If an engine is the heart of a heavy-duty truck, then it’s fair to say that the chassis is its backbone. No one can argue a chassis isn’t vital for a construction truck. Its design determines how the truck will maneuver and handle on the road and how smooth the ride will be. More importantly, the chassis distributes weight across the vehicle platform, regulates the type, style and size of bodies that can be fitted to the truck and directly correlates to the size of payload the truck can effectively carry.
Calling its new Advantage chassis a “next generation” frame for future Mack on-highway trucks, Tom Kelly, vice president of marketing for Mack, says the company has moved away from its previous straight-rail design. “This new chassis configuration gives us more room for engines and cooling systems,” he notes. “It also simplifies the body installation process and provides up to 50-degree wheel cuts, greatly enhancing the truck’s turning radius. In addition, the new chassis will be stronger, with a 120,000 psi rating, and offer significant weight savings for most Mack customers.”
New chassis is stronger, taller and lighter
The new frame is stronger, but lighter than Mack’s previous chassis. Four rail options will be offered, including 6-, 7-, 8- and 9-1/2-millimeter versions. All feature increased resistant bending movement – a truck frame’s primary strength measurement – compared to previous Mack frames.
“This increased RBM provides greater strength,” says Tom Davis, marketing manager, highway products. “Weight-sensitive haulers will appreciate our new 7- millimeter rail, which has a higher RBM than our current 8 millimeter unit, but, depending upon wheelbase, is up to 100 pounds lighter.”
Davis says owners requiring a heavy-duty rail have traditionally spec’d Mack’s 6 millimeter rail with 1/4-inch inside channel reinforcement. Now, he says, those customers will find the 9.5-millimeter Advantage rail an excellent alternative. “Not only is this rail lighter than the 6 millimeter version,” he notes, “but it also eliminates the need for an inner channel. This prevents potential corrosion from occurring in this area and enhances chassis durability and service life.”
One impetus for designing the Advantage chassis was looming 2007 federally mandated diesel emission regulations. But Mack engineers took lessons learned during the run-up to the 2002 emission regulations to heart and designed the Advantage chassis to meet any foreseeable technological challenges brought out by these regulatory demands.
To that end, engines mounted in Mack Advantage chassis are now placed deeper in the frame to give the truck a lower center of gravity. This is made possible by a flared front chassis design that also allows for a 10-percent larger cooling system – an obvious advantage for trucks powered by hotter-running, low-emission diesels. Specialized “snubber” brackets provide increased stability and vibration dampening for the cooling system and help extend the cooling package’s life.
At the same time, the flared front frame provides optimal axle positioning. This, in turn, helped Mack engineers design improved wheel cuts into the Advantage chassis. These cuts – up to 50 degrees on some models – result in a turning radius improvement of approximately 15 feet on a truck with a 185-inch wheelbase compared to similar pre-Advantage Mack chassis.
Advantage’s ride and handling characteristics are enhanced as well. The chassis’s standard front taper leaf suspension has new taper leaf springs spaced slightly apart to reduce friction and deliver a smoother ride. A new engine support crossmember and new cab mounting system decrease in-cab noise and vibration levels significantly, helping to reduce driver fatigue.