what's new in: Hubs and drums

With the new emissions requirements adding to every truck and trailer 200 lb. or more in equipment such as larger exhaust stacks and heavy filters, it's become more important than ever for manufacturers of wheel-end components to take weight out of their products wherever possible. The trick is not to sacrifice strength and longevity while doing so.

Gunite Corp.'s Tom Parsons, director of product marketing, says in 2006 the company launched Gunite GOLD (Gunite Optimum Lightweight Drum). “It took many years of R&D to come up with a unique iron that would enable us to reduce the weight of the product while still giving us the strength and thermal capability we desired,” he notes.

The benefit for fleet owners is that they can replace standard 16.50×7.00 brake drums weighing 112 lb. with 94-lb. Gunite GOLD drums on rear truck or trailer axles and achieve a 16% weight savings, or a total of approximately 170 lb. for a typical tractor-trailer application, Parsons points out.

“We're seeing extremely good performance with this product, including longer life spans on brake linings and the drums themselves, as well as increased life expectancies on the steer axles of anywhere from 50% to 75%, drive axles from 20% to 50%, and trailer axles 20% to 40%, compared with other lightweight drums on the market today.”

At last month's Mid-America Trucking Show, Gunite introduced another brand new product called TRU-SET. “This is a new bearing spacer set system that incorporates both our patented lightweight disc wheel hub technologies along with a high-tolerance bearing spacer set system to eliminate installation errors associated with bearing adjustment,” Parsons explains. “TRU-SET is interchangeable with several other systems in the marketplace. One of its key features is that it can be serviced in the field without having to replace the hub.”

On the horizon, according to Parsons, Gunite sees a migration by the industry toward the use of air disc brake systems. “There are issues like compatibility, clearances with the wheels, cost barriers and service life that still need to be worked out, but eventually it will probably come.” How soon, he says, depends on a number of issues, not the least of which is the federal mandate on stopping distances.

Steve Slesinski, director of product planning for Dana Corp.'s Commercial Vehicle Systems and Roadranger, says that as the industry moves toward air disc brakes for increased service intervals and increased safety through reduced stopping distances, long-life wheel-end bearing and sealing systems will be necessary to match the life expectations of the entire system.

“Unitized hubs and pre-adjusted hub systems such as the Spicer LMS hub continue to grow in acceptance due to positive results achieved on the road,” Slesinski reports. “Fleets benefit from the extended service interval and ease of serviceability.”

He says that synthetic oil-lubricated wheel ends like the LMS hub system with high performance seals also offer consistent lubrication performance for a greater range of temperature and moisture conditions over many grease-packed wheel-end systems.

Last year Dana introduced the LMSTM wide-based hub system for drive and trailer axles. The system is “compatible with standard-track axles, which allows for application flexibility between wide-based tires and standard dual tire axle configurations to keep installed costs low and maximize vehicle resale value,” Slesinski notes.

LMS hub systems include a unique identification system so service technicians can easily identify the wheel-end type to determine the proper service strategy before disassembling the wheel end unnecessarily. Slesinski says a patented LMS hubcap is also available to exclude water contamination while allowing for proper venting of the wheel end under elevated temperature conditions and even temperature extremes.

On the brake drum side, “Our Bendix Spicer Foundation Brake joint venture continues to enhance braking performance and brake life of drum brakes through development of better lining composition and brake design and manufacturing techniques,” he advises.

ArvinMeritor says it also continually works at optimizing the performance of its brake drums, as well as other wheel-end components. Greg Smith, CVS program manager, wheel-end division of ArvinMeritor, notes that a systems approach allows the company to test different drum material configurations and chemistries and the impact on related components so it can offer customers the best solution for their vocation, whether it be on-highway tractor or specialty vehicle application.

The lightweight SteelLite X30 brake drum from ArvinMeritor is built as a one-piece shell with gray iron liner. The design saves a conventional tractor/trailer combination up to 200 lb. over a full cast-drum setup, Smith explains.

ArvinMeritor also offers a full line of air disc brake hub and rotor combinations to complement the MeritorWabco EX air disc brakes. “The current trend in hub design for heavy trucks,” Smith states, “is toward advanced wheel-end design, including unitized bearing packages and other non-conventional bearing configurations and adjustment.”

According to Smith, ArvinMeritor has recently signed a commercial agreement to sell, service and warrant “Preset by ArvinMeritor” for trailers. The agreement combines the strength and positioning of MeritorLite TN and TP ductile iron trailer hubs and Consolidated Metco's (ConMet's) Preset bearing arrangement for a 5-yr//500,000-mi. package for the trailer industry.

ConMet says its PreSet aluminum hub assemblies combine lightweight, easy installation, low maintenance and long life to improve vehicle performance and lower the cost of ownership. The manufacturer also offers PreSet ductile iron hubs, which are designed specifically for trailer applications where low maintenance and extended life benefits are required.

Hendrickson Trailer Suspension Systems' program manager, Jeff Shahan, says current trends in hubs and wheel ends for trailers include longer service life, lighter weight and flexibility between traditional dual and wide-based single tires.

According to Shahan, two major factors contribute to wheel-end damage — high operating temperatures (often from inadequate lubrication or loss of lubricant) and contamination affecting the integrity of the lubricant. “Factory pre-assembled and sealed trailer wheel ends (unitized systems) such as the Hendrickson Unitized System (HUS) address these issues and provide exceptional reliability over millions of miles of operation,” he advises.

Hendrickson Trailer Suspension Systems recently introduced a new trailer hub/spindle design, the HNP hub and P90 spindle. The HNP hub is manufactured with austempered ductile iron (ADI), which “delivers excellent strength-to-weight ratio and often may be used as a replacement material for more costly aluminum castings or forgings,” Shahan reports. The HNP hub on Hendrickson's P90 spindles also provides the flexibility to switch between duals and wide-based single tires.

Byron Cornett, product engineer manager-aftermarket business unit, Webb Wheel Products, says unitized and pre-set systems are “steadily gaining prominence in the industry as both reduce the interaction between technicians and the wheel end. Lighter weight hub designs continue to increase in the industry as owners continue to look for ways to increase cargo weight and fuel economy.”

Webb Wheel Products, Cornett reports, has recently enhanced its analysis and testing programs to optimize the design of its hubs, brake drums and rotors. He notes that the most effective step the company has taken to improve the life and performance of its brake drums is to work closely with lining manufacturers to improve brake drums and linings as a system rather than as individual components.