Oh-Oh! Over She Goes!
August 5, 2010
A short video now making the rounds of truck folks' e-mail boxes shows a huge and heavy steel I-beam girder, and the trailer dollies it's on, falling over in a freeway curve.
The long rig's driver seems to have taken the shallow curve too fast and the top-heavy load went on its side.
We don't know where or when this occurred, or who the company was. We imagine the driver is now pursuing other opportunities in or out of trucking. And, what happened to the SUV that entered the freeway and was scooting ahead of the rig?
Would an electronic anti-rollover device have prevented this? Probably not, one manufacturer says. Roll Stability Control and Electronic Roll Stability (ESC), names for two Meritor Wabco products, uses sensors to measure lateral g-forces to sense an impending rollover, then applies brakes on the tractor and trailer (if both are fitted with it) to slow down the rig. Brake applications are on individual wheels to try to specifically reduce the lateral forces. (Bendix and Haldex also offer such products.)
In this case, road speed did not generate high lateral forces, but seemed to be enough to cause the load's high center of gravity to pull itself over. Tracking between tractor and trailer axles might be another factor.
"It seems the turn was very gradual and little lateral acceleration would have developed on the tractor or trailer," says Alan Korn, chief engineer at Meritor Wabco. "It seems the accident resulted from a tracking issue between the tractor, the non-steerable dolly and the I-beam that was fixed to each respective unit."
Could any anti-rollover device be programmed for such an occurrence? No, Korn says.
"These types of stability control systems rely on lateral acceleration or divergent yaw rate to initiate a stability control intervention. To prevent the rollover accident shown in the video, some form of roll angle sensor would have to be integrated in the system to detect the type of roll instability that occurred."
This load was a structural I-beam, but windmill components are often seen on the highways because wind energy construction has boomed in North America. September's Heavy Duty Trucking, will carry a story about the hauling of windmill pieces, which to our knowledge have stayed rightside-up.
Posted @ Thursday, August 5, 2010 7:57 AM