Cold-Spinning of Engines via the Perfect Drivetrain: Static and Eigenvalue Analysis
When new car or truck engines are manufactured, a cold spin-up test is often performed. During this test, the engine is spun while vibration transducers, accelerometers and pressure gauges measure the engine’s performance.
Ideally, the drive motor that is doing the spinning only transmits pure, clean torque energy to the test motor. Development of a high-stiffness yet well damped drivetrain between the drive motor and the test engine has been and still is a development challenge for many companies.
Drivetrain analysis is mainly about getting the right dynamic response out of a collection of mechanical components. The proposed drivetrain started out with a Lovejoy torsional coupler and then proceeded through a steel driveline shaft followed by a very tricky steel bellows. At both ends of this system, we had a varous assortment of steel couplers. Although each component had its own linear dynamic response, the assembleage of these components presented an interesting numerical challenge.
The finite element model was built using brick elements (hexes), tetrahedrals (tets), beam elements, spring elements and rigid links. Although all of these elements are linear in nature, their combined response was not easily predictable. Once assemblied the model was run as an eigenvalue analysis and predictions were made.
Software tools: Femap and NX Nastran