Taking weight out of trailers reduces operating costs. Businesses that operate fleets of trailers certainly want that, but not if it comes at the cost of reduced strength and durability. So can these apparently conflicting goals be solved? Mick Jagger likes to tell us, “You can’t always get what you want,” but we’re going to explain how you can. The answer lies in harnessing the advantages of aluminum extrusion.
Challenges Facing Trailer Owners/Operators
Fuel consumption is a huge issue, but it’s far from the only headache. Durability and maintenance costs come a close second and third, after which there’s resale value to consider.
Fuel consumption is dictated by aerodynamics and weight. The former predominates on the highway and the latter in urban environments, (and when climbing gradients.) Complicating things further, aerodynamic devices like skirts and cab extenders increase weight. It really does seem you can’t have it all.
Reduce trailer weight and you can improve mileage or increase payload. However, as it’s more common to cube-out than weigh-out, a lighter trailer yields immediate savings. And even if a trailer weighs-out, more payload reduces the fuel cost per pound transported. (Alternatively, add some aerodynamic aids for a net zero on weight.)
Fuel savings vary by use case, but Overdrive.com quotes Paccar as saying, “for every 300 pounds you eliminate, you gain 0.2 percent in fuel efficiency.” Meanwhile, “Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles” (National Academy of Sciences, 2020,) notes that, “reducing weight by 1,000 lb … reduces the payload-specific fuel consumption, by 2.2 percent.”
So weight matters, but less weight can often mean less strength, and that’s a problem. Even when a trailer isn’t loaded to the maximum weight it must handle fork lift trucks, pallet impacts, loading bays, potholes and temperature extremes. Time off the road for repairs is lost income and increased maintenance costs. If a lightweight trailer doesn’t last as long as one that’s heavier, the costs could outweigh the fuel savings.
Aluminum: Stronger Than it Looks
Steel is strong, but it’s also heavy. Pound for pound, aluminum is stronger. Even though you’ll need more metal to achieve a given load-bearing strength, the aluminum version will weigh less than one formed from steel. (For specifics, take a look at “Lightweight Comparison: Steel vs. Aluminum vs. GFRP.”)
Aluminum even compares well to wood. Admittedly, it depends on the type of wood, but there are reasons why aluminum bats are common in baseball. (Read this Penn State study, “Why Aluminum Bats Can Perform Better than Wood Bats” if you’re interested.)
High specific strength isn’t all aluminum has going for it though. It’s also corrosion-resistant and very form-able. Let’s address those in that order.
Steel needs a coating to prevent it rusting. Aluminum doesn’t. It naturally forms a surface oxide layer that stops further corrosion. That makes aluminum trailer components more durable and lower maintenance than their steel equivalents. And if you want to compare aluminum to wood, it’s not going to rot, split or warp.
Aluminum also has greater ductility, which is what makes it very form-able. Try bending steel and it will likely crack. Aluminum bends much more readily, (though this is somewhat series-dependent.)
A major benefit of this ductility is that some grades of aluminum, notably the 6000 series, are readily extruded. This is a big deal because it opens the door to higher strength, lighter weight trailer components.
Extruded Aluminum Applications
Extrusion produces long lengths of material with a uniform cross-section. The tooling is relatively low-cost and high throughputs are achievable, making it an inexpensive process when compared to casting or forging.
Extruded sections can range from simple circular and rectangular tubes and beams to complex shapes that interlock, accept captive nuts or are easily tapped to take screws and bolts. Profiles can be designed for high stiffness in deflection and torsion, making them lightweight load-bearing members.
While symmetrical shapes extrude best, asymmetric profiles are possible, subject to certain limitations. (If this is a topic of interest, contact us to discuss your application.)
After extrusion the lengths are cut to size for secondary processing. They may also be bent into complex shapes, albeit with a radius rather than a sharp angle. There are at least five bending and stretch forming methods for aluminum extrusion. Forming like this is appropriate for various trailer components such as roof spars.
Extruded section is often used in long lengths, as uprights between panels for example, but the benefits of shorter lengths shouldn’t be overlooked. Aluminum extrusion makes excellent, and lightweight, corner braces and brackets. It makes mounting points for other accessories, support rods and hinges. Look around a trailer: there’s practically nowhere it can’t be used.
Benefits of Aluminum Extrusion in Trailers
When replacing steel, aluminum saves weight. Without meaning to labor the point, that’s important, but it’s far from the only benefit. Aluminum trailer components can be more durable than their steel equivalents thanks to a combination of ductility and corrosion-resistance. There’s less maintenance too as they won’t need painting.
For trailer operators, aluminum not only reduces fuel bills, but lowers repair costs and cuts off-the-road time. Plus, the trailer will last longer and likely have higher resale value when time comes to part company with it.
At Wiley we talk to experienced design engineers all the time. Many are familiar with the advantages of aluminum yet don’t always appreciate the flexibility that extrusion can provide. If you’re looking to lightweight a trailer and need more ideas, let’s talk. Perhaps you can actually get what you want.