If a well balanced system starts moving, it should not vibrate ! Or if it does, it should vibrate even more at high speeds !
But a car clearly vibrates hard during the startup, to then stabilize.
Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. It only takes a minute to sign up.
Sign up to join this communityIf a well balanced system starts moving, it should not vibrate ! Or if it does, it should vibrate even more at high speeds !
But a car clearly vibrates hard during the startup, to then stabilize.
The core reason is that the core of an engine is a series of explosions moving asymmetric components by pressure and then venting gases. At speed, these happen so fast that there is no obvious bang before the next one, but think about what happens at the initial stages of starting your engine:
You can see from the diagram that there is a counterweight, but to get it started is a bit asymmetric. Usually the firing of the cylinders is not smooth at first as well, so until the idle speed is reached, there may be explosions happening at irregular times - leading to vibration.
It is a well balanced system, but remember that it is not purely circular...the main shaft is circular, but the pistons are at an angle to the circular shaft, thus during low engine RPMs (startup, stall, etc) the vibration is increased as the system is cast out of balance.