FOCUS ON: BUS SUSPENSIONS
Transit’s weight loss challenge
By Gerry Remus
Of the many obstacles bus operators face today, maintaining or lowering the bus curb weight while complying with regulatory mandates, emission standards and evolving passenger needs is a key challenge facing our market today. The modern transit bus has come a long way over the years with many positive changes to passenger comfort and accessibility, alternative fuel usage, and adoption of technology that improves bus safety and security. While these changes are positive overall, they often times mean incremental weight to the bus. One example relates to alternative fuels, which can add up to over 2,000 pounds of weight to a typical transit bus. The mission to counter these additions and lower overall vehicle weight is of paramount importance.
The industry has a few options to address the problem.
• Change the rules to allow buses to run heavier and accept the consequences that this will ultimately impact the infrastructure.
• Encourage OEMs to add additional axles to spread out the heavier loads, at additional cost and manufacturing complexity.
• Engage in “lightweighting.”
The most sure-fire way to cut out the weight is through improved specifications, seeking out lighter weight materials or developing efficient designs in a process known as lightweighting. As new materials and manufacturing methods progress, it’s becoming easier and more cost effective for manufacturers to achieve a lighter weight chassis and body components. Buses are getting heavier and, as a key industry supplier partner for the bus market, Hendrickson places heavy emphasis on lowering gross vehicle weights while optimizing for performance and long life. For transit buses, this aids in offsetting the mounting increase in weight of additional systems and componentry. Hendrickson’s approach to lightweighting is three-fold.
The first approach is design efficiency. Hendrickson starts with a true understanding of the application and what the suspension or axle must withstand to meet the customers performance & durability requirements when in real world operation. With this knowledge, non-essential weight can be eliminated and the components can be designed to meet the application needs. Hendrickson utilizes advanced methods of design, analysis and testing to drive out weight while delivering best-in-class reliability and achieving the benchmark for performance.
Second, integration of components to create systems is used to reduce weight as well as cost; essentially combining two or more components into one to arrive at efficiencies. One example of how Hendrickson is approaching component integration for buses involves the next generation of steer axle and braking systems. Air-disc brakes have become very common in many bus applications. The axle installation of an air-disc brake requires a torque plate to attach the brake to the axle; this is a wasteful component that adds cost and complexity to the system. Hendrickson has pioneered a way to integrate the torque plate into the axle structure, reducing weight and simplifying assembly by reducing the part count. Having one supplier deliver a system also benefits the OEM and end user in the area of parts and service support; one point of contact for a particular system.
Third, Hendrickson has broad expertise in the use of lightweight materials. Hendrickson has a number of options to balance cost and weight through the use of different materials for each product need. Robotically welded, steel fabrications are a core competency at Hendrickson that result in a very positive cost to weight ratio. In addition, aluminum castings are a great option for applications where weight is paramount. Composite materials have emerged over the past several years for the heavy duty segment and the future looks promising as this lightweight technology is proven on the road. Having the ability to draw from a multitude of material options allows Hendrickson to meet customer objectives.
Looking ahead, the pressure to add weight to transit buses will not subside and changes will be made that affect the future transit bus. While a number of strategies need to be employed to tackle this issue, Hendrickson stands ready to deliver lightweight, reliable suspension & axle solutions that improve driver handling, passenger comfort and overall equipment protection.
Gerry Remus serves as business unit director – Global Bus for Hendrickson Commercial Vehicle Systems, Woodridge, IL. Visit Hendrickson online at