7 Trends in axles and suspensions

February 2013, - Feature

by Deborah Lockridge, Editor-in-Chief - Also by this author

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The ECAS-equipped tandem automatically dumps air from the non-powered axle's air springs to effect the weight transfer. A FueLite 6x2 also can have electronic traction control added to the standard antilock braking system to augment the mechanical difflock.

Meritor is also preparing an advanced 6x2, called SmarTandem, which has a proprietary controller that automatically handles the diff lock and weight-transfer functions.

3. Faster axle ratios

Officials at both Dana and Meritor believe more truck operators will begin asking for “faster” axle gearing, or lower numeric axle ratios, to save fuel and cut greenhouse gas emissions.

Modern trucks and tractors are electronically speed governed to keep engine revs low, a practice that used to be called “gear fast, run slow.” Fast axles are paired with transmissions with direct-drive top gears, which themselves reduce friction and save fuel.

“The key here is selecting the correct ratio for the application,” says Dana's Slesinski. “Gearing the vehicle too fast may result in having to shift too often on slight grades,” he says. “A good rule of thumb is to gear the vehicle to allow it to pull a 1% grade in top gear at nominal load conditions.”

Meritor's current fastest ratio is 2.47 to 1, and is used by customers who want a tractor to cruise at 60 or 65 mph with the engine turning only 1,300 rpm or so. But truck makers, under new federal mandates to reduce carbon dioxide emissions, have begun offering even slower engine operation, with cruise at 1,100 rpm.

Meritor engineers are looking ahead and preparing ratios in the 2.20 range, according to Allen and Stevenson. Altered metal alloys and gear designs are being explored to make the upcoming gear sets durable as well as economical.

4. Integration

“The North American marketplace will continue to see suspension/ axle suppliers pursue an integration strategy to provide their customer base more complete, engineered solutions system packages that continue to redefine the ‘best’ balance of weight, cost and performance to the end user,” says Bill Hicks, product planning director for SAF Holland Trailer Systems.

The company's SAF CBX integrated suspension/axle systems also include integrated brakes.

Another example is Meritor's new low-mount trailer suspensions, specifically designed as part of a fully integrated system to optimize performance and weight, which are integrated with Meritor trailer axles and Q Plus Cam Brakes.

Reyco Granning also sees continued integration in van trailer air ride slider suspensions.

“Once upon a time, the trailer manufacturer purchased a slider sub-frame from one supplier, suspension components from another, an axle from another, hub, drums, bearings and seals from yet others,” says Mueller. “The trend has been for one supplier to integrate those disparate components into one, ready-to-install unit.”

Another example is Firestone's Air-ide Integrative Air-Damping System, which offers a lighter-weight alternative to cab mount suspension applications, providing the functionality of an air spring and shock absorber in a single part.

5. Less maintenance, longer life

Suspensions have come a long way in reducing maintenance, notes David Clark, corporate warranty manager for Pacific Power Products, which has 10 truck service locations in the Pacific Northwest and is a member of the WheelTime Network.

Clark started out his career as a suspension technician. “When I first started doing suspensions, it wasn't uncommon to do suspension repairs every day, all day long,” replacing pins and bushings and more. Today, he says, suspension repairs are so sporadic, “the suspension specialist like I was is no longer someone who just tears apart trucks. Now they have to do other things. Otherwise it's like the Maytag repairman, they're going to sit there waiting.”

Trailer OEMs, suspension/axle suppliers and component system suppliers are all developing or currently providing several premium wheel end package options delivered direct from the factory that offer longer service life/maintenance intervals with extended warranty coverage.

“While the premium wheel end packages are an upcharge, they offer peace of mind to a fleet knowing they will likely recoup their investment in reduced maintenance, increased uptime and reduced field failures due to bearing issues,” says SAF Holland's Hicks.

Corrosion protection is another trend. SAF Holland's Black Armour solution is standard on SAF-branded trailer suspension systems, and Hal-dex offers a Self Setting Automatic brake adjuster, which encloses the critical moving parts to protect them from corrosive road salts.

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