Key UC Contact
What We Did
On request from Maritime NZ, components of a steering linkage were assessed to determine the cause of failure. As part of a steering linkage mechanism in a jet boat, two D-ring shackle pins were safety wired together in order to prevent either of the shackle pins from falling out. Relative movement of the D-ring shackles from maneuvering the boat caused fluctuating stresses in the stainless steel safety wire, resulting in a fatigue fracture of the wire. Without the constraint of the safety wire, a pin from one of the D-ring shackles became dislodged, resulting in the failure of the steering mechanism, loss of control and crash of the boat. As well as a demonstration of the key features of the components that led to the determination of a fatigue fracture, the significant flaws in the installation and configuration of the steering linkage are discussed.
Who Was Involved
Maritime NZ, University of Canterbury Department of Mechanical Engineering
Why It Matters
The analysis showed that the design of the steering linkage was flawed. Steering is a safety-critical function, and failure can lead to loss of life. This work resulted in a safety bulletin about how to prevent such occurrence and wider publication in a peer-reviewed international journal
Learn More
- Beardsley, A.L., Kral, M.V. Failure Analysis of a Jet Boat Steering Linkage. J Fail. Anal. and Preven. 19, 1551–1555 (2019). https://doi.org/10.1007/s11668-019-00786-9
- www.maritimenz.govt.nz/commercial/safety/safety-updates/equipment-cranes-cargo/d-shackles.asp
