Pivotal Pieces

Power Services Shops Aid Wilson Lock Gate Repair

More than 3,700 vessels pass through Wilson Lock and Dam near Florence, Alabama, each year, carrying freight along the Tennessee River to destinations near and far.

“Locks are like a water elevator,” said Joseph Hardwick, a machine tool specialist at the Tennessee Valley Authority Power Service Shops in Muscle Shoals, Alabama.

The main Wilson Lock is 110 feet by 600 feet with a 115-foot-tall gate, making it one of the largest lifts in the country. In September, operators with the U.S. Army Corps of Engineers reported hearing concerning noises and vibrations. They reached out to the Power Services Shop where the team jumped into action.

“We are basically the emergency room of TVA,” Hardwick said.

Inspections revealed gate damage that included a hinge at the bottom of the gate. In addition to carrying most of the weight, the bottom hinge also acts as a seal, preventing the lock from emptying while in use.

Decades of wear and tear rendered the hinge no longer operable. The team began drafting a plan. Instead of going back to the drawing board, Hardwick said they were using the same specifications and tolerances as the original design fabricated in the 1950s. They even have the original handwritten blueprints.

“The first thing we did was create a 3D model of the components,” Hardwick said, reaching for several colorful plastic pieces on his desk.

Using a 3D printer, Hardwick and his team were able to create a scaled-down model of each component for visual reference. Then they were able to begin generating a toolpath, a set of programming instructions for the fabrication process.

The pintle casting will be made from a rectangular block of steel. The pintle bushing, installed and nested into the casting, will be made from leaded bronze, a material that exhibits qualities of lubricity when paired with a hardened steel. The pintle ball, the hardened steel counterpart, rests inside the bushing like a ballpoint pen. This heat-treated steel provides a better wear surface and is more resistant to movement fatigue. And finally, there’s the pintle base, a steel piece on which the ball will glide.

Hardwick grew up working on cars alongside his dad and eventually worked at a tool and die shop. His affinity for tinkering followed him to TVA where he began as a contract machinist before becoming a full-time machine tool specialist.

“Every day is different,” Hardwick said, remarking on what he loves most about the job. “The work scope changes, keeps things interesting. I also get to train people and see them grow.”

Hardwick mentors young machinists in the apprenticeship program every day, telling them to consume as much knowledge as possible. Be a sponge, he says.

“I tell them to be patient, to grow their skill set, and they can be really successful here at TVA. But it’s a long game,” Hardwick said.

Hardwick’s work on the Wilson lock gate project is a long game, too — one that will continue to be a collaborative effort between TVA and the Army Corps of Engineers.

Up next is machining — a process in which these blocks of steel will be shaped into components with tolerances measured in microns, thinner than a strand of hair. The components will also undergo non-destructive examination testing to verify that the material is not defective. Using ultrasonic sound waves, this testing detects any flaws that are imperceptible to the human eye.

The main chamber of the lock remains inoperable. River traffic is continuing through the auxiliary lock. The Army Corps of Engineers Nashville District estimates the timeline for repairs and reopening for June 2025.

Joseph Hardwick, machine tool specialist at the TVA Power Services Shop in Muscle Shoals, Alabama, reviews plans for the pintle bushings that will help repair the Wilson Lock gate.