An automotive manufacturer was seeing frequent failures of the extension springs used in an engine assembly. The failures were leading to costly repairs and were hurting the brand’s reputation for reliability. The cause was clear enough: the springs did not have enough resistance to the high temperatures and mechanical stress found in a modern, high-performance engine.
Why Heat Is Hard on Springs
A spring that sits hot under load slowly loses force. This is called relaxation, and ordinary spring materials such as music wire and hard-drawn steel begin to suffer from it at only moderately elevated temperatures. Add engine vibration and the repeated loading of every cycle, and a spring that tests well at room temperature can fail early in service. That is why material choice comes first in an application like this one.
Our Approach
Our engineers worked closely with the manufacturer’s R&D department to develop a custom extension spring that could survive the conditions inside the engine. The project had four parts.
- Material analysis: we compared several materials and selected a heat-resistant alloy suited to the temperature and stress at the spring’s location.
- Design optimization: we redesigned the spring geometry to spread stress more evenly, adjusting the coil diameter, the number of coils and the overall length. In an extension spring the hooks are usually the most highly stressed area, so the end design received the same attention as the body.
- Precision manufacturing: the springs were made to close tolerances, so that every part performs and fits the same way in the assembly.
- Testing: the springs went through fatigue testing, load testing and simulations of engine conditions to confirm their endurance.
Results
The new extension springs were fitted to the engine assemblies and the improvement showed quickly.
- Spring-related failures dropped sharply.
- The manufacturer saw fewer warranty claims connected to the problem.
- Reliability improved, which helped restore customer confidence.
What This Project Shows
When a spring fails in a hot environment, making the same spring more carefully does not help. The material has to be right for the temperature first. After that, the geometry has to keep the stress low enough for that material to last.
If your extension springs work in heat or under vibration, tell us about the application through our contact page, or read more about our custom extension springs.
