Trailer Suspensions: Package deal

More and more suspension makers are offering products that integrate axle and brake componentsA trend in the heavy-duty component market that dates back only a few years is really starting to take off - the integration of suspensions with axles and brakes.Such integration has been the norm in Europe for decades and it is clearly now catching on in the North American market.Integrated suspensions are

More and more suspension makers are offering products that integrate axle and brake components

A trend in the heavy-duty component market that dates back only a few years is really starting to take off - the integration of suspensions with axles and brakes.

Such integration has been the norm in Europe for decades and it is clearly now catching on in the North American market.

Integrated suspensions are delivered to trailer OEMs with axles, brakes, and if so equipped, slider boxes installed.

In general, integrated suspensions are more advanced than conventional setups. They are constructed with fewer parts and therefore weigh less. Nonetheless, manufacturers say integrated units are more durable and require less maintenance than conventional air-ride units.

According to suspension makers, the advantage of integration is twofold. On the production side, prepackaged suspensions save trailer builders both labor and handling costs.

On the sales side, fleet buyers can be assured that trailers will arrive capable of carrying more payload and with suspensions that are precisely squared, resulting in fewer alignment problems. There is also the argument that integrated suspensions are easier to maintain because their parts were engineered as a whole in the first place.

Of course, there's a potential downside to all this good news. Plain and simple, fleet managers who opt for integrated suspensions are giving up some of their control over spec'ing their trailers.

But suppliers counter that in return, the fleet gains a more finely engineered suspension and undercarriage, as well as a single source to contact for warranty or other service issues.

Hendrickson International gets credit for getting this packaging concept off the ground. Back in 1995 it rolled out the Intraax, the first air-ride trailer suspension offered with integrated, application-specific axles and brakes.

According to the manufacturer, the key advantage to the groundbreaking design for fleets was a saving in weight that can be translated into more cargo capacity.

Developed primarily to boost payload on platform, tanker and other specialty trailer types, the original Intraax shaved as much as 400 lb. off compared to competitive tandem air-ride units. That brought the weight of the integrated system down into the realm of a four-spring suspension setup.

Hendrickson followed up the Intraax two years later with the Vantraax, a tandem air-ride slider system expressly for dry vans and reefer trailers. The design incorporated the Intraax and the company's K-2 slider. It resulted in an assembly weighing just 1,753 lb.

Currently, three Vantraax tandem models are offered, differentiated by their weight capacities: 40,000, 46,000 or 50,000 lb.

According to John Morgan, product manager for Hendrickson Trailer Suspension Systems, the newest Intraax will be released this fall. The 30,000-lb. severe-service unit will join the 23,000- and 25,000-lb. models already offered.

Morgan points out that all Intraax suspensions can be ordered as top-mount or low-ride/liftable units. "The low-ride/liftable option was added last year to provide for both drop-deck trailers and conventional units with lift axles," he notes.

"We plan to bring out other niche products as well," Morgan reports. "We're expanding our offerings because the integrated design has proved popular with both OEM and fleet customers.

"The growth in integrated suspensions is coming from two directions," Morgan continues. "Trailer makers find we're making life easier for them by absorbing some labor and liability. And fleets like the weight savings and the greater durability designed into these systems."

The latest innovation being offered on both Intraax and Vantraax suspensions is a special wheel-end "value package."

According to Gary Ciapetta, Hendrickson's director of marketing for trailer suspension systems, spec'ing the package gives fleets a set of "popular extended-service wheel-end options" without having to wade through a complex selection process.

The package includes a ductile iron-hub assembly, cast iron drums, slack adjusters, brake chambers and Hendrickson's 16.5x7-in. HXS brakes. It also incorporates the Stemco Advantage system, which includes that maker's Discover seal, Pro-Torq advanced axle spindle nuts, and Sentinel hub cap.

Ciapetta points out that the package expands on the integrated-suspension approach. "It not only provides one-stop shopping," he says, "but also more competitive pricing and a single source for warranty." Naturally, other manufacturers have not sat idly by. They've headed down the trail blazed by Hendrickson with their own innovations and variations on the integrated-suspension theme.

No walking For example, ArvinMeritor offers the RHP Highway Parallelogram suspension. The tandem trailer air-suspension system features an integrated slider, axles and brakes, and is aimed at dry vans and reefers.

According to ArvinMeritor, the design's chief attributes are lower weight, easier maintenance, and the elimination of trailer "dock walking."

The design of this sliding tandem centers around two V-shaped control arm brackets in place of two separate trailing arms. The RHP has air springs mounted directly over the axle, which allow the suspension to only move up and down.

The result of all this engineering is a more compact and lighter (up to 275 lb. less than competitive units) suspension system that ArvinMeritor says will also provide a better ride and longer component life.

What's more, the unit sends dock walking on a hike. That's because the upper and lower control arms move up and down in a parallel motion - as the product's name suggests - when weight shifts on the trailer, rather than moving in the forward arc typical of trailing-arm units. Since the axles don't rotate, there's no forward movement of the trailer.

The tandem RHP comes standard with Meritor TQ trailer axles and 16.5x7-in Q Series cam brakes. Other axles and Q brakes are optional as are Meritor auto slacks.

"The whole key to suspension integration," says Frank Maly, ArvinMeritor's product manager for trailer suspensions, "is getting the one-stop shop effect. There can be one supplier for the trailer axles, brakes, air ride, ABS, auto slacks and even a tire-inflation system."

