Aluminum frame rails, new alloy castings from Alcoa help cut 2500 lb from tractor-trailers

The “centerpiece” of the technical display, according to Marquez, is a new roll-formed aluminum frame rail that engineers at Alcoa Technical Center developed with counterparts at structural-component manufacturer Metalsa.

“As the central attachment point for the truck’s major components, an aluminum frame rail can save almost 900 lb (410 kg) over a traditional steel frame rail—that’s game-changing weight savings,” Marquez said.

The companies developed the new frame over the past two years as part of the U.S. Department of Energy SuperTruck program, according to Russell Long, Chief Design Engineer, Ground Transportation, Alcoa Technical Center.

“The challenges are not as great as one would expect because we’ve been working with Metalsa, who makes steel frame rails, and they were able to use their current tooling on their current roll-forming line with the material change. So it’s mainly just design differences,” Long told SAE Magazines at the recent Mid-America Trucking Show (MATS).

Long noted that Alcoa had previous conversations with truck manufacturers regarding the use of its flat-rolled product for aluminum frame rails, “but it really accelerated with the SuperTruck programs…Once we get through that testing phase, we’ll be ready to move forward” with production plans. He declined to share on which SuperTruck program(s) the technology is employed.

The rails are around 9 mm (0.35 in) thick and made of high-strength 6000 series aluminum, Long said. Alcoa expects the frame to be available in 2018.

In addition to fuel efficiency and payload-increase benefits, the lightweight rails offer enhanced strength and corrosion-resistance performance compared to steel, said Kurt Johnson, Central Region Sales Manager, Global Aerospace, Transportation and Industrial Rolled Products.

“Durability is one area that we get challenged on—aluminum vs. steel,” Johnson explained. “So one of the data points that we have on this new frame rail is that from a durability standpoint it’s equal to or greater than that of steel—actually two times the rigidity, which would lead to a more comfortable ride.”

Corrosion testing was not finalized yet as of late May, but Johnson said that early results indicated that aluminum is the “superior product” in this measure.

“That corrosion benefit has been there all along—wheels and fuel tanks have benefitted for many years. It’s just moving on to the next bigger item,” added Long. “None of it’s that new; aluminum’s been used for major structures all over the place. It just takes time for acceptance.”

Regarding pricing when the technology becomes available, Marquez said that “it’s going to be a premium. Again, you’re talking about almost 900 lb of weight savings—how much is that worth to a fleet? What we see is different fleets value it differently. Those that cube out before they weigh out, probably not so much—but for reefers and fuel tankers, that’s big bucks right there.”

Another new technology showcased in the demonstrator was Alcoa VersaCast aluminum alloy castings that are stronger and simpler to cast while lowering vehicle weight and improving suspension rigidity, according to Marquez.

The new alloy outperforms cast iron by up to 94% and typical aluminum alloy alternatives by at least 40%, according to Alcoa. That enables it to be used for critical structural parts in commercial trucks, such as mounting brackets for suspension systems.

Alcoa has validated the benefits of the new alloy with help from aluminum casting supplier Eck Industries.

“VersaCast enables commercial truck manufacturers to lightweight new and legacy structures traditionally made of iron, such as hanger brackets that attach the truck’s suspension system to the vehicle frame,” said Christine Keener, Vice President, Commercial, Alcoa Casting. “It outperforms alternatives in the key areas of strength, corrosion resistance, thermal fatigue resistance, and ease of casting across applications.”

VersaCast has two times less density than iron and can be produced in high-volume applications. The alloy is currently in customer trials.

Many other solutions contributed to the 2500-lb (1135-kg) weight savings claimed for the technology demonstrator. Alcoa Ultra One wheels with MagnaForce alloy, launched at the 2014 MATS, are employed. Each wheel weighs 40 lb (18 kg), which Marquez claims is “the lightest in the industry.” The proprietary MagnaForce alloy offers a 17% increase in strength compared to existing alloys, according to Alcoa.

Structural sheet is used for the doors, which reduces the weight of a typical cab by about 60 lb (27 kg), Marquez said. “Underneath our chassis is an aluminum propshaft tube, which can lower the mass of a typical shaft up to 100 lb (45 kg). And our aluminum fifth wheel, marketed through SAF-Holland, can save 100 lb” compared to a steel one, he added.