Thordon optimizes articulating rudder with new bearing-seal combo

Written by Heather Ervin
ThorPlas-Blue bearings installed in an articulating rudder with Thorseals in-situ

ThorPlas-Blue bearings installed in an articulating rudder with Thorseals in-situ. (Credit: Thordon)

When a 9,280 horsepower towboat returned to service following extensive repairs at the James Marine Paducah River Service yard in Kentucky, it marked the first application of Thordon’s new seal-embedded bearing to an articulating rudder.

Articulating rudders are unlike conventional rudders and can be more costly to repair when things go wrong. They are more susceptible to wear and tear, due to the higher operating pressures and abrasives, and as a result, require a more robust bearing and seal solution.

For one marine transportation service provider in the United States, however, a key requirement was a grease-free bearing capable of increasing the intervals between dry dockings and reducing operational costs.

To meet the requirement, Thordon engineers recommended a bearing using the company’s ThorPlas-Blue material, a material for articulating types of rudders, and integrating a Thordon lip seal into the design.

“We found that by embedding a lip seal into the bearing, we could better prevent ingress of river water, sand, silt, and debris, which would otherwise rapidly wear the pins and bushings down, reducing the workboat’s in-service time,” said Kasey Cummings, technical sales manager, Thordon Bearings.

The towboat operator needed this type of rudder to do what it was designed to do—reduce fuel costs—however frequent drydocking for rudder bearing replacement was eating into any fuel savings. With a fleet of more than 50 linehaul vessels and 800 dry cargo barges, the operator’s fleet transports over 40 million bushels of grain each month, so fuel savings can really add up.

“The new design certainly optimizes the operational and cost efficiencies associated with an articulated rudder,” said Cummings.

Thordon introduced the design back in 2020 and installed the 3.149-inch (79.98-mm) diameter bearing in March 2021. This was the first towboat reference for the new seal-embedded bearing and the first time that ThorPlas-Blue was used in the flap portion of an articulating rudder. Thordon has since supplied 60 bearings for an additional 15 articulating rudders installed on other vessels operating in the U.S. inland waterways. 

As part of a comprehensive engine and propulsion overhaul, Thordon’s robust bearings were also installed to the 168- by 45-foot (48- by 13.7-meter) vessel’s rudder flaps, main trunk, and pivot pins. In total, 16 ThorPlas-Blue bearings were supplied and fitted.

Cummings continued: “ThorPlas-Blue can handle three times the operating pressures and forces of other bearing materials used on the inland waterways; however, for inland waterway vessels operating articulating rudders, we do recommend machining flap bores to facilitate the installation of the ThorPlas-Blue bearing seal combination.”

Cummings furthered that the installation was very straightforward; the only modification was to the rudder flap pins. Yard staff added a chamfer on the leading edge so that it could pass through the edge of the embedded lip seals in the ThorPlas-Blue material.

The 994 gt, 1993-built towboat has been operating ThorPlas-Blue for over two years now and the owner is confident that the new bearing and seal design has delivered greater operational efficiencies to the vessel’s articulating rudder.

Thordon expects to receive additional orders to replace the articulating rudder bearings on other vessels in the fleet with ThorPlas-Blue bearings.

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