the vehicle rolls along.
4. Reducing gaps
There is yet another type of fairing called as gap reducer. It works similarly as the others and is mounted on the front part of trailer between the trailer and the truck. If you have ever seen a Tesla Semi truck, you would notice that there’s almost no gap between the tractor and the trailer. Such gaps generate high drag especially while turning and these gap reducers do a great job reducing that 😉
Tesla motors has done a great job when it comes to aerodynamics of trucks. The Tesla Semi truck has an aerodynamic coefficient of just 0.36, less than that on Bugatti Chiron, one of the fastest cars in the world! Now that is an amazing achievement. Read more about Tesla Semi truck here.
Dealing with aerodynamic drag could bring substantial economic rewards. A 15 percent improvement in the aerodynamics of a truck could reduce its fuel consumption by more than 2,000 gallons per year, easily paying for the modifications!