It Takes An Axle

Integrated trailer air suspensions could mean more payload and lower maintenance costs. Nobody loves an axle, except maybe another axle. But two major suspension makers are beginning to break some new ground by supplying trailer makers with air suspensions that have axles and brakes already installed. One of these suspension manufacturers has an axle supplier produce axles to especially tight tolerances,

Integrated trailer air suspensions could mean more payload and lower maintenance costs. Nobody loves an axle, except maybe another axle. But two major suspension makers are beginning to break some new ground by supplying trailer makers with air suspensions that have axles and brakes already installed. One of these suspension manufacturers has an axle supplier produce axles to especially tight tolerances, while the other produces its own axles. Other leading suspension makers say they plan to provide packaged trailer air suspensions, too, and are readying product introductions for the near future.

Suspension integration, as the practice is known, has been standard operating procedure in Europe for years. Trailer makers there routinely receive suspensions with air tanks mounted, sliders plumbed, and axles and brakes installed.

In North America, however, suspension integration began in 1995 when Hendrickson Trailer Suspension Systems introduced its 23,000 lb./axle fixed-tandem Intraax for platform and tank trailers. More recently, the suspension maker widened its range of modular air offerings with a dry freight/ refrigerated van model known as the VanTraax HKA200. It is basically an Intraax mated to the K-2 slide. Reyco Industries also entered the market this year with an integrated version of its 86 AR for vans, which it calls the InnovAir.

These trailing arm-type air suspensions can be considered value-added products. They are delivered to trailer plants in ready-to-bolt-in condition. This is a departure from current industry practice in which most trailer makers take on the responsibility for connecting axles to the suspension by welding, or welding and bolting and also installing brakes and air tanks.

Some of the integrated suspensions that have thus far been introduced differ from conventional suspensions in design and engineering respects. They are advanced designs, with fewer parts. This means more weldment points, but reduced reliance on treaded fasteners to hold things together. In addition, integrateds are significantly lighter than conventional trailer air suspensions. Manufacturers claim that these products are more durable and need less maintenance than conventional air rides.

From the perspective of the trailer makers, there are potential advantages to using integrated suspensions. For one thing, suspension and brake-parts purchasing are simplified. Not only do trailer makers receive ready-to-install air-suspension units, but the suspension makers become the single-source suppliers for just about every suspension-related item trailer makers need -- except, of course, wheels and tires. This enables trailer makers to reduce the size of their suspension and brake-parts inventories.

There are also some potential disadvantages: Most trailers consist of 80% purchased material and 20% labor. If a trailer maker gives up some labor margin, it gives up some profit leverage, which may be difficult to recoup. Also, what would happen if two assembly lines were needed -- one for installing complete bogies and one for assembling suspensions? Would it drive up costs?

With suspension makers taking responsibility for performing the crucial axle-connection task in their own plants, trailer makers are relieved of a labor-intensive task. They can then more confidently assure their fleet customers of the highest levels of suspension integrity.

While a prepackaged suspension could certainly cost a trailer maker more than separate suspension, axle, and brake elements, it's not clear that this added cost will be passed on to the end user. This is because the integrateds may ultimately save money by reducing trailer makers' suspension-handling time.

When the market for new trailers peaked a couple of years ago, trailer makers were desperate to find ways to maximize vehicle throughput. Some agonized over lost sales and late deliveries because of production bottlenecks, which often occurred during the crucial axle and brake assembly processes.

Since activity in the trailer market is moderate today, bottlenecks aren't much of a problem. However, things could change if the trailer market heats up again in the next year or two. It's possible that integrateds could then become the key to helping trailer makers fill demand.

But integrated suspensions have not been developed solely for the convenience of trailer makers. Manufacturers also have fleets in mind. For example, these suspensions contain distinctive features, such as proprietary anti-trailer-walk systems, which can help prevent injuries when trailers are parked at loading docks.

Most carriers track suspension costs closely, and react to high maintenance costs by selecting suspension/brake/axle setups that will provide the best value and service. By opting for integrated packages, however, fleets would give up some spec'ing latitude. With this in mind, suspension makers have been thinking in terms of "optimizing" their integrated products so that end users would not feel they were losing out by having less control over specifications.

Although the integrated air suspension market is still in its infancy, many makers have yet to introduce their products. Companies that have been first off the dime are eager to expand the concept. They are even inviting some upgrade spec'ing with regard to the wheel ends by providing the latest unitized hubs, as well as the new wider brakes and drums.

The unitized hubs, which house permanently adjusted wheel bearings and are lubed by synthetics, are sealed against leakage. This helps resolve a major maintenance issue: Brake lining damage due to oil leakage ranks as the No. 1 trailer maintenance problem. These premium-priced hub assemblies can also help trailer makers save some time in the vehicle-building process.

Although wider brake packages won't help trailer makers, they can help fleets. The brakes' greater swept area means that fleets can cut operating costs by holding down braking temperatures for longer lining life.

Some suspension makers use the integration concept as an opportunity to streamline and simplify, designing one part to function where previously two might have been needed. The central idea, though, is to ensure all the elements in an integrated system -- from slide assembly, axles, and brakes to brackets, torque arms, and beams -- function as a tightly coordinated unit. In theory, this should increase the durability of the suspensions and enable them to remain more closely aligned for reduced tire wear and better vehicle handling.

Suspension makers are demonstrating their confidence in this durability by taking on an unprecedented responsibility for long-term product performance. The suspensions are backed with five-year warranties on major system and wheel-end elements; other key elements are being granted even longer coverage.

At CFI in Joplin, Mo., 2,426 53-ft. van trailers are underpinned with Intraax AA-230 suspensions and Hendrickson slides. "By spec'ing the lighter weight suspensions in conjunction with plate trailers, the carrier was able to get the cube capacity of the 53's but at the lower tare weight of sheet-and-post 48's," says maintenance director Randy Cornell.

According to Frank Stevens, Hendrickson International's vp-sales and marketing, the weight savings of an integrated product is very significant. "Intraax gives a fleet a 236 lb./tandem weight savings compared to one of our own HT air suspensions, but as much as a 400 lb. weight reduction compared to some other air rides."

A key to the high level of optimization in the Intraax system is that the company produces its own round, exceedingly straight axle tubes, which it welds precisely to trailing arms, forming them into one-piece units. By using a 1/2-in.-thick tube, a friction-welded spindle that's manufactured to tighter-than-standard tolerances, and a patented axle wrap that is circular-welded at the axle's neutral axis, axle-beam perpendicularity and beam parallelism are achieved. "In the integrated approach," continues Hendrickson's Stevens, "potential trouble spots such as U-bolts and axle seats are eliminated."

Inboard gussets are used on the Intraax frame hanger in place of the "C" channels that are commonly found on conventional suspensions. According to Stevens, this is what allows more payload per axle and provides more lateral support.

In the Intraax and VanTraax systems, S-cams, brake chambers, and connecting hardware are also mounted directly to the trailing beams. This allows for shorter S-cam shafts, meaning less windup during braking, and quicker brake response.

The VanTraax HKA200, which is available in 40,000- to 46,000-lb. load capacities and 42- or 48-in. widths, incorporates the SureLock control to minimize trailer walk. The system also features an extended life Tri-Functional bushing that carries a seven-year warranty.

Hendrickson's Ready-To-Roll option is available for both Intraax and VanTraax. It consists of fully dressed axles with aluminum or ADI hubs, Centrifuse or cast drums, various brake sizes, and a choice of slacks, as well as associated air controls and plumbing.

Reyco Industries' InnovAir is a fully assembled slider/air suspension/axle/ brake package that has been carefully engineered for brake performance, bearing life, and properly operating auto slacks. InnovAir is mounted to 0.46-in.- thick axle tubes made of high-strength seamless material. The lightweight design incorporates the company's RS 1035 anti-dock system (reversed rearmost rear axle) and carries a five-year warranty on the system. Exceptions to this warranty are two years on the air spring and one year on shocks.

According to Reyco, driver fatigue and cargo shift are minimized through the use of double-convoluted air springs, vertically mounted shocks, and wide trailing beam centers, all of which contribute to increased roll stability.

"The brake spider is a new two-piece design that delivers more precise brake geometry for more positive braking action, longer brake life, and more even lining wear, and ensures crisper slack adjuster action," explains Bob Voss, director of OEM trailer sales for Reyco. According to Voss, a track rod design that extends suspension hanger and sub-frame life is a major contributor to reduced maintenance. A transverse track rod helps reduce stress on the axle connection to ensure long service life. Voss notes that use of huckbolts and pre-torqued fasteners at key points also contribute to low maintenance.

As a result of last year's alliance with Suspensions Inc., Rockwell Automotive will soon make its entry into the air suspension arena. Rockwell Heavy Vehicle Suspension Systems (as the alliance is currently called), combines Rockwell's trailer-axle expertise with Suspension Inc.'s experience in air-suspension development. Their first effort, a new trailer air suspension, is now being field-tested. A trailer with the new suspension appeared at the Mid-America Trucking Show. A quick look beneath the vehicle showed the suspension to be a parallelogram design with a big center bracket. In some ways it is reminiscent of the tractor suspension GMC had under its Astro.

Roger Storey, general manager of Rockwell Worldwide Trailer Products, says that Suspension Inc. has been noted for producing leading-edge suspensions. Rockwell's diversity makes it a good bet that the TB Series trailer axle and Rockwell Wabco Easy-Stop trailer ABS will be integrated into the new suspension product, as well as the full range of Rockwell's foundation brake parts.

Neway Anchorlok International's entry into the integrated trailer air suspension market is expected sometime this year. Neway intends to build some additional serviceability into its design. In some integrated products, if a bearing fails it could lead to a burned-out wheel spindle. In that case, the entire axle-trailing arm assembly might have to be replaced. To address this, Neway is incorporating a way for fleets to make economical repairs. The suspension maker is also looking at ways to maximize the quality of welds and make the absolute minimum number of them to optimize the upcoming suspension's strength and durability.

With the recent acquisition of Fruehauf Trailer's Delphos Axle Products division by parent Holland Group, The Binkley Co. will be integrating its new AirLite suspension/slider with the square Delphos axle. Larry Hasenberg, engineer for technical sliders, predicts that a new integrated trailer air suspension product will be out later this year.

Hasenberg speculates that if the integrated suspension concept takes hold in the trailer market, it just may spread to the tractor market. Only time will tell.

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