Maly points out that in the case of the RHP, its no-dock-walk design also means the driver suffers no "backslap" action as the tractor-trailer moves down the road.

"The parallelogram design also makes for a very roll-stable ride, even in severe situations like hauling loads with a high center of gravity," he says. "For example, one customer that transports hanging sides of beef reports our suspension has prevented their trailers from swaying."

According to Maly, the long-lived polyurethane bushings found in RHP suspensions minimize maintenance. He also credits a patent-pending laser process, which aligns the suspension as a system before it leaves the factory, with heading off problems.

He notes that ArvinMeritor is so confident in the appeal of the RHP that it's the only sliding-tandem suspension offered for vans and reefers.

"The cost advantages to OEMs of integrated suspensions can't be overlooked," says Maly. "And by using one supplier, both spec'ing and servicing is greatly simplified for the fleet buyer."

Holland Neway now offers two integrated trailer suspension packages for trailers. The iPAC is a suspension/axle package designed for specialty trailers, including flatbeds, chip vans, tankers and other vocational units. The vPAC is a slider/suspension/axle package designed specifically for vans and reefers.

"One of the prime benefits of an integrated product to the trailer OEM," says Ken Griswold, Holland Neway's director of business development-trailer products, "is reduced liability - especially in the critical suspension-to-axle assembly.

"At the same time," he continues, "end users can be assured that a systems approach has been taken by suspension experts to optimize the trailer undercarriage. So, the end customer enjoys greater reliability due to a higher level of engineering and assembly control."

Griswold also points out that the fleet customer ends up with "one point of contact - it cleans up customer service from everyone's perspective."

Field serviceability was a central design factor in developing the iPAC and vPAC packages. "We wanted to specifically address the real world, where extreme curbing or other abuse can fail a trailing arm," says Griswold. "So we built ours so it can be taken apart, component by component. If part of the suspension fails," he continues, "you don't have to replace the whole system."

According to Russ Franks, commercial manager-trailer air suspensions, the "heart and soul" of iPAC and vPAC is Holland Neway's NEWeld technology.

"NEWeld is what we call our weld-free axle connection," Franks relates. "It dramatically cuts axle stress so we can use a thinner axle wall yet still offer a lifetime warranty on that connection to the original buyer."

By contrast, Franks says welding of the axle connection has always been a "loose link" in suspension design. "The heat of traditional welding results in microscopic cracks. Later, as the axle bends and twists, those cracks propagate due to the high stress, and will eventually fail.

"But NEWeld is a clamped connection," he continues, "that increases cycle life immensely - to beyond the normal life of most trailers."

Franks says the engineering concept was carried a step further for even greater durability. He says the iPAC and vPAC are the only units with axle tubes that are completely weld-free inboard of the brake spiders.

Where's suspension integration headed next? "Technology that increases product reliability and performance will be the driving factor," says Griswold. "Extended warranties augmented with single source service will be key for the end customer. OEMs will be looking for assemblies and suppliers that add value to their production process. Whatever the level of integration the OEMs want," he adds, "we'll make it their way to meet any specific need."

Integrating choice Wayne Powell, director of marketing for Tuthill Transport Technologies, which makes Reyco/ Granning suspensions, says there's another tack to take on suspension integration.

"Rather than limit the buyer to a proprietary set of axles," he explains, "we build our 86AR InnovAIR van slider package complete with axles developed for us by IMT - or with any manufacturer's axles the customer wants. And we'll warrant the complete package in any case.

"The end user," he continues, "likes having one place to go for warranty work without having to give up their choice of components."

According to Powell, Tuthill is working on putting together a more extensive undercarriage package that will draw together components from other suppliers.

"The idea," he relates, "is to allow customers to spec the components they want within the offerings of a select group of suppliers. As the suspension system builder, we would assemble those components and become the single warranty source for all of them."

Powell says this approach stems from recognizing what fleets go through when dealing with wheel-end issues.

"The customer doesn't know if it was the seal, the lube or the assembly that failed," he reasons. "All he knows is that a component is ruined and he wants someone to take responsibility for it. We're willing to take on that warranty responsibility."

In the end, that ability to simplify matters perhaps is the ultimate value suspension integration holds for the fleet buyer.

Trailer OEMs are also simplifying vehicle assembly by line-installing onboard scale systems with suspensions. According to Peter Powell, vp-marketing, Air-Weigh Scales now has approval for such installation from 43 trailer builders.

That makes sense. "Our technology uses a measurement of the changing air pressure within the suspension to indicate the trailer's on-the-ground weight," Powell points out. "Once our scale is calibrated to a specific suspension and vehicle," he adds, "it will give a very accurate reading."

But why an onboard scale in the first place? Powell says the reasoning is simple. "Spec'ing an Air-Weigh gives you a scale at every loading site. We've found that fewer than 25% of loading sites have scales. So, the driver must instead go off-site and use a commercial fixed scale.

"That means out-of-route miles and wasting anywhere from half an hour to 45 minutes of driving time," he figures. "The cost to use the scale may be only $7. But use one several times a week and it adds up."

Another advantage Powell cites for onboard weighing is its sales appeal. "Truckload carriers want to put a full 80,000-lb. load on every trailer they can," he says. "And, naturally, their customers want them to, too."

Powell reports the latest development is Air-Weigh's new ComLink, a device which stores all calibrations in the trailer's computer unit to allow for drop-and-hook movements.

More information on the ComLink and other features can be found at the company's web site. www.air-weigh.com.

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