Air-ride suspensions have found a steady updraft in the van market during the past decade. Dry-van operators have migrated to air-ride at such a rate that it now makes up more than 65 percent of the market, up from 30 percent 10 years ago.
That’s quite a lift for what is traditionally a low-budget lot who bristle at anything that might cost more money or is heavier than the next-best alternative.
Volume production combined with better designs have helped cut the price-premium of air-ride suspensions by more than 50 percent on some trailers and have narrowed the gap on weight compared to their mechanical counterparts.
The bigger impact, though, has come from the way manufacturers are integrating the suspension with a slider, axles, and brake components.
In doing so they’ve developed features that not only protect the freight and reduce shock to the trailer but also make trailer air-ride suspensions more functional. Major van suspension suppliers market most of these things as options. Before you pass them off as superfluous, think again about the value. They’re worth a closer look.
SPEEDY ALIGNMENT: You don’t get paid to go sideways. Yet misaligned axles cause you to drag your trailer a few feet to the right or left for every kilometre you turn. If the average alignment job took 30 minutes instead of three hours the problem would be easier to deal with.
That’s the idea behind SwingAlign, developed by Holland for its 40,000-lb tandem trailer air suspension and slider, the CB400/CB4000. SwingAlign requires no special tools or disassembly during the realignment process. You simply apply 250 lb ft of torque on an adjustment nut, which turns a screw that’s threaded through a bushing connected to each trailing arm. It shifts the arm fore or aft using the same roll-thread screw technology found on Holland’s landing gear products.
PIN RELEASES: What’s the cost of a driver who yanks on a bound-up pin and slips on the ice? Or the value of the 20 minutes your driver could save repositioning a slider by himself? What if your driver simply can’t generate 80 or 90 lb of pull effort by himself? Or herself?
Consider a pin release like Hendrickson’s Quik-Draw, an air-operated pin-pull mechanism that allows a single person to reposition the slider with minimal effort. When activated, it applies continuous pressure until the pins disengage. As an added safety measure, the pins automatically reset with the release of the emergency brake.
TIRE INFLATION: Aftermarket trailer tire inflation systems can be ungainly. With access to an air supply, suspension designers are integrating tire-pressure monitors at the factory level.
One example is the Meritor Tire Inflation System by PSI, available on ArvinMeritor’s trailer suspensions (including the DuraSlide tandem suspension for vans which went into production last month). When it detects low air pressure, MTIS routes air to a control box, then into the axle and to each tire. A sensor in the spindle press plug will detect high heat in the tire and alert the driver.
HEIGHT CONTROLS: With no air supply, bags can squat under the weight of the lift truck moving on and off the trailer deck. Trailing-arm suspensions are especially prone to this, a phenomenon called dock walk or trailer creep.
Hendrickson’s SURELOK option is designed to maintain the trailer deck at ride height during loading and unloading.
When you set the trailer’s parking brakes, a pair of supports automatically swings into place over the suspension beams, holding the trailer at ride height. The supports disengage when the parking brakes are released. Combined with an air-dump valve, SURELOK also eliminates dock walk.
While some suspensions address the problem with devices to keep the bags from collapsing as they deflate, others address it by design. A parallelogram design puts the air bags directly over the axles and positions them with upper and lower control arms that are parallel to each other.
About 10 years ago engineers at Reyco reversed one rear suspension on a Reyco 86AR tandem slider. They effectively cancelled each other out without the need for dump valves or air-activated block mechanisms. The ReycoGranning Dockmaster II, a tandem air-ride slider, axle, and brakes assembly, introduced last year, operates on a similar principle.
BETTER BRAKING: Dana’s RS40 slider suspension (which joined the family of Dana Spicer SmartRide trailer suspensions late last year) uses truck-style brakes for parts commonality. The result: you can cut your parts inventories by up to 40 percent.
As an option, Dana offers Bendix air disc brakes, a product of a joint venture between Bendix and Dana. Earlier this year, TransX, the Winnipeg fleet, ordered 500 Dana Spicer SmartRide trailer suspension modules with Bendix disc brakes.
SmartRide suspensions and axles can be specified with an array of Bendix products, including double or single anchor-pin air drum brakes; extended service and 8.625-in wide brakes; and Bendix TABS-6, a scalable ABS technology for trailers.
Dana’s work with Bendix and Eaton-its partner in the Roadranger marketing alliance-is a reminder that product engineering agreements are critical to air-ride suspension systems for the fickle van trailer market.
Collaboration helps designers cut weight, maximize strength, and create an enticing package of components. Some designers work across the hall from one another, others across the globe. What’s important is how the elements work together once they’re under your trailer.