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Taking the wiggle out of the wagon

PORTLAND, Ore. - Doubles and triples are obviously more efficient than single trailers, they're simply bigger. (That is why they're called long combination vehicles [LCVs].) But under certain conditio...


PORTLAND, Ore. – Doubles and triples are obviously more efficient than single trailers, they’re simply bigger. (That is why they’re called long combination vehicles [LCVs].) But under certain conditions stability has been an issue earning certain configurations the unflattering monikers of ‘wiggle wagons’.

Fleets trying to take advantage of the extra carrying capacity have always had to balance increased revenues with higher exposure to accidents. Only a carrier’s top drivers are generally trusted with the oft-volatile LCV trailer configurations.

However, Haldex is working with Michigan State University to stabilize the ride and minimize the risk. Dave Englebert, chief engineer with Haldex Brake Products, says the company is looking to combine anti-lock braking with electronic load sensing (ELS) and control area network technologies to create the RAMS, trailer-only, electronic braking system.

Advanced skid-pad testing at Michigan State has shown the system suppresses rearward amplification (the wiggle at the back end of the wagon). Researchers have seen it drop from a factor of 2.3 to only 1.7 in wet conditions, at speeds of 48mph or higher, when making an eight-foot lane change, within a distance of 200 feet.

“Obviously we’d like to see that number reduced to one,” says a researcher from the university. “We’d like the trailer to go exactly were the tractor goes, but we have managed to significantly reduce this rearward amplification.”

RAMS’ hardware includes a dual modulator valve package and is available in two sensor/two modulator (2S/2M) and 4S/2M configurations.

The heart of the system is a micro-machined angular yaw rate sensor that features a vibrating quartz gyroscope. It operates on five volts of DC power and its internal circuitry provides protection for reverse voltage and over voltage conditions.

Each trailer in a given combination is rigged with a RAMS unit networked to the electronic braking systems of each set of duals. When the yaw sensor detects a possible rollover situation, diagonally-opposite brakes are fired in unison. Braking force alternates between the left front/right rear and right front/left rear positions, which produces the stabilizing effect.

While Englebert insists RAMS is only in the testing phase, Haldex is working to bring the advanced LCV trailer-only braking system to market as soon as possible. n


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