Military vehicles endure extreme conditions during their lifetime. How can the steering systems of these vehicles take on temperatures as low as minus 40 degrees Celsius?
It's not just low temperatures that are problematic for military vehicles; other challenges include moisture and road debris. Solid environmental testing can address these issues in the design process.
The environmental testing process for steering systems needs to be bespoke to the vehicle and end application. For example, a military vehicle used for semi-submersed and wading applications will have different requirements to an armoured vehicle designed for warfare. Bespoke tests should be arranged based on the end application.
While all military vehicles can differ, when it comes to the environmental testing of military-grade steering components, there are some crucial parameters to consider that form three core tests:
Salt spray test
A salt spray test rig uses up to six steering parts at a time to test resistance against salt spray at varying temperatures. This rig is a large container with a rotary arm that controls the movement of steering components, normally at a rate of one cycle every three seconds.
The salt spray test does not necessarily represent dirt or grit but mimics any debris that might enter a part, potentially causing it to corrode or fail. The test can use varying concentrations of salt, with higher concentrations for the more extreme applications faced by military vehicles.
For example, a test could check the effects of repetitive salt spray, with periodical temperatures of minus 40 degrees Celsius— this is the automotive industry standard for low temperature testing. This will ensure the steering system can withstand grit on the roads, even at low temperatures.
The results will illustrate changes in torque, rate of corrosion, overall effect of grit on the vehicle and its steering system, as well as any potential for water ingression.
The same test rig can also be used to test the system against other factors, such as water. During rotary submersion, the parts are fully submerged in water. If a part can endure underwater movement at one cycle every three seconds at varying temperatures without corroding or failing, then it can confidently be used in the end environment.
Other developments include using different finishes and upgraded sealing and greases to improved design features and pass rotary submersion testing.
Low temperature evaluation
Low temperature testing also forms a standalone test for military steering systems. Low temperatures can bring about issues with the viscosity of the fluid in lubricated component, which can have detrimental effects on steering torque or even cause parts to lock up entirely.
Using a low temperature chamber, parts can be tested at as low as minus 40 degrees Celsius for a set period of time based the end application. This low temperature can be applied constantly or periodically for dynamic testing. The parameters measured in this test include assessing changes to the part cause by low temperatures, checking rotation and measuring torque.
In short, there are plenty of variables to consider when developing a steering system for military applications. In accounting for these variables, the testing process should always be designed to the needs of the end user.
Note: Emma Cygan is a design and development engineer at Pailton Engineering.