SmithCo Develops Kingpin Housing for Side-Dump Trailers

Patent-Pending Design Intended to Improve Durability, Reduce Maintenance Costs
SmithCo kingpin
(SmithCo via Facebook)

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SmithCo Inc. has developed a patent-pending kingpin housing for its side-dump trailers that’s intended to improve durability and reduce maintenance costs.

Kingpins, which connect trailers to a truck’s fifth wheel, undergo stress in side-dump operations due to heavy loads and repeated dumping cycles. Common marketplace options include removable kingpins that can require frequent replacement or welded designs that require significant work to replacement.

“We listened to our customers, and one thing they wanted was a longer-lasting kingpin and housing,” said SmithCo Director of Engineering Dan Dohman. “Our engineers developed a collet-chuck style kingpin housing that presses together and locks everything in place. This design eliminates movement without requiring the kingpin to be welded to the fifth-wheel plate.”



Testing at Iowa State University’s structures lab subjected the design to 500,000 fully loaded start-and-stop cycles. According to Dohman, the kingpin and housing showed no movement or wear after testing.

“The new design started more secure, and it did not loosen up at all,” Dohman said. “The connection to the fifth wheel was still secure.”

SmithCo, based in Le Mars, Iowa, plans to begin producing trailers with the new design late in the fourth quarter. The kingpin will be standard on all its over-the-road side-dump trailers starting in 2025.

The company has manufactured side-dump trailers for three decades, serving construction, agriculture, mining, government, waste handling and environmental markets.

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