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This is a Multi Flexible Body Transient Response Dynamics Finite Element Analysis of the crank piston connecting rod assembly. Below the Von Misses plot at 9000 RPM. This plot shows the maximum stress during the entire simulation. The crank rod piston assembly is simulated from 0 to 13000 RPM.
Shown in red is the RPM of the engine, and shown in blue is the axial displacement of the flywheel on the outer most point. One can clearly see that like most 4 cylinder engines there is a spike right about 4000 to 5000 RPM as well as a spike around 9000 RPM. There is no combustion load nor compression load on the top of the pistons in this simulation, it's just the inertia of the connecting rods and pistons plus a 100 Nm of torque to spin up the crank, that's simulated in this case. A 100000 iterations / steps are made to get a good result for this simulation.
This is a zoomed portion of the same graph right about 9000 RPM where the maximum oscillation occurs
This is a Multi Flexible Body Transient Response Dynamics Finite Element Analysis of a part of the valve train of a BMW M10 engine. this simulation runs the engine at 12000 RPM. clearly seen are the harmonics of the spring. In the simulation below there is no contact so the rocker is sort of glued to the camshaft and valve. But what is clear in this simulation is that a beehive / interference fit double spring is needed to mitigate these oscillations.
The simulation below is with contact AT 12000 RPM. Although the contact algorithm in this simulation leaves much to be desired, one can clearly see that at 12000 RPM the rocker no longer is in contact with the camshaft at all times. Thus more spring force in needed. Doing further simulations "no video's available" it seems that a single spring will not hold the rocker in place much above 6000 RPM.
